Model 7230 - Princeton Applied Research

Model 7230
DSP Lock-in Amplifier
Instruction Manual
198004-A-MNL-B
Copyright © 2011 AMETEK ADVANCED MEASUREMENT TECHNOLOGY, INC
Firmware Version
The instructions in this manual apply to operation of a Model 7230 DSP Lock-in Amplifier that is fitted with
Version 1.96 or later operating firmware. Users of instruments that are fitted with earlier firmware
versions can update them to the current version free of charge by downloading an Update Pack from our
website at www.signalrecovery.com The pack includes full instructions for use.
Trademarks
AMETEK® and the b® and a logos are registered trademarks of AMETEK, Inc
Other product and company names mentioned are trademarks or trade names of their respective
companies.
Company Names
SIGNAL RECOVERY is part of Advanced Measurement Technology, Inc, a division of AMETEK, Inc. It
includes the businesses formerly trading as EG&G Princeton Applied Research, EG&G Instruments
(Signal Recovery), EG&G Signal Recovery and PerkinElmer Instruments (Signal Recovery).
Table of Contents
Table of Contents
General Safety Precautions .............................................................................................................. vii
Chapter One, Introduction
1.1 How to Use This Manual.................................................................................................................................. 1-1
1.2 What is a Lock-in Amplifier?........................................................................................................................... 1-2
1.3 Key Specifications and Benefits....................................................................................................................... 1-3
Chapter Two, Installation and Initial Checks
2.1 Installation ........................................................................................................................................................ 2-1
2.1.01 Introduction ............................................................................................................................................. 2-1
2.1.02 Rack Mounting ........................................................................................................................................ 2-1
2.1.03 Inspection ................................................................................................................................................ 2-1
2.1.04 Line Cord Plug ........................................................................................................................................ 2-1
2.1.05 Line Voltage Selection ............................................................................................................................ 2-1
2.2 Initial Checks.................................................................................................................................................... 2-1
2.2.01 Introduction ............................................................................................................................................. 2-1
2.2.02 Procedure................................................................................................................................................. 2-2
Chapter Three, Technical Description
3.1 Introduction ...................................................................................................................................................... 3-1
3.2 Operating Modes .............................................................................................................................................. 3-1
3.2.01 Introduction ............................................................................................................................................. 3-1
3.2.02 Single Reference / Dual Reference.......................................................................................................... 3-1
3.2.03 Tandem Demodulation ............................................................................................................................ 3-1
3.2.04 Single Harmonic / Dual Harmonic .......................................................................................................... 3-1
3.2.05 Internal / External Reference Mode......................................................................................................... 3-2
3.2.06 Virtual Reference Mode .......................................................................................................................... 3-2
3.3 Principles of Operation..................................................................................................................................... 3-2
3.3.01 Block Diagram......................................................................................................................................... 3-2
3.3.02 Signal Channel Inputs.............................................................................................................................. 3-3
3.3.03 Line Frequency Rejection Filter .............................................................................................................. 3-4
3.3.04 AC Gain and Dynamic Reserve............................................................................................................... 3-4
3.3.05 Anti-Aliasing Filter.................................................................................................................................. 3-6
3.3.06 Main Analog-to-Digital Converter .......................................................................................................... 3-7
3.3.07 Reference Channel Inputs........................................................................................................................ 3-7
3.3.08 Reference Channel................................................................................................................................... 3-7
3.3.09 Phase-Shifter............................................................................................................................................ 3-8
3.3.10 Internal Oscillator - General .................................................................................................................... 3-9
3.3.11 Internal Oscillator - Update Rate............................................................................................................. 3-9
3.3.12 Internal Oscillator - Frequency & Amplitude Sweeps............................................................................. 3-9
3.3.13 Internal Oscillator - Voltage Control....................................................................................................... 3-9
3.3.14 Demodulators - Dual Phase Multipliers .................................................................................................. 3-9
3.3.15 Demodulators - Output Filters ............................................................................................................... 3-10
3.3.16 Fast Curve Buffer .................................................................................................................................. 3-11
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TABLE OF CONTENTS
3.3.17 Main Output Processor - General .......................................................................................................... 3-11
3.3.18 Main Output Processor - Output Offset and Expand............................................................................. 3-11
3.3.19 Main Output Processor - Vector Magnitude and Phase ........................................................................ 3-11
3.3.20 Main Output Processor - Noise Measurements ..................................................................................... 3-12
3.3.21 Main Output Processor - Standard Curve Buffer .................................................................................. 3-13
3.3.22 Analog Outputs (DACs) ........................................................................................................................ 3-14
3.3.23 Auxiliary Analog Inputs (ADCs) .......................................................................................................... 3-14
3.3.24 Main Microprocessor - General............................................................................................................. 3-14
3.3.25 Main Microprocessor - Auto Functions ................................................................................................ 3-14
3.4 General ........................................................................................................................................................... 3-16
3.4.01 Accuracy................................................................................................................................................ 3-16
3.4.02 Power-up Defaults................................................................................................................................. 3-16
Chapter Four, Front and Rear Panels
4.1 Front Panel ....................................................................................................................................................... 4-1
4.1.01 A and B (I) Signal Input Connectors....................................................................................................... 4-1
4.1.02 REF IN Connector................................................................................................................................... 4-1
4.1.03 OSC OUT Connector .............................................................................................................................. 4-1
4.1.04 STATUS Indicator .................................................................................................................................. 4-1
4.2 Rear Panel......................................................................................................................................................... 4-3
4.2.01 Power Input Connector............................................................................................................................ 4-3
4.2.02 Power Switch........................................................................................................................................... 4-3
4.2.03 DIGITAL I/O Connector......................................................................................................................... 4-3
4.2.04 RS232 Connector .................................................................................................................................... 4-3
4.2.05 LAN Connector ....................................................................................................................................... 4-3
4.2.06 USB Connector........................................................................................................................................ 4-4
4.2.07 CONFIG Switches................................................................................................................................... 4-4
4.2.08 SIG MON Connector............................................................................................................................... 4-4
4.2.09 TRIG IN Connector................................................................................................................................. 4-4
4.2.10 TRIG OUT Connector............................................................................................................................. 4-5
4.2.11 ADC 1, ADC 2, ADC 3, and ADC 4 Connectors ................................................................................... 4-5
4.2.12 DAC 1, DAC 2, DAC 3, and DAC 4 Connectors ................................................................................... 4-5
Chapter Five, Web Control Panel Operation
5.1 Introduction ...................................................................................................................................................... 5-1
5.2 Ethernet Connection Methods .......................................................................................................................... 5-1
5.2.01 Direct Wired Connection to a Single Computer...................................................................................... 5-1
5.2.02 Wireless Connection to an iPad, Laptop, or Netbook Computer ............................................................ 5-1
5.2.03 Wired Connection to a Company or Corporate Network Using a Static IP Address .............................. 5-5
5.2.04 Wired Connection to a Company or Corporate Network Using a DHCP Allocated IP Address ............ 5-9
5.3 Web Control Panels........................................................................................................................................ 5-11
5.3.01 Main Controls: Overview ...................................................................................................................... 5-11
5.3.02 Main Controls: Display Indictors .......................................................................................................... 5-13
5.3.03 Main Controls: Input ............................................................................................................................. 5-14
5.3.04 Main Controls: Reference 1................................................................................................................... 5-17
5.3.05 Main Controls: Oscillator ...................................................................................................................... 5-19
5.3.06 Main Controls: Output 1........................................................................................................................ 5-19
5.3.07 Main Controls: Reference 2................................................................................................................... 5-21
5.3.08 Main Controls: Output 2........................................................................................................................ 5-22
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TABLE OF CONTENTS
5.3.09 Main Controls: Output Filters................................................................................................................ 5-23
5.3.10 Main Controls: Demodulator Control.................................................................................................... 5-24
5.3.11 Main Controls: Status Indictors............................................................................................................. 5-25
5.3.12 Oscillator: Overview.............................................................................................................................. 5-26
5.3.13 Oscillator: Sweep Control ..................................................................................................................... 5-26
5.3.14 Oscillator: Modulation Control ............................................................................................................. 5-28
5.3.15 Oscillator: Amplitude and Frequency Controls..................................................................................... 5-30
5.3.16 Rear Panel: Overview............................................................................................................................ 5-30
5.3.17 Rear Panel: DACs.................................................................................................................................. 5-31
5.3.18 Rear Panel: ADCs.................................................................................................................................. 5-35
5.3.19 Rear Panel: RS232................................................................................................................................. 5-36
5.3.20 Rear Panel: Ref Mon ............................................................................................................................. 5-37
5.3.21 Rear Panel: Expand ............................................................................................................................... 5-37
5.3.22 Rear Panel: Bind.................................................................................................................................... 5-37
5.3.23 Rear Panel: Digital Port......................................................................................................................... 5-38
5.3.24 Rear Panel: DIP switches ...................................................................................................................... 5-38
5.3.25 Rear Panel: USB Status ......................................................................................................................... 5-39
5.3.26 Equations: Overview ............................................................................................................................. 5-40
5.3.27 Equations: Equation 1 and Equation 2 .................................................................................................. 5-40
5.3.28 Equations: Command Interface ............................................................................................................. 5-42
5.3.29 Equations: Auto Default ........................................................................................................................ 5-42
Chapter Six, Computer Operation
6.1 Introduction ...................................................................................................................................................... 6-1
6.2 Capabilities ....................................................................................................................................................... 6-1
6.2.01 General .................................................................................................................................................... 6-1
6.2.02 Operation ................................................................................................................................................. 6-1
6.2.03 Compound Commands ............................................................................................................................ 6-1
6.3 RS232 Operation .............................................................................................................................................. 6-1
6.3.01 Introduction ............................................................................................................................................. 6-1
6.3.02 General Features ...................................................................................................................................... 6-1
6.3.03 Choice of Baud Rate................................................................................................................................ 6-2
6.3.04 Choice of Number of Data Bits ............................................................................................................... 6-2
6.3.05 Choice of Parity Check Option................................................................................................................ 6-2
6.3.06 Handshaking and Echoes......................................................................................................................... 6-3
6.3.07 Terminators.............................................................................................................................................. 6-3
6.3.08 Delimiters ................................................................................................................................................ 6-3
6.3.09 Status Byte, Prompts and Overload Byte ................................................................................................ 6-4
6.4 USB Operation ................................................................................................................................................. 6-5
6.4.01 Introduction ............................................................................................................................................. 6-5
6.4.02 General Features ...................................................................................................................................... 6-5
6.4.03 Terminator, Status Byte, and Overload Byte........................................................................................... 6-5
6.4.04 Delimiters ................................................................................................................................................ 6-6
6.5 Ethernet Operation............................................................................................................................................ 6-6
6.5.01 Introduction ............................................................................................................................................. 6-6
6.5.02 IP Address ............................................................................................................................................... 6-6
6.5.03 Main Controls.......................................................................................................................................... 6-6
6.5.04 Sockets..................................................................................................................................................... 6-6
6.5.05 Terminator, Status Byte, and Overload Byte........................................................................................... 6-6
6.5.06 Delimiters ................................................................................................................................................ 6-7
6.6 Command Format ............................................................................................................................................. 6-7
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TABLE OF CONTENTS
6.7 Command Descriptions .................................................................................................................................... 6-8
6.7.01 Signal Channel ........................................................................................................................................ 6-8
6.7.02 Reference Channel ................................................................................................................................ 6-10
6.7.03 Signal Channel Output Filters ............................................................................................................... 6-12
6.7.04 Signal Channel Output Amplifiers ........................................................................................................ 6-14
6.7.05 Instrument Outputs ................................................................................................................................ 6-14
6.7.06 Internal Oscillator.................................................................................................................................. 6-17
6.7.07 Analog Outputs...................................................................................................................................... 6-20
6.7.08 Digital I/O.............................................................................................................................................. 6-22
6.7.09 Auxiliary Inputs..................................................................................................................................... 6-22
6.7.10 Output Data Curve Buffer ..................................................................................................................... 6-23
6.7.11 Computer Interfaces .............................................................................................................................. 6-30
6.7.12 Instrument Identification ....................................................................................................................... 6-32
6.7.13 Auto Default and Calibration ................................................................................................................ 6-32
6.7.14 Dual Mode Commands......................................................................................................................... 6-33
6.5 Programming Examples ................................................................................................................................. 6-33
6.5.01 Introduction ........................................................................................................................................... 6-33
6.5.02 Basic Signal Recovery........................................................................................................................... 6-34
6.5.03 Frequency Response Measurement ....................................................................................................... 6-34
6.5.04 X and Y Output Curve Storage Measurement....................................................................................... 6-35
Appendix A, Specifications
Appendix B, Pinouts
B1 RS232 Connector Pinout .................................................................................................................................B-1
B2 Digital I/O Port Connector................................................................................................................................B-1
Appendix C, Cable Diagrams
C1 RS232 Cable Diagrams...................................................................................................................................... C1
Appendix D, Default Settings
Auto Default Function.............................................................................................................................................D1
Appendix E, Alphabetical Listing of Commands
Index
Warranty .......................................................................................................................................End of Manual
iv
TABLE OF CONTENTS
GENERAL SAFETY PRECAUTIONS
The equipment described in this manual has been designed in accordance with EN61010 "Safety
requirements for electrical equipment for measurement, control and laboratory use", and has been
supplied in a safe condition. To avoid injury to an operator or service technician the safety precautions
given below, and throughout the manual, must be strictly adhered to, whenever the equipment is
operated, serviced or repaired. For specific safety details, please refer to the relevant sections within
the manual.
The equipment is intended solely for electronic measurement and should be used for no other purpose.
SIGNAL RECOVERY accepts no responsibility for accidents or damage resulting from any failure to
comply with these precautions.
Grounding
To minimize the hazard of electrical shock, it is essential that the equipment be connected to a
protective ground through the AC supply cable. The continuity of the ground connection should be
checked periodically.
AC Supply Voltage
Never operate the equipment from a line voltage or frequency in excess of that specified. Otherwise,
the insulation of internal components may break down and cause excessive leakage currents.
Fuses
Before switching on the equipment check that the fuses accessible from the exterior of the equipment
are of the correct rating. The rating of the AC line fuse must be in accordance with the voltage of the
AC supply.
Should any fuse continually blow, do not insert a fuse of a higher rating. Switch the equipment off,
clearly label it "unserviceable" and inform a service technician.
Explosive Atmospheres
This equipment must NEVER BE OPERATED in a potentially explosive atmosphere. The equipment is
NOT designed for use in these conditions and could possibly cause an explosion.
Safety Symbols
For the guidance and protection of the user, the following safety symbols may appear on the
equipment, together with details of the hazard where appropriate:
Symbol
Meaning
General safety hazard. Refer to the operating manual for detailed instructions.
Electrical safety hazard. This symbol may appear alongside the general safety
hazard symbol, together with a voltage.
Notes and Cautions
For the guidance and protection of the user, Notes and Cautions appear throughout the manual. The
significance of these is as follows:
NOTES
highlight important information for the reader’s special attention.
CAUTIONS
guide the reader in avoiding damage to the equipment.
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TABLE OF CONTENTS
Avoid Unsafe Equipment
The equipment may be unsafe if any of the following statements apply:
Equipment shows visible damage.
Equipment has failed to perform an intended operation.
Equipment has been stored in unfavorable conditions.
Equipment has been subjected to severe physical stress.
If in any doubt as to the serviceability of the equipment, don't use it. Get it properly checked out by a
qualified service technician.
Live Conductors
When the equipment is connected to its measurement inputs or supply, the opening of covers or
removal of parts could expose live conductors. The equipment must be disconnected from all power
and signal sources before it is opened for any adjustment, replacement, maintenance or repair.
Adjustments, maintenance or repair must only be done by qualified personnel, who should refer to the
relevant maintenance documentation.
Equipment Modification
To avoid introducing safety hazards, never install non-standard parts in the equipment, or make any
unauthorized modification. To maintain safety, always return the equipment to your
SIGNAL RECOVERY service provider for service and repair.
European WEEE Directive
This product is subject to Directive 2002/96/EC of the European Parliament and the Council of the
European Union on waste electrical and electronic equipment (WEEE) and, in jurisdictions adopting
that Directive, is marked as being put on the market after August 13, 2005, and should not be disposed
of as unsorted municipal waste. Please use your local WEEE collection facilities for the disposal of this
product and otherwise observe all applicable requirements.
FCC Notice
This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used
in accordance with this instruction manual, may cause harmful interference with radio communications.
Operation of this equipment in a residential area is likely to cause harmful interference, in which case
the user is required to correct the interference at his own expense.
Acknowledgment
Operation of the Ethernet interface in the model 7230 relies on software code developed by the
Swedish Institute of Computer Science, copyright 2001-2004, all rights reserved. In accordance with
the license under which it is used, we reproduce here the following disclaimer:
THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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TABLE OF CONTENTS
DECLARATION OF CONFORMITY
The directives covered by this declaration
73/23/EEC
Low Voltage Equipment Directive, amended by 93/68/EEC
89/336/EEC
Electromagnetic Compatibility Directive, amended by 92/31/EEC
& 93/68/EEC
Product(s)
Model 7230 DSP Lock-in Amplifier
Basis on which conformity is being declared
The product(s) identified above comply with the requirements of the EU directives by
meeting the following standards:
BS EN61326-1:2006
Electrical equipment for measurement control and laboratory use EMC requirements – Class A.
BS EN61010-1:2001
Safety requirements for electrical equipment for measurement, control
and laboratory use.
Accordingly the CE mark has been applied to this product.
Signed
For and on behalf of SIGNAL RECOVERY
Authority:
Business Element Manager
Date:
November 2010
vii
Introduction
Chapter 1
1.1 How to Use This Manual
This manual gives detailed instructions for setting up and operating the
SIGNAL RECOVERY Model 7230 DSP Lock-in Amplifier. It is split into the
following chapters:Chapter 1 - Introduction
Provides an introduction to the manual, briefly describes the function of a lock-in
amplifier and the types of measurements it may be used for, and lists the major
specifications of the model 7230.
Chapter 2 - Installation and Initial Checks
Describes how to install the instrument and gives a simple test procedure which may
be used to check that the unit has arrived in full working order.
Chapter 3 - Technical Description
Provides an outline description of the design of the instrument and discusses the
effect of the various controls. A good understanding of the design will enable the user
to get the best possible performance from the unit.
Chapter 4 - Front and Rear Panels
Describes the instrument’s connectors and indicator as referred to in the subsequent
chapters.
Chapter 5 - Web Control Panel Operation
Describes the capabilities of the instrument when operated via the built-in web
control panels.
Chapter 6 - Computer Operation
This chapter provides detailed information on operating the instrument from a
computer via the built-in interfaces. It includes information on how to establish
communications, the functions available, the command syntax and a detailed
command listing.
Appendix A
Gives the detailed specifications of the unit.
Appendix B
Details the pinouts of the multi-way connectors on the rear panel of the unit.
Appendix C
Shows the connection diagrams for suitable RS232 null-modem cables to couple the
unit to a compatible computer.
Appendix D
Provides a listing of the instrument settings produced by using the Auto-Default
functions.
Appendix E
Gives an alphabetical listing of the computer commands for easy reference.
New users are recommended to unpack the instrument and carry out the procedure in
chapter 2 to check that it is working satisfactorily. They should then make themselves
familiar with the information in chapters 3, 4 and 5, even if they intend that the unit
will eventually be used under computer control. Only when they are fully conversant
with operation from the front panel should they then turn to chapter 6 for information
1-1
Chapter 1, INTRODUCTION
on how to use the instrument remotely. Once the structure of the computer commands
is familiar, appendix E will prove convenient as it provides a complete alphabetical
listing of these commands in a single easy-to-use section.
1.2 What is a Lock-in Amplifier?
Since their invention back in the 1960's, lock-in amplifiers have been used whenever
the need arises to measure the amplitude and/or phase of a signal of known frequency
in the presence of noise. Unlike other AC measuring instruments they have the ability
to give accurate results even when the noise is much larger than the signal - in
favorable conditions even up to a million times larger.
Early instruments used analog technology, with manual controls and switches, and
with output readings being taken from large panel meters. Later, microprocessors
were added to give more user-friendly operation, digital output displays, and to
support computer control. More recently the analog phase sensitive detectors forming
the heart of the instrument have been replaced by DSP (digital signal processing)
designs, further improving performance.
The model 7230 DSP lock-in amplifier uses the latest DSP technology for signal
detection, and a powerful processor for easy user operation. The low-noise analog
signal channel, with its choice of input mode and impedance, complements the digital
technology, giving an instrument that will be of use in many fields of scientific
research, such as optics, electrochemistry, materials science, fundamental physics and
electrical engineering.
In these and other experiments it can function as a: AC Signal Recovery Instrument
Transient Recorder
Vector Voltmeter
DSP Oscillator
Phase Meter
Frequency Meter
Spectrum Analyzer
Noise Measurement Unit
These characteristics, all available in a single compact console, make it an invaluable
addition to any laboratory.
1-2
Chapter 1, INTRODUCTION
1.3 Key Specifications and Benefits
The SIGNAL RECOVERY Model 7230 represents a further significant advance in
the application of DSP technology in the design of a lock-in amplifier.
Key specifications include:
Frequency range:
Standard unit
With 7230/99 option
0.001 Hz to 120.000 kHz
0.001 Hz to 250.000 kHz
Voltage sensitivity:
10 nV to 1 V full-scale
Current input mode sensitivities:
10 fA to 1 µA full-scale
10 fA to 10 nA full-scale
Line frequency rejection filter
Dual phase demodulator with X-Y and R-θ outputs
Very low phase noise of < 0.0001° rms
Output time constant:
10 µs to 100 ks
5-digit output readings
Dual reference mode - allows simultaneous measurement of two signals at
different reference frequencies.
Single and dual harmonic mode - allows simultaneous measurement of up to two
different harmonics of a signal
Tandem demodulation capability - suitable for double demodulation experiments
that would previously have required two lock-in amplifiers
Virtual reference mode - allows reference free measurements
Direct Digital Synthesizer (DDS) oscillator with variable amplitude and
frequency
Oscillator frequency and amplitude sweep generator
Voltage controlled oscillator frequency or amplitude
8-bit programmable digital I/O port for external system control
Four configurable DAC outputs which can be used as analog signal outputs
and/or as auxiliary DAC outputs
Four auxiliary ADC inputs
Full range of auto functions
Standard USB, Ethernet, and RS232 interfaces
100,000 point internal curve storage buffer
1-3
Chapter 1, INTRODUCTION
1-4
Installation and
Initial Checks
Chapter 2
2.1 Installation
2.1.01 Introduction
Installation of the model 7230 is very straightforward. The instrument can be
operated on almost any laboratory bench or be rack mounted at the user's
convenience. With an ambient operating temperature range of 0 °C to 35 °C, it is
highly tolerant to environmental variables, needing only to be protected from
exposure to corrosive agents and liquids.
The model 7230 does not use forced-air ventilation; however it should be located so
that there is reasonable flow of air around it to aid cooling.
2.1.02 Rack Mounting
An optional accessory kit, part number K02006, is available from
SIGNAL RECOVERY to allow the model 7230 to be mounted in a standard 19-inch
rack.
2.1.03 Inspection
Upon receipt the model 7230 Lock-in Amplifier should be inspected for shipping
damage. If any is noted, SIGNAL RECOVERY should be notified immediately and
a claim filed with the carrier. The shipping container should be saved for inspection
by the carrier.
2.1.04 Line Cord Plug
The model 7230 is powered from the model PS0110 remote power module that in
turn is fitted with a standard IEC 320 input socket. A suitable line power cord is
supplied.
2.1.05 Line Voltage Selection
The model PS0110 is suitable for line voltages in the range 100 - 240 V AC, 47 63 Hz, and no adjustment is needed to accommodate this range. It is internally
protected against short circuit and overload and in the event of failure cannot be
repaired and must be replaced.
2.2 Initial Checks
2.2.01 Introduction
The following procedure checks the performance of the model 7230. In general, this
procedure should be carried out after inspecting the instrument for obvious shipping
damage.
NOTE: Any damage must be reported to the carrier and to SIGNAL RECOVERY
immediately. In addition the shipping container must be retained for inspection by
the carrier.
Note that this procedure is intended to demonstrate that the instrument has arrived in
good working order, not that it meets specifications. Each instrument receives a
2-1
Chapter 2, INSTALLATION AND INITIAL CHECKS
careful and thorough checkout before leaving the factory, and normally, if no
shipping damage has occurred, will perform within the limits of the quoted
specifications. If any problems are encountered in carrying out these checks, contact
SIGNAL RECOVERY or the nearest authorized representative for assistance.
The procedure requires the use of a computer with an Ethernet 10 or 100 Base T
adaptor with RJ45 connector set to support TCP/IP protocol with an installed web
browser. As an example, a Windows 7 PC with Internet Explorer 8 is suitable, but so
are many other computer systems.
2.2.02 Procedure
1) Check that the rear panel Config 2 switch is set to 0. This will set the model 7230
to use the default static IP address of 169.254.150.230
2) Close all open programs on the computer and unplug any existing network
connection.
3) Plug one end of the supplied RJ45 patch cord to the computer and the other end
into the LAN connector on the rear panel of the model 7230
5) With the rear-panel mounted power switch set to 0 (off), plug the line cord into
the model PS0110 power supply unit and the 5-pin DIN plug on the power cable
from the PS0110 to the 7230’s rear panel POWER INPUT connector.
6) Turn on the model 7230. The front panel status light should be green.
7) Open a browser session on the computer. Since there is no connection to the
internet you will not see the normal opening page, but an error message. If using
Internet Explorer the message will be as shown in figure 2-2
Figure 2-2, Initial Browser Window
8) Type 169.254.150.230 into the address bar and press <return>. The 7230's Main
Controls panel should be displayed, as shown below in figure 2-3.
2-2
Chapter 2, INSTALLATION AND INITIAL CHECKS
Figure 2-3, Model 7230 Main Controls Panel
9) Click the Equations tab, to show the Equations panel, as shown below in figure
2-4
Figure 2-4, Model 7230 Equations Panel
10) Click the Auto Default button. This will set all instrument controls to the factory
default values,
11) Connect a BNC cable from the front panel OSC OUT to A input connectors on
the front panel. The X1 and Magnitude outputs should read 100%, and the Y1
and Phase 1 outputs should read close to zero, as shown in figure 2-5 below.
2-3
Chapter 2, INSTALLATION AND INITIAL CHECKS
Figure 2-5, Model 7230 Main Controls Panel – Default Settings
12) Save the address as a favorite, bookmark, or shortcut (figure 2-6) so that you can
quickly reach the model 7230 again if repeating the test, as in figure 2-7
Figure 2-6, Saving the Model 7230’s IP address as a favorite
Figure 2-7, Accessing the favorite
13) This completes the initial checks. Even though the procedure leaves many
functions untested, if the indicated results were obtained then the user can be
reasonably sure that the unit incurred no hidden damage in shipment and is in
good working order.
2-4
Technical Description
Chapter 3
3.1 Introduction
The model 7230 lock-in amplifier is a sophisticated instrument with many
capabilities beyond those found in other lock-in amplifiers. This chapter discusses the
various operating modes provided and then describes the design of the instrument by
considering it as a series of functional blocks. In addition to describing how each
block operates, the sections also include information on the effect of the various
controls.
3.2 Operating Modes
3.2.01 Introduction
The model 7230 incorporates a number of different operating modes which are
referred to in the following technical description, so in order to help the reader's
understanding they are defined here.
3.2.02 Single Reference / Dual Reference
Conventionally, a lock-in amplifier makes measurements such as signal magnitude,
phase, etc. on the applied signal at a single reference frequency. In the model 7230
this is referred to as the single reference mode.
The dual reference mode incorporated in the model 7230 allows the instrument to
make simultaneous measurements at two different reference frequencies, an ability
that previously required two lock-in amplifiers. This flexibility incurs a few
restrictions. These include the requirement that one of the reference signals be
external and the other be derived from the internal oscillator, and the requirement that
both signals be passed through the same input signal channel. This last restriction
implies either that both signals are derived from the same detector (for example two
chopped light beams falling onto a single photodiode) or that they can be summed
prior to measurement, either externally or by using the differential input mode of the
instrument. Nevertheless, the mode will prove invaluable in many experiments.
3.2.03 Tandem Demodulation
A further development of the dual reference mode is Tandem Demodulation. In this
mode, the input to the second set of demodulators is taken not from the main ADC as
is the case with normal dual reference mode, but from the filtered X-channel output
of the first set of demodulators. Hence, for example, the mode can be used to measure
the modulation amplitude of an amplitude-modulated “carrier” frequency. The first
set of demodulators operates at the carrier frequency. If the output time constant of
this first stage is short enough, then the X output will represent a signal at the
modulation frequency. The second set of demodulators, this time operating at the
modulation frequency, then measure the amplitude and/or phase of this modulation.
3.2.04 Single Harmonic / Dual Harmonic
Normally, a lock-in amplifier measures the applied signal at the reference frequency.
However, in some applications such as Auger Spectroscopy and amplifier
characterization, it is useful to be able to make measurements at some multiple n, or
harmonic, of the reference frequency, f. The model 7230 allows this multiple to be set
to any value between 2 (i.e. the second harmonic) and 127, as well as unity, which is
the normal mode. The only restriction is that the product n × f cannot exceed the
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Chapter 3, TECHNICAL DESCRIPTION
upper frequency limit of the instrument, normally 120 kHz, but 250 kHz in
instruments fitted with the 7230/99 option.
Dual harmonic mode allows the simultaneous measurement of two different
harmonics of the input signal. As with dual reference mode, there are a few
restrictions, such as a maximum value of n × f of 250 kHz.
3.2.05 Internal / External Reference Mode
In the internal reference mode, the instrument's reference frequency is derived from
its internal oscillator and the oscillator signal is used to drive the experiment.
In the external reference mode, the experiment includes some device, for example an
optical chopper, which generates a reference frequency that is applied to the lock-in
amplifier's external reference input. The instrument's reference channel "locks" to this
signal and uses it to measure the applied input signal.
3.2.06 Virtual Reference Mode
If the instrument is operated in internal reference mode, measuring a signal which is
phase-locked to the internal oscillator, with the reference phase correctly adjusted,
then it will generate a stable non-zero X channel output and a zero Y channel output.
If, however, the signal is derived from a separate oscillator, then the X channel and
Y channel outputs will show variations at a frequency equal to the difference between
the signal and internal oscillator frequencies. If the latter is now set to be equal to the
former then in principle the variation in the outputs will cease, but in practice this
will not happen because of slow changes in the relative phase of the two oscillators.
In the virtual reference mode, unique to SIGNAL RECOVERY lock-in amplifiers,
the Y channel output is used to make continuous adjustments to the internal oscillator
frequency and phase to achieve phase-lock with the applied signal, such that the
X channel output is maximized and the Y channel output zeroed.
If the instrument is correctly adjusted, particularly ensuring that the full-scale
sensitivity control is maintained at a suitable setting in relation to changes in the
signal level, then the virtual reference mode is capable of making signal recovery
measurements which are not possible with most other lock-in amplifiers.
3.3 Principles of Operation
3.3.01 Block Diagram
The model 7230 is a very compact instrument that uses digital signal processing
(DSP) techniques implemented in field-programmable gate arrays (FPGA), a
microprocessor and very low-noise analog circuitry to achieve its specifications. A
block diagram of the unit is shown in figure 3-1, and the sections that follow describe
how each functional block operates and the effect it has on the instrument's
performance.
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Chapter 3, TECHNICAL DESCRIPTION
Figure 3-1, Model 7230 - Block Diagram
3.3.02 Signal Channel Inputs
The signal input amplifier can be set for either single-ended or differential voltage
mode operation, or single-ended current mode operation. In voltage mode a choice of
AC or DC coupling is available using an FET or bipolar input device. In current
mode a choice of two conversion gains is available to give optimum matching to the
applied signal. In both modes the input connector shells may be either floated via a
1 kΩ resistor or grounded to the instrument's chassis ground. These various features
are discussed in the following paragraphs.
Input Connector Selection, A / -B / A - B
When set to the A mode, the lock-in amplifier measures the voltage between the
center and the shell of the A input BNC connector, whereas when set to the A-B
mode it measures the difference in voltage between the center pins of the A and B (I)
input BNC connectors.
The latter, differential, mode is often used to eliminate ground loops, although it is
worth noting that at very low signal levels it may be possible to make a substantial
reduction in unwanted offsets by using this mode with a short-circuit terminator on
the B (I) connector, rather than by simply using the A input mode.
The specification defined as the Common Mode Rejection Ratio, C.M.R.R., describes
how well the instrument rejects common mode signals applied to the A and B (I)
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Chapter 3, TECHNICAL DESCRIPTION
inputs when operating in differential input mode. It is usually given in decibels.
Hence a specification of > 100 dB implies that a common mode signal (i.e. a signal
simultaneously applied to both A and B (I) inputs) of 1 V will give rise to less than
10 µV of signal out of the input amplifier.
The input can also be set to the –B mode, in which case the lock-in amplifier
measures the voltage between the center and the shell of the B (I) input connector.
This extra mode effectively allows the input to be multiplexed between two different
single-ended signals, subject to the limitation that the user must allow for the signal
inversion (equivalent to a 180° phase-shift) which it introduces when reading the
outputs.
Input Connector Shell, Ground / Float
The input connector shells may be connected either directly to the instrument's
chassis ground or floated via a 1 kΩ resistor. When in the float mode, the presence of
this resistor substantially reduces the problems that often occur in low-level lock-in
amplifier measurements due to ground loops.
Input Signal Selection, V / I
Although the voltage mode input is most commonly used, a current-to-voltage
converter may be switched into use to provide current mode input capability, in
which case the signal is connected to the B (I) connector. High impedance sources
(> 100 kΩ) are inherently current sources and need to be measured with a low
impedance current mode input. Even when dealing with a voltage source in series
with a high impedance, the use of the current mode input may provide advantages in
terms of improved bandwidth and immunity from the effects of cable capacitance.
The converter may be set to low-noise or wide bandwidth conversion settings, but it
is worth noting that if the best possible performance is required a separate current
preamplifier, such as the SIGNAL RECOVERY models 181 or 5182, should be
considered.
3.3.03 Line Frequency Rejection Filter
Following the signal input amplifier there is an option to pass the signal through a
line frequency rejection filter, which is designed to give greater than 40 dB of
attenuation at the power line frequencies of 50 Hz or 60 Hz and their second
harmonics at 100 Hz and 120 Hz.
The filter uses two cascaded rejection stages with "notch" characteristics, allowing it
to be set to reject signals at frequencies equal to either of, or both of, the fundamental
and second harmonic of the line frequency.
3.3.04 AC Gain and Dynamic Reserve
The signal channel contains a number of analog filters and amplifiers whose overall
gain is defined by the AC Gain parameter, which is specified in terms of decibels
(dB). For each value of AC Gain there is a corresponding value of the INPUT LIMIT
parameter, which is the maximum instantaneous (peak) voltage or current that can be
applied to the input without causing input overload, as shown in table 3-1 below.
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Chapter 3, TECHNICAL DESCRIPTION
AC Gain (dB) INPUT LIMIT (zero to peak)
0
2.5 V
6
1.2 V
12
625 mV
18
312 mV
24
156 mV
30
78 mV
36
39 mV
42
19 mV
48
10 mV
54
5.0 mV
60
2.5 mV
66
1.2 mV
72
625 µV
78
312 µV
84
156 µV
90
78 µV
Table 3-1, Input Limit vs. AC Gain
It is a basic property of the digital signal processing (DSP) lock-in amplifier that the
best demodulator performance is obtained by presenting as large a signal as possible
to the main analog-to-digital converter (ADC). Therefore, in principle, the AC Gain
value should be made as large as possible without causing the signal channel
amplifier or converter to overload. This constraint is not too critical however and the
use of a value one or two steps below the optimum value makes little difference. Note
that as the AC Gain value is changed, the demodulator gain (described later in section
3.3.14) is also adjusted in order to maintain the selected full-scale sensitivity.
The full-scale sensitivity is set by a combination of AC Gain and demodulator gain.
Since the demodulator gain is entirely digital, changes in full-scale sensitivity which
do not change the AC Gain do not cause any of the errors which might arise from a
change in the AC Gain.
The user is prevented from setting an illegal AC Gain value, i.e. one that would result
in overload on a full-scale input signal. Similarly, if the user selects a full-scale
sensitivity that causes the present AC Gain value to be illegal, the AC Gain will
change to the nearest legal value.
In practice, this system is very easy to operate. However, the user may prefer to make
use of the AUTOMATIC AC Gain feature that gives very good results in most cases.
When this is active the AC Gain is automatically controlled by the instrument, which
determines the optimum setting based on the full-scale sensitivity currently being
used.
At any given setting, the ratio
DR = 0.7 ×
Input Limit (pk)
Full-Scale Sensitivity (rms)
represents the factor by which the largest acceptable sinusoidal interference input
exceeds the full-scale sensitivity and is called the Dynamic Reserve of the lock-in
amplifier at that setting. (The factor 0.7 is a peak-to-rms conversion). The dynamic
reserve is often expressed in decibels, for which
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Chapter 3, TECHNICAL DESCRIPTION
DR(in dB) = 20 × log(DR(as a ratio))
Applying this formula to the model 7230 at the maximum value of INPUT LIMIT
(2.5 V) and the smallest available value of FULL-SCALE SENSITIVITY (10 nV),
gives a maximum available dynamic reserve of about 165 dB. Figures of this
magnitude are available from any DSP lock-in amplifier but are based only on
arithmetical identities and do not give any indication of how the instrument actually
performs. In fact, all current DSP lock-in amplifiers become too noisy and inaccurate
for most purposes at reserves of greater than about 100 dB.
3.3.05 Anti-Aliasing Filter
The signal then passes through an anti-aliasing filter to remove unwanted frequencies
which would cause a spurious output from the main ADC as a result of the sampling
process.
Consider the situation when the lock-in amplifier is measuring a sinusoidal signal of
frequency fsignal Hz, which is sampled by the main ADC at a sampling frequency
fsampling Hz. In order to ensure correct operation of the instrument the output values
representing the fsignal frequency must be uniquely generated by the signal to be
measured, and not by any other process.
However, if the input to the ADC has, in addition, an unwanted sinusoidal signal
with frequency f1 Hz, where f1 is greater than half the sampling frequency, then this
will appear in the output as a sampled-data sinusoid with frequency less than half the
sampling frequency, falias = |f1 - nfsampling|, where n is an integer. This alias signal is
indistinguishable from the output generated when a genuine signal at frequency falias
is sampled. Hence if the frequency of the unwanted signal were such that the alias
signal frequency produced from it was close to, or equal to, that of the wanted signal
then it is clear that a spurious output would result.
For example, at the sampling frequency of 1.0 MHz then half the sampling frequency
is 500 kHz. If a signal of 40 kHz accompanied by an interfering signal of 950 kHz
was then applied, the output of the ADC would include a sampled-data sinusoid of
40 kHz (the required signal) and, applying the above formula, an alias signal of
50 kHz (i.e. |950 kHz - 1000 kHz|). If the signal frequency were now increased
towards 50 kHz then the output of the lock-in amplifier would increasingly be
affected by the presence of the alias signal and the accuracy of the measurement
would deteriorate.
To overcome this problem the signal is fed through the anti-aliasing filter which
restricts the signal bandwidth to 400 kHz The filter is a conventional elliptic-type,
low-pass, stage, giving the lowest possible noise bandwidth.
It should be noted that the dynamic range of a lock-in amplifier is normally so high
that practical anti-alias filters are not capable of completely removing the effect of a
full-scale alias. For instance, even if the filter gives 100 dB attenuation, an alias at the
input limit and at the reference frequency will give a one percent output error when
the dynamic reserve is set to 60 dB, or a ten percent error when the dynamic reserve
is set to 80 dB.
In a typical low-level signal recovery situation, many unwanted inputs need to be
dealt with and it is normal practice to make small adjustments to the reference
frequency until a clear point on the frequency spectrum is reached. In this context an
unwanted alias is treated as just another interfering signal and its frequency is
avoided when setting the reference frequency.
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Chapter 3, TECHNICAL DESCRIPTION
A buffered version of the analog signal just prior to the main ADC is available at the
signal monitor (SIG MON) connector on the rear panel of the instrument; it may be
viewed on an oscilloscope to monitor the effect of the line frequency rejection and
anti-aliasing filters and signal-channel amplifiers.
3.3.06 Main Analog-to-Digital Converter
The analog signal is then routed to the main analog-to-digital converter, which runs
at a sampling rate of 1.0 MHz. The output from the converter feeds one of the two
demodulators, which uses DSP techniques to implement the digital multipliers and
output low-pass filters for each of the X and Y channels.
The ADC output also passes to the fast output curve buffer where it can be stored for
direct user use by downloading the data to a computer.
In dual reference and dual harmonic mode a second demodulator is active, and in
normal operation the input to this is also taken from the main ADC output.
Before discussing the demodulators and the output stages of the lock-in amplifier, the
reference channel, which provides the other input to the demodulators, will be
described.
3.3.07 Reference Channel Inputs
External reference signals are applied to the model 7230 via the front panel REF IN
connector. Internally this can be switched to function as a general-purpose input,
designed to accept virtually any periodic waveform with a 50:50 mark-space ratio
and of suitable amplitude, or specifically set to accept TTL-logic level signals.
Following the trigger buffering circuitry the selected reference signal is routed to the
reference channel.
3.3.08 Reference Channel
The reference channel circuitry is responsible for implementing a phase-locked loop
to lock onto the selected external reference signal (when in external reference mode),
or processing signals from the internal oscillator (when in internal reference mode).
The reference channel generates a series of phase values, output at a rate of one every
1 µs, which are used to drive the reference channel inputs of the two demodulators.
In dual reference mode, the first reference is derived from either the internal
oscillator or external reference input, with the second reference from the other source.
The reference circuit generates new phase values for each individual channel and
sends these to the demodulators.
In single harmonic mode, the reference circuit generates the phase values of a
waveform at the selected harmonic of the reference frequency. Dual harmonic mode
operates in a similar way to dual reference mode, but in this case the reference circuit
generates phase values for both of the selected harmonics of the reference frequency.
Dual harmonic mode may therefore be used with either internal or external
references.
External Reference Mode
In external reference mode the reference is taken from the front panel external
reference input.
Internal Reference Mode
With internal reference operation the reference circuit is free-running at the selected
reference frequency and is not dependent on a phase-locked loop (PLL), as is the case
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Chapter 3, TECHNICAL DESCRIPTION
in most other lock-in amplifiers. Consequently, the phase noise is extremely low, and
because no time is required for a PLL to acquire lock, reference acquisition is
immediate.
Both the signal channel and the reference channel contain calibration parameters that
are dependent on the reference frequency. These include corrections to the anti-alias
filter and to the analog circuits in the reference channel. In external reference
operation the processor uses a reference frequency meter to monitor the reference
frequency and updates these parameters when a change of about 2 percent has been
detected.
In all cases, it is possible to configure the rear panel TRIG OUT connector to output
a TTL logic signal at the present reference frequency.
3.3.09 Phase-Shifter
Each demodulator has a digital reference phase-shifter, allowing the phase values
being sent to the in-phase and quadrature multipliers to be adjusted to the required
value. If the reference input is a sinusoid applied to one of the two REF IN
connectors, the reference phase is defined as the phase of the X demodulation
function with respect to the reference input.
This means that when the reference phase is zero and the signal input to the
demodulator is a full-scale sinusoid in phase with the reference input sinusoid, the X
channel output of the demodulator is a full-scale positive value and the Y channel
output is zero.
The general-purpose setting of the external reference channel input detects positivegoing crossings of the mean value of the applied reference voltage. Therefore when
the reference input is not sinusoidal, its effective phase is the phase of a sinusoid with
a positive-going zero crossing at the same point in time, and accordingly the
reference phase is defined with respect to this waveform. Similarly, the effective
phase of a reference input when the channel is configured for TTL-logic level signals
is that of a sinusoid with a positive-going zero crossing at the same point in time.
In basic lock-in amplifier applications the purpose of the experiment is to measure
the amplitude of a signal which is of fixed frequency and whose phase with respect to
the reference input does not vary. This is the scalar measurement, often implemented
with a chopped optical beam. Many other lock-in amplifier applications are of the
signed scalar type, in which the purpose of the experiment is to measure the
amplitude and sign of a signal which is of fixed frequency and whose phase with
respect to the reference input does not vary apart from reversals of phase
corresponding to changes in the sign of the signal. A well-known example of this
situation is the case of a resistive bridge, one arm of which contains the sample to be
measured. Other examples occur in derivative spectroscopy, where a small
modulation is applied to the angle of the grating (in optical spectroscopy) or to the
applied magnetic field (in magnetic resonance spectroscopy). Double beam
spectroscopy is a further common example.
In this signed scalar measurement the phase-shifter must be set, after removal of any
zero errors, to maximize the X channel or the Y channel output of the demodulator.
This is the only method that will give correct operation as the output signal passes
through zero, and is also the best method to be used in an unsigned scalar
measurement where any significant amount of noise is present.
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Chapter 3, TECHNICAL DESCRIPTION
3.3.10 Internal Oscillator - General
The model 7230, in common with many other lock-in amplifiers, incorporates an
internal oscillator, which may be used to drive the experiment. However, unlike older
instruments, the oscillator in the model 7230 is digitally synthesized with the result
that the output frequency is extremely accurate and stable. The oscillator operates
over the same frequency range as the lock-in amplifier, that is 1 mHz to 120.0 or
250.0 kHz. The oscillator signal is available at the OSC OUT connector.
3.3.11 Internal Oscillator - Update Rate
The direct digital synthesis (DDS) technique generates a waveform at the DAC
output, which is not a pure sinusoid, but rather a stepped approximation to one. This
is then filtered by the buffer stage, which follows the DAC, to reduce the harmonic
distortion to an acceptable level. The update rate is 2.0 MHz.
3.3.12 Internal Oscillator - Frequency & Amplitude Sweeps
The internal oscillator output may be swept in both frequency and amplitude. In both
cases the sweeps take the form of a series of steps between starting and finishing
values. Frequency sweeps may use equal increment step sizes, giving a linear change
of frequency with time as the sweep proceeds, or may use step sizes proportional to
the present frequency, which produces a logarithmic sweep. The amplitude sweep
function offers only linear sweeps.
A special form of the frequency sweep function is used to acquire lock when the
instrument is operating in the virtual reference mode. When this "seek" sweep is
activated, the oscillator starts at a user-specified frequency, which should be just
below that of the applied signal, and increments until the calculated magnitude output
is greater than 50%. At this point the sweep then stops and the virtual reference mode
achieves lock, by continuously adjusting the internal oscillator frequency to maintain
the Y channel output at zero.
It is important to note that this type of phase-locked loop, unlike a conventional edgetriggered type using a clean reference, does not automatically re-acquire lock after it
has been lost. Lock can be lost as a result of a signal channel transient or a phase
reversal of the signal, in which case it may be necessary to repeat the lock acquisition
procedure. However, if the measurement system is set up with sufficient precautions,
particularly ensuring that the full-scale sensitivity is maintained at a suitable setting
in relation to the signal level, then the virtual reference mode is capable of making
signal recovery measurements which are not possible with other lock-in amplifiers.
When virtual reference mode is in use, the signal at the OSC OUT connector is a
sinusoid which is phase-locked to the signal. This cannot, of course, be used as a
source for the measurement.
3.3.13 Internal Oscillator - Voltage Control
The auxiliary ADC 1 input can be used to modulate the internal oscillator output
frequency or amplitude. Controls allow a quiescent amplitude and/or frequency to be
set, and a translation function (i.e. frequency and/or amplitude change per volt
change at the input) to be specified.
3.3.14 Demodulators - Dual Phase Multipliers
The function of each of the two demodulators is to multiply the digitized output of
the signal channel by digital representations of cosine and sine waves at the
demodulation frequency, to generate respectively the X and Y channel outputs. In
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Chapter 3, TECHNICAL DESCRIPTION
normal operation the demodulation frequency is at the internal or external reference
frequency, but when detecting at a harmonic of this then it is at some multiple, n (the
reference harmonic number) of it.
The demodulator outputs are digitally scaled to provide the demodulator gain control.
As discussed earlier in section 3.3.04 this gain is adjusted as the AC Gain is adjusted
to maintain the selected full-scale sensitivities.
In normal single reference mode the Demodulator 2 function is inactive, but it is
brought into operation when dual reference or dual harmonic modes are selected.
3.3.15 Demodulators - Output Filters
The outputs from the X channel and Y channel multipliers feed the X channel and Y
channel output low-pass filters, implemented as Finite Impulse Response (FIR)
stages with selectable 6 or 12 dB/octave slope (roll-off). Further filtering can be
carried out within the main output processor, to allow 18 and 24 dB/octave slopes.
In traditional audio terminology, a first-order low-pass filter is described as having a
slope of 6 dB per octave. This is because in the high frequency limit its gain is
inversely proportional to frequency (6 dB is approximately a factor of 2 in amplitude
and an octave is a factor of 2 in frequency). Similarly, a second-order low-pass filter
is described as having a slope of 12 dB per octave. These terms have become part of
the accepted terminology relating to lock-in amplifier output filters and are used in
the model 7230 to apply to the envelope of the frequency response function of the
digital finite impulse response (FIR) output filters. Accordingly the web control panel
control which selects the configuration of the output filters is labeled SLOPE and the
options are labeled 6, 12, 18, 24 dB/octave. Note that at the shorter time constant
settings the filter slope options are limited to 6 or 12 dB/octave.
The 6 dB/octave filters are not satisfactory for most purposes because they do not
give good rejection of non-random interfering signals, which can cause aliasing
problems as a result of the sampling process in the main ADC. However, the
6 dB/octave filter finds use where the lock-in amplifier is incorporated in a feedback
control loop, and in some situations where the form of the time-domain response is
critical. The user is recommended to use 12 dB/octave unless there is some definite
reason for not doing so.
The filters are of the finite impulse response type with the averaging time of each
section being equal to double the nominal time constant. This in turn defines the
settling time following a step change in input signal as being 2 × TC × n, where TC is
the time constant and n = 1 for 6 dB, 2 for 12 dB, 3 for 18 dB and 4 for 24 dB slope
settings. Hence, for example, the settling time after a step change at the input when
the TC is 100 ms and the slope is 12 dB/octave will be 400 ms.
When the reference frequency is below 10 Hz the synchronous filter option is
available. When selected, the actual time constant of the filters is not generally the
selected value TC, but the closest smaller value equal to an integer number of
reference cycles. If TC is greater than 1 reference cycle, then the time constant is
between TC/2 and TC. Where random noise is relatively small, synchronous filter
operation gives a major advantage in low-frequency measurements by enabling the
system to give a constant output even when the output time constant is equal to only
1 reference cycle.
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Chapter 3, TECHNICAL DESCRIPTION
3.3.16 Fast Curve Buffer
The fast curve buffer is a new feature common to the models 7124, 7270, and 7230
lock-in amplifiers. It allows up to 100,000 sets of eight signals to be recorded at rates
of up to 1 MSa/s (1 µs per point), and supports a variety of trigger modes. The buffer
can also be used in a circular fashion, with new data overwriting the oldest data, to
allow capture of events up to the time of an applied trigger.
Although eight signals can be recorded, these include the X2 and Y2 outputs that are
only generated in the dual reference and dual harmonic modes, and the input to the
second demodulator. Hence unless one of these modes is selected, only five signals
are stored.
The signals that are stored are therefore as follows:
Single Reference/Virtual Reference Mode
SIG ADC
This is the raw digitized data out of the main ADC
X(1)
The X channel output from the first demodulator
Y(1)
The Y channel output from the first demodulator
ADC 1
The digitized representation of the input to the auxiliary ADC1
ADC 2
The digitized representation of the input to the auxiliary ADC2
Dual Reference/Dual Harmonic Mode
DEMOD 2
The digital signal input to the second demodulator
X2
The X channel output from the second demodulator
Y2
The Y channel output from the second demodulator
Data that has been stored to the buffer can be downloaded to a computer.
3.3.17 Main Output Processor - General
The same eight signals that pass to the fast curve buffer also pass to the main output
processor. This carries out further output filtering if required, generates derived
outputs, such as signal magnitude and phase, drives four DACs that in turn generate
analog representations of the instrument outputs, and implements the standard curve
buffer. These features are described in more detail in the following sections.
3.3.18 Main Output Processor - Output Offset and Expand
Following the output filter, an output offset facility enables ±300% full-scale offset to
be applied to any or all of the X(1), Y(1), X2, Y2 output signals. The output expand
facility allows a ×10 expansion, performed by simple internal digital multiplication,
to be applied to the same output signals.
3.3.19 Main Output Processor - Vector Magnitude and Phase
The processor also implements the magnitude and signal phase calculation, which is
useful in many situations. If the input signal Vs(t) is a reference frequency sinusoid of
constant amplitude, and the output filters are set to a sufficiently long time constant,
2
2
the X and Y channel demodulator outputs are constant levels. The function √(X + Y )
is dependent only on the amplitude of the required signal Vs(t) (i.e. it is not dependent
on the phase of Vs(t) with respect to the reference input) and is computed by the
output processor, and made available as the magnitude output. The phase angle
between Vs(t) and the X demodulation function is called the signal phase: this is equal
to the angle of the complex quantity (X + jY) (where j is the square root of -1) and is
also computed by the processor.
The magnitude and signal phase outputs are used in cases where phase is to be
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Chapter 3, TECHNICAL DESCRIPTION
measured, or alternatively where the magnitude is to be measured under conditions of
uncertain or varying phase.
One case of varying phase is that in which the reference input is not derived from the
same source as that which generates the signal, and is therefore not at exactly the
same frequency. In this case, if the input signal is a sinusoid of constant amplitude,
the X channel and Y channel demodulator outputs show slow sinusoidal variations at
the difference frequency, and the magnitude output remains steady.
However, the magnitude output has disadvantages where significant noise is present
at the outputs of the demodulator. When the required signal outputs (i.e. the mean
values of the demodulator outputs) are less than the noise, the outputs take both
positive and negative values but the magnitude algorithm gives only positive values.
This effect, sometimes called noise rectification, gives rise to a zero error which in
the case of a Gaussian process has a mean value equal to 0.798 times the combined
root-mean-square (rms) value of the X and Y demodulator noise. Note that unlike
other forms of zero error this is not a constant quantity which can be subtracted from
all readings, because when the square root of the sum of the squares of the required
outputs becomes greater than the total rms noise the error due to this mechanism
disappears.
A second type of signal-dependent error in the mean of the magnitude output occurs
as a result of the inherent non-linearity of the magnitude formula. This error is always
positive and its value, expressed as a fraction of the signal level, is half the ratio of
the mean-square value of the noise to the square of the signal.
Hence when the magnitude output is being used, the output filter time constants
should be set to give the required signal-to-noise ratio at the X channel and Y channel
demodulator outputs, rather than attempting to improve the signal-to-noise ratio by
averaging the magnitude output.
For analogous reasons, the magnitude function also shows signal-dependent errors
when zero offsets are present in the demodulator. For this reason, it is essential to
reduce zero offsets to an insignificant level (usually by the use of the Auto-Offset
function) when the magnitude output is to be used.
Note that the majority of signal recovery applications are scalar measurements, where
the phase between the required signal and the reference voltage is constant apart from
possible phase reversals corresponding to changes in the sign of the quantity being
measured. In this situation the lock-in amplifier is used in the normal X-Y mode, with
the phase-shifter adjusted to maximize the X output and to bring the mean Y output
to zero. (Refer to section 3.3.26 for further information on the correct use of the
Auto-Phase function for this purpose.)
3.3.20 Main Output Processor - Noise Measurements
The noise measurement facility uses the output processor to perform a noise
computation on the X output of the demodulator. A noise buffer continuously
calculates the mean level of X, representing the measured output signal, by summing
the last n samples of the X output and dividing by n. The processor then calculates
the modulus of the difference between each X-output value and the mean value and
uses this figure to derive the noise. The displayed noise value is correct for input
noise where the amplitude distribution of the waveform is Gaussian, which is
normally the case. The indicated value (in V/√Hz or A/√Hz) is the square root of the
mean spectral density over the equivalent noise bandwidth defined by the setting of
the output filter time constant and slope.
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Chapter 3, TECHNICAL DESCRIPTION
When used for noise measurements, the available range of output time constants is
restricted to 500 µs to 10 ms inclusive, , and the slope to 6 or 12 dB/octave. The
corresponding actual bandwidth for the present time constant and slope settings can
be found from the table 3-2 below, or by using the ENBW. command. In addition, the
synchronous time constant control is turned off, and the fast analog outputs mode is
turned on.
Time
Constant
500 µs
1 ms
2 ms
5 ms
10 ms
Equivalent Noise Bandwidth at Output Filter Slope (Hz)
6 dB/octave
12 dB/octave
500.00
333.33
250.00
166.67
125.00
83.33
50.00
33.33
25.00
16.67
Table 3-2, ENBW vs. Time Constant and Slope
The noise buffer length n can be set to 1, 1000, 2000, 3000 or 4000. Since new input
values to the buffer are supplied at a 1 kHz rate, these correspond to averaging times
of zero, 1 second, 2 seconds, 3 seconds and 4 seconds respectively. Hence the control
on the Main Controls web panel that adjusts this buffer length is labeled Noise Buffer
Length and can be set to Off, 1 s, 2 s, 3 s or 4 s. Setting a shorter time means that the
system responds more quickly to changes in the mean X-output level, but the noise
reading itself exhibits more fluctuation. Conversely, the fluctuation can be reduced
by setting a longer time, but at the expense of increased settling time following
changes in the mean X-output level.
If a noise output (N calibrated in volts or amps per root hertz, or as a percentage of
full scale) is read via the computer interfaces while the time constant or slope are
outside the permitted range, or if the synchronous time constant control is enabled,
then the response will be -1. Since noise readings can only be zero or positive, this
negative number clearly indicates that the reading is invalid and should be ignored.
In order to make noise measurements easier, the instrument includes a noise
measurement mode, activated by a control on Main Controls web panel or by a
computer command. When this is turned on, the outputs are set to the four types most
commonly required, and the filter time constant, slope and synchronous time constant
setting are forced to values within the permitted ranges. When turned off, these
restrictions are removed.
When making noise measurements the user is strongly advised to use an oscilloscope
to monitor the signal at the SIG MON output on the rear panel as this is the best way
of ensuring that a random process is being measured rather than line pick-up or other
non-random signals.
3.3.21 Main Output Processor - Standard Curve Buffer
The output processor also operates the standard curve buffer, which is a 100,000
point memory which can be used for storage of selected instrument outputs as curves,
prior to their transfer to a computer via the computer interfaces. In addition to using
this function for the instrument outputs, such as the X channel and Y channel output
signals, it may also be used to store derived outputs and reference frequency
information.
Unlike the fast curve buffer, the available points are split between the number of
outputs to be stored, so that if for example X1 and Y1 outputs were selected, the
maximum recording length would be 50,000 points. Storage operates at rates of up to
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Chapter 3, TECHNICAL DESCRIPTION
1 kSa/s (1 ms per point).
3.3.22 Analog Outputs (DACs)
Earlier SIGNAL RECOVERY DSP lock-in amplifiers provided two different types
of analog outputs. Typically there were two outputs driven by DACs that in turn were
connected to the main instrument outputs, and separate auxiliary outputs, essentially
simply programmable DC voltages typically used as control signals for the
experiment. However this architecture created a number of restrictions. In particular,
in the dual modes it was not possible to get both X and Y outputs for both
demodulators when using short time constants, and in some cases it was necessary to
take the analog output from different connectors for different time constant ranges.
This design has been updated and so the 7230 is fitted with four general-purpose
DAC outputs, which can be driven from a variety of output signals, as well as the
traditional programmable “auxiliary DAC” signal, now referred to as the “User
DACs”.
Selection of the required outputs for the DACs is made on the Rear Panel web control
panel. For each DAC output there is a selection control, which is used to choose
which instrument output will be sent to the relevant DAC, or to specify that it will be
a User DAC. If the latter is selected then a further control allows the DAC voltage to
be set.
Each DAC output is driven by a 16 bit converter operating at a raw update rate of
1 MSa/s, although depending on the output it is generating the actual update rate is
either 1 MSa/s or 1 kSa/s. When used for instrument outputs, full scale corresponds
to ±2.5 V, but the output remains linear to up to ±7.5 V; when used as a User DAC,
the range is ±10.000 V.
3.3.23 Auxiliary Analog Inputs (ADCs)
The model 7230 incorporates four auxiliary ADC inputs offering a resolution of
1 mV in ±10.000 V. These converters may be used at slow sample rates for digitizing
slowly changing or DC signals which are associated with an experiment, such as
those generated by temperature and pressure transducers, so that they can be
incorporated into ratio calculations or transferred to a controlling computer. They
may also be used in conjunction with the instrument's fast curve buffer to form a
transient recorder operating at sample rates of up to 200 kHz (one channel) or 40 kHz
(two channels).
3.3.24 Main Microprocessor - General
All functions of the instrument are under the control of a microprocessor, which in
addition supports the computer interfaces. It also controls the instrument's 8-bit
digital (TTL) programmable input/output port, which may be used for controlling
auxiliary apparatus or reading the status of external logic lines.
A particularly useful feature of the design is that only part of the controlling firmware
program code, which the microprocessor runs, is permanently resident in the
instrument. The remainder is held in a flash EEPROM and can be updated via the
USB or RS232 computer interface, using an Update Pack that can be downloaded
from the www.signalrecovery.com website.
3.3.25 Main Microprocessor - Auto Functions
The microprocessor also controls the instrument's auto functions. These allow easier,
faster operation in most applications, although direct manual operation or special
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Chapter 3, TECHNICAL DESCRIPTION
purpose control programs may give better results in certain circumstances. During
operation of several of the auto functions, decisions are made on the basis of output
readings taken at a particular moment. Where this is the case, it is important for the
output time constant set by the user to be long enough to reduce the output noise to a
sufficiently low level so that valid decisions can be made and that sufficient time is
allowed for the output to settle.
The following sections contain brief descriptions of the auto functions.
Auto-Sensitivity
This function only operates when the reference frequency is above 1 Hz. A single
Auto-Sensitivity operation consists of decreasing the full-scale sensitivity range if the
magnitude output is greater than 90% of full-scale, or increasing the full-scale
sensitivity range if the magnitude output is less than 30% of full-scale. After the
Auto-Sensitivity function is called, Auto-Sensitivity operations continue to be made
until the required criterion is met.
In the presence of noise, or a time-varying input signal, it may be a long time before
the Auto-Sensitivity sequence comes to an end, and the resulting setting may not be
what is really required.
Auto-Phase
In an Auto-Phase operation the value of the signal phase is computed and an
appropriate phase-shift is then introduced into the reference channel so as to bring the
value of the signal phase to zero. The intended result is to null the output of the Y
channel while maximizing the output of the X channel.
Any small residual phase can normally be removed by calling Auto-Phase for a
second time, after a suitable delay to allow the outputs to settle.
The Auto-Phase facility is normally used with a clean signal that is known to be of
stable phase. It usually gives very good results provided that the X channel and Y
channel outputs are steady when the procedure is called.
If a zero error is present on the outputs, such as may be caused by unwanted coupling
between the reference and signal channel inputs, then the following procedure should
be adopted:1) Remove the source of input signal, without disturbing any of the connections to
the signal input which might be picking up interfering signals from the reference
channel. In an optical experiment, for example, this could be done by shielding
the detector from the source of chopped light.
2) Execute an Auto-Offset operation, which will reduce the X channel and Y
channel outputs to zero.
3) Re-establish the source of input signal. The X channel and Y channel outputs will
now indicate the true level of input signal, at the present reference phase setting.
4) Execute an Auto-Phase operation. This will set the reference phase-shifter to the
phase angle of the input signal. However, because the offset levels which were
applied in step 2 were calculated at the original reference phase setting, they will
not now be correct and the instrument will in general display a non-zero Y
channel output value.
5) Remove the source of input signal again.
6) Execute a second Auto-Offset operation, which will reduce the X channel and Y
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Chapter 3, TECHNICAL DESCRIPTION
channel outputs to zero at the new reference phase setting.
7) Re-establish the source of input signal.
This technique, although apparently complex, is the only way of removing the effect
of crosstalk, which is not generally in the same phase as the required signal.
Auto-Offset
In an Auto-Offset operation the X offset and Y offset functions are turned on and are
automatically set to the values required to give zero values at both the X and the Y
outputs. Any small residual values can normally be removed by calling Auto-Offset
for a second time after a suitable delay to allow the outputs to settle.
The primary use of the Auto-Offset is to cancel out zero errors which are usually
caused by unwanted coupling or crosstalk between the signal channel and the
reference channel, either in the external connections or possibly under some
conditions in the instrument itself. Note that if a zero error is present, the Auto-Offset
function should be executed before any execution of Auto-Phase.
3.4 General
3.4.01 Accuracy
When the demodulator is operating under correct conditions, the absolute gain
accuracy of the instrument is limited by the analog components in the signal channel,
and the absolute phase accuracy is limited by the analog components in both the
signal channel and the reference channel. The resulting typical accuracy is ±1.0
percent of the full-scale sensitivity and ±0.5 degree respectively.
3.4.02 Power-up Defaults
When the rear panel CONFIG Switch 1 is set to 1, all instrument settings are
retained when the unit is switched off. When the instrument is switched on again the
settings are restored but with the following exceptions:a) The curve buffer is cleared.
b) Any sweep that was in progress at switch-off is terminated.
3-16
Front and Rear Panels
Chapter 4
4.1 Front Panel
Figure 4-1, Model 7230 Front Panel Layout
As shown in figure 4-1, the model 7230's front panel has four BNC connectors and
an LED Status indicator. The following sections describe the function and location of
these items.
4.1.01 A and B (I) Signal Input Connectors
The A connector is the signal input connector for use in single-ended and differential
voltage mode. The B (I) connector is the signal input connector for use in differential
voltage mode (A-B) and for inverting single-ended voltage mode (-B mode). It is also
the signal input connector when the current input mode is selected.
4.1.02 REF IN Connector
This is the general-purpose input connector for an external reference signal. It will
accept either analog waveforms (e.g. sinusoidal or pulse), or TTL logic signals,
depending on the setting of the reference input control.
NOTE: If the best possible phase accuracy at low external reference frequencies is
required, then a TTL reference signal should be used.
4.1.03 OSC OUT Connector
This is the output connector for the internal oscillator.
4.1.04 STATUS Indicator
Thus bicolor LED indicates various operating conditions within the instrument, as
follows:
Instrument Turned Off
The Status indicator is unlit
Instrument Turned On and Operating Normally
The Status indicator is permanently green
Instrument Turned On and Displaying Ethernet IP Address
When the model 7230 is turned on and has determined a valid IP address, either from
a DHCP server, or the Auto IP address function, or is using a static address, then the
Status indicator flashes as it “counts out” the actual IP address. If these flashes are
counted then it is possible to determine the address, as follows.
An IP address consists of four numbers, each known as an octet and each of which
can range from 0 t0 255. The model 7230 displays these numbers by using red and
green flashes of the Status indicator, as follows. A long red flash indicates the start
and end of the address, short red flashes are digit separators, and the number of green
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Chapter 4, FRONT AND REAR PANELS
flashes equals the digit value, except that 10 green flashes equates to a value of 0
Step No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Status Color
Long Red
Green Flashes
Short Red
Green Flashes
Short Red
Green Flashes
Short Red
Green Flashes
Short Red
Green Flashes
Short Red
Green Flashes
Short Red
Green Flashes
Short Red
Green Flashes
Short Red
Green Flashes
Short Red
Green Flashes
Short Red
Green Flashes
Short Red
Green Flashes
Long Red
Description
Start of 1st octet
Octet 1, digit 1
End of 1st digit, start of 2nd
Octet 1, digit 2
End of 2nd digit, start of 3rd
Octet 1, digit 3
End of 1st octet, start of 2nd
Octet 2, digit 1
End of 1st digit, start of 2nd
Octet 2, digit 2
End of 2nd digit, start of 3rd
Octet 2, digit 3
End of 2nd octet, start of 3rd
Octet 3, digit 1
End of 1st digit, start of 2nd
Octet 3, digit 2
End of 2nd digit, start of 3rd
Octet 3, digit 3
End of 3rd octet, start of 4th
Octet 4, digit 1
End of 1st digit, start of 2nd
Octet 4, digit 2
End of 2nd digit, start of 3rd
Octet 4, digit 3
End of 4th octet and address
If one loses track of the number of flashes, or miscounts them, then the display
process can be restarted by changing the setting of the rear panel Config 3 switch, as
described in section 4.2.07 It can also be restarted by cycling the instrument’s power,
but if using an auto IP allocated address, or if the DHCP server takes time to allocate
an address, then it cannot begin until the new IP address has been determined, so it
will take longer.
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Chapter 4, FRONT AND REAR PANELS
4.2 Rear Panel
Figure 4-5, Model 7230 Rear Panel Layout
As shown in figure 4-5, the power input socket, power switch, digital I/O port,
RS232, USB, LAN connectors, and eleven BNC signal connectors are mounted on
the rear panel of the instrument. Brief descriptions of these are given in the following
text.
4.2.01 Power Input Connector
The model 7230 requires regulated DC power supply voltages of ±15 V and +5 V to
operate, which are provided via the SIGNAL RECOVERY Model PS0110 power
supply module that plugs into this 5-pin DIN power input connector.
CAUTION: The Model 7230 must only be powered from the Model PS0110 power
supply module provided with it. Use of other power supplies, except with the prior
written permission of SIGNAL RECOVERY, will invalidate the warranty.
4.2.02 Power Switch
Press the end of the switch marked I to turn on the instrument's power, and the other
end marked O to turn it off.
4.2.03 DIGITAL I/O Connector
This connector provides eight TTL lines, each of which can be configured as an input
or output. When set as an output, the line can be set high or low, and when set as an
input, the applied logic state can be read.
The port is most commonly used for controlling auxiliary apparatus, such as lamps,
shutters and heaters, and reading status signals from auxiliary equipment. Pinouts for
this connector are given in appendix B.
4.2.04 RS232 Connector
This 9-pin D type RS232 interface connector implements pins 1, 2, 3 and 7 (Earth
Ground, Transmit Data, Receive Data, Logic Ground) of a standard DTE interface.
To make a connection to a PC-compatible computer, it is normally sufficient to use a
three-wire cable connecting Transmit Data to Receive Data, Receive Data to
Transmit Data, and Logic Ground to Logic Ground. Appendix C shows the
connection diagrams of cables suitable for computers with 9-pin and 25-pin serial
connectors. Pinouts for this connector are given in appendix B.
4.2.05 LAN Connector
This connector allows the instrument to be connected to a 100-BaseT or 10-BaseT
network for control from a computer connected to the same network using either the
built-in web based control panels or separate software packages, such as a LabVIEW
driver, SIGNAL RECOVERY Acquire, or SRInstComms. The IP address can be set
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Chapter 4, FRONT AND REAR PANELS
to a static value, or to use an automatic IP address assignment, or to accept an address
allocated by a DHCP server on the network. The position of CONFIG Switch 2 (see
section 4.2.07) controls this behavior.
4.2.06 USB Connector
This connector allows the instrument to be connected to a PC-style computer running
a Windows operating system via the USB bus. The instrument supports connection at
both Full Speed and Hi-Speed (USB 2.0) protocols.
4.2.07 CONFIG Switches
These three switches are used to set the instrument’s configuration, as follows:
Switch 1: Retain Settings
This switch determines whether the instrument will retain its settings during powerdown, according to the following table:
Position
0
1
Description
Unit powers on with all settings set to factory default values (see
Appendix D)
Unit powers on with the same settings as when it was powered off
Hence to perform a reset to the factory default settings, turn off the power switch, set
switch 1 to position 0, and turn the power switch back on. Switch 1 can then be set
back to 1 if desired.
Switch 2: IP Address Control
This switch selects the mode of operation of the Ethernet interface, according to the
following table:
Position
Description
0
The model 7230 uses a static IP address, as set by the command
IPADDR. This command can be sent via any one of the three interfaces,
but if used via the Ethernet interface and specifying a different address to
that currently in use, then communications will be lost.
1
Unit uses a DHCP or AutoIP allocated address. It initially tries to get an
IP address via a DHCP server but if one is not assigned then it will auto
assign an IP address and test that it does not conflict with anything else
on the network. The AutoIP address will be in the range
169.254.XXX.XXX
Switch 3: IP Address Display
When this is switch is changed from 0 to 1 or from 1 to 0 then the current IP address
(static, DHCP, or Auto IP allocated) will be shown by means of flashing the front
panel STATUS light red and green.
4.2.08 SIG MON Connector
The signal at this connector is that immediately prior to conversion by the main
ADC.
4.2.09 TRIG IN Connector
This connector accepts a TTL-compatible input and can be used for triggering the
digitization of the voltages present at the auxiliary analog-to-digital converters
(ADCs), and for triggering acquisition into the data buffer. The input operates on the
positive edge only.
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Chapter 4, FRONT AND REAR PANELS
4.2.10 TRIG OUT Connector
This connector can be set to generate a TTL-compatible output pulse, for example to
indicate when date is being sampled when using the internal curve buffer. It can also
be switched to perform an alternative function as a Reference Monitor, in which it
outputs a TTL signal at the same frequency as the main reference channel.
4.2.11 ADC 1, ADC 2, ADC 3, and ADC 4 Connectors
The input voltages at these connectors are sampled and held when the ADC is
triggered, and are then digitized. Several different trigger modes are available. The
input voltage range is ±10.000 V and the resolution is 1 mV.
4.2.12 DAC 1, DAC 2, DAC 3, and DAC 4 Connectors
There are four digital-to-analog converter (DAC) output connectors. The output
voltages at these connectors can be configured to represent instrument outputs (e.g. X
and Y channel outputs) or be used as general purpose programmable voltages. When
used as instrument outputs the full-scale output range is ±2.500 V, with the ability to
operate linearly at up to three times this range. When used as general-purpose
outputs, the output range is ±10.000 V
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Chapter 4, FRONT AND REAR PANELS
4-6
Web Control Panel Operation
Chapter 5
5.1 Introduction
This chapter describes how to operate the model 7230 using the built in web control
panels via the Ethernet interface, and discusses its capabilities when used in this way.
Chapter 6 provides similar information for when the unit is operated remotely by
commands sent via the Ethernet, USB, or serial interfaces.
In order to use the built in web control panels, the instrument must be connected to an
Ethernet network, it must be possible to access this same network from the computer
that will be used to operate it, and the instrument’s IP address must be known. The
following sections describe four different configurations that allow this; use
whichever is appropriate to your requirements.
5.2 Ethernet Connection Methods
5.2.01 Direct Wired Connection to a Single Computer
This is the method described in section 2.2.02 in which the model 7230 is operated
using its default static IP address of 169.254.150.230 It has the advantage of
simplicity but the disadvantage that the controlling computer does not have access to
other network resources or the internet.
With this configuration, it is possible to add internet access to the computer by
adding a second Ethernet interface, either internal or via a USB-Ethernet adaptor, and
connecting this second port to an Ethernet network that has internet access. However
the model 7230 will still only be able to be controlled from the original computer.
5.2.02 Wireless Connection to an iPad, Laptop, or Netbook
Computer
To operate the instrument from a wireless device, such as an iPad, you will need a
wireless router that includes a DHCP server. These are widely available from
electronics stores and there are many different suppliers. The following procedure
uses a Sitecom Model 54g, but the same principles can be applied to using routers
from other manufacturers. Proceed as follows:
1) Unpack the wireless router and follow the instructions supplied with it to connect
it to the local line power.
2) Turn the router on. After a short delay its wireless network will be activated,
which will normally be unsecured.
3) Using the wireless device that you want to use to control the model 7230, such as
an iPad, laptop, or smartphone, find the wireless network that you have just
created. For the Sitecom Model 54g. the default wireless network name is
Sitecom825AC6, as shown in figure 5-1 below
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Chapter 5, WEB CONTROL PANEL OPERATION
Figure 5-1, Connecting to a Wireless Network
4) Connect to this network. In the example shown in figure 5-1, click the Connect
button.
5) You now need to access the router’s web control panel, for which you will need
to know its IP address, which is typically at the beginning of one of the private IP
address ranges, such as 192.168.0.1 or 10.0.0.1. Consult the documentation that
came with the router to find out more; for the Sitecom Model 54g the default
address is 192.168.0.1
6) Open a browser session and type the router’s IP address into the address bar. You
may then be prompted for a username and password as in figure 5-2, which in the
case of the Sitecom Model 54g are simply both “admin” by default.
Figure 5-2, Router Home Page Login Screen
7) Enter the user name and password to access the configuration page; the panel for
the Sitecom 54g is shown in figure 5-3 below.
5-2
Chapter 5, WEB CONTROL PANEL OPERATION
Figure 5-3, Router Home Page
8) Locate the DHCP information/controls page; for the Sitecom 54g this is done by
clicking the DHCP tab. The page is shown in figure 5-4.
Figure 5-4, Router DHCP Status Page
9) Allow a few minutes for the router to be updated. After this, the DHCP server
page should show a single IP address – this will be address of the computer from
which you are accessing the router. In the above example the controlling
computer’s IP address is 192.168.0.100, and the router’s address (not shown, but
what you used to access the control pages) is 192.168.0.1
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Chapter 5, WEB CONTROL PANEL OPERATION
10) Take the RJ45 patch cord and plug one end into the router and other into the
LAN connector of the rear panel of the model 7230.
11) Set the Config 2 switch on the rear panel of the model 7230 to position 1. This
will cause the instrument to be allocated an IP address by the DHCP server in the
router.
12) With the rear-panel mounted power switch set to 0 (off), plug the line cord into
the model PS0110 power supply unit and the 5-pin DIN plug on the power cable
from the PS0110 to the 7230’s rear panel POWER INPUT connector.
13) Turn on the model 7230. The front panel status light should initially be green,
but will then flash red and green as it “counts out” the IP address it has been
allocated by the router. It is not necessary to wait until this finishes before
continuing.
14) Refresh the router’s control DHCP control panel. The newly connected model
7230 will now appear as a second entry in the table:
Figure 5-5, Router DHCP Status Page with Model 7230 Active
In the above example the controlling computer’s IP address is 192.168.0.100 and
the model 7230 has been allocated an IP address of 192.168.0.101
15) Open a new browser session and type the IP address for the model 7230
determined in section 14, which in this example is 192.168.0.101, into the
address bar and press <return>. The 7230's Main Controls panel should be
displayed, as shown below in figure 5-6.
5-4
Chapter 5, WEB CONTROL PANEL OPERATION
Figure 5-6, Model 7230 Main Controls Panel
15) Save the address as a favorite, bookmark, or shortcut so that you can quickly
reach the model 7230 again.
With this configuration you should always be able to access the 7230 again in future
if you are connected to the same wireless network, simply by selecting the favorite,
bookmark, or shortcut. This is because the DHCP server in the wireless router will
generally allocate the same IP address to the model 7230 each time they are both
powered up and connected.
As with the wired connection described in section 5.2.01, the iPad or other wireless
device will have no general internet access while it is connected to the wireless router
to which the 7230 is wired, but can of course switch to another wireless network to
reach the internet, although obviously at that point losing connection to the model
7230.
5.2.03 Wired Connection to a Company or Corporate Network
Using a Static IP Address
Consult your network administrator to see if they can allocate a static IP address on
the network for the model 7230. If this is possible, then use the following procedure
to program this address into the model 7230 – this must be done before connecting
the instrument to the network.
The procedure requires the use of a computer with an Ethernet 10 or 100 Base T
adaptor with RJ45 connector set to support TCP/IP protocol with an installed web
browser. As an example, a Windows 7 PC with Internet Explorer 8 is suitable, but so
are many other computer systems.
1) Close all open programs on the computer and unplug any existing network
connection.
2) Plug one end of the supplied RJ45 patch cord to the computer and the other end
into the LAN connector on the rear panel of the model 7230.
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Chapter 5, WEB CONTROL PANEL OPERATION
3) With the rear-panel mounted power switch set to 0 (off), plug the line cord into
the model PS0110 power supply unit and the 5-pin DIN plug on the power cable
from the PS0110 to the 7230’s rear panel POWER INPUT connector.
4) Set the rear panel Config 2 switch to position 0
5) Turn on the model 7230. The front panel status light should be green.
6) Open a browser session on the computer. Since there is no connection to the
internet you will not see the normal opening page, but an error message. If using
Internet Explorer the message will be as shown in figure 5-7
Figure 5-7, Initial Browser Window
8) Type 169.254.150.230 into the address bar and press <return>. The 7230's Main
Controls panel should be displayed, as shown below in figure 5-8.
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Chapter 5, WEB CONTROL PANEL OPERATION
Figure 5-8, Model 7230 Main Controls Panel
9) Click the Equations tab, to show the Equations panel, as shown below in figure
5-9
Figure 5-9, Model 7230 Equations Panel
10) In the Command input box type
IPADDR XXX XXX XXX XXX
where XXX XXX XXX XXX is the static IP address given to you by your
network administrator. Note that there are no periods (full stops) between the
digit groups. So if, for example, you were given an IP address of 10.150.11.2,
5-7
Chapter 5, WEB CONTROL PANEL OPERATION
type IPADDR 10 150 11 2 as shown in figure 5-10, and press <return>.
Figure 5-10, Entering New IP Address
11) Once this is done, communications will immediately be lost and an error
message, similar to that shown in figure 5-11, will be shown:
Figure 5-11, Communication Error Message
12) Now unplug the network connection linking the model 7230 and the computer.
Connect the 7230’s LAN connector to the company or corporate network.
Similarly, connect the computer back to the corporate network.
13) Open a browser session and use the saved a shortcut, bookmark, or favorite to
verify that you can access the model 7230.
With this configuration you should always be able to access the 7230 again in future
simply by selecting the favorite, bookmark, or shortcut. In addition, of course, you
will also have access to the internet, and the model 7230 can be controlled from any
computer on the same network. If the network has wireless access points then it will
also be possible to control the model 7230 from wireless devices.
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Chapter 5, WEB CONTROL PANEL OPERATION
5.2.04 Wired Connection to a Company or Corporate Network
Using a DHCP Allocated IP Address
Connecting the model 7230 to a company or corporate network using that network’s
DHCP server involves no effort from the corporate or company IT department in
allocating a fixed IP address, but consequently can require a little more effort by the
end user.
1) Connect the LAN connector on the rear panel of the model 7230 to an active
network connection on the company or corporate network
2) Set the rear panel Config 2 switch to position 1. This will cause the model 7230
to be allocated an IP address by the DHCP server in company network.
3) With the rear-panel mounted power switch set to 0 (off), plug the line cord into
the model PS0110 power supply unit and the 5-pin DIN plug on the power cable
from the PS0110 to the 7230’s rear panel POWER INPUT connector.
4) Turn on the model 7230. The front panel status light should initially be green,
but will then flash red and green as it “counts out” the IP address it has been
allocated by the network DHCP server.
5) Most company and corporate networks use a domain controller, but the model
7230 cannot log onto a domain and so you will not in general be able to “see” it
by browsing network resources. However, once the allocated IP address is known
you will be able to access the instrument by typing this into a browser’s address
bar.
There are several possible ways of identifying the IP address
Using SRInstFinder
This is a simple utility for a PC which searches for any model 7230's on the
network. It can be downloaded from the www.signalrecovery.com website.
When run, it displays the dialog shown in figure 5-12 below
Figure 5-12, SRInstFinder Utility
Click the Find Instruments button. If any model 7230’s are found on the network,
the Instrument field will be updated, as shown in Figure 5-13.
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Chapter 5, WEB CONTROL PANEL OPERATION
Figure 5-13, SRInstFinder Utility, Model 723 S/N 10257684
found at IP Address 169.254.90.12
If there are several instruments then the up/down buttons allow you to scroll
through them until the required unit is found. The Instrument field displays the
stored instrument name (see command NAME in section 6.7.12) that can be used
in addition to the serial number to aid identification. In the case of figure 5-13,
the name is “Optical lab”.
Click the IP address hyperlink to access the model 7230. This will open your
default browser and display the model 7230’s Main Controls page. If you check
the “Close program…” box then the SRInstFinder utility will also be closed
automatically.
Use the FindLockin Page on the www.signalrecovery.com website.
This page, accessible via a link from the Model 7230 page on the website, will
search for model 7230’s on the same network where their IP address shares the
same first three octets as the computer from which it is being run. This will
typically be the case where the controlling computer is in the same location or
department as the model 7230 (there can be up to 255 devices with IP addresses
that share the first three octets) so in most cases this will not be a limitation.
Count the Status Light Flashes
If neither of the above methods will work, then it is possible to count the flashes
of the front panel STATUS light, in accordance with the information in section
4.1.04
6) Once the IP address for the 7230 has been found, type it into the browser's
address bar and press <return>. The 7230's Main Controls panel should be
displayed.
7) Save the address as a shortcut, bookmark, or favorite.
Using this configuration you should be able to access the 7230 again in future simply
by selecting the favorite, bookmark, or shortcut. However, depending on the policy
of the DHCP server, and the length of leases that it grants, it may be that if the model
7230 is powered down and then turned back on again after a delay (e.g. over a
weekend) it may be allocated a different IP address by the DHCP server.
However, many DHCP servers keep a table of past IP address assignments, so that
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Chapter 5, WEB CONTROL PANEL OPERATION
they can preferentially assign to a client (such as the model 7230) the same IP
address that the client previously had. In this case the 7230 will normally get the
same address.
If, however, the address changes, then you will need to repeat the above procedure to
find the new address. One way of avoiding having to do this is, of course, to leave the
model 7230 permanently switched on and connected to the network.
5.3 Web Control Panels
5.3.01 Main Controls: Overview
Figure 5-14, Main Controls Panel
The Main Controls panel, shown above in Figure 5-14, is displayed when a browser
session is opened on the instrument’s IP address. There are four digital indicators
along the bottom of the screen, and controls for all the most common functions in the
upper section.
There are several ways of operating the controls. Some, such as the Sensitivity
control, have a range of fixed settings. To adjust these, simply click on the control
and then click the required setting (see figure 5-15).
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Chapter 5, WEB CONTROL PANEL OPERATION
Figure 5-15, Adjusting Sensitivity Control
Other controls, such as the Phase and Oscillator Frequency controls, are adjusted by
typing the required value directly into a text box.
Figure 5-16, Adjusting Phase Control
To change the units applying to the digital indicators between “%” (percentage of full
scale sensitivity) and calibrated units (e.g. mV or mA), click the Units indicator, as
shown in figure 5.17.
Figure 5-17, Switching between % and mV Units
Operation of radio button and check boxes is the same as on other web pages.
The instrument may be operated in one of four modes, as follows:Single Reference
This is the normal operating mode of the unit, where it functions as a conventional
dual phase lock-in amplifier. It includes both internal and external reference modes
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Chapter 5, WEB CONTROL PANEL OPERATION
and provides detection either at the reference frequency or one harmonic of it.
Virtual Reference
Virtual reference mode is an extension of internal single reference mode operation,
where the Y channel output is used to make continuous adjustments to the internal
oscillator frequency and phase. The effect is to achieve phase-lock with the applied
signal such that the X channel output is maximized and the Y channel output is
zeroed. Virtual reference mode operation is only possible with signals at frequencies
between 100 Hz and 250 kHz.
Dual Reference
In dual reference mode the model 7230 can make simultaneous measurements at two
different reference frequencies, of which one must be external and the other must be
derived from the internal oscillator.
Tandem Demodulation
Some experiments, such as pump-probe optical work, generate an amplitude
modulated carrier signal. The carrier signal is at one, typically higher, frequency, and
the modulation at another, lower, frequency. The required measurement is the
amplitude and/or phase of the modulation.
Conventionally, lock-in detection of this signal would require two instruments. The
first would be run at the carrier frequency with its output filters set to a sufficiently
short time constant to allow the amplitude modulation to pass. Hence the X-channel
analog output would be the modulation that was to be measured; to achieve this the
signal would then be passed to the signal input of a second lock-in amplifier running
at the modulation frequency.
The built-in Tandem Demodulation mode, which is essentially the same as dual
reference mode but with the input to the second set of demodulators taken as the Xchannel output from the first, allows the 7230 to make this measurement in a single
instrument.
Dual Harmonic
Dual harmonic mode allows the simultaneous measurement of two different
harmonics of the input signal.
5.3.02 Main Controls: Display Indicators
Figure 5-18, Selecting Instrument Outputs
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Chapter 5, WEB CONTROL PANEL OPERATION
Each of the four digital indicators along the bottom of the screen can be set to display
the following instrument outputs (see figure 5-18).
Output
X1
Y1
Mag1
Phase1
Noise1
X2
Y2
Mag2
Phase2
Eqn1
Eqn2
Description
X1 channel output. In Single Reference mode this is the X output
Y1 channel output. In Single Reference mode this is the Y output
Resultant (Magnitude1) output. In Single Reference mode this is the Mag
output
Phase1 output. In Single Reference mode this is the Phase output
Noise output for the first demodulator.
X2 channel output, valid only in when demodulator 2 is active
Y2 channel output, valid only in when demodulator 2 is active
Resultant (Magnitude2) output, valid only in when demodulator 2 is
active
Phase2 output, valid only in when demodulator 2 is active
Output value of User Equation 1
Output value of User Equation 2
If an output is in overload, the display is shown in red text (figure 5-19).
Figure 5-19, Output Overload Indication
5.3.03 Main Controls: Input
Figure 5-20, Main Controls: Input
The Input controls, shown in figure 5-20, affect the signal channel.
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Chapter 5, WEB CONTROL PANEL OPERATION
AC Gain
The AC gain control allows the AC gain to be adjusted from 0 dB to 90 dB in 6 dB
steps, although not all settings are available at all full-scale sensitivity settings.
To obtain the best accuracy, use the highest value of AC Gain that is possible without
causing signal input overload, indicated by bit 6 in the Status Byte (see section
5.3.11) being red. The Input Limit value, displayed in the Status panel, is the zero to
peak signal that may be applied without causing signal overload.
Input mode
This control sets the preamplifier input configuration to either voltage or current
mode.
A (voltage)
The signal channel input is a single-ended voltage input to the BNC connector on
the front panel marked A.
-B (voltage)
The signal channel input is an inverting single-ended voltage input to the BNC
connector on the front panel marked B (I).
A-B (voltage)
In this setting the signal channel input is a differential voltage input connected to
the BNC connectors on the front panel marked A and B (I).
B (current^6)
In this setting the signal channel input is a single-ended current input connected
to the BNC connector on the front panel marked B (I), and uses the wide
bandwidth current-to-voltage converter (10E6 V/A transimpedance).
B (current^8)
In this setting the signal channel input is a single-ended current input connected
to the BNC connector on the front panel marked B (I), and uses the low noise
current-to-voltage converter (10E8 V/A transimpedance).
Off
In this setting, used for test purposes, the signal channel input is disconnected.
Input coupling
The input coupling can be set as follows:AC
The signal channel is AC coupled at the input with a lower-frequency –3 dB
cut-off of < 0.2 Hz, although it is recommend to use DC coupling at frequencies <
1.0 Hz for best results. If phase (as opposed to magnitude) readings are important
then DC coupling should be used at higher frequencies, since no correction is
made for amplitude or phase changes caused by the AC coupling capacitor.
Bipolar mode cannot be AC coupled.
DC
The signal channel is DC coupled
Input device
This control selects the type of input device used for the signal channel connections
in voltage mode input settings.
FET
Uses a FET as the input device, for which case the input impedance is 10 MΩ.
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Chapter 5, WEB CONTROL PANEL OPERATION
This is the usual setting.
Bipolar
Uses a bipolar device in the input stage, for the lowest possible voltage input
noise. In this case the input impedance is 10 kΩ. Note that this selection is not
possible when using the AC-coupled input modes.
Input shield
The input connector shells can optionally be floated or connected to chassis ground
as follows:Float
The shells of the A and B (I) connectors are connected to chassis ground via a
1 kΩ resistor.
Ground
The shells of the A and B (I) connectors are connected directly to chassis ground.
Line filter
This control selects the mode of operation of the line frequency rejection filter and
offers the following settings:Selection
50 Hz
100 Hz
50Hz + 100Hz
60Hz
120Hz
60Hz + 120Hz
Function
Enable 50 Hz notch filter
Enable 100 Hz notch filter
Enable 50 and 100 Hz notch filters
Enable 60 Hz notch filter
Enable 120 Hz notch filter
Enable 60 and 120 Hz notch filters
Demod2 source
When the demodulators are configured for dual reference operation, this control
selects the signal source for the second set of demodulators
Sig Chan ADC
In this setting the signal input to the second set of demodulators is taken from the
main signal channel ADC. This is the normal mode of operation. In dual
reference or dual harmonic mode this means that the two signals being measured
are applied to the same input connector and share a common path through the
main ADC.
Rear ADC1
In this setting the signal input to the second set of demodulators is taken from the
rear panel auxiliary input ADC1. The full-scale sensitivity is adjustable over the
normal range of 1 V to 2 nV, but because there is no AC Gain, the effective
maximum sensitivity is 1 mV.
Demod1 output (Tandem demodulator mode)
In this setting the signal input to the second set of demodulators is taken from the
X-channel output of the first set of demodulators
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Chapter 5, WEB CONTROL PANEL OPERATION
5.3.04 Main Controls: Reference 1
Figure 5-21, Main Controls: Reference 1
The Reference 1 controls, figure 5-21, affect the reference channel of the first set of
demodulators.
Source
This control allows selection of the source of reference signal used to drive the
reference 1 circuitry, and has four settings:Internal
The lock-in amplifier's reference is taken from the instrument's internal oscillator.
Note that this setting gives the best phase and gain measurement accuracy under
all operating conditions, and it is always to be preferred, if possible, to design the
experiment so that the lock-in amplifier acts as the source of the reference signal.
External digital
In this setting the reference channel is configured to accept a TTL reference
source applied to the front panel REF IN input connector
External analog
In this setting the reference channel is configured to accept an analog reference
source applied to the front panel REF IN input connector
Virtual
This activates the virtual reference mode, and the Main Controls page is
reconfigured to support the additional controls that are required (figure 5-22)
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Chapter 5, WEB CONTROL PANEL OPERATION
Figure 5-22, Virtual Reference Controls
The virtual reference mode is very similar to the single reference mode with
internal reference, and is the simplest of the three additional modes of operation.
NOTE: This mode is only suitable for signals at frequencies between 100 Hz
and the upper frequency limit of the instrument (120 or 250 kHz).
The controls operate as follows:Start Freq
This control defines the start frequency from which the instrument will begin to
try to find the applied signal. It should be set to a value close to, but less than, the
expected signal frequency.
Stop Freq
This control defines the stop frequency at which the instrument abandons its
search for the signal, and should be set to a value greater than the expected signal
frequency.
Step Size
This control defines the frequency step size used during the automatic search.
Time/Step
This control defines the time per point within the automatic search.
Search
Clicking the Search button starts the internal oscillator at the defined start
frequency and increases it at the selected step size and rate. If the instrument
detects a signal greater than 50% of full-scale then the search stops.
Frequency
This indicator shows the current frequency at which the Reference 1 channel is
operating.
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Chapter 5, WEB CONTROL PANEL OPERATION
Harmonic
This control allows selection of the harmonic of the reference frequency at which the
reference 1 channel of the lock-in amplifier operates. It can be set to any value
between 1F and 127F, but most commonly is set to 1F.
Phase
This control allows the reference phase for the first set of demodulators to be adjusted
over the range -180° to +180° in 1 m° steps.
+90 Deg
Each click of this button adds 90° to the reference 1 phase setting.
Auto Phase
Clicking this button initiates an Auto-Phase operation, where the value of the signal
phase with respect to the reference is computed and an appropriate phase-shift is then
introduced into the reference 1 channel so as to bring the difference between them to
zero. The intended result is to null the output of the Y channel while maximizing the
output of the X channel.
5.3.05 Main Controls: Oscillator
Figure 5-23, Oscillator Controls
The Oscillator controls, shown in figure 5-23, affect the internal oscillator.
Amplitude
This control sets the amplitude of the signal at the front panel OSC OUT connector
to any value between 1 mV and 5 V rms.
Frequency
The frequency of the instrument's internal oscillator may be set, using this control, to
any value between 0.001 Hz and 120.000 kHz (or 250.000 kHz if the instrument is
fitted with the 7230/99 option) with a 1 mHz resolution.
5.3.06 Main Controls: Output 1
Figure 5-24, Output 1 Controls
The Output 1 controls, shown in figure 5-24, affect the first set of demodulators
Sensitivity
When set to voltage input mode, using the control in the Input section, the
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Chapter 5, WEB CONTROL PANEL OPERATION
instrument's full-scale voltage sensitivity may be set to any value between 10 nV and
1 V in a 1-2-5 sequence.
When set to current input mode, using the control in the Input section, the
instrument's full-scale current sensitivity may be set to any value between 10 fA and
1 µA (wide bandwidth 10^6 mode), or 10 fA and 10 nA (low-noise 10^8 mode), in a
1-2-5 sequence.
The Dynamic Reserve figure, expressed in decibels, as calculated by the following
equation and shown on the display in the Status block:-
⎛ 2 ⎞
DR = 20 × log 10 ⎜
⎟ − ACGain (in dB)
⎝ SEN ⎠
Example:If AC Gain = 12 dB and SEN = 2 mV then
⎛ 2 ⎞
DR = 20 × log 10 ⎜
⎟ − 12
⎝ 0.002 ⎠
DR = 48 dB
Auto Sen
This button operates when the reference frequency is above 1 Hz. A single AutoSensitivity operation consists of increasing the full-scale sensitivity range if the
magnitude output is greater than 90% of full-scale, or reducing the range if the
magnitude output is less than 30% of full-scale. After the Auto-Sensitivity function is
called, Auto-Sensitivity operations continue to be made until the required criterion is
met.
In the presence of noise, or a time-varying input signal, it may be a long time before
the Auto-Sensitivity sequence comes to an end, and the resulting setting may not be
necessarily what is really required.
Time Constant
The time constant of the output filters is set using this control. When the Fast control
in the Output Filters section is checked, the range is 10 µs to 100 ks in a 1-2-5
sequence; when it is not checked the minimum time constant is 5 ms.
Slope
The roll-off of the output filters is set, using this control, to values from 6 dB to
24 dB/octave, in 6 dB steps. Note that there are some restrictions in that it is not
possible to select 18 or 24 dB/octave settings at Time Constants of 500 ms or shorter
when using the fast time constant mode.
X Offset and Y Offset
These controls allow manual adjustment of the X1 channel and Y1 channel output
offsets. The offset level set by the controls, which can be any value between -300%
and +300% in 0.01% steps, is added to the X1 channel or Y1 channel output when
the corresponding check boxes are checked.
The values are also set automatically and turned on by the Auto-Offset function,
which is activated by clicking the Auto Offset button.
Auto Offset
This button adjusts the X1 offset and Y1 offset values so that the X1 channel and Y1
channel outputs are zero. Any small residual values can normally be removed by
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Chapter 5, WEB CONTROL PANEL OPERATION
calling Auto-Offset for a second time after a suitable delay to allow the outputs to
settle.
Noise Measurement
This control is used to configure the instrument for noise measurements. When
checked, the available output time constant is restricted to the values in the range
500 µs to 10 ms inclusive, since it is only at these values that the noise measurements
are calibrated, and the synchronous time constant control is turned off.
The output filter slope is also restricted to either 6 or 12 dB/octave.
When the control is unchecked then the instrument is configured for normal lock-in
amplifier operation.
Noise Buffer LengthThis control, which is only active when the above Noise
Measurement control is checked, sets the averaging time of the buffer used to
determine the mean value of the output signal when making noise measurements.
Settings of Off, 1 s, 2 s, 3 s and 4 s can be selected.
The operation of this feature is described in more detail in section 3.3.20
5.3.07 Main Controls: Reference 2
Figure 5-25, Main Controls: Reference 2
When the Demodulator is set to Dual mode, the Reference 2 controls section of the
panel, shown in figure 5-25, is active. These controls affect the second set of
demodulators.
Source
This control allows selection of the source of reference signal used to drive the
reference 2 circuitry, and has three settings. The corresponding control in the
Reference 1 section also offers the same choices when in dual mode:Internal
The lock-in amplifier's reference is taken from the instrument's internal oscillator.
Note that this setting gives the best phase and gain measurement accuracy under
all operating conditions, and it is always to be preferred, if possible, to design the
experiment so that the lock-in amplifier acts as the source of the reference signal.
External digital
In this setting the reference channel is configured to accept a TTL reference
source applied to the front panel REF IN input connector
External analog
In this setting the reference channel is configured to accept an analog reference
source applied to the front panel REF IN input connector
Note that it is not possible to use virtual reference mode when the instrument is in
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Chapter 5, WEB CONTROL PANEL OPERATION
dual mode, so there is no selection to allow this.
Frequency
This indicator shows the current frequency at which the Reference 2 channel is
operating.
Harmonic
This control allows selection of the harmonic of the reference frequency at which the
reference 2 channel of the lock-in amplifier operates. It can be set to any value
between 1F and 127F, but most commonly is set to 1F.
Phase
This control allows the reference phase for the second set of demodulators to be
adjusted over the range -180° to +180° in 1 m° steps.
+90 Deg
Each click of this button adds 90° to the reference 2 phase setting.
Auto Phase
Clicking this button initiates an Auto-Phase operation, where the value of the signal
phase with respect to the reference is computed and an appropriate phase-shift is then
introduced into the reference 2 channel so as to bring the difference between them to
zero. The intended result is to null the output of the Y channel while maximizing the
output of the X channel.
5.3.08 Main Controls: Output 2
Figure 5-26, Output 2 Controls
The Output 2 controls, shown in figure 5-26, affect the second set of demodulators
Sensitivity
When set to voltage input mode, using the control in the Input section, the
instrument's full-scale voltage sensitivity may be set to any value between 10 nV and
1 V in a 1-2-5 sequence.
When set to current input mode, using the control in the Input section, the
instrument's full-scale current sensitivity may be set to any value between 10 fA and
1 µA (wide bandwidth 10^6 mode), or 10 fA and 10 nA (low-noise 10^8 mode), in a
1-2-5 sequence.
Auto Sen
This function only operates when the reference frequency is above 1 Hz. A single
Auto-Sensitivity operation consists of increasing the full-scale sensitivity range if the
magnitude output is greater than 90% of full-scale, or reducing the range if the
magnitude output is less than 30% of full-scale. After the Auto-Sensitivity function is
called, Auto-Sensitivity operations continue to be made until the required criterion is
met.
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Chapter 5, WEB CONTROL PANEL OPERATION
In the presence of noise, or a time-varying input signal, it may be a long time before
the Auto-Sensitivity sequence comes to an end, and the resulting setting may not be
necessarily what is really required.
Time Constant
The time constant of the output filters is set using this control. When the Fast control
in the Output Filters section is checked, the range is 10 µs to 100 ks in a 1-2-5
sequence; when it is not checked the minimum time constant is 5 ms.
Slope
The roll-off of the output filters is set, using this control, to values from 6 dB to
24 dB/octave, in 6 dB steps. Note that there are some restrictions in that it is not
possible to select 18 or 24 dB/octave settings at Time Constants of 500 ms or shorter
when using the fast time constant mode.
X Offset and Y Offset
These controls allow manual adjustment of the X2 channel and Y2 channel output
offsets. The offset level set by the controls, which can be any value between -300%
and +300% in 0.01% steps, is added to the X2 channel or Y2 channel output when
the corresponding check boxes are checked.
The values are also set automatically and turned on by the Auto-Offset function,
which is activated by clicking the Auto Offset button.
Auto Offset
This control adjusts the X2 offset and Y2 offset values so that the X2 channel and
Y2 channel outputs are zero. Any small residual values can normally be removed by
calling Auto-Offset for a second time after a suitable delay to allow the outputs to
settle.
5.3.09 Main Controls: Output Filters
Figure 5-27, Output 2 Controls
The Output Filters controls, shown in figure 5-27, affect both sets of demodulators.
Synchronous
When this box is unchecked, which is the normal mode, time constants are not related
to the reference frequency period. When it is checked and the reference frequency is
10 Hz or lower, the actual time constant used is chosen to be some multiple of the
reference frequency period, giving a much more stable output at low frequencies than
would otherwise be the case. Note that in this mode, depending on the reference
frequency, output time constants shorter than 100 ms cannot be used.
Fast mode
When this box is unchecked, the instrument’s analog outputs are derived from the
output processor. The update rate is always 1 kHz, the output filter time constant can
be set to values between 5 ms and 100 ks in a 1-2-5 sequence, and all four output
filter slope settings are available.
When it is checked, the analog outputs are derived directly from the core FPGA
running the demodulator algorithms. The update rate is increased to 1.0 MHz when
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Chapter 5, WEB CONTROL PANEL OPERATION
the time constant is set to any value from 10 µs to 500 ms but remains at 1 kHz for
longer time constants. The output filter slope is restricted to either 6 or 12 dB/octave.
5.3.10 Main Controls: Demodulator Control
Figure 5-28, Demodulator Control
The Demodulator control, shown in figure 5-28, determines whether the second set of
demodulators is active.
Single
When selected the instrument functions as a conventional dual phase lock-in
amplifier, and only the first set of demodulators is active. It includes both internal
and external reference modes and provides detection either at the reference frequency
or one harmonic of it. Virtual Reference mode can only be used when in Single
Reference mode.
Dual
When selected both sets of demodulators are active, and can be used in the following
ways:
Dual Reference
In dual reference mode the model 7230 can make simultaneous measurements at
two different reference frequencies, of which one must be external and the other
must be derived from the internal oscillator. The Reference controls under
Reference 1 and Reference 2 are used to select the source of reference for each
demodulator, and for this mode will be set to different sources.
Dual Channel Detection
Normally the signal input in dual reference mode is common to both
demodulators, and uses the main signal channel. However, it is possible to use
the auxiliary ADC 1 input as the signal input to the second set of demodulators,
allowing the instrument to function as two independent lock-in amplifiers, Note,
however, that in this mode there is no adjustable AC Gain in the ADC 1 input
channel so the range of full-scale sensitivity settings for the second set of
demodulators is limited.
Dual Harmonic
Dual harmonic mode allows the simultaneous measurement of two different
harmonics of the input signal. The Reference controls under Reference 1 and
Reference 2 are used to select the source of reference for each demodulator, and
for this mode will be set to the same source, with each Harmonic control set to a
different value.
Tandem Demodulation
This is essentially the same as dual reference mode but with the input to the
second set of demodulators taken not from the main signal channel or ADC 1
input but from the X-channel output from the first set of demodulators. It allows
the instrument to detect the amplitude of a low frequency modulation of a higherfrequency carrier signal.
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Chapter 5, WEB CONTROL PANEL OPERATION
5.3.11 Main Controls: Status Indicators
Figure 5-29, Status Indicators
The Status section gives a quick overview of the instrument status.
Input limit
This is the zero to peak value above which the instrument will be in input overload,
based on the present AC gain setting.
Dynamic reserve
This is the calculated level of Dynamic Reserve based on the present sensitivity and
AC gain settings.
Status byte and Overload byte
These two arrays of LED’s show the bit values in these two bytes, which are defined
in the following table:
Bit
bit 0
bit 1
bit 2
bit 3
bit 4
bit 5
bit 6
bit 7
Status Byte
command complete
invalid command
command parameter error
reference unlock
output overload
new ADC values available
after trigger
input overload
data available
Overload Byte
X(1) output overload
Y(1) output overload
X(2) output overload
Y(2) output overload
CH1 output overload
CH2 output overload
CH3 output overload
CH4 output overload
Table 5-1, Status and Overload Byte Bit Definitions
The LEDs are green when the corresponding bit is asserted and when this is a “no
fault” condition, and red when it is asserted but this indicates a fault. Bit 0 in each
case is on the right and bit 7 on the left.
If the mouse cursor is hovered over a bit then the bit function is indicated in a pop up
box. In Figure 5-29, for example, the cursor has been hovered over bit 3 in the Status
byte; the fact that this is red indicates a loss of reference lock, while bit 1 indicates
“command done” and bit 5 that the auxiliary ADC inputs have been triggered.
This completes the description of the Main Controls panel.
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Chapter 5, WEB CONTROL PANEL OPERATION
5.3.12 Oscillator: Overview
Figure 5-30, Oscillator Panel
The Oscillator panel, shown above in Figure 5-30, gives access to the full set of
controls for the internal oscillator. Note, however, that the basic controls setting its
amplitude and frequency are also displayed on the Main Controls panel.
5.3.13 Oscillator: Sweep Control
Figure 5-31, Oscillator Panel, Sweep Controls
The internal oscillator output in the model 7230 can be swept in frequency or
amplitude, or in both parameters, using these controls.
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Chapter 5, WEB CONTROL PANEL OPERATION
Time/Step
This control defines the time per point during a frequency or amplitude sweep
Start
This button is used to start or stop a frequency and/or amplitude sweep. The Armed
checkbox in the required sweep type controls must also be checked in order to run a
sweep.
Frequency Sweep group
Start frequency
This control defines the start frequency from which the instrument will start a
frequency sweep.
Stop frequency
This control defines the end frequency for the frequency sweep
Step size
This control defines the amount by which the oscillator frequency is changed at
each step. Depending on the sweep law selected (linear or logarithmic) it is set
either in hertz, or as a percentage of the present frequency. If Start Frequency is
greater than Stop Frequency then the output frequency will decrease with time.
Armed
If this box is checked then the defined sweep will be run when the Start button is
clicked.
Linear
When this radio button is selected, all frequency steps are equal and the
frequency increases linearly with time.
Logarithmic
When this radio button is selected, the frequency is defined in terms of a
percentage of the current frequency. For example, if the step size were set to
10%, the start frequency to 1 kHz and the stop frequency to 2 kHz, then the
frequencies generated during the sweep would be:1000.000 Hz
1100.000 Hz
1210.000 Hz
1331.000 Hz
1464.100 Hz
1610.510 Hz
1771.561 Hz
1948.717 Hz
2000.000 Hz
Amplitude Sweep group
Start amplitude
This control defines the start amplitude for the amplitude sweep, which may be
set to any value between 0.000 V rms and 5.000V rms with a 1 µV resolution
Stop amplitude
This control defines the stop amplitude for the amplitude sweep, which may be
set to any value between 0.000 V rms and 5.000V rms with a 1 µV resolution
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Chapter 5, WEB CONTROL PANEL OPERATION
Step size
This control defines the amount by which the oscillator amplitude is changed at
each step. It may be set to any value between 0.000 V rms and 5.000V rms with a
1 µV resolution.
Armed
If this box is checked then the defined sweep will be run when the Start button is
clicked. If Start Amplitude is greater than Stop Amplitude then the oscillator
amplitude will decrease with time.
5.3.14 Oscillator: Modulation Control
Figure 5-32, Oscillator Panel, Modulation Controls
The internal oscillator output in the model 7230 can be amplitude or frequency
modulated using an external control voltage using the controls on this panel, shown
on figure 5-32.
Frequency (VCO) group
Enable FM
When checked, this control turns the frequency modulation on; when cleared, it
turns it off.
Center frequency
This control may be set to any value between 0.001 Hz and 120.000 or
250.000 kHz.
Frequency span
This control defines the maximum frequency span that will be applied to the
oscillator signal. For example, when set to ±100.00 Hz, the change will be
±100.00 Hz about the centre frequency.
Note: The center frequency ± the span frequency must not exceed the
frequency limits of the oscillator (0 to 120 or 250 kHz). Hence the center
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Chapter 5, WEB CONTROL PANEL OPERATION
frequency plus the span frequency cannot exceed 120 or 250.0 kHz and the
center frequency must be greater than or equal to the span frequency. For
example, for an instrument fitted with the 7230/99 option at 125 kHz center
frequency the maximum span frequency is ± 125 kHz; at 10k Hz center
frequency the maximum span frequency is ± 10 kHz; at 240 kHz center
frequency the maximum span frequency is also ± 10 kHz..
Center voltage
This control sets the input voltage corresponding to the centre frequency.
Voltage span
This control sets the range of input voltages that will be translated into the
specified frequency span.
Filter control
The FM control signal can be filtered by a simple digital low-pass FIR filter
before being applied to the oscillator, which can be useful for eliminating noise
or glitches on the signal. This control adjusts the filter; when set to 0 the filter is
turned off; as the number is increased, increased filtering is applied.
Amplitude group
Enable AM
When checked, this control turns the amplitude modulation on; when cleared, it
turns it off.
ADC1 as source and Ext ref as source
These radio buttons set the source of the signal that is used for amplitude
modulation. When set to ADC1 as source, the signal should be applied to the
rear panel ADC1 input, and the Center voltage and Voltage span controls are
active.
When set to Ext ref as source the control signal should be applied to the
external reference channel REF IN input. Because the reference channel
internally generates a fixed signal amplitude that is used as the control signal for
the amplitude modulation, the Center voltage and Voltage span controls are
inactive.
Modulation depth
This control defines the maximum amplitude change that will be applied to the
oscillator signal. For example, when set to 100%, the change can be from full
signal output to zero; while if set to 50% the amplitude will change by 50% of its
quiescent level.
Center voltage
This control sets the input voltage corresponding to the quiescent oscillator
output amplitude.
Voltage span
This control sets the range of input voltages that will be translated into the set
range of modulation.
Filter control
The AM control signal can be filtered by a simple digital low-pass FIR filter
before being applied to the oscillator, which can be useful for eliminating noise
or glitches on the signal. This control adjusts the filter; when set to 0 the filter is
turned off; as the number is increased, increased filtering is applied.
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Chapter 5, WEB CONTROL PANEL OPERATION
5.3.15 Oscillator: Amplitude and Frequency Controls
These two controls duplicate the controls on the Main Controls panel.
Amplitude
This control sets the amplitude of the signal at the front panel OSC OUT connector
to any value between 1 µV and 5 V rms.
Frequency
The frequency of the instrument's internal oscillator may be set, using this control, to
any value between 0.001 Hz and 120.000 kHz (or 250.000 kHz if the instrument is
fitted with the 7230/99 option) with a 1 mHz resolution.
This completes the description of the Oscillator panel.
5.3.16 Rear Panel: Overview
Figure 5-33, Rear Panel Controls
The Rear Panel, shown above in Figure 5-33, is used to configure the instrument’s
analog outputs, to read the auxiliary ADC input voltages, to set the communications
parameters used for the RS232 interface, to set and read the digital IO port, and for
other peripheral controls.
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Chapter 5, WEB CONTROL PANEL OPERATION
5.3.17 Rear Panel: DACs
Figure 5-34, DACs Controls
These controls, shown in figure 5-34, are used to configure the signals that will
appear on the four DAC connectors on the rear panel of the instrument. Each control
has a signal selector; if this is set to User setting then the text box below is used to
specify the corresponding voltage; otherwise it is grayed out.
The controls operate as follows:
DAC1, DAC2, DAC3, and DAC4
These four controls select which signal will be made available at the corresponding
DAC 1 to DAC 4 connectors on the rear panel of the instrument. The following
settings are available, but note that internal connection limitations mean that not all
settings are available for each DAC connector.
X% (2.5V fs)
In this setting the corresponding DAC connector on the rear panel of the
instrument outputs a voltage related to the X1%fs display as follows:X1%
+300
+100
0
-100
-300
DAC Voltage
7.5 V
2.5 V
0.0 V
-2.5 V
-7.5 V
Y% (2.5V fs)
In this setting the corresponding DAC connector on the rear panel of the
instrument outputs a voltage related to the Y1%fs display as follows:Y1%
+300
+100
0
-100
-300
DAC Voltage
7.5 V
2.5 V
0.0 V
-2.5 V
-7.5 V
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Chapter 5, WEB CONTROL PANEL OPERATION
Magnitude% (2.5V fs)
In this setting the corresponding DAC connector on the rear panel of the
instrument outputs a voltage related to the MAG1%fs display as follows:MAG%fs
+300
+100
0
DAC Voltage
7.5 V
2.5 V
0.0 V
Phase (+9 V = +180°)
In this setting the corresponding DAC connector on the rear panel of the
instrument outputs a voltage related to the Phase 1 display as follows:PHA deg
+180
+90
0
-90
-180
DAC Voltage
9.0 V
4.5 V
0.0 V
-4.5 V
-9.0 V
Noise (2.5V fs)
When set to Noise the corresponding DAC connector on the rear panel of the
instrument outputs a voltage related to the Noise%fs display as follows:Noise%fs
+300
+100
0
DAC Voltage
7.5 V
2.5 V
0.0 V
NOTE: When Noise is selected as an output, the noise measurement mode
(Main Controls panel) must be ON.
Ratio (10.X%/ADC1)
When set to Ratio the corresponding DAC connector on the rear panel of the
instrument outputs a voltage related to the result of the Ratio calculation, which
is defined as follows:-
⎛ 10 × X output ⎞
RATIO = ⎜
⎟
⎝ ADC1 Input ⎠
where X output is the X channel output as a percentage of the full-scale
sensitivity and ADC 1 is the voltage (expressed in volts) applied to the ADC 1
input connector on the rear panel of the instrument. Hence, for example, if the
instrument were measuring a 100 mV signal when set to the 500 mV sensitivity
setting, the X channel output were maximized and a 1 V signal were applied to
the ADC1 input, then the value of RATIO would be:-
0.1 ⎞
⎛
⎜ 10 × 0.5 ⎟
RATIO = ⎜
⎟
⎜ 1.000 ⎟
⎝
⎠
RATIO = 2
The relationship between the voltage at the DAC connector and the RATIO value
is defined as follows:-
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Chapter 5, WEB CONTROL PANEL OPERATION
RATIO
+7.5
+2.5
0
-2.5
-7.5
DAC Voltage
7.5 V
2.5 V
0.0 V
-2.5 V
-7.5 V
Log ratio
When set to Log ratio the corresponding DAC connector on the rear panel of the
instrument outputs a voltage related to the Log ratio calculation, which is defined
as follows:-
⎛ 10 × X output ⎞
LOG RATIO = log 10 ⎜
⎟
⎝ ADC1 input ⎠
where X output is the X channel output as a percentage of the full-scale
sensitivity and 1 is the voltage (expressed in volts) applied to the ADC 1 input
connector on the rear panel of the instrument. Hence, for example, if the
instrument were measuring a 100 mV signal when set to the 500 mV sensitivity
setting, the X1 channel output were maximized and a 1 V signal were applied to
the ADC1 input, then the value of Log ratio would be:-
0.1 ⎞
⎛
⎜ 10 × 0.5 ⎟
LOG RATIO = log 10 ⎜
⎟
⎜ 1.000 ⎟
⎝
⎠
LOG RATIO = 0.301
The relationship between the voltage at the DAC connector and the Log ratio
value is defined as follows:Log ratio
+2.000
0
-3.000
DAC Voltage
2.000 V
0.0 V
-3.000 V
Note: If Ratio < 0 then Log ratio = -3.000
Equation 1
When set to Equation 1 the corresponding DAC connector on the rear panel of
the instrument outputs a voltage related to Equation 1, which is defined using the
Output Equations panel, as follows:Equation 1
+10000
0
-10000
DAC Voltage
10.0 V
0.0 V
-10.0 V
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Chapter 5, WEB CONTROL PANEL OPERATION
Equation 2
When set to Equation 2 the corresponding DAC connector on the rear panel of
the instrument outputs a voltage related to Equation 2, which is defined using the
Output Equations panel, as follows:Equation 1
+10000
0
-10000
DAC Voltage
10.0 V
0.0 V
-10.0 V
User setting
When User setting is selected the corresponding DAC connector on the rear
panel of the instrument outputs the voltage set by the corresponding control, in
the range ±10.000 V.
Digital Sig Mon
When set to the Digital Sig Mon setting the corresponding DAC connector on the
rear panel of the instrument outputs a voltage representing the digital output of
the main signal channel ADC
Digital Sig Mon2
When set to the Digital Sig Mon2 setting the corresponding DAC connector on
the rear panel of the instrument outputs a voltage representing the digital input to
the second demodulator.
ADC1 Monitor
When set to the ADC1 Monitor setting the corresponding DAC connector on the
rear panel of the instrument outputs a voltage representing the voltage at the rearpanel ADC1 input connector.
Sync Osc
When set to the Sync Osc setting the corresponding DAC connector on the rear
panel of the instrument outputs a voltage representing the sinusoidal waveform
applied to the first in-phase demodulator. If the reference mode is external, this
allows generation of a sinusoidal signal that is phase locked, and with adjustable
phase relationship, to it.
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Chapter 5, WEB CONTROL PANEL OPERATION
5.3.18 Rear Panel: ADCs
Figure 5-35, ADC Indicators
The ADCs indicators show the voltages present at the instrument’s rear-panel ADC1
to ADC4 inputs, and a radio button allows selection of two trigger modes, as follows.
Internal trigger (1kHz)
A conversion is performed on ADC1, ADC2, ADC3 and ADC4 every 1 ms, with the
results being displayed above and being available via the computer interfaces.
External trigger (1kHz)
A conversion is performed on ADC1, ADC2, ADC3 and ADC4 on receipt of a rising
edge at the TTL ADC TRIG IN connector on the rear panel on the instrument. The
maximum trigger rate is 1 kHz. The results are displayed above and are available via
the computer interfaces.
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Chapter 5, WEB CONTROL PANEL OPERATION
5.3.19 Rear Panel: RS232
Figure 5-36, RS232 Controls
These controls, shown in figure 5-36, set the parameters which control the RS232
communications port, as follows:
Baud rate
This control sets the baud rate to one of the following values:Baud Rate (bits per second)
75
110
134.5
150
300
600
1200
Baud Rate (bits per second)
1800
2000
2400
4800
9600
19200
38400
Data bits
This control sets the data transmission to either 7 or 8 data bits
Parity
This control sets the data transmission to use no parity bit, or one bit with either even
or odd parity.
Delimiter
The character selected is that sent by the lock-in amplifier to separate two numeric
values in a two-value response, such as that generated by the MP command.
Echo on
When this box is checked, the instrument echoes each character received over the
RS232 interface back to the controlling computer. The computer should wait until the
echoed character is returned before it sends the next character. When unchecked,,
character echo is suppressed.
Prompt on
When this box is checked, a prompt character is generated by the model 7230 after
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Chapter 5, WEB CONTROL PANEL OPERATION
each command response to indicate that the instrument is ready for a new command.
The prompt character is either a "*" or a "?" If a "?" is generated, it indicates that an
overload, reference unlock, parameter error or command error has occurred. When
unchecked, no prompt character is generated.
5.3.20 Rear Panel: Ref Mon
Figure 5-37, Ref Mon Control
When checked, this control, shown in figure 5-37, is used to configure the rear-panel
TRIG OUT connector as a TTL reference monitor output. In this setting the signal at
this connector is a TTL signal at the present reference frequency (either internal or
external) which can be used to monitor correct operation of the reference channel.
5.3.21 Rear Panel: Expand
Figure 5-38, Expand Control
These two controls, shown in figure 5-38, control the output expansion status of the
X1 and Y1 outputs when they are specified as analog signals at the DAC connectors.
X1 expand
When this box is checked and the DAC1 output is set to X% then the voltage present
at the output will be multiplied by 10. Hence if the X% output is 10% and X1 expand
is checked, the voltage at DAC1 will be 2.5 V rather than the 0.25 V that would
apply otherwise.
Y1 expand
When this box is checked and the DAC2 output is set to Y% then the voltage present
at the output will be multiplied by 10. Hence if the Y% output is 10% and Y1 expand
is checked, the voltage at DAC1 will be 2.5 V rather than the 0.25 V that would
apply otherwise.
5.3.22 Rear Panel: Bind
Figure 5-38, Bind Control
When the bind control, shown in figure 5-38, is checked, it is only possible to operate
the instrument using the web pages from the computer at which this box was
5-37
Chapter 5, WEB CONTROL PANEL OPERATION
checked. This prevents another user on the same network trying to control the same
instrument.
5.3.23 Rear Panel: Digital Port
Figure 5-39, Digital Port
The Digital Port controls and indicators, shown above in figure 5-39, allow the
operating mode of each of the eight pins of the DIGITAL I/O connector on the rear
panel of the instrument to be set and its logic status to be set and read. This port may
be used for controlling or reading the status of external equipment, for example the
switching of heaters or attenuators, via a suitable user-supplied external interface
circuit.
Each of the eight pins is configured as an input or output by the Direction buttons;
when the digit is set to OP it is an output; when set to IP it is an input.
For those bits configured as outputs, the Output value buttons define whether they
are high (value = 1) or low (value = 0); simply click the buttons to change the value.
The Input value indicators show the current logic state of all eight bits, regardless
of whether they are inputs or outputs.
5.3.24 Rear Panel: DIP switches
Figure 5-40, DIP Switches
The DIP switch indicator, shown above in figure 5-40, displays the current position
of the three rear panel CONFIG DIP switches. the function of these switches is as
follows:
Switch 1: Retain Settings
This switch determines whether the instrument will retain its settings during powerdown, according to the following table:
Position
0
1
Description
Unit powers on with all settings set to factory default values (see
Appendix D)
Unit powers on with the same settings as when it was powered off
Hence to perform a reset to the factory default settings, turn off the power switch, set
switch 1 to position 0, and turn the power switch back on. Switch 1 can then be set
back to 1 if desired.
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Chapter 5, WEB CONTROL PANEL OPERATION
Switch 2: IP Address Control
This switch selects the mode of operation of the Ethernet interface, according to the
following table:
Position
Description
0
The model 7230 uses a static IP address, as set by the command
IPADDR. This command can be sent via any one of the three interfaces,
but if used via the Ethernet interface and specifying a different address to
that currently in use, then communications will be lost.
1
Unit uses a DHCP or AutoIP allocated address. It initially tries to get an
IP address via a DHCP server but if one is not assigned then it will auto
assign an IP address and test that it does not conflict with anything else
on the network. The AutoIP address will be in the range
169.254.XXX.XXX
Switch 3: IP Address Display
When this switch is changed from 0 to 1 or from 1 to 0 then the current IP address
(static, DHCP, or Auto IP allocated) will be shown by means of flashing the front
panel STATUS light red and green.
5.3.25 Rear Panel: USB Status
Figure 5-41, USB Status
The USB Status indicator, shown above in figure 5-41, displays the current status of
the USB communications port, and, if connected, the speed at which it is operating.
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Chapter 5, WEB CONTROL PANEL OPERATION
5.3.26 Equations: Overview
Figure 5-42, Equations
The Equations panel, shown above in Figure 5-42, allows the two user equations that
are built in to the instrument to be defined, as well as giving access to a Command
Interface that allows instrument commands to be sent to the unit and the response, if
any, displayed.
5.3.27 Equations: Equation 1 and Equation 2
Figure 5-43, Equation 1
The Equation 1(shown above in figure 5-43) and Equation 2 controls are used to
define more complex calculations on the instrument outputs than are possible using
the basic ratio and log ratio options. Each equation takes the following form:-
⎛ (A ± B) × C ⎞
Equation = ⎜
⎟
D
⎝
⎠
where the operator "±" may be set to either addition or subtraction, and the variables
A, B, C and D can be chosen from the following list:-
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Chapter 5, WEB CONTROL PANEL OPERATION
Variable
Range
X1
±30000
Y1
±30000
MAG1
0 to +30000
PHA1 (Phase)
±18000
ADC1
±10000
ADC2
±10000
ADC3
±10000
ADC4
±10000
C1
0 to 100000
C2
0 to 100000
0
Zero
1
Unity
FRQ (Reference Frequency)
0 to 120000000 or 250000000
(Only available in position C)
OSCF(Oscillator Frequency)
0 to 120000000 or 250000000
(Only available in position C)
In the dual modes X2, Y2, MAG2 and PHA2 variables can also be selected.
Use the up/down buttons to select the required variable settings.
The values C1 and C2 within each equation are user-defined integer constants and are
adjusted by typing the required value into the text entry boxes and pressing <return>.
The equations are calculated using 64-bit integers to maintain full accuracy through
to the 32-bit result that can be shown on the digital indicators. Care should be taken
when defining the equations so as to make the best use of the available output range.
If the equation outputs are set to appear at any of the analog output connectors on the
rear panel using the Configuration menu, then the output range should be adjusted to
lie in the range -10000 to +10000. Values outside this range will result in these
analog outputs limiting at ±10.000 V, although the digital value will still appear
correctly on the screen.
Note that the equations continue to be calculated even when the Equations panel is
not displayed, if they are selected for output to the analog output connectors.
Otherwise they are calculated when requested by computer command.
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Chapter 5, WEB CONTROL PANEL OPERATION
5.3.28 Equations: Command Interface
Figure 5-44, Command Interface
The Command interface, shown above in figure 5-44, allows commands to be sent to
the instrument and the response displayed. Commands are listed in Chapter 6 and
Appendix E of this manual.
Type the command in the Command input box and press <return>. The response
will be shown in the Command response box. In the figure above, the command
ID was sent and the response is "7230", the instrument's model number.
5.3.29 Equations: Auto Default
Figure 5-45, Auto Default Button
Clicking the Auto Default button, shown above in figure 5-45, sets all the controls to
a defined state. This is most often used as a rescue operation to bring the instrument
into a known condition when it is giving unexpected results. A listing of the settings
which are invoked by the use of this function can be found in appendix D.
This completes the description of the instrument's web control panels.
5-42
Computer Operation
Chapter 6
6.1 Introduction
The model 7230 includes RS232, USB and Ethernet interface ports, designed to
allow it to be completely controlled from a remote computer. All of the instrument's
controls may be operated, and all of the outputs can be read, via these interfaces.
This chapter describes the capabilities of the instrument when operated remotely and
discusses how this is done. Refer to Chapter 5 for a description of how to operate the
instrument via its built in web control panels.
6.2 Capabilities
6.2.01 General
All instrument controls can be set, with the exception of the functions selected by the
rear panel CONFIG switches, and all instrument outputs may be read remotely.
6.2.02 Operation
Control of the lock-in amplifier from a computer consists of the computer sending
commands to the instrument, with it responding either by sending back some data or
by changing the setting of one of its controls. The commands and responses are
generally ASCII text strings, although transfer of data from the instrument’s curve
buffer can also be done using a binary dump of values, with each value being two
bytes long.
The computer ports cannot be used simultaneously, but when a command has been
completed, the lock-in amplifier will accept the next command from any port, and
respond to that port.
6.2.03 Compound Commands
Unlike some older SIGNAL RECOVERY instruments, the model 7230 does not
support compound commands, which are two or more simple commands separated by
semicolons (ASCII 59) and terminated by a single command terminator.
6.3 RS232 Operation
6.3.01 Introduction
The RS232 interface is primarily intended to enable the lock-in amplifier to be
operated from a computer program specially written for an application, although it
can also be used in the direct, or terminal, mode. In this mode the user enters
commands on a keyboard and reads the results from the display.
The simplest way to establish this terminal mode is to connect the instrument to a
computer running a terminal emulator, such Windows HyperTerminal.
6.3.02 General Features
The RS232 interface in the model 7230 is implemented with three wires; one carries
digital transmissions from the computer to the lock-in amplifier, the second carries
digital transmissions from the lock-in amplifier to the computer and the third is the
Logic Ground to which both signals are referred. The logic levels are ±12 V referred
to Logic Ground, and the connection may be a standard RS232 cable in conjunction
with a null modem or, alternatively, may be made up from low-cost general-purpose
6-1
Chapter 6, COMPUTER OPERATION
cable. The pinout of the RS232 connectors is shown in appendix B and cable
diagrams suitable for coupling the instrument to a computer are shown in
appendix C.
The main advantages of the RS232 interface are:
1) It communicates via a serial port which is either already fitted or can be added at
low cost via an adaptor to any computer, using leads and connectors which are
available from suppliers of computer accessories or can be constructed at
minimal cost in the user's workshop.
2) It requires no more software support than is normally supplied with the computer,
for example Windows HyperTerminal.
A single RS232 transmission consists of a start bit followed by 7 or 8 data bits, an
optional parity bit, and 1 stop bit. The rate of data transfer depends on the number of
bits per second sent over the interface, usually called the baud rate. In the model 7230
the baud rate can be set to a range of different values up to 38,400, corresponding to
a minimum time of less than 0.25 ms for a single character.
Mainly for historical reasons, there are a very large number of different ways in
which RS232 communications can be implemented. Apart from the baud rate
options, there are choices of data word length (7 or 8 bits), parity check operation
(even, odd or none), and number of stop bits (1 or 2). With the exception of the
number of stop bits, which is fixed at 1, these settings may be adjusted using the
RS232 Settings controls, discussed in chapter 5. They may also be adjusted by means
of the RS command.
NOTE: In order to achieve satisfactory operation, the RS232 settings must be set to
exactly the same values in the terminal or computer as in the lock-in amplifier.
6.3.03 Choice of Baud Rate
Where the lock-in amplifier is connected to a terminal or to a computer implementing
an echo handshake, the highest available baud rate of 38,400 is normally used if, as is
usually the case, this rate is supported by the terminal or computer. Lower baud rates
may be used in order to achieve compatibility with older equipment or where there is
some special reason for reducing the communication rate.
6.3.04 Choice of Number of Data Bits
For most transmissions, the model 7230 lock-in amplifier uses the standard ASCII
character set, containing 127 characters represented by 7-bit binary words. If an 8-bit
data word is selected, the most significant bit is set to zero on output from the lock-in
amplifier and ignored on input.
The binary dump commands, used for the fastest data transfer rates from the internal
curve buffers, require 8 bit transmission.
6.3.05 Choice of Parity Check Option
Parity checks are not required at the baud rates available in the model 7230 with
typical cable lengths of up to a few meters. Therefore no software is provided in the
model 7230 for dealing with parity errors. Where long cables are in use, it may be
advisable to make use of a lower baud rate. The result is that any of the parity check
options may be used, but the no-parity option will result in slightly faster
communication.
Where the RS232 parameters of the terminal or computer are capable of being set to
6-2
Chapter 6, COMPUTER OPERATION
any desired value, an arbitrary choice must be made. In the model 7230 the
combination set at the factory is even parity check, 7 data bits, and one stop bit
(fixed).
6.3.06 Handshaking and Echoes
A handshake is a method of ensuring that the transmitter does not send a data byte
until the receiver is ready to receive it.
In the RS232 standard there are several control lines called handshake lines (RTS,
DTR outputs and CTS, DSR, DCD inputs) in addition to the data lines (TD output
and RD input). However, these lines are not capable of implementing the
handshaking function required by the model 7230 on a byte-by-byte basis and are not
connected in the model 7230 apart from the RTS and DTR outputs, which are
constantly asserted.
Note that some computer applications require one or more of the computer's RS232
handshake lines to be asserted. If this is the case, and if the requirement cannot be
changed by the use of a software switch, the cable may be used in conjunction with a
null modem. A null modem is an adapter that connects TD on each side through to
RD on the other side, and asserts CTS, DSR, and DCD on each side when RTS and
DTR are asserted on the opposite sides.
With most modern software there is no need to assert any RS232 handshake lines and
a simple three-wire connection can be used. The actual handshake function is then
performed by means of bytes transmitted over the interface.
The more critical handshake is the one controlling the transfer of a command from
the computer to the lock-in amplifier, because the computer typically operates much
faster than the lock-in amplifier and bytes can easily be lost if the command is sent
from a program. (Note that because of the limited speed of human typing, there is no
problem in the terminal mode.) To overcome the problem an echo handshake should
be used. This works in the following way: after receiving each byte, the lock-in
amplifier sends back an echo, that is a byte which is a copy of the one that it has just
received, to indicate that it is ready to receive the next byte. Correspondingly, the
computer should not send the next byte until it has read the echo of the previous one.
The computer can compare each byte with its echo to provide a useful check on the
validity of the communications.
Where the echo is not required, it can be suppressed by negating bit 3 in the RS232
parameter byte. The default (power-up) state of this bit is for it to be asserted.
6.3.07 Terminators
In order for communications to be successfully established between the lock-in
amplifier and the computer, it is essential that each transmission, i.e. command or
command response, is terminated in a way which is recognizable by the computer
and the lock-in amplifier as signifying the end of that transmission.
In RS232 communications, the lock-in amplifier automatically accepts either <CR>
or <CR,LF> as an input command terminator, and sends out <CR,LF> as an output
response terminator except when the noprompt bit (bit 4 in the RS232 parameter
byte) is set, in which case the terminator is <CR>. The default (power-up) state of
this bit is zero.
6.3.08 Delimiters
Most response transmissions consist of one or two numbers followed by a response
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Chapter 6, COMPUTER OPERATION
terminator. Where the response of the lock-in amplifier consists of two numbers in
succession, they are separated by a byte called a delimiter. This delimiter can be one
of several ASCII characters and is common to all interfaces; it is set via the RS232
Settings controls or by the use of the DD command. The default value is a comma.
6.3.09 Status Byte, Prompts and Overload Byte
It is useful for a controlling program to be able to quickly determine the status of the
connected instrument. Internally, this is represented by two 8-bit values, known as
the status and overload bytes.
In RS232 communications, comparatively rapid access to the status byte is provided
by the prompt character, which is sent by the lock-in amplifier at the same time as
bit 0 (indicating command complete) becomes asserted in the status byte. This
character is sent out by the lock-in amplifier after each command response (whether
or not the response includes a transmission over the interface) to indicate that the
response is finished and the instrument is ready for a new command. The prompt
takes one of two forms. If the command contained an error, either in syntax or by a
command parameter being out of range, or alternatively if an overload or reference
unlock is currently being reported by the web control panel indicators, the prompt is
a question mark character ? (ASCII 63). Otherwise the prompt is an asterisk *
(ASCII 42).
These error conditions correspond to the assertion of bits 1, 2, 3, 4 or 6 in the status
byte. When the ? prompt is received by the computer, the ST command may then be
issued in order to discover which type of fault exists and to take appropriate action.
The prompts are a rapid way of checking on the instrument status and enable a
convenient keyboard control system to be set up simply by attaching a standard
terminal, or a simple computer-based terminal emulator, to the RS232 port. Where
the prompt is not required it can be suppressed by setting the noprompt bit, bit 4 in
the RS232 parameter byte. The default (power-up) state of this bit is zero.
Because of the limited number of bits in the status byte, it can indicate that an
overload exists but cannot give more detail. An auxiliary byte, the overload byte
returned by the N command, gives details of the location of the overload.
A summary of the bit assignments in the status byte and the overload byte is given in
table 6-1 below.
Bit
bit 0
bit 1
bit 2
bit 3
bit 4
bit 5
bit 6
bit 7
Status Byte
Overload Byte
command complete
X(1) output overload
invalid command
Y(1) output overload
command parameter error
X(2) output overload
reference unlock
Y(2) output overload
output overload - read
CH1 output overload
overload byte to determine location
new ADC values available
CH2 output overload
after trigger
input overload
CH3 output overload
data available
CH4 output overload
Table 6-1, Status and Overload Byte Bit Definitions
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Chapter 6, COMPUTER OPERATION
6.4 USB Operation
6.4.01 Introduction
The USB interface in the instrument supports operation at both Full and High Speed
settings. It provides two bulk data transfer endpoints, with endpoint 1 being used to
send commands to the instrument, and endpoint 2 being used to receive responses
from it.
Operation of the instrument via the USB is made a great deal simpler if the user
installs the relevant SIGNAL RECOVERY USB driver software. Two versions of
driver are available; the first, a bulk USB driver SRUSBXP.SYS is compatible with
several software packages supplied by SIGNAL RECOVERY, while the second,
based on National Instrument’s VISA software, allows operation both from
SIGNAL RECOVERY software and a free LabVIEW driver. The only disadvantage
of using the VISA software driver is the need to download and install the complete
VISA environment in order to use the driver.
Readers should refer to the document “USB Drivers for the Model 7124, 7230, and
7270 Lock-in Amplifiers”, available from the www.signalrecovery.com website, for
further information about installing these drivers.
6.4.02 General Features
Unlike the RS232 interface, there is no difficulty ensuring that the correct cable type
is used for USB operation. All that is required is a standard USB-A to USB-B cable,
which if the driver is correctly installed on the computer will then allow operation
without further adjustment.
6.4.03 Terminator, Status Byte, and Overload Byte
Commands sent to the instrument over the USB interface should be terminated with a
null character (ASCII 0).
Responses from the instrument consist of a string that is terminated with three bytes,
in the following order:
1) A null character (ASCII 0)
2) A byte representing the value of the Status Byte (table 6-1)
3) A byte representing the value of the Overload Byte (table 6-1)
In the case of commands that generate a single response, the controlling program
should send the null-terminated command string to the instrument and then read the
response bytes sent back from it until the null is detected. Two further bytes (the
status and overload bytes) should then be read to complete the transfer.
Commands that do not return data still always return the three terminator bytes,
allowing the controlling program to know that the command has been implemented.
Data stored in the instrument’s curve buffer can be transferred in two ways. In the
ASCII mode, each value is terminated in a null character until the last value, which is
then terminated as above, whereas in the binary dump mode each data point occupies
two bytes, with the complete dump being terminated as above.
In either case it is necessary to know how much data will be transferred, by sending
the M (monitor) command and reading the response, before initiating the transfer.
This is because in the ASCII dump mode the controlling program needs to “count”
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Chapter 6, COMPUTER OPERATION
each instance of a null character until all available points have been read, while in the
binary dump mode it needs to know exactly how many bytes to read, since the data
itself can contain null characters. Only by doing this can the program be prevented
from requesting more data from the USB endpoint than the lock-in has actually sent.
6.4.04 Delimiters
Most response transmissions consist of one or two numbers (expressed as ASCII text)
followed by a response terminator. Where the response of the lock-in amplifier
consists of two numbers in succession, they are separated by a byte called a delimiter.
This delimiter can be one of several ASCII characters and is common to all
interfaces; it is set via the RS232 Settings controls or by the use of the DD command.
6.5 Ethernet Operation
6.5.01 Introduction
The Ethernet interface in the instrument supports operation on 10-BaseT and
100-BaseT networks via straight through or crossover RJ45 patch cables. The
instrument includes a built-in web server allowing any browser to communicate with
it using http protocol, as well as support for direct communication via TCP/IP.
6.5.02 IP Address
The IP address of the instrument needs to be unique on the network to which it is
connected. Consult section 5.2 for a discussion of the various ways of ensuring that
this is the case.
6.5.03 Main Controls
When the instrument has a valid IP address the browser on a computer on the same
network can then access it, simply by typing the IP address in the address bar. As
discussed in section 5.4, this will open the Main Controls remote front panel.
6.5.04 Sockets
The instrument normally accepts commands sent to socket 50000 on its IP address.
Any response is sent back to the IP address from which the initiating command was
sent.
Clearly, if an instrument is present on a large network then it is possible that several
users may accidentally try to control the same instrument. To prevent this it is
possible to use the Bind control on the Rear Panel web control panel to restrict access
to the computer from which it is being viewed, which then becomes the only one
from which commands will be accepted.
6.5.05 Terminator, Status Byte, and Overload Byte
Commands sent to the instrument over the Ethernet interface should be terminated
with a null character (ASCII 0).
Responses from the instrument consist of a string that is terminated with three bytes,
in the following order:
1) A null character (ASCII 0)
2) A byte representing the value of the Status Byte (table 6-1)
3) A byte representing the value of the Overload Byte (table 6-1)
In the case of commands that generate a single response, the controlling program
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Chapter 6, COMPUTER OPERATION
should send the null-terminated command string to the instrument and then read the
response bytes sent back from it until the null is detected. Two further bytes (the
status and overload bytes) should then be read to complete the transfer.
Commands that do not return data still always return the three terminator bytes,
allowing the controlling program to know that the command has been implemented.
Data stored in the instrument’s curve buffer can be transferred in two ways. In the
ASCII mode, each value is terminated in a null character until the last value, which is
then terminated as above, whereas in the binary dump mode each data point occupies
two bytes, with the complete dump being terminated as above.
In either case it is necessary to know how much data will be transferred, by sending
the M (monitor) command and reading the response, before initiating the transfer.
This is because in the ASCII dump mode the controlling program needs to “count”
each instance of a null character until all available points have been read, while in the
binary dump mode it needs to know exactly how many bytes to read, since the data
itself can contain null characters. Only by doing this can the program be prevented
from requesting more data from the socket than the lock-in has actually sent.
6.5.06 Delimiters
Most response transmissions consist of one or two numbers (expressed as ASCII text)
followed by a response terminator. Where the response of the lock-in amplifier
consists of two numbers in succession, they are separated by a byte called a delimiter.
This delimiter can be one of several ASCII characters and is common to all
interfaces; it is set via the RS232 Settings controls or by the use of the DD
command..
6.6 Command Format
The simple commands listed in section 6.7 have one of five forms:
CMDNAME terminator
CMDNAME n terminator
CMDNAME [n] terminator
CMDNAME [n1 [n2]] terminator
CMDNAME n1 [n2] terminator
where CMDNAME is an alphanumeric string that defines the command, and n, n1, n2
are parameters separated by spaces. When n is not enclosed in square brackets it must
be supplied. [n] means that n is optional. [n1 [n2]] means that n1 is optional and if
present may optionally be followed by n2. Upper-case and lower-case characters are
equivalent. Terminator bytes are defined in section 6.3.09.
Where the command syntax includes optional parameters and the command is
sent without the optional parameters, the response consists of a transmission of
the present values of the parameter(s).
Any response transmission consists of one or more numbers followed by a response
terminator. Where the response consists of two or more numbers in succession, they
are separated by a delimiter (sections 6.3.09, 6.3.04, and 6.5.05).
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Chapter 6, COMPUTER OPERATION
Some commands have an optional floating point mode which is invoked by
appending a . (full stop) character to the end of the command and before the
parameters. This allows some parameters to be entered or read in floating point
format. The floating point output format is given below.
±1.234E±01
The number of digits between the decimal point and the exponent varies depending
on the number but is a minimum of one and a maximum of eight. The input format is
not as strict but if a decimal point is used there must be a digit before it. An exponent
is optional. The following are all legal commands for setting the oscillator frequency
to 100.1 Hz:OF.
OF.
OF.
OF.
100.1
1.001E2
+1.001E+02
1001E-1
6.7 Command Descriptions
This section lists the commands in logical groups, so that, for example, all commands
associated with setting controls which affect the signal channel are shown together.
Appendix G gives the same list of commands but in alphabetical order.
6.7.01 Signal Channel
IMODE [n]
Current/Voltage mode input selector
The value of n sets the input mode according to the following table
n
0
1
2
Input mode
Current mode off - voltage mode input enabled
High bandwidth current mode enabled - connect signal to B (I) input connector
Low noise current mode enabled - connect signal to B (I) input connector
If n = 0 then the input configuration is determined by the VMODE command.
If n > 0 then current mode is enabled irrespective of the VMODE setting.
VMODE [n]
Voltage input configuration
The value of n sets up the input configuration according to the following table:
n Input configuration
0 Both inputs grounded (test mode)
1 A input only
2 -B input only
3 A-B differential mode
Note that the IMODE command takes precedence over the VMODE command.
DEMOD2SRC [n] Second stage demodulator signal source
In the dual reference mode, the value of n sets the source of the signal for the second
stage demodulators according to the following table:
n
0
1
2
6-8
Signal source
Main signal channel ADC (i.e. both demodulators are fed the same signal)
ADC1 - rear panel auxiliary ADC input
Demodulator 1 X channel output - this is the Tandem demodulation mode
Chapter 6, COMPUTER OPERATION
FLOAT [n]
n
0
1
Input connector shield float/ground control
Selection
Ground
Float (connected to ground via a 1 kΩ resistor)
FET [n] ]
FET input selection
The value of n controls the input device used at the signal input according to the
following table:
n
0
1
Input device
Bipolar
FET
DCCOUPLE [n]
Input coupling control
The value of n sets the input coupling mode according to the following table:
n Coupling mode
0 AC coupled
1 DC coupled
SEN [n]
SEN.
Full-scale sensitivity control
The value of n sets the full-scale sensitivity according to the following table,
depending on the setting of the IMODE control:
n
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
full-scale sensitivity
IMODE=0
IMODE=1
10 nV
10 fA
20 nV
20 fA
50 nV
50 fA
100 nV
100 fA
200 nV
200 fA
500 nV
500 fA
1 µV
1 pA
2 µV
2 pA
5 µV
5 pA
10 µV
10 pA
20 µV
20 pA
50 µV
50 pA
100 µV
100 pA
200 µV
200 pA
500 µV
500 pA
1 mV
1 nA
2 mV
2 nA
5 mV
5 nA
10 mV
10 nA
20 mV
20 nA
50 mV
50 nA
100 mV
100 nA
200 mV
200 nA
500 mV
500 nA
1V
1 µA
IMODE=2
n/a
n/a
n/a
n/a
2 fA
5 fA
10 fA
20 fA
50 fA
100 fA
200 fA
500 fA
1 pA
2 pA
5 pA
10 pA
20 pA
50 pA
100 pA
200 pA
500 pA
1 nA
2 nA
5 nA
10 nA
Floating point mode can only be used for reading the sensitivity, which is reported in
6-9
Chapter 6, COMPUTER OPERATION
volts or amps. For example, if IMODE = 0 and the sensitivity is 1 mV the command
SEN would report 18 and the command SEN. would report +1.0E-03. If IMODE was
changed to 1, SEN would still report 18 but SEN. would report +1.0E-09
AS
Perform an Auto-Sensitivity operation
The instrument adjusts its full-scale sensitivity so that the magnitude output lies
between 30% and 90% of full-scale.
ASM
Perform an Auto-Measure operation
The instrument adjusts its full-scale sensitivity so that the magnitude output lies
between 30% and 90% of full-scale, and then performs an auto-phase operation to
maximize the X channel output and minimize the Y channel output.
ACGAIN [n]
AC Gain control
Sets the gain of the signal channel amplifier according to the following table:n
0
1
2
3
4
5
6
7
AC Gain
0 dB
6 dB
12 dB
18 dB
24 dB
30 dB
36 dB
42 dB
n
8
9
10
11
12
13
14
15
AC Gain
48 dB
54 dB
60 dB
66 dB
72 dB
78 dB
84 dB
90 dB
AUTOMATIC [n] AC Gain automatic control
n
0
1
Status
AC Gain is under manual control, either using the Main Controls panel or the
ACGAIN command
Automatic AC Gain control is activated, with the gain being adjusted according
to the full-scale sensitivity setting
LF [n1 n2]
Signal channel line frequency rejection filter control
The LF command sets the mode and frequency of the line frequency rejection (notch)
filter according to the following tables:
n1
0
1
2
3
Selection
Off
Enable 50 or 60 Hz notch filter
Enable 100 or 120 Hz notch filter
Enable both filters
n2 Notch Filter Center Frequencies
0 60 Hz (and/or 120 Hz)
1 50 Hz (and/or 100 Hz)
6.7.02 Reference Channel
REFMODE [n]
Reference mode selector
The value of n sets the reference mode of the instrument according to the following
table:
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Chapter 6, COMPUTER OPERATION
n
0
1
2
Mode
Single Reference / Virtual Reference mode
Dual Harmonic mode
Dual Reference mode
NOTE: When in either of the dual reference modes the command set changes to
accommodate the additional controls. These changes are detailed in section 6.7.14
IE [n]
Reference channel source control (Internal/External)
In Single Reference and Dual Harmonic mode, the value of n sets the reference input
mode according to the following table:
n
0
1
2
Selection
INT (internal)
EXT TTL (external front panel REF input)
EXT ANALOG (external front panel REF input)
In Dual Reference mode, the value of n sets the External channel reference input
mode according to the following table:
n
1
2
Selection
EXT TTL (external front panel REF input)
EXT ANALOG (external front panel REF input)
INT [n]
Internal Reference Channel Selection
This command is functional only in Dual Reference mode. The value of n sets the
reference channel that is operated in internal reference mode, and hence also the
external reference channel, according to the following table
n
1
2
Reference channel
Reference Channel 1 = Internal; Reference Channel 2 = External
Reference Channel 2 = Internal; Reference Channel 1 = External
Use the IE command with parameter values of 1 or 2 to select which input type
(analog or TTL) is active for the external reference channel.
REFN [n]
Reference harmonic mode control
The value of n sets the reference channel to one of the NF modes, or restores it to the
default 1F mode. The value of n is in the range 1 to 127.
REFMON [n]
Reference monitor control
The value of n sets the function of the rear panel TRIG OUT connector according to
the following table:
n
0
1
Mode
Trig Out signal is generated by curve buffer triggering
Trig Out signal is a TTL signal at the reference frequency (i.e. it is a Reference
Monitor output)
REFP[.] [n]
Reference phase control
In fixed point mode n sets the phase in millidegrees in the range ±360000.
In floating point mode n sets the phase in degrees.
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Chapter 6, COMPUTER OPERATION
AQN
Auto-Phase (auto quadrature null)
The instrument adjusts the reference phase to maximize the X channel output and
minimize the Y channel output signals.
FRQ[.]
Reference frequency meter
If the lock-in amplifier is in the external reference source modes, the FRQ command
causes the lock-in amplifier to respond with 0 if the reference channel is unlocked, or
with the reference input frequency if it is locked.
If the lock-in amplifier is in the internal reference source mode, it responds with the
frequency of the internal oscillator.
In fixed point mode the frequency is in mHz, and in floating point mode the
frequency is in Hz.
LOCK
System lock control
Updates all frequency-dependent gain and phase correction parameters.
VRLOCK [n]
Virtual reference mode lock
The Seek option of the frequency sweep mode must be used before issuing this
command, for which the value of n has the following significance:
n
0
1
Mode
Disables virtual reference mode
Enters virtual reference mode by enabling tracking of the signal frequency
6.7.03 Signal Channel Output Filters
NOISEMODE [n] Noise Measurement Mode control
The value of n sets the noise measurement mode according to the following table:
n
0
1
Function
Noise measurement mode off
Noise measurement mode on.
When the noise measurement mode is turned on, the output filter time constant is
automatically adjusted until it lies in the range 500 µs to 10 ms inclusive, the
synchronous time constant control is turned off, the fast analog output mode is turned
on (FASTMODE 1), and the output filter slope is set to 12 dB/octave if it had
previously been 18 or 24 dB/octave.
NNBUF [n]
Noise Buffer Length control
The value of n sets the noise buffer length according to the following table:
n
0
1
2
3
4
TC [n]
TC.
Function
Noise buffer off
1 second noise buffer
2 second noise buffer
3 second noise buffer
4 second noise buffer
Filter time constant control
The value of n sets the output filter time constant in accordance with the following
table:
6-12
Chapter 6, COMPUTER OPERATION
n
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
NOISEMODE
=0
NOISEMODE
=1
time constant
10 µs
20 µs
50 µs
100 µs
200 µs
500 µs
1 ms
2 ms
5 ms
10 ms
20 ms
50 ms
100 ms
200 ms
500 ms
1s
time constant
N/A
N/A
N/A
N/A
N/A
500 µs
1 ms
2 ms
5 ms
10 ms
N/A
N/A
N/A
N/A
N/A
N/A
n
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
NOISEMODE
=0
NOISEMODE =
1
time constant
2s
5s
10 s
20 s
50 s
100 s
200 s
500 s
1 ks
2 ks
5 ks
10 ks
20 ks
50 ks
100 ks
time constant
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A means that n is an illegal value under these conditions.
The TC. command is only used for reading the time constant, and reports the current
setting in seconds. Hence if a TC 12 command were sent and the noise measurement
mode was turned off, TC would report 12 and TC. would report 1.0E-01, i.e. 0.1 s or
100 ms.
SYNC [n]
n
0
1
Synchronous time constant control
Effect
Synchronous time constant disabled
Synchronous time constant enabled
SLOPE [n]
Output low-pass filter slope (roll-off) control
When the fast analog output mode and noise measurement mode are turned off
(FASTMODE 0 and NOISEMODE 0), the selection is according to the following
table:
n
0
1
2
3
Slope
6 dB/octave
12 dB/octave
18 dB/octave
24 dB/octave
When:
a) The fast output filter mode is turned on, or
b) Noise measurement mode is turned ON (NOISEMODE 1)
the selection is according to the following table:
n
0
1
Slope
6 dB/octave
12 dB/octave
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Chapter 6, COMPUTER OPERATION
6.7.04 Signal Channel Output Amplifiers
XOF [n1 [n2]]
X channel output offset control
n1 Selection
0 Disables offset
1 Enables offset facility
The range of n2 is ±30000 corresponding to ±300% full-scale.
YOF [n1 [n2]]
Y channel output offset control
n1 Selection
0
1
Disables offset facility
Enables offset facility
The range of n2 is ±30000 corresponding to ±300% full-scale.
AXO
Auto-Offset
The X and Y channel output offsets are turned on and set to levels giving zero X and
Y channel outputs. Any changes in the input signal then appear as changes about zero
in the outputs.
EX [n]
Output expansion control
Expands X and/or Y channel outputs by a factor of 10. This changes the analog
outputs full-scale to ±10% if X or Y selected. The value of n has the following
significance:
n
0
1
2
3
Expand mode
Off
Expand X
Expand Y
Expand X and Y
FASTMODE [n] Output Filter Mode Control
The value of n sets the output filter mode control according to the following table:
n
0
1
Function
Fast mode off
Fast mode on
When the fast analog output mode is turned off, the available output filter time
constant is restricted to 5 ms or greater, but all four filter slopes are available (i.e. 6,
12, 18 and 24 dB/octave). Conversely, when the mode is turned on, time constants
down to 10 µs can be selected, but the slope is limited to either 6 or 12 dB/octave.
6.7.05 Instrument Outputs
X[.]
X channel output
In fixed point mode causes the lock-in amplifier to respond with the X demodulator
output in the range ±30000, full-scale being ±10000.
In floating point mode causes the lock-in amplifier to respond with the X
demodulator output in volts or amps.
Y[.]
Y channel output
In fixed point mode causes the lock-in amplifier to respond with the Y demodulator
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Chapter 6, COMPUTER OPERATION
output in the range ±30000, full-scale being ±10000.
In floating point mode causes the lock-in amplifier to respond with the Y
demodulator output in volts or amps.
XY[.]
X, Y channel outputs
This returns the X and Y outputs separated by the defined delimiter.
MAG[.]
Magnitude
In fixed point mode causes the lock-in amplifier to respond with the magnitude value
in the range 0 to 30000, full-scale being 10000.
In floating point mode causes the lock-in amplifier to respond with the magnitude
value in the range +3.000E0 to +0.001E-9 volts or +3.000E-6 to +0.001E-15 amps.
PHA[.]
Signal phase
In fixed point mode causes the lock-in amplifier to respond with the signal phase in
centidegrees, in the range ±18000.
In floating point mode causes the lock-in amplifier to respond with the signal phase
in degrees.
MP[.]
Magnitude, phase
This returns the MAG and PHA outputs separated by the defined delimiter.
RT[.]
Ratio output
In integer mode the RT command reports a number equivalent to 1000×X/ADC1
where X is the value that would be returned by the X command and ADC1 is the
value that would be returned by the ADC1 command.
In floating point mode the RT. command reports a number equivalent to X/ADC1.
LR[.]
Log Ratio output
In integer mode, the LR command reports a number equivalent to
1000×log(X/ADC1) where X is the value that would be returned by the X command
and ADC1 is the value that would be returned by the ADC1 command. The response
range is -3000 to +2079
In floating point mode, the LR. command reports a number equivalent to
log(X/ADC1). The response range is -3.000 to +2.079
NHZ.
Causes the lock-in amplifier to respond with the square root of the noise spectral
density measured at the Y channel output, expressed in volt/√Hz or amps/√Hz
referred to the input. This measurement assumes that the Y channel output is
Gaussian with zero mean. (Section 3.3.20). The command is only available in
floating point mode.
ENBW[.]
Equivalent noise bandwidth
In fixed point mode, reports the equivalent noise bandwidth of the output low-pass
filters at the current time constant setting in microhertz.
In floating point mode, reports the equivalent noise bandwidth of the output low-pass
filters at the current time constant setting in hertz.
6-15
Chapter 6, COMPUTER OPERATION
NN[.]
Noise output
In fixed point mode causes the lock-in amplifier to respond with the mean absolute
value of the Y channel output in the range 0 to 12000, full-scale being 10000. If the
mean value of the Y channel output is zero, this is a measure of the output noise.
In floating point mode causes the lock-in amplifier to respond in volts.
DEFEQU [n1 n2 n3 n4 n5 n6]
Define user equation
The DEFEQU command is used to define the user equations, which take the
following form:
⎛ (A ± B) × C ⎞
Equation = ⎜
⎟
⎝
⎠
D
Parameter n1 is used to specify the equation to be modified, and is either 1 for
Equation 1 or 2 for Equation 2.
Parameter n3 is used to set the addition/subtraction operator in the numerator
according to the following table:n3 Operator
0 Subtraction
1 Addition
The parameters n2, n4, n5 and n6 specify the variables A, B, C and D respectively
according to the following table:
n
0
1
2
3
4
5
6
7
8
9
10
11
12
13
Variable
X or X1
Y or Y1
MAG or MAG1
PHA or PHA1
ADC1
ADC2
ADC3
ADC4
C1
C2
0
1
FRQ
OSC
Dual modes only:14 X2
15 Y2
16 MAG2
17 PHA2
Range
±30000
±30000
0 to 30000
±18000
±10000
±10000
±10000
±10000
0 to 100000
0 to 100000
zero
unity
0 to 250000000 (i.e. reference frequency in mHz)*
0 to 250000000 (i.e. oscillator frequency in mHz)*
±30000
±30000
0 to 30000
±18000
*Parameter n5 is the only one that can be set to values of 12 or 13.
EQU n
Output result of equation #1 or equation #2
The value returned is the output of the user equation #1 (n = 1) or equation #2 (n =
2), where the equations are defined using the Output equations control panel (see
section 5.3.27). The possible range is ±2,147,483,647 (signed 32-bit integer).
6-16
Chapter 6, COMPUTER OPERATION
C1 n1 [n2]
Equation Constant C1
The value of n2 sets the value of constant C1 for equation #1 (n1 = 1) or equation #2
(n1 = 2) in the range -30,000 to +30,000
C2 n1 [n2]
Equation Constant C2
The value of n2 sets the value of constant C2 for equation #1 (n1 = 1) or equation #2
(n1 = 2) in the range -30,000 to +30,000
?
Fast Data Transfer command
The ? command offers a method of reading a combination of instrument outputs
which are sampled at the same time, thereby ensuring that they are correlated.
The response to the ? command is the output(s), expressed in floating point mode,
specified by the present setting of the Curve Buffer Define (CBD) command (see
section 6.7.09) and separated by delimiter character(s) defined by the DD command.
Hence for example, if CBD is set to 3, the response to the ? command will be:
<X output, in floating point mode><delimiter>
<Y output, in floating point mode><terminator>
6.7.06 Internal Oscillator
OA[.] [n]
Oscillator amplitude control
In fixed point mode n sets the oscillator amplitude in microvolts rms. The range of n
is 0 to 5000000 representing 0 V to 5 V rms.
In floating point mode n sets the amplitude in volts.
ASTART[.] [n]
Oscillator amplitude sweep start amplitude
Sets the start amplitude for a subsequent sweep of the internal oscillator amplitude, in
the range 0 to 5.000 V
In fixed point mode, n is in microvolts rms, and in floating point mode n is in volts
rms
ASTOP[.] [n]
Oscillator amplitude sweep stop amplitude
Sets the stop amplitude for a subsequent sweep of the internal oscillator amplitude, in
the range 0 to 5.000 V
In fixed point mode, n is in microvolts rms and in floating point mode n is in volts
rms
ASTEP[.] [n]
Oscillator amplitude sweep step size
Sets the amplitude step size for a subsequent sweep of the internal oscillator
amplitude, in the range 0 to 5.000 V
In fixed point mode, n is in microvolts rms and in floating point mode n is in volts
rms
OF[.] [n]
Oscillator frequency control
In fixed point mode n sets the oscillator frequency in mHz. The range of n is 0 to
120000000 or 250000000 representing 0 to 120 kHz or 250 kHz.
In floating point mode n sets the oscillator frequency in Hz. The range of n is 0 to
1.2E5 or 2.5E5
6-17
Chapter 6, COMPUTER OPERATION
FSTART[.] [n]
Oscillator frequency sweep start frequency
Sets the start frequency for a subsequent sweep of the internal oscillator frequency, in
the range 0 to 120 or 250 kHz.
In fixed point mode, n is in millihertz, and in floating point mode n is in hertz.
FSTOP[.] [n]
Oscillator frequency sweep stop frequency
Sets the stop frequency for a subsequent sweep of the internal oscillator frequency, in
the range 0 to 120 or 250 kHz.
In fixed point mode, n is in millihertz and in floating point mode n is in hertz.
FSTEP[.] [n1 n2]
Oscillator frequency sweep step size and type
The frequency may be swept either linearly or logarithmically, as specified by
parameter n2. The step size is specified by parameter n1.
Log sweep n2 = 0
In fixed point mode, n1 is the step size in thousandths of a percent.
In floating point mode n1 is in percent. The range of n1 is 0 to 100.000%
Linear sweep n2 = 1
In fixed point mode, n1 is the step size in millihertz.
In floating point mode n1 is in hertz. The range of n1 is 0 to 120 or 250 kHz
Linear seek sweep n2 = 2
In fixed point mode, n1 is the step size in millihertz.
In floating point mode n1 is in hertz. The range of n1 is 0 to 120 or 250 kHz
The seek sweep mode automatically stops when the signal magnitude exceeds
50% of full scale. This mode is most commonly used when setting up the virtual
reference mode.
SRATE[.] [n]
Oscillator frequency and amplitude sweep step rate
In fixed point mode, sets the sweep rate in milliseconds per step, and in floating point
mode sets the rate in seconds. The range of n is 1 to 1000000 (1 ms to 1000 s)
SWEEP [n]
n
0
1
2
3
5
6
7
9
10
11
Oscillator frequency and amplitude sweep control
Sweep status
Stop
Start/continue frequency sweep
Start/continue amplitude sweep
Start/continue frequency sweep and amplitude sweep
Pause frequency sweep
Pause amplitude sweep
Pause frequency sweep and amplitude sweep
Link frequency sweep to curve buffer acquisition
Link amplitude sweep to curve buffer acquisition
Link frequency and amplitude sweep to curve buffer acquisition
This command is used to start or stop the internal oscillator frequency or amplitude
sweep, or to specify that the sweep should be linked to the curve buffer data
acquisition.
In the normal mode, when a frequency and/or amplitude sweep has been defined,
applying SWEEP with a parameter of 1 2 or 3 will start it. The sweep can be paused
6-18
Chapter 6, COMPUTER OPERATION
using the command with the correct value of n for the sweep in progress. For
example, if a frequency sweep is started using SWEEP 1 then it can only be paused
by sending SWEEP 5. Similarly, it can only be continued by sending SWEEP 1. The
command SWEEP 0 will, however, stop either or both types of sweep.
When n is equal to 9, 10 or 11 the instrument is set to link the oscillator frequency
and/or amplitude sweeps to the curve buffer. The SWEEP command continues to
function as a write/read command except when the curve buffer acquisition is
actually running. In such cases, the SWEEP command changes to read-only and will
only report values of 9, 10 or 11, indicating what type of linking is active. The sweep
can then only be stopped by stopping the curve buffer, using the HC command.
However, the user can still determine the progress of the sweep using the curve
buffer monitor “M” command and the OF and/or OA (oscillator frequency and
amplitude) commands.
MENABLE [n]
Oscillator amplitude/frequency modulation enable command
The value of n enables the oscillator amplitude modulation function in accordance
with the following table:
n
0
1
2
Function
Oscillator amplitude/frequency modulation disabled
Oscillator amplitude modulation enabled
Oscillator frequency modulation enabled
AMCENTERV[.] [n]
Oscillator amplitude modulation center voltage command
The value of n sets the oscillator amplitude modulation center voltage; in fixed point
mode n is an integer in the range -10000 to +10000, corresponding to voltages from 10.000 V to +10.000 V, and in floating point mode it is in volts.
Note: The span voltage plus the center voltage cannot exceed ±10.000 V
AMDEPTH [n]
Oscillator amplitude modulation depth control
The value of n sets the oscillator amplitude modulation depth in percent, from 0 to
100
AMFILTER [n]
Oscillator amplitude modulation filter control command
The value of n sets the oscillator amplitude modulation voltage low-pass filter control
in the range 0 to 10. The value of 0 gives the widest bandwidth for this filter, with the
value of 10 the lowest.
AMSOURCE [n] Oscillator amplitude modulation voltage source command
The value of n selects the source of signal used to modulate the oscillator amplitude
in accordance with the following table:
n
0
1
Function
ADC 1 input
Signal from external reference channel
AMVSPAN[.] [n] Oscillator amplitude modulation voltage span command
The value of n sets the oscillator amplitude modulation span voltage; in fixed point
mode n is an integer in the range 0 to +10000, corresponding to a range from
±0.000 V to ±10.000 V, and in floating point mode it is in volts.
Note: The span voltage plus the center voltage cannot exceed ±10.000 V
6-19
Chapter 6, COMPUTER OPERATION
FMCENTERF[.] [n]
Oscillator frequency modulation center frequency command
In fixed point mode n sets the oscillator frequency modulation center frequency in
mHz. The range of n is 0 to 120000000 or 250000000 representing 0 to 120.0 or
250.0 kHz; in floating point mode n sets the center frequency in the range 0 to 1.2E5
or 2.5E5
Note: The span frequency plus the center frequency cannot exceed 120.0 or
250.0kHz; the center frequency must also be greater than the span frequency.
FMCENTERV[.] [n]
Oscillator frequency modulation center voltage command
The value of n sets the oscillator frequency modulation center voltage; in fixed point
mode n is an integer in the range -10000 to +10000, corresponding to voltages from 10.000 V to +10.000 V, and in floating point mode it is in volts.
Note: The span voltage plus the center voltage cannot exceed ±10.000 V
FMFILTER [n]
Oscillator frequency modulation filter control command
The value of n sets the oscillator frequency modulation voltage low-pass filter control
in the range 0 to 10. The value of 0 gives the widest bandwidth for this filter, with the
value of 10 the lowest.
FMSPANF[.] [n] Oscillator frequency modulation span frequency command
In fixed point mode n sets the oscillator frequency-modulation span frequency in
mHz. The range of n is 0 to 60000000 or 125000000 representing 0 to ± 60 kHz or
125 kHz; in floating point mode n sets the span frequency in the range 0 to 6.0E4 or
1.25E5.
Note: The center frequency ± the span frequency must not exceed the frequency
limits of the oscillator (0 to 120 or 250 kHz). Hence the center frequency plus the
span frequency cannot exceed 120.0 or 250.0 kHz and the center frequency must
be greater than or equal to the span frequency. For example, with an instrument
fitted with the 7230/99 upper frequency extension option and a 125 kHz center
frequency the maximum span frequency is ± 125 kHz; at 10k Hz center frequency
the maximum span frequency is ± 10 kHz; at 240 kHz center frequency the
maximum span frequency is also ± 10 kHz. When setting the center frequency and
span frequency under computer control it is recommended to first set the span
frequency to zero followed by the center frequency to the required value and finally
the span frequency to the required value. This will avoid potential problems with
the new center frequency being rejected because it is not a legal value when
compared with the old span frequency.
FMVSPAN[.] [n] Oscillator frequency modulation voltage span command
The value of n sets the oscillator frequency modulation span voltage; in fixed point
mode n is an integer in the range 0 to +10000, corresponding to a range from
±0.000 V to ±10.000 V, and in floating point mode it is in volts.
Note: The span voltage plus the center voltage cannot exceed ±10.000 V
6.7.07 Analog Outputs
CH n1 [n2]
DAC analog output control
Defines what outputs appear on the DAC1, DAC2, DAC3 and DAC4 connectors on
the rear panel.
6-20
Chapter 6, COMPUTER OPERATION
n1 is compulsory and is 1 for DAC1, 2 for DAC2, 3 for DAC3, or 4 for DAC4
n2
0
1
2
3
4
5
6
7
8
Signal (DAC1)
X1% (2.5 V FS)
Noise % (2.5 V FS)
Ratio: (10 × X1%/ADC 1)
Log Ratio: log10 (10 × X1%/ADC1)
Equation 1
Equation 2
User DAC1
Main signal channel ADC output (digital signal monitor 1)
Magnitude2 % (2.5 V FS) (dual mode only)
n2
0
1
2
3
4
5
6
7
8
Signal (DAC2)
Y1 % (2.5 V FS)
Noise % (2.5 V FS)
Ratio: (10 × X1%/ADC 1)
Log Ratio: log10 (10 × X1%/ADC1)
Equation 1
Equation 2
User DAC2
Ext ADC1 monitor
Phase2 : +9 V = +180°, -9 V = -180° (dual mode only)
n2
0
1
2
3
4
5
6
7
8
Signal (DAC3)
Magnitude1 % (2.5 V FS)
Noise % (2.5 V FS)
Ratio: (10 × X1%/ADC 1)
Log Ratio: log10 (10 × X1%/ADC1)
Equation 1
Equation 2
User DAC3
Input to second demodulator (digital signal monitor 2)
X2 % (2.5 V FS) (dual mode only)
n2
0
1
2
3
4
5
6
7
8
Signal (DAC4)
Phase1: +9 V = +180°, -9 V = -180°
Noise % (2.5 V FS)
Ratio: (10 × X1%/ADC 1)
Log Ratio: log10 (10 × X1%/ADC1)
Equation 1
Equation 2
User DAC4
Synchronous oscillator
Y2 % (2.5 V FS) (dual mode only)
NOTE: n2 = 1 is only permitted if the noise measurement mode is on
(NOISEMODE 1) or if the present settings of output filter slope and time constant
are within the permitted range and the synchronous time constant control is off.
DAC[.] n1 [n2]
Set user DAC output voltage controls
The first parameter n1, which specifies the DAC, is compulsory and is either 1, 2, 3 or
4.
The value of n2 specifies the voltage to be output.
6-21
Chapter 6, COMPUTER OPERATION
In fixed point mode it is an integer in the range -10000 to +10000, corresponding to
voltages from -10.000 V to +10.000 V, and in floating point mode it is in volts.
6.7.08 Digital I/O
PORTDIR [n]
Digital port direction control
The value of n determines which of the eight lines on the digital port are configured
as inputs and which as outputs. The parameter n is a decimal number whose bit-wise
interpretation defines whether the corresponding line is an input or output. The line is
an input if the corresponding bit is a “1”. For example:
n
0
1
2
4
8
16
32
64
128
255
BYTE [n]
status
All lines configured as inputs
D0 = output, D1 - D7 = inputs
D1 = output, D0 and D2 - D7 = inputs
D2 = output, D0 - D1 and D3 - D7 = inputs
D3 = output, D0 - D2 and D4 - D7 = inputs
D4 = output, D0 - D3 and D5 - D7 = inputs
D5 = output, D0 - D4 and D6 - D7 = inputs
D6 = output, D0 - D5 and D7 = inputs
D7 = output, D0 - D6 inputs
All lines configured as outputs
Digital port output control
The value of n, in the range 0 to 255, determines the bits to be output on those lines
of the rear panel digital port that are configured as outputs. Hence, for example, if
PORTDIR = 255 and BYTE = 0, all outputs are low, and when BYTE = 255, all are
high.
READBYTE
Read digital port input
The response to the READBYTE command is an integer between 0 and 255
representing the binary value of all eight lines of the rear panel digital port. Hence,
for example, if PORTDIR = 0 and the response to READBYTE is 255, then all lines
are high, and if the response to READBYTE is 0, then all lines are low. Note that
because the command does not differentiate between whether a line is configured as
an input or output, it can be used as a single command to determine the present status
of all eight lines, both inputs and outputs, of the port.
6.7.09 Auxiliary Inputs
ADC[.] n
Read auxiliary analog-to-digital inputs
The response for ADC1 to ADC4 (n = 1 to 4 respectively) in fixed point mode is an
integer in the range -11000 to +11000, corresponding to voltages from -11.000 V to
+11.000 V, and in floating point mode it is in volts.
TADC [n]
Auxiliary analog-to-digital input trigger mode
The value of n sets the trigger modes for the auxiliary ADC inputs according to the
following table:
6-22
Chapter 6, COMPUTER OPERATION
n
0
1
2
3
Trigger Mode
Internal (1 kHz)
External - apply trigger to ADC TRIG IN connector
Burst ADC1 (5 µs per point, only ADC1 is converted)
Burst ADC1 & ADC2
6.7.10 Output Data Curve Buffer
CMODE [n]
Curve buffer mode
The value of n sets the curve buffer acquisition mode in accordance with the
following table:
n
0
1
CBD [n]
mode
Standard
Fast
Curve buffer define for Standard Mode Buffer
Defines which data outputs are stored in the standard curve buffer when subsequent
TD (take data), TDT (take data triggered) or TDC (take data continuously)
commands are issued. Up to 17 (or 22 in dual reference and dual harmonic modes)
curves, or outputs, may be acquired, as specified by the CBD parameter.
The CBD parameter is an integer between 1 and 131,071, being the decimal
equivalent of a 17-bit binary word. In either of the dual reference modes, it is an
integer between 1 and 4,194,303, being the decimal equivalent of a 22-bit binary
number. When a given bit is asserted, the corresponding output is selected for
storage. When a bit is negated, the output is not stored. The bit function and range for
each output are shown in the table below:
Bit
0*
1*
2*
3*
4
Decimal value
1
2
4
8
16
5*
6*
7*
8*
9*
10*
11*
12*
13*
14
15
16
32
64
128
256
512
1024
2048
4096
8192
16384
32768
65536
Output and range
X Output (±10000 FS)
Y Output (±10000 FS)
Magnitude Output (0 to +10000 FS)
Phase (±18000 = ±180°)
Sensitivity setting (1 to 27) + IMODE (0, 1, 2, 3 =
0, 32, 64, 128)
Noise (0 to +10000 FS)
Ratio (±10000 FS)
Log ratio (-3000 to +2000)
ADC1 (±10000 = ±10.0 V)
ADC2 (±10000 = ±10.0 V)
ADC3 (±10000 = ±10.0 V)
ADC4 (±10000 = ±10.0 V)
DAC1 (±10000 = ±10.0 V)
DAC2 (±10000 = ±10.0 V)
EVENT variable (0 to 32767)
Reference Frequency bits 0 to 15 (millihertz)
Reference frequency bits 16 to 31 (millihertz)
6-23
Chapter 6, COMPUTER OPERATION
Dual modes only:Bit
Decimal value
17*
131072
18*
262144
19*
524288
20*
1048576
21
2097152
Output and range
X2 Output (±10000 FS)
Y2 Output (±10000 FS)
Magnitude2 Output (0 to +10000 FS)
Phase2 Output (±18000 = ±180°)
Sensitivity2 setting (1 to 27) + IMODE
(0, 1, 2 = 0, 32, 64)
100,000 points are available for data storage in the standard curve buffer mode,,
shared equally between the specified curves. For example, if 16 outputs are stored
then the maximum number of storage points would be 6250 (i.e. 100000/16). The
only exception to this rule is that the Frequency curve (curves 15 and 16) occupies
the equivalent of any two other curves. The LEN command sets the actual curve
length, which cannot therefore be longer than 100000 divided by the number of
curves selected. If more curves are requested than can be stored with the current
buffer length, then the buffer length will be automatically reduced. Its actual length
can of course be determined by sending the LEN command without a parameter.
The reason why bit 4 and, for dual reference modes, bit 21, which store both the
sensitivity and the IMODE setting, are needed, is to allow the instrument to transfer
the acquired curves to the computer in floating point mode. Without this information,
the unit would not be able to determine the correct calibration to apply.
Note that the CBD command directly determines the allowable parameters for the
DC, DCB and DCT commands. It also interacts with the LEN command and affects
the values reported by the M command.
Since the reference frequency requires 32-bit wide data points, it occupies two curve
positions. For ease of use, if bit 15 is selected for storage then bit 16 will be
automatically selected as well, and vice-versa.
NOTE: At least one of the curves selected for storage in the curve buffer must be
chosen from those marked with an asterisk(*) in the above table.
LEN [n]
Curve length control
The value of n sets the curve buffer length in effect for data acquisition. In fast curve
buffer mode the maximum allowed value is 100,000; in standard mode it depends on
the number of curves requested using the CBD command, and a parameter error
results if the value given is too large. For this reason, in standard mode if the number
of points is to be increased and the number of curves to be stored is to be reduced
using the CBD command, then the CBD command should be issued first.
NC
New curve
Initializes the curve storage memory and status variables. All record of previously
taken curves is removed.
STR [n]
Storage interval control
Sets the time interval between successive points being acquired into the curve buffer.
n specifies the time interval in microseconds with a resolution of 1 µs. In fast curve
buffer mode, the shortest time that can be specified is 1 µs; in standard mode it is
1000 µs, or 1 ms
6-24
Chapter 6, COMPUTER OPERATION
TD
Take data
Initiates data acquisition. Acquisition starts at the current position in the curve buffer
and continues at the rate set by the STR command until the buffer is full. If an
oscillator frequency and/or amplitude sweep has been defined and linked to the curve
buffer using the SWEEP command with a parameter of 9, 10 or 11, then this sweep
will be started as well.
TDT n
Take data triggered
Sets the instrument so that data acquisition is initiated on receipt of various trigger
conditions at the TRIG connector on the rear panel. If an oscillator frequency and/or
amplitude sweep has been defined and linked to the curve buffer using the SWEEP
command with a parameter of 9, 10 or 11, then this sweep will be started as well.
There are two basic triggers. The Acquisition trigger is a "per curve" (start) or "per
point" (sample) trigger and can be active on either the rising or falling edge. The Stop
trigger sets the condition by which acquisition finishes. In normal operation this is
simply when the number of points specified by the LEN command parameter have
been acquired, but it is also possible to leave acquisition running until an HC
command is sent or until either a rising or falling edge occurs at the trigger input.
The trigger modes, set by the value of n, are as follows:
n
0
1
2
3
4
5
6
7
8
9
Start condition
Ext rising edge
On command
Ext falling edge
On command
Ext rising edge
On command
Ext falling edge
On command
Ext rising edge
Ext falling edge
Sample condition
Ext rising edge
Ext falling edge
Ext rising edge
Ext falling edge
-
Stop condition
Points = LEN
Points = LEN
Points = LEN
Points = LEN
On HC command
On HC command
On HC command
On HC command
Ext falling edge
Ext rising edge
Note that in modes 1, 3, 5 and 7 the maximum trigger rate is 1000 Hz and the storage
interval control setting has no effect.
TDC n
Take data continuously
Initiates data acquisition. Acquisition starts at the current position in the curve buffer
and continues at the rate set by the STR command until halted by an HC command or
on receipt of a trigger at the TRIG in connector, in accordance with the following
table:
n
0
1
2
Start condition
On command
On command
On command
Stop condition
On HC command
Ext rising edge
Ext falling edge
Note also that if sent without a parameter the command functions as if TDT 0 had
been sent.
The buffer is circular in the sense that when it has been filled, new data overwrites
earlier points.
6-25
Chapter 6, COMPUTER OPERATION
TRIGOUT [n]
Curve buffer trigger output
The value of n defines the type of trigger output generated when a buffer acquisition
is run in accordance with the following table:
n
0
1
Trigger
Trigger generated once per curve, at start of curve
Trigger generated once per point
TRIGOUTPOL [n]
Curve buffer trigger output polarity
The value of n defines the polarity of the trigger output generated when a buffer
acquisition is run in accordance with the following table:
n
0
1
Trigger Output
Rising-edge
Falling edge
EVENT [n]
Event marker control
During a curve acquisition into the standard curve buffer, if bit 13 in the CBD
command has been asserted, the lock-in amplifier stores the value of the Event
variable at each sample point. This can be used as a marker indicating the point at
which an experimental parameter was changed. The EVENT command is used to set
this variable to any value between 0 and 32767.
HC
Halt curve acquisition
Halts curve acquisition in progress. It is effective during both single (data acquisition
initiated by TD command) and continuous (data acquisition initiated by TDC
command) curve acquisitions. The curve may be restarted by means of the TD, TDT
or TDC command, as appropriate. If an oscillator frequency and/or amplitude sweep
has been defined and linked to the curve buffer using the SWEEP command with a
parameter of 9, 10 or 11, then this sweep will be stopped as well.
M
Curve acquisition status monitor
Causes the lock-in amplifier to respond with four values that provide information
concerning data acquisition, as follows:
First value, Curve Acquisition Status: a number with five possible values, defined
by the following table:
First Value
0
1
2
5
6
Significance
No curve activity in progress.
Acquisition via TD command in progress and running.
Acquisition via TDC command in progress and running.
Acquisition via TD command in progress but halted by HC
command.
Acquisition via TDC command in progress but halted by
HC command.
Second value, Number of Sweeps Acquired: This number is incremented each
time a TD is completed and each time a full cycle is completed on a TDC acquisition.
It is zeroed by the NC command and also whenever a CBD or LEN command is
applied without parameters.
Third value, Status Byte: The same as the response to the ST command. The
number returned is the decimal equivalent of the status byte and refers to the
6-26
Chapter 6, COMPUTER OPERATION
previously applied command.
Fourth value, Number of Points Acquired: This number is incremented each time a
point is taken. It is zeroed by the NC command and whenever CBD or LEN is
applied without parameters.
DC[.] n
Dump acquired curve(s) to computer
The operation of this command depends on whether data has been stored into the
Standard or Fast Mode curve buffers.
Standard Mode
In fixed point mode, causes a stored curve to be dumped via the computer interface in
decimal format.
In floating point mode the SEN curve (bit 4 in CBD) must have been stored if one or
more of the following outputs are required in order that the lock-in amplifier can
perform the necessary conversion from %FS to volts or amps:- X, Y, Magnitude,
Noise. Similarly, if the dual reference or harmonic modes are active then the SEN2
curve (bit 21 in CBD) must have been stored in order to perform a similar conversion
from %FS to volts or amps for X2, Y2 and Magnitude2.
One curve at a time is transferred. The value of n is the bit number of the required
curve, which must have been stored by the most recent CBD command. Hence n can
range from 0 to 16, or 0 to 21 if a dual mode is active. If for example CBD 5 had
been sent, equivalent to asserting bits 0 and 2, then the X and Magnitude outputs
would be stored. The permitted values of n would therefore be 0 and 2, so that DC 0
would transfer the X channel output curve and DC 2 the Magnitude curve.
NOTE: When transferring the Frequency curve, which is saved when bit 15 in the
CBD parameter is asserted, the instrument automatically reads the data for each
stored point in both frequency curves (i.e. the lower and upper 16 bits) and sends it
as a single data point.
Fast Mode
Only fixed point mode is supported. One curve at a time is transferred, with the
selected curve being dumped via the computer interface in decimal format.
The value of n defines the curve to be transferred according to the following table:
n
0
1
2
3
4
Output and range
X Output (±10000 FS)
Y Output (±10000 FS)
Main signal channel ADC output (digital signal monitor 1
ADC1 (±10000 = ±10.0 V)
ADC2 (±10000 = ±10.0 V)
Dual modes only:5
X2 Output (±10000 FS)
6
Y2 Output (±10000 FS)
7
Input to second demodulator (digital signal monitor 2)
The computer program's subroutine which reads the responses to the DC command
needs to run a program loop that continues until all the data has been transferred.
DCB n
Dump acquired curve(s) to computer in binary format
The operation of this command depends on whether data has been stored into the
6-27
Chapter 6, COMPUTER OPERATION
Standard or Fast Mode curve buffers.
Standard Mode
This command causes a stored curve to be dumped via the computer interface in
binary format, using two bytes per point. All curves other than the lower 16-bits of
the reference frequency curve (curve 15) use 16-bit 2’s complement encoding, and all
data points are sent with the MSB first. The number of data bytes sent is therefore
equal to twice the current curve length. Each point is sent in fixed point mode, there
being no floating point version of the command, and hence if floating point values
are required the user may need to additionally store and read the Sensitivity curve
and then perform the correction in his own software. In order to achieve the
maximum transfer rate, no terminators are used within the transmission, although the
response is terminated normally at the end.
One curve at a time is transferred. The value of n is the bit number of the required
curve, which must have been stored by the most recent CBD command. Hence n can
range from 0 to 16 in Single Reference Mode, and 0 to 21 in the dual modes. If for
example CBD 5 had been sent, equivalent to asserting bits 0 and 2, then the X and
Magnitude outputs would be stored. The permitted values of n would therefore be 0
and 2, so that DCB 0 would transfer the X channel output curve and DCB 2 the
Magnitude curve.
Curves 15 and 16 store the reference frequency in millihertz. When using the DCB
command (although not with the other curve transfer commands), both curves need to
be transferred separately. They should then be converted to two arrays of integer
values, allowing for the fact that the data points in curve 15 are unsigned 16-bit
values, while those in curve 16 are signed 2’s complement 16-bit values (although in
practice they are never negative). Finally they should be assembled into a single
curve using the following algorithm:
Reference Frequency = (65536 × value in Curve 16) + (value in Curve 15)
The computer program's subroutine which reads the responses to the DCB command
needs to be able to handle the potentially very large data blocks (200 k bytes in the
case of one 100 k curve) that can be generated.
NOTE: When using RS232 communications, the interface must be set to use 8 data
bit transmission.
Fast Mode
One curve at a time is transferred, with the selected curve being dumped via the
computer interface in binary format, using two bytes per point. Data is sent using 16bit 2’s complement encoding, with the MSB sent first.
The value of n defines the curve to be transferred according to the following table:
n
0
1
2
3
4
6-28
Output and range
X Output (±10000 FS)
Y Output (±10000 FS)
Main signal channel ADC output (digital signal monitor 1
ADC1 (±10000 = ±10.0 V)
ADC2 (±10000 = ±10.0 V)
Chapter 6, COMPUTER OPERATION
Dual modes only:n
Output and range
5
X2 Output (±10000 FS)
6
Y2 Output (±10000 FS)
7
Input to second demodulator (digital signal monitor 2)
The computer program's subroutine which reads the responses to the DC command
needs to run a program loop that continues until all the data has been transferred.
DCT n
Dump acquired curves to computer in tabular format
NOTE: This command is only available when the curve buffer is set to Standard
Mode.
This command is similar to the DC command described above, but allows transfer of
several curves at a time and only operates in fixed point mode. Stored curve(s) are
transferred via the computer interface in decimal format.
In single reference mode, the DCT parameter is an integer between 1 and 131,071,
being the decimal equivalent of a 17-bit binary number. In either of the dual
reference modes, it is an integer between 1 and 4,194,303, being the decimal
equivalent of a 22-bit binary number. When a given bit in the number is asserted, the
corresponding curve is selected for transfer. When a bit is negated, the curve is not
transferred. The bit corresponding to each curve is shown in the table below:
Bit Decimal value
0
1
1
2
2
4
3
8
4
16
5
6
7
8
9
10
11
12
13
14
15
32
64
128
256
512
1024
2048
4096
8192
16384
32768
Dual modes only:17*
131072
18*
262144
19*
524288
20*
1048576
21
2097152
Output and range
X Output (±10000 FS)
Y Output (±10000 FS)
Magnitude Output (0 to +10000 FS)
Phase (±18000 = ±180°)
Sensitivity setting (1 to 27) + IMODE (0, 1, 2, 3 =
0, 32, 64, 128)
Noise (0 to +10000 FS)
Ratio (±10000 FS)
Log ratio (-3000 to +2000)
ADC1 (±10000 = ±10.0 V)
ADC2 (±10000 = ±10.0 V)
ADC3 (±10000 = ±10.0 V)
ADC4 (±10000 = ±10.0 V)
DAC1 (±10000 = ±10.0 V)
DAC2 (±10000 = ±10.0 V)
EVENT variable (0 to 32767)
Reference frequency (millihertz)
X2 Output (±10000 FS)
Y2 Output (±10000 FS)
Magnitude2 Output (0 to +10000 FS)
Phase2 Output (±18000 = ±180°)
Sensitivity2 setting (1 to 27) + IMODE
(0, 1, 2 = 0, 32, 64)
The values of the selected curves at the same sample point are transferred as a group
in the order of the above table, separated by the chosen delimiter character and
terminated with the selected terminator. This continues until all the points have been
6-29
Chapter 6, COMPUTER OPERATION
transferred.
NOTE: When transferring the Frequency curve, which is saved when bit 15 in the
CBD parameter is asserted, the instrument automatically reads the data for each
stored point in both frequency curves (i.e. the lower and upper 16 bits) and sends it
as a single data point.
6.7.11 Computer Interfaces
RS [n1 [n2]]
n1
0
1
2
3
4
5
6
Set/read RS232 interface parameters
Baud rate (bits per second)
75
110
134.5
150
300
600
1200
n1
7
8
9
10
11
12
13
Baud rate (bits per second)
1800
2000
2400
4800
9600
19200
38400
The lowest five bits in n2 control the other RS232 parameters according to the
following table:
bit number
0
1
2
3
4
DD [n]
bit negated
data = 7 bits
no parity bit
even parity
echo disabled
prompt disabled
bit asserted
data = 8 bits
1 parity bit
odd parity
echo enabled
prompt enabled
Define delimiter control
The value of n, which can be set to 13 or from 32 to 125, determines the ASCII value
of the character sent by the lock-in amplifier to separate two numeric values in a twovalue response, such as that generated by the MP (magnitude and phase) command.
ST
Report status byte
Causes the lock-in amplifier to respond with the status byte, an integer between 0 and
255, which is the decimal equivalent of a binary number with the following bitsignificance:
Bit 0
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Bit 6
Bit 7
N
Command complete
Invalid command
Command parameter error
Reference unlock
Output overload - read overload byte to determine location
New ADC values available after external trigger
Input overload
Data available
Report overload byte
Causes the lock-in amplifier to respond with the overload byte, an integer between 0
and 255, which is the decimal equivalent of a binary number with the following bitsignificance:
6-30
Chapter 6, COMPUTER OPERATION
Bit 0
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Bit 6
Bit 7
X(1) channel output overload (> ±300 %FS)
Y(1) channel output overload (> ±300 %FS)
X2 channel output overload (> ±300 %FS)
Y2 channel output overload (> ±300 %FS)
CH1 output overload
CH2 output overload
CH3 output overload
CH4 output overload
IPADDR [n1 n2 n3 n4]
Ethernet IP Address
When this command is sent without parameters, the instrument responds with the
current IP address e.g. 169.254.0.10
When sent with the four parameters, the command sets the IP address that will be
used when the model 7230 is set to static IP address mode (via the rear panel Config
Switch 2, see section 4.2.07)
The parameters are separated by a space character and not by a dot, e.g.
IPADDR 169 254 0 10
sets the IP address to 169.254.0.10 Based on the IP address, this command will also
generate a default subnet mask and gateway address so if values other than the
defaults are required set the IP address before setting the subnet mask and gateway
address otherwise they will be overwritten.
SNMASK [n1 n2 n3 n4] Ethernet Subnet Mask
When this command is sent without parameters, the instrument responds with the
current subnet mask e.g. 255.255.0.0
When sent with the four parameters, the command sets the subnet mask that will be
used when the model 7230 is set to static IP address mode (via the rear panel Config
Switch 2, see section 4.2.07)
The parameters are separated by a space character and not by a dot, e.g.
SNMASK 255 255 0 0
sets the subnet mask to 255.255.0.0
Note that the setting can be overridden if the IP address is set using the IPADDR
command.
GWADDR [n1 n2 n3 n4] Ethernet Gateway Address
When this command is sent without parameters, the instrument responds with the
current gateway address e.g. 169.254.0.1
When sent with the four parameters, the command sets the gateway address that will
be used when the model 7230 is set to static IP address mode (via the rear panel
Config Switch 2, see section 4.2.07)
The parameters are separated by a space character and not by a dot, e.g.
GWADDR 169 254 0 1
sets the gateway address 169.254.0.1
Note that the setting can be overridden if the IP address is set using the IPADDR
command.
6-31
Chapter 6, COMPUTER OPERATION
IPLOCK
Restrict Ethernet Access
When this command is sent via the Ethernet interface, subsequent connection
requests and hence commands will only be accepted if sent from the same IP address,
preventing unauthorized access to the instrument.
IPUNLOCK
Remove Ethernet Access Restrictions
When this command is sent via the Ethernet interface, subsequent connection
requests and hence commands will be accepted from any computer on the same
network as the instrument.
6.7.12 Instrument Identification
ID
Identification
Causes the lock-in amplifier to respond with the number 7230.
VER
Report firmware version
Causes the lock-in amplifier to respond with the firmware version number, as also
displayed on the Configuration menu.
DATE
Last calibration date
The response is a six digit number giving the date of the last calibration where the
first two digits are the day, the second two digits are the month and the last two digits
are the year (in the 21st century).
NAME
Set/Read Instrument Name
The NAME command allows the user to store an ASCII text string as a “name” to
help identify the instrument. This is especially useful when there are several
instruments connected to the same Ethernet network, since it can be used as a more
convenient alternative to the serial number as an aid to identification.
When sent with a string of up to 64 characters as a parameter, the string will be
stored. When sent without characters the instrument will respond with the stored
string. For example:
NAME Optical absorption lab lock-in amplifier
will set the name to “Optical absorption lab lock-in amplifier”; sending NAME with
no parameters will return:
Optical absorption lab lock-in amplifier
6.7.13 Auto Default and Calibration
ADF n
Auto Default
The ADF command performs an auto-default operation according to the following
table:
n
0
1
Significance
All instrument settings are returned to their factory default values
All instrument settings, with the exception of the communications settings, are
returned to their factory default values
NOTE: If the ADF 0 command is used when the communications settings are at
values other than their default settings, then communication will be lost.
6-32
Chapter 6, COMPUTER OPERATION
6.7.14 Dual Mode Commands
When either dual reference or dual harmonic modes are selected, some commands
change so that both channels can be controlled independently, as listed in the
following table:
Single Reference or
Virtual Reference mode command
Dual Reference or
Dual Harmonic mode command
EX
MAG[.]
not available
MAG1[.]
MAG2[.]
MP1[.]
MP2[.]
PHA1[.][n]
PHA2[.][n]
REFP1[.][n]
REFP2[.][n]
REFN1[n]
REFN2[n] (n = 1 in dual
reference mode)
SEN1[.][n]
SEN2[.][n]
SLOPE1[n]
SLOPE2[n]
not available
TC1[.][n]
TC2[.][n]
X1[.]
X2[.]
XOF1[n1[n2]]
XOF2[n1[n2]]
XY1[.]
XY2[.]
Y1[.]
Y2[.]
YOF1[n1[n2]]
YOF2[n1[n2]]
AQN1
AQN2
AS1
AS2
AXO1
AXO2
MP[.]
PHA[.][n]
REFP[.][n]
REFN[n]
SEN[.][n]
SLOPE[n]
SWEEP
TC[.][n]
X[.]
XOF[n1[n2]]
XY[.]
Y[.]
YOF[n1[n2]]
AQN
AS
AXO
6.5 Programming Examples
6.5.01 Introduction
This section gives some examples of the commands that need to be sent to the lock-in
amplifier for typical experimental situations.
6-33
Chapter 6, COMPUTER OPERATION
6.5.02 Basic Signal Recovery
In a typical simple experiment, the computer is used to set the instrument controls
and then to record the chosen outputs, perhaps as a function of time. At sampling
rates of up to a few points per second, there is no need to use the internal curve
buffer. The commands to achieve this would therefore be similar to the following
sequence:
IE 2
VMODE 1
AUTOMATIC 1
FLOAT 1
LF 0 0
ASM
TC 13
Set reference to external front panel input
Single-ended voltage input mode
AC Gain control automatic
Float input connector shell using 1 kΩ to ground
Turn off line frequency rejection filter
Auto-Measure (assumes reference frequency > 1 Hz)
Set time constant to 200 ms, since previous ASM changed it
Then the outputs could be read as follows:
X.
Y.
MAG.
PHA.
FRQ.
Reads X channel output in volts
Reads Y channel output in volts
Reads Magnitude in volts
Reads Phase in degrees
Reads reference frequency in hertz
The controlling program would send a new output command each time a new reading
were required. Note that when using an output filter slope of 12 dB/octave a good
"rule of thumb" is to wait for a period of four time-constants after the input signal has
changed before recording a new value. Hence in a scanning type experiment, the
program should issue the commands to whatever equipment causes the input signal to
the lock-in amplifier to change, wait for four time-constants, and then record the
required output.
6.5.03 Frequency Response Measurement
In this example, the lock-in amplifier's internal oscillator output signal is fed via the
filter stage under test back to the instrument's signal input. The oscillator frequency is
stepped between a lower and an upper frequency and the signal magnitude and phase
recorded. At sampling rates of up to a few points per second, there is no need to use
the internal curve buffer or oscillator frequency sweep generator. The commands to
achieve this would therefore be similar to the following sequence:
IE 0
VMODE 1
AUTOMATIC 1
FLOAT 1
LF 0
OA. 1.0E0
OF. 100.0
SEN 27
TC 11
AQN
Set reference mode to internal
Single-ended voltage input mode
AC Gain control automatic
Float input connector shell using 1 kΩ to ground
Turn off line frequency rejection filter
Set oscillator amplitude to 1.0 V rms
Set oscillator frequency to 100 Hz (starting frequency)
Set sensitivity to 1 V full-scale
Set time constant to 50 ms
Auto-Phase
The frequency sweep would be performed and the outputs recorded by sending the
following commands from a FOR...NEXT program loop:
OF. XX
6-34
Set oscillator frequency to new value XX hertz
Software delay of 200 ms (4 × 50 ms) allowing output to
Chapter 6, COMPUTER OPERATION
MAG.
PHA.
FRQ.
stabilize
Read Magnitude in volts
Read Phase in degrees
Read reference frequency in hertz. This would be same as
the oscillator frequency since the unit is operating in
the internal reference mode.
until the stop frequency is reached.
6.5.04 X and Y Output Curve Storage Measurement
In this example, the lock-in amplifier is measuring a current input signal applied to
the B input connector and the measured X channel output and Y channel output are
recorded for 10 seconds at a 100 Hz sampling rate. The acquired curves as read back
to the computer are required in floating point mode.
The sequence of commands is therefore as follows:
IE 2
IMODE 1
AUTOMATIC 1
FLOAT 1
LF 0 0
SEN 18
TC 11
AQN
Set reference mode to external front panel input
Normal current input mode
AC Gain control automatic
Float input connector shell using 1 kΩ to ground
Turn off line frequency rejection filter
Set sensitivity to 1 nA full-scale
Set time constant to 50 ms
Auto-Phase
Now the curve storage needs to be set up:
NC
CBD 19
LEN 1000
STR 10000
Clear and reset curve buffer
Stores X channel output, Y channel output and sensitivity
(i.e. bits 0, 1 and 4)
Number of points = 100 Hz × 10 seconds
Store a point every 10 ms (10,000 µs)
The data is acquired by issuing:
TD
Acquires data
As the acquisition is running, the M command reports the status of the curve
acquisition. Once this indicates the acquisition is complete (i.e. parameter 1 = 0,
parameter 2 = 1), the acquired data may be transferred to the computer using:
DC. 0
DC. 1
Transfers X channel output values in floating point mode.
Transfers Y channel output values in floating point mode.
The input routine of the program must be prepared to read and store 1000 responses
to each of these commands.
6-35
Chapter 6, COMPUTER OPERATION
6-36
Specifications
Appendix A
Measurement Modes
X
Y
R
θ
In-phase
Quadrature
Magnitude
Phase Angle
Noise
⎫
⎪
⎬
⎪
⎭
The unit can simultaneously show any
four of these outputs on the front panel
display
Harmonic
nF, n ≤ 127
Dual Harmonic
Simultaneously measures the signal at two different
harmonics F1 and F2 of the reference frequency
Dual Reference
Simultaneously measures the signal at two different
reference frequencies, F1 and F2, where F1 and F2 can be
set to be derived from the internal and external reference
sources or vice-versa.
Tandem Reference
A variation of the Dual Reference mode, where the
signal is demodulated using the internal reference
frequency F1, and the resulting X1 channel output is
passed to a second demodulator running at an external
reference frequency F2
Virtual Reference
Locks to and detects a signal without a reference
(100 Hz ≤ F ≤ 120 or 250 kHz)
Noise
Measures noise in a given bandwidth centered at the
reference frequency F
Signal Channel
Voltage Inputs
Modes
Frequency Response
Full-scale Sensitivity
Input Impedance
FET Input
Bipolar Input
Maximum Safe Input
Voltage Noise (typ)
FET Input
Bipolar Input
C.M.R.R.
Gain Accuracy
Distortion
Current Input
Mode
A only, -B only or Differential (A-B)
0.001 Hz ≤ F ≤ 250 kHz
10 nV to 1 V in a 1-2-5 sequence (e.g. 10 nV,
20 nV, 50 nV)
10 MΩ // 25 pF, AC or DC coupled
10 kΩ // 25 pF, input must be DC coupled
±12.0 V
5 nV/√Hz @ 1 kHz
2 nV/√Hz @ 1 kHz
>100 dB @ 1 kHz degrading by no more than
6 dB/octave with increasing frequency
±1.0% typ, ±2.0% max.
–90 dB THD (60 dB AC gain, 1 kHz)
Low Noise (108 V/A) or Wide B/W (106 V/A)
A-1
Appendix A, SPECIFICATIONS
Full-scale Sensitivity
Low Noise
Wide Bandwidth
Frequency Response (-3dB)
Low Noise
Wide Bandwidth
Impedance
Low Noise
Wide Bandwidth
Noise
Low Noise
Wide Bandwidth
Gain Accuracy
Either Input Mode:
Max. Dynamic Reserve
Line Filter
Grounding
Signal Monitor
Amplitude
Output Impedance
10 fA to 10 nA in a 1-2-5 sequence
10 fA to 1 µA in a 1-2-5 sequence
0.001 Hz ≤ F ≤ 500 Hz minimum
0.001 Hz ≤ F ≤ 50 kHz minimum
< 2.5 kΩ @ 100 Hz
< 250 Ω @ 1 kHz
13 fA/√Hz @ 500 Hz
130 fA/√Hz @ 1 kHz
± 2.0% typ, midband
> 100 dB
Filter can be set to attenuate 50/60 Hz,
100/120 Hz, or both frequency bands
BNC shields can be grounded or floated via
1 kΩ to ground
±1 V FS. This is the signal after
preamplification and filtering, immediately prior
to the main ADC
1 kΩ
Reference Input
TTL Signal
Frequency Range
Analog Signal
Impedance
Sinusoidal Input
Level
Frequency Range
Squarewave Input
Level
Frequency Range
0.001 Hz to 120 or 250 kHz
1 MΩ // 30 pF
1.0 V rms
0.3 Hz to 120 or 250 kHz
250 mV rms
2 Hz to 120 or 250 kHz
Reference Channel
Phase Set Resolution
0.001º increments
Phase Noise at 100 ms TC, 12 dB/octave slope
Internal Reference
< 0.0001º rms
External Reference
< 0.01º rms @ 1 kHz
Orthogonality
90º ±0.0001º
Acquisition Time
Internal Reference
instantaneous acquisition
External Reference
2 cycles + 1 s
Reference Frequency Meter Resolution
4 ppm or 1 mHz, whichever is the greater
A-2
Appendix A, SPECIFICATIONS
Demodulators and Output Processing
Output Zero Stability
Digital Outputs
Displays
DAC Analog Outputs
Harmonic Rejection
Output Filters
Time Constant
Slope (roll-off)
TC ≤ 5 ms
TC > 10 ms
Synchronous Filter
Offset
Phase Measurement Resolution
Reference Monitor
No zero drift on all settings
No zero drift on all settings
< 100 ppm/ºC
-90 dB
10 µs to 100 ks in a 1-2-5 sequence
6 or 12 dB/octave
6, 12, 18 or 24 dB/octave
Available for F < 10 Hz
Auto/Manual on X and/or Y: ±300% F.S.
≤ 0.01º
Rear panel TRIG OUT connector can be
configured to generate TTL signal at current
reference frequency, internal or external
Oscillator - General
Frequency
Range
Setting Resolution
Absolute Accuracy
Amplitude
Range
Setting Resolution
Accuracy
Stability
Distortion (THD)
Output Impedance
Sweep
Frequency
Output Range
Law
Step Rate
Amplitude Sweep
Output Range
Law
Step Rate
0.001 Hz to 120 or 250 kHz
1 mHz
± 50 ppm
1 µV to 5 V
1 µV when set to less than 1 mV
10 µV when set between 1 mV and 40 mV
250 µV when set between 40.001 mV and 1 V
1.25 mV when set between 1.000001 V and 5 V
±0.2% typ
50 ppm/ºC
-80 dB @ 1 kHz and 100 mV rms
50 Ω
0.001 Hz to 120 or 250 kHz
Linear or Logarithmic
1000 Hz maximum (1 ms/step)
0.000000 to 5.000000 V rms
Linear
20 Hz maximum (50 ms/step)
Auxiliary Inputs
ADC 1, 2, 3 and 4
Maximum Input
Resolution
Accuracy
Input Impedance
Sample Rate
Trigger Mode
±11 V
1 mV
±20 mV
1 MΩ // 30 pF
200 kHz maximum (one ADC only)
Internal, External or burst
A-3
Appendix A, SPECIFICATIONS
Trigger Input
TTL compatible, rising or falling edge
Outputs
Analog Outputs
DAC1
DAC2
DAC3
DAC4
Output Functions
X, X1, Mag2, User DAC1, Output function
Y, Y1, Pha2, User DAC2, Output function
X2, Mag, Mag1, User DAC3, Output function
Y2, Pha, Pha2, User DAC4, Output function
Noise, Ratio, Log Ratio and
User Equations 1 & 2.
Amplitude
X(1), Y(1), Mag(1), Pha(1)
±2.5 V full-scale; linear to ±300% F.S.
User DACs and Output Functions
±11.0 V full-scale
Impedance
1 kΩ
Update Rate
X(1/2), Y(1/2), Mag(1/2), Pha(1/2) @ TC < 1 s
1 MHz
User DACs, Output Functions and TC’s ≥ 1 s
1 kHz
8-bit Digital Port
Mode
0 to 8 lines can be configured as inputs, with the
remainder being outputs
Status
Each output line can be set high or low and the
status of each input line read
Data Storage Buffer
Size
Max Storage Rate
Fast Mode
Normal Mode
100,000 data points max.
1 MHz (X1, Y1, X2, Y2, ADC1, Demod I/P 1,
Demod I/P 2)
1 kHz
Interfaces
Built-in web server displays pages containing instrument controls and outputs on any
computer running a compatible browser that is connected to the same Ethernet
network. USB 2.0, Ethernet, and RS232 allow complete control of instrument
settings, and data readout, from other software packages.
General
Power
Voltage
Frequency
Power
Dimensions
Width
Depth
Height
With feet
A-4
Via external model PS0110 universal power
supply
100 - 240 VAC
47 - 63 Hz
40 VA max
15½" (390 mm)
10" (250 mm)
3" (75 mm)
Appendix A, SPECIFICATIONS
Without feet
Weight
2½" (64 mm)
6.6 lb (3.0 kg)
All specifications subject to change without notification
A-5
Appendix A, SPECIFICATIONS
A-6
Pinouts
Appendix B
B.1 RS232 Connector Pinout
Figure B-1, RS232 Connector (Female)
Pin
2
3
5
7
Function
RXD
TXD
GND
RTS
Description
Data In
Data Out
Signal Ground
Request to Send - always +12 V
All other pins are not connected
B.2 Digital I/O Port Connector
Figure B-3, Digital I/O Port Connector
8-bit TTL-compatible port. Each bit is configurable as an input or output. If
configured as an output, the bit status can be set, and if configured as an input it can
be read, from the front panel or via the computer interfaces.
When set as an output, each line can drive three LSTTL loads. When set as an input
each input presents one LSTTL load. The connector will mate with a 20-pin IDC
header plug (not supplied). The pinout is as follows:Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Function
Ground
Ground
D0
Ground
D1
Ground
D2
Ground
D3
Ground
D4
Ground
D5
Ground
D6
Ground
D7
Ground
B-1
Appendix B, PINOUTS
19
20
N/C
+5 V
D0 = Least Significant Bit
D7 = Most Significant Bit
B-2
Cable Diagrams
Appendix C
C.1 RS232 Cable Diagrams
Users who choose to use the RS232 interface to connect the model 7230 lock-in
amplifier to a standard serial port on a computer will need to use one of two types of
cable. The only difference between them is the number of pins used on the connector
which goes to the computer. One has 9 pins and the other 25; both are null-modem
(also called modem eliminator) cables in that some of the pins are cross-connected.
Users with reasonable practical skills can easily assemble the required cables from
parts which are widely available through computer stores and electronics components
suppliers. The required interconnections are given in figures D-1 and D-2.
Figure C-1, Interconnecting RS232 Cable Wiring Diagram
C-1
Appendix C, CABLE DIAGRAMS
Figure C-2, Interconnecting RS232 Cable Wiring Diagram
C-2
Default Settings
Appendix D
Auto Default Function
The Auto-Default computer command ADF 1 sets the model 7230's controls as
follows:General
Full-scale sensitivity
AC Gain
Time constant
Oscillator frequency
AUX DAC1 output
AUX DAC2 output
AUX DAC3 output
AUX DAC4 output
Ref Phase
Phase quadrant
X channel output offset
Y channel output offset
Ref Harmonic
200 mV
0 dB
100 ms
1000.000 Hz
0.000 V
0.000 V
0.000 V
0.000 V
0.00°
0.00°
0.00%
0.00%
1st
Signal Channel
Input coupling
Input Shell
Input mode
Input connector
Input Device
Line notch filter
Automatic AC Gain
AC
Ground
Single-ended voltage mode
A input connector
FET
Off
Off
Reference Channel
Reference mode
Reference harmonic
Internal
1st
Output Filters
Slope
Sync Time Constant
Time Constant Mode
12 dB/octave
ON
FAST
Output Offset & Expand
Offset Status
Output Expand
Off
Off
Output Equations
Equation #1
Equation #2
Equations 1 & 2; C1, C2
((X-X) × X)/X = zero
((X-X) × X)/X = zero
0
Frequency Sweep
Start Frequency
Stop Frequency
Step Size
Time/Step
Armed
0.000 Hz
0.000 Hz
0.000 Hz
0.000 s
No
D-1
Appendix D, DEFAULT SETTINGS
Law
Logarithmic
Amplitude Sweep
Start Amplitude
Stop Amplitude
Step Size
Time/Step
Armed
0.000 V
0.000 V
0.000 V
0.000 s
No
Configuration
Operating mode
Display screen
Noise Measurement Mode
Noise Buffer Length
Single Reference
Turned on
OFF
4 seconds
Curve Buffer
Curve Mode
Time/Point
Length
Curve Start Trigger
Curve Stop Trigger
Standard
10 ms
100,000
Internal
Internal
Curve Select
Selected curve
X
ADC Menu
ADC Trigger Mode
Time Per Point
Internal
1 ms
DACs
USER DAC1 - USER DAC 4
DAC1
DAC2
DAC3
DAC4
0.000 V
X%
Y%
User setting
User setting
Digital Port
D0 to D7 direction
D0 to D7 status
All configured as outputs
Logic zero
The Auto-Default function on the Rear Panel web control page and the ADF 0
computer command set the model 7230's controls and output displays as above, and
in addition sets the communications interface parameters as follows:RS232 Settings
Baud rate
Data bits
Delimiter
Character echo
Parity
Prompt character
19,200
7 + 1 Parity
, (044)
On
Even
On
Ethernet Settings
(Note: These only apply if the CONF1G switch 1 is set to position "0")
IP Address
169.254.150.230
Subnet Mask
255.255.255.000
Default Gateway
000.000.000.000
D-2
Alphabetical Listing of Commands
?
Appendix E
Fast Data Transfer command
The ? command offers a method of reading a combination of instrument outputs
which are sampled at the same time, thereby ensuring that they are correlated.
The response to the ? command is the output(s), expressed in floating point mode,
specified by the present setting of the Curve Buffer Define (CBD) command (see
section 6.7.09) and separated by delimiter character(s) defined by the DD command.
Hence for example, if CBD is set to 19, the response to the ? command will be:
<X output, in floating point mode><delimiter>
<Y output, in floating point mode><terminator>
ACGAIN [n]
AC Gain control
Sets the gain of the signal channel amplifier according to the following table:n
0
1
2
3
4
5
6
7
AC Gain
0 dB
6 dB
12 dB
18 dB
24 dB
30 dB
36 dB
42 dB
ADC[.] n
n
8
9
10
11
12
13
14
15
AC Gain
48 dB
54 dB
60 dB
66 dB
72 dB
78 dB
84 dB
90 dB
Read auxiliary analog-to-digital inputs
The response for ADC1 to ADC4 (n = 1 to 4 respectively) in fixed point mode is an
integer in the range -11000 to +11000, corresponding to voltages from -11.000 V to
+11.000 V, and in floating point mode it is in volts.
ADF n
Auto Default
The ADF command performs an auto-default operation according to the following
table:
n
0
1
Significance
All instrument settings are returned to their factory default values
All instrument settings, with the exception of the communications settings, are
returned to their factory default values
NOTE: If the ADF 0 command is used when the communications settings are at
values other than their default settings, then communication will be lost.
AMCENTERV[.] [n]
Oscillator amplitude modulation center voltage command
The value of n sets the oscillator amplitude modulation center voltage; in fixed point
mode n is an integer in the range -10000 to +10000, corresponding to voltages from 10.000 V to +10.000 V, and in floating point mode it is in volts.
NOTE: The span voltage plus the center voltage cannot exceed ±10.000 V
AMDEPTH [n]
Oscillator amplitude modulation dept control
The value of n sets the oscillator amplitude modulation depth in percent, from 0 to
100
E-1
Appendix E, ALPHABETICAL LISTING OF COMMANDS
AMFILTER [n]
Oscillator amplitude modulation filter control command
The value of n sets the oscillator amplitude modulation voltage low-pass filter control
in the range 0 to 10. The value of 0 gives the widest bandwidth for this filter, with the
value of 10 the lowest.
AMSOURCE [n] Oscillator amplitude modulation voltage source command
The value of n selects the source of signal used to modulate the oscillator amplitude
in accordance with the following table:
n
0
1
Function
ADC 1 input
Signal from external reference channel.
AMVSPAN[.] [n] Oscillator amplitude modulation voltage span command
The value of n sets the oscillator amplitude modulation span voltage; in fixed point
mode n is an integer in the range 0 to +10000, corresponding to a range from
±0.000 V to ±10.000 V, and in floating point mode it is in volts.
NOTE: The span voltage plus the center voltage cannot exceed ±10.000 V
AQN
Auto-Phase (auto quadrature null)
The instrument adjusts the reference phase to maximize the X channel output and
minimize the Y channel output signals.
AS
Perform an Auto-Sensitivity operation
The instrument adjusts its full-scale sensitivity so that the magnitude output lies
between 30% and 90% of full-scale.
ASM
Perform an Auto-Measure operation
The instrument adjusts its full-scale sensitivity so that the magnitude output lies
between 30% and 90% of full-scale, and then performs an auto-phase operation to
maximize the X channel output and minimize the Y channel output.
ASTART[.] [n]
Oscillator amplitude sweep start amplitude
Sets the start amplitude for a subsequent sweep of the internal oscillator amplitude, in
the range 0 to 5.000 V
In fixed point mode, n is in microvolts rms, and in floating point mode n is in volts
rms
ASTEP[.] [n]
Oscillator amplitude sweep step size
Sets the amplitude step size for a subsequent sweep of the internal oscillator
amplitude, in the range 0 to 5.000 V
In fixed point mode, n is in microvolts rms and in floating point mode n is in volts
rms
ASTOP[.] [n]
Oscillator amplitude sweep stop amplitude
Sets the stop amplitude for a subsequent sweep of the internal oscillator amplitude, in
the range 0 to 5.000 V
In fixed point mode, n is in microvolts rms and in floating point mode n is in volts
rms
E-2
Appendix E, ALPHABETICAL LISTING OF COMMANDS
AUTOMATIC [n] AC Gain automatic control
n
0
1
AXO
Status
AC Gain is under manual control, either using the Main Controls panel or the
ACGAIN command
Automatic AC Gain control is activated, with the gain being adjusted according
to the full-scale sensitivity setting
Auto-Offset
The X and Y channel output offsets are turned on and set to levels giving zero X and
Y channel outputs. Any changes in the input signal then appear as changes about zero
in the outputs.
BYTE [n]
Digital port output control
The value of n, in the range 0 to 255, determines the bits to be output on those lines
of the rear panel digital port that are configured as outputs. Hence, for example, if
PORTDIR = 255 and BYTE = 0, all outputs are low, and when BYTE = 255, all are
high.
C1 n1 [n2]
Equation Constant C1
The value of n2 sets the value of constant C1 for equation #1 (n1 = 1) or equation #2
(n1 = 2) in the range -30,000 to +30,000
C2 n1 [n2]
Equation Constant C2
The value of n2 sets the value of constant C2 for equation #1 (n1 = 1) or equation #2
(n1 = 2) in the range -30,000 to +30,000
CBD [n]
Curve buffer define for Standard Mode Buffer
Defines which data outputs are stored in the standard curve mode curve buffer when
subsequent TD (take data), TDT (take data triggered) or TDC (take data
continuously) commands are issued. Up to 17 (or 22 in dual reference and dual
harmonic modes) curves, or outputs, may be acquired, as specified by the CBD
parameter.
The CBD parameter is an integer between 1 and 131,071, being the decimal
equivalent of a 17-bit binary word. In either of the dual reference modes, it is an
integer between 1 and 4,194,303, being the decimal equivalent of a 22-bit binary
number. When a given bit is asserted, the corresponding output is selected for
storage. When a bit is negated, the output is not stored. The bit function and range for
each output are shown in the table below:
Bit Decimal value
0*
1
1*
2
2*
4
3*
8
4
16
5*
6*
7*
8*
9*
32
64
128
256
512
Output and range
X Output (±10000 FS)
Y Output (±10000 FS)
Magnitude Output (0 to +10000 FS)
Phase (±18000 = ±180°)
Sensitivity setting (1 to 27) + IMODE (0, 1, 2, 3 =
0, 32, 64, 128)
Noise (0 to +10000 FS)
Ratio (±10000 FS)
Log ratio (-3000 to +2000)
ADC1 (±10000 = ±10.0 V)
ADC2 (±10000 = ±10.0 V)
E-3
Appendix E, ALPHABETICAL LISTING OF COMMANDS
Bit Decimal value
10*
1024
11*
2048
12*
4096
13*
8192
14
16384
15
32768
16
65536
Dual modes only:17
131072
18
262144
19
524288
20
1048576
21
2097152
Output and range
ADC3 (±10000 = ±10.0 V)
ADC4 (±10000 = ±10.0 V)
DAC1 (±10000 = ±10.0 V)
DAC2 (±10000 = ±10.0 V)
EVENT variable (0 to 32767)
Reference Frequency bits 0 to 15 (millihertz)
Reference frequency bits 16 to 31 (millihertz)
X2 Output (±10000 FS)
Y2 Output (±10000 FS)
Magnitude2 Output (0 to +10000 FS)
Phase2 Output (±18000 = ±180°)
Sensitivity2 setting (1 to 27) + IMODE
(0, 1, 2 = 0, 32, 64)
100,000 points are available for data storage in the standard curve buffer mode,,
shared equally between the specified curves. For example, if 16 outputs are stored
then the maximum number of storage points would be 6250 (i.e. 100000/16). The
only exception to this rule is that the Frequency curve (curves 15 and 16) occupies
the equivalent of any two other curves. The LEN command sets the actual curve
length, which cannot therefore be longer than 100000 divided by the number of
curves selected. If more curves are requested than can be stored with the current
buffer length, then the buffer length will be automatically reduced. Its actual length
can of course be determined by sending the LEN command without a parameter.
The reason why bit 4 and, for dual reference modes, bit 21, which store both the
sensitivity and the IMODE setting, are needed, is to allow the instrument to transfer
the acquired curves to the computer in floating point mode. Without this information,
the unit would not be able to determine the correct calibration to apply.
Note that the CBD command directly determines the allowable parameters for the
DC, DCB and DCT commands. It also interacts with the LEN command and affects
the values reported by the M command.
Since the reference frequency requires 32-bit wide data points, it occupies two curve
positions. For ease of use, if bit 15 is selected for storage then bit 16 will be
automatically selected as well, and vice-versa.
NOTE: At least one of the curves selected for storage in the curve buffer must be
chosen from those marked with an asterisk(*) in the above table.
CH n1 [n2]
DAC analog output control
Defines what outputs appear on the DAC1, DAC2, DAC3 and DAC4 connectors on
the rear panel.
n1 is compulsory and is 1 for DAC1, 2 for DAC2, 3 for DAC3, or 4 for DAC4
n2
0
1
2
3
4
5
E-4
Signal (DAC1)
X1% (2.5 V FS)
Noise % (2.5 V FS)
Ratio: (10 × X1%/ADC 1)
Log Ratio: log10 (10 × X1%/ADC1)
Equation 1
Equation 2
Appendix E, ALPHABETICAL LISTING OF COMMANDS
n2
6
7
8
Signal (DAC1)
User DAC1
Main signal channel ADC output (digital signal monitor 1)
Magnitude2 % (2.5 V FS) (dual mode only)
n2
0
1
2
3
4
5
6
7
8
Signal (DAC2)
Y1 % (2.5 V FS)
Noise % (2.5 V FS)
Ratio: (10 × X1%/ADC 1)
Log Ratio: log10 (10 × X1%/ADC1)
Equation 1
Equation 2
User DAC2
Ext ADC1 monitor
Phase2 : +9 V = +180°, -9 V = -180° (dual mode only)
n2
0
1
2
3
4
5
6
7
8
Signal (DAC3)
Magnitude1 % (2.5 V FS)
Noise % (2.5 V FS)
Ratio: (10 × X1%/ADC 1)
Log Ratio: log10 (10 × X1%/ADC1)
Equation 1
Equation 2
User DAC3
Input to second demodulator (digital signal monitor 2)
X2 % (2.5 V FS) (dual mode only)
n2
0
1
2
3
4
5
6
7
8
Signal (DAC4)
Phase1: +9 V = +180°, -9 V = -180°
Noise % (2.5 V FS)
Ratio: (10 × X1%/ADC 1)
Log Ratio: log10 (10 × X1%/ADC1)
Equation 1
Equation 2
User DAC4
Synchronous oscillator
Y2 % (2.5 V FS) (dual mode only)
NOTE: n2 = 1 is only permitted if the noise measurement mode is on
(NOISEMODE 1) or if the present settings of output filter slope and time constant
are within the permitted range and the synchronous time constant control is off.
CMODE [n]
Curve buffer mode
The value of n sets the curve buffer acquisition mode in accordance with the
following table:
n
0
1
mode
Standard
Fast
DAC[.] n1 [n2]
Set user DAC output voltage controls
The first parameter n1, which specifies the DAC, is compulsory and is either 1, 2, 3 or
4.
The value of n2 specifies the voltage to be output.
E-5
Appendix E, ALPHABETICAL LISTING OF COMMANDS
In fixed point mode it is an integer in the range -10000 to +10000, corresponding to
voltages from -10.000 V to +10.000 V, and in floating point mode it is in volts.
DATE
Last calibration date
The response is a six digit number giving the date of the last calibration where the
first two digits are the day, the second two digits are the month and the last two digits
are the year (in the 21st century).
DC[.] n
Dump acquired curve(s) to computer
The operation of this command depends on whether data has been stored into the
Standard or Fast Mode curve buffers.
Standard Mode
In fixed point mode, causes a stored curve to be dumped via the computer interface in
decimal format.
In floating point mode the SEN curve (bit 4 in CBD) must have been stored if one or
more of the following outputs are required in order that the lock-in amplifier can
perform the necessary conversion from %FS to volts or amps:- X, Y, Magnitude,
Noise. Similarly, if the dual reference or harmonic modes are active then the SEN2
curve (bit 21 in CBD) must have been stored in order to perform a similar conversion
from %FS to volts or amps for X2, Y2 and Magnitude2.
One curve at a time is transferred. The value of n is the bit number of the required
curve, which must have been stored by the most recent CBD command. Hence n can
range from 0 to 16, or 0 to 21 if a dual mode is active. If for example CBD 5 had
been sent, equivalent to asserting bits 0 and 2, then the X and Magnitude outputs
would be stored. The permitted values of n would therefore be 0 and 2, so that DC 0
would transfer the X channel output curve and DC 2 the Magnitude curve.
NOTE: When transferring the Frequency curve, which is saved when bit 15 in the
CBD parameter is asserted, the instrument automatically reads the data for each
stored point in both frequency curves (i.e. the lower and upper 16 bits) and sends it
as a single data point.
Fast Mode
Only fixed point mode is supported. One curve at a time is transferred, with the
selected curve being dumped via the computer interface in decimal format.
The value of n defines the curve to be transferred according to the following table:
n
0
1
2
3
4
Output and range
X Output (±10000 FS)
Y Output (±10000 FS)
Main signal channel ADC output (digital signal monitor 1
ADC1 (±10000 = ±10.0 V)
ADC2 (±10000 = ±10.0 V)
Dual modes only:5
X2 Output (±10000 FS)
6
Y2 Output (±10000 FS)
7
Input to second demodulator (digital signal monitor 2)
The computer program's subroutine which reads the responses to the DC command
needs to run a program loop that continues until all the data has been transferred.
E-6
Appendix E, ALPHABETICAL LISTING OF COMMANDS
DCCOUPLE [n]
Input coupling control
The value of n sets the input coupling mode according to the following table:
n Coupling mode
0 AC coupled
1 DC coupled
DCB n
Dump acquired curve(s) to computer in binary format
The operation of this command depends on whether data has been stored into the
Standard or Fast Mode curve buffers.
Standard Mode
This command causes a stored curve to be dumped via the computer interface in
binary format, using two bytes per point. All curves other than the lower 16-bits of
the reference frequency curve (curve 15) use 16-bit 2’s complement encoding, and all
data points are sent with the MSB first. The number of data bytes sent is therefore
equal to twice the current curve length. Each point is sent in fixed point mode, there
being no floating point version of the command, and hence if floating point values
are required the user may need to additionally store and read the Sensitivity curve
and then perform the correction in his own software. In order to achieve the
maximum transfer rate, no terminators are used within the transmission, although the
response is terminated normally at the end.
One curve at a time is transferred. The value of n is the bit number of the required
curve, which must have been stored by the most recent CBD command. Hence n can
range from 0 to 16 in Single Reference Mode, and 0 to 21 in the dual modes. If for
example CBD 5 had been sent, equivalent to asserting bits 0 and 2, then the X and
Magnitude outputs would be stored. The permitted values of n would therefore be 0
and 2, so that DCB 0 would transfer the X channel output curve and DCB 2 the
Magnitude curve.
Curves 15 and 16 store the reference frequency in millihertz. When using the DCB
command (although not with the other curve transfer commands), both curves need to
be transferred separately. They should then be converted to two arrays of integer
values, allowing for the fact that the data points in curve 15 are unsigned 16-bit
values, while those in curve 16 are signed 2’s complement 16-bit values (although in
practice they are never negative). Finally they should be assembled into a single
curve using the following algorithm:
Reference Frequency = (65536 × value in Curve 16) + (value in Curve 15)
The computer program's subroutine which reads the responses to the DCB command
needs to be able to handle the potentially very large data blocks (200 k bytes in the
case of one 100 k curve) that can be generated.
NOTE: When using RS232 communications, the interface must be set to use 8 data
bit transmission.
Fast Mode
One curve at a time is transferred, with the selected curve being dumped via the
computer interface in binary format, using two bytes per point. Data is sent using 16bit 2’s complement encoding, with the MSB sent first.
The value of n defines the curve to be transferred according to the following table:
E-7
Appendix E, ALPHABETICAL LISTING OF COMMANDS
n
0
1
2
3
4
Output and range
X Output (±10000 FS)
Y Output (±10000 FS)
Main signal channel ADC output (digital signal monitor 1
ADC1 (±10000 = ±10.0 V)
ADC2 (±10000 = ±10.0 V)
Dual modes only:5
X2 Output (±10000 FS)
6
Y2 Output (±10000 FS)
7
Input to second demodulator (digital signal monitor 2)
The computer program's subroutine which reads the responses to the DC command
needs to run a program loop that continues until all the data has been transferred.
NOTE: When using RS232 communications, the interface must be set to use 8 data
bit transmission.
DCT n
Dump acquired curves to computer in tabular format
NOTE: This command is only available when the curve buffer is set to Standard
Mode.
This command is similar to the DC command described above, but allows transfer of
several curves at a time and only operates in fixed point mode. Stored curve(s) are
transferred via the computer interface in decimal format.
In single reference mode, the DCT parameter is an integer between 1 and 131,071,
being the decimal equivalent of a 17-bit binary number. In either of the dual
reference modes, it is an integer between 1 and 4,194,303, being the decimal
equivalent of a 22-bit binary number. When a given bit in the number is asserted, the
corresponding curve is selected for transfer. When a bit is negated, the curve is not
transferred. The bit corresponding to each curve is shown in the table below:
Bit Decimal value
0
1
1
2
2
4
3
8
4
16
5
6
7
8
9
10
11
12
13
14
15
E-8
32
64
128
256
512
1024
2048
4096
8192
16384
32768
Output and range
X Output (±10000 FS)
Y Output (±10000 FS)
Magnitude Output (0 to +10000 FS)
Phase (±18000 = ±180°)
Sensitivity setting (1 to 27) + IMODE (0, 1, 2, 3 =
0, 32, 64, 128)
Noise (0 to +10000 FS)
Ratio (±10000 FS)
Log ratio (-3000 to +2000)
ADC1 (±10000 = ±10.0 V)
ADC2 (±10000 = ±10.0 V)
ADC3 (±10000 = ±10.0 V)
ADC4 (±10000 = ±10.0 V)
DAC1 (±10000 = ±10.0 V)
DAC2 (±10000 = ±10.0 V)
EVENT variable (0 to 32767)
Reference frequency (millihertz)
Appendix E, ALPHABETICAL LISTING OF COMMANDS
Dual modes only:Bit Decimal value
17
131072
18
262144
19
524288
20
1048576
21
2097152
Output and range
X2 Output (±10000 FS)
Y2 Output (±10000 FS)
Magnitude2 Output (0 to +10000 FS)
Phase2 Output (±18000 = ±180°)
Sensitivity2 setting (1 to 27) + IMODE
(0, 1, 2 = 0, 32, 64)
The values of the selected curves at the same sample point are transferred as a group
in the order of the above table, separated by the chosen delimiter character and
terminated with the selected terminator. This continues until all the points have been
transferred.
NOTE: When transferring the Frequency curve, which is saved when bit 15 in the
CBD parameter is asserted, the instrument automatically reads the data for each
stored point in both frequency curves (i.e. the lower and upper 16 bits) and sends it
as a single data point.
DD [n]
Define delimiter control
The value of n, which can be set to 13 or from 32 to 125, determines the ASCII value
of the character sent by the lock-in amplifier to separate two numeric values in a twovalue response, such as that generated by the MP (magnitude and phase) command.
DEFEQU [n1 n2 n3 n4 n5 n6]
Define user equation
The DEFEQU command is used to define the user equations, which take the
following form:
⎛ (A ± B) × C ⎞
Equation = ⎜
⎟
⎠
⎝
D
Parameter n1 is used to specify the equation to be modified, and is either 1 for
Equation 1 or 2 for Equation 2.
Parameter n3 is used to set the addition/subtraction operator in the numerator
according to the following table:n3 Operator
0 Subtraction
1 Addition
The parameters n2, n4, n5 and n6 specify the variables A, B, C and D respectively
according to the following table:
n
0
1
2
3
4
n
5
6
7
8
Variable
X or X1
Y or Y1
MAG or MAG1
PHA or PHA1
ADC1
Variable
ADC2
ADC3
ADC4
C1
Range
±30000
±30000
0 to 30000
±18000
±10000
Range
±10000
±10000
±10000
0 to 100000
E-9
Appendix E, ALPHABETICAL LISTING OF COMMANDS
n
9
10
11
12
13
Variable
C2
0
1
FRQ
OSC
Range
0 to 100000
zero
unity
0 to 2000000000 (i.e. reference frequency in mHz)*
0 to 2000000000 (i.e. oscillator frequency in mHz)*
Dual modes only:14 X2
15 Y2
16 MAG2
17 PHA2
±30000
±30000
0 to 30000
±18000
*Parameter n5 is the only one that can be set to values of 12 or 13.
DEMOD2SRC [n] Second stage demodulator signal source
In the dual reference mode, the value of n sets the source of the signal for the second
stage demodulators according to the following table:
n
0
1
2
Signal source
Main signal channel ADC (i.e. both demodulators are fed the same signal)
ADC1 - rear panel auxiliary ADC input
Demodulator 1 X channel output - this is the Tandem demodulation mode
ENBW[.]
Equivalent noise bandwidth
In fixed point mode, reports the equivalent noise bandwidth of the output low-pass
filters at the current time constant setting in microhertz.
In floating point mode, reports the equivalent noise bandwidth of the output low-pass
filters at the current time constant setting in hertz.
EQU n
Output result of equation #1 or equation #2
The value returned is the output of the user equation #1 (n = 1) or equation #2 (n =
2), where the equations are defined using the Output equations control panel (see
section 5.3.27). The possible range is ±2,147,483,647 (signed 32-bit integer).
EVENT [n]
Event marker control
During a curve acquisition into the standard curve buffer, if bit 13 in the CBD
command has been asserted, the lock-in amplifier stores the value of the Event
variable at each sample point. This can be used as a marker indicating the point at
which an experimental parameter was changed. The EVENT command is used to set
this variable to any value between 0 and 32767.
EX [n]
Output expansion control
Expands X and/or Y channel outputs by a factor of 10. This changes the analog
outputs full-scale to ±10% if X or Y selected. The value of n has the following
significance:
n
0
1
2
3
E-10
Expand mode
Off
Expand X
Expand Y
Expand X and Y
Appendix E, ALPHABETICAL LISTING OF COMMANDS
FASTMODE [n] Output Filter Mode Control
The value of n sets the output filter mode control according to the following table:
n
0
1
Function
Fast mode off
Fast mode on
When the fast analog output mode is turned off, the available output filter time
constant is restricted to 5 ms or greater, but all four filter slopes are available (i.e. 6,
12, 18 and 24 dB/octave). Conversely, when the mode is turned on, time constants
down to 10 µs can be selected, but the slope is limited to either 6 or 12 dB/octave.
FET [n] ]
FET input selection
The value of n control the input device used at the signal input according to the
following table:
n
0
1
Input device
Bipolar
FET
FLOAT [n]
n
0
1
Input connector shield float/ground control
Selection
Ground
Float (connected to ground via a 1 kΩ resistor)
FMCENTERF[.] [n]
Oscillator frequency modulation center frequency command
In fixed point mode n sets the oscillator frequency modulation center frequency in
mHz. The range of n is 0 to 120000000 or 250000000 representing 0 to 120.0 or
250.0 kHz; in floating point mode n sets the center frequency in the range 0 to 1.2E5
or 2.5E5
Note: The span frequency plus the center frequency cannot exceed 120.0 or
250.0kHz; the center frequency must also be greater than the span frequency.
FMCENTERV[.] [n]
Oscillator frequency modulation center voltage command
The value of n sets the oscillator frequency modulation center voltage; in fixed point
mode n is an integer in the range -10000 to +10000, corresponding to voltages from 10.000 V to +10.000 V, and in floating point mode it is in volts.
NOTE: The span voltage plus the center voltage cannot exceed ±10.000 V
FMFILTER [n]
Oscillator frequency modulation filter control command
The value of n sets the oscillator frequency modulation voltage low-pass filter control
in the range 0 to 10. The value of 0 gives the widest bandwidth for this filter, with the
value of 10 the lowest.
FMSPANF[.] [n] Oscillator frequency modulation span frequency command
In fixed point mode n sets the oscillator frequency-modulation span frequency in
millihertz. The range of n is 0 to 60000000 or 125000000 representing 0 to ± 60 kHz
or 125 kHz; in floating point mode n sets the span frequency in the range 0 to 6.0E4
or 1.25E5.
Note: The center frequency ± the span frequency must not exceed the frequency
limits of the oscillator (0 to 120 or 250 kHz). Hence the center frequency plus the
E-11
Appendix E, ALPHABETICAL LISTING OF COMMANDS
span frequency cannot exceed 120.0 or 250.0 kHz and the center frequency must
be greater than or equal to the span frequency. For example, with an instrument
fitted with the 7230/99 upper frequency extension option and a 125 kHz center
frequency the maximum span frequency is ± 125 kHz; at 10k Hz center frequency
the maximum span frequency is ± 10 kHz; at 240 kHz center frequency the
maximum span frequency is also ± 10 kHz. When setting the center frequency and
span frequency under computer control it is recommended to first set the span
frequency to zero followed by the center frequency to the required value and finally
the span frequency to the required value. This will avoid potential problems with
the new center frequency being rejected because it is not a legal value when
compared with the old span frequency.
FMVSPAN[.] [n] Oscillator frequency modulation voltage span command
The value of n sets the oscillator frequency modulation span voltage; in fixed point
mode n is an integer in the range 0 to +10000, corresponding to a range from
±0.000 V to ±10.000 V, and in floating point mode it is in volts.
NOTE: The span voltage plus the center voltage cannot exceed ±10.000 V
FRQ[.]
Reference frequency meter
If the lock-in amplifier is in the external reference source modes, the FRQ command
causes the lock-in amplifier to respond with 0 if the reference channel is unlocked, or
with the reference input frequency if it is locked.
If the lock-in amplifier is in the internal reference source mode, it responds with the
frequency of the internal oscillator.
In fixed point mode the frequency is in mHz, and in floating point mode the
frequency is in Hz.
FSTART[.] [n]
Oscillator frequency sweep start frequency
Sets the start frequency for a subsequent sweep of the internal oscillator frequency, in
the range 0 to 120 or 250 kHz.
In fixed point mode, n is in millihertz, and in floating point mode n is in hertz.
FSTEP[.] [n1 n2]
Oscillator frequency sweep step size and type
The frequency may be swept either linearly or logarithmically, as specified by
parameter n2. The step size is specified by parameter n1.
Log sweep n2 = 0
In fixed point mode, n1 is the step size in thousandths of a percent.
In floating point mode n1 is in percent. The range of n1 is 0 to 100.000%
Linear sweep n2 = 1
In fixed point mode, n1 is the step size in millihertz.
In floating point mode n1 is in hertz. The range of n1 is 0 to 120 or 250 kHz
Linear seek sweep n2 = 2
In fixed point mode, n1 is the step size in millihertz.
In floating point mode n1 is in hertz. The range of n1 is 0 to 120 or 250 kHz
The seek sweep mode automatically stops when the signal magnitude exceeds
50% of full scale. This mode is most commonly used when setting up the virtual
reference mode.
E-12
Appendix E, ALPHABETICAL LISTING OF COMMANDS
FSTOP[.] [n]
Oscillator frequency sweep stop frequency
Sets the stop frequency for a subsequent sweep of the internal oscillator frequency, in
the range 0 to 120 or 250 kHz.
In fixed point mode, n is in millihertz and in floating point mode n is in hertz.
GWADDR [n1 n2 n3 n4] Ethernet Gateway Address
When this command is sent without parameters, the instrument responds with the
current gateway address e.g. 169.254.0.1
When sent with the four parameters, the command sets the gateway address that will
be used when the model 7230 is set to static IP address mode (via the rear panel
Config Switch 2, see section 4.2.07)
The parameters are separated by a space character and not by a dot, e.g.
GWADDR 169 254 0 1
sets the gateway address 169.254.0.1
Note that the setting can be overridden if the IP address is set using the IPADDR
command.
HC
Halt curve acquisition
Halts curve acquisition in progress. It is effective during both single (data acquisition
initiated by TD command) and continuous (data acquisition initiated by TDC
command) curve acquisitions. The curve may be restarted by means of the TD, TDT
or TDC command, as appropriate. If an oscillator frequency and/or amplitude sweep
has been defined and linked to the curve buffer using the SWEEP command with a
parameter of 9, 10 or 100, then this sweep will be stopped as well.
ID
Identification
Causes the lock-in amplifier to respond with the number 7230.
IE [n]
Reference channel source control (Internal/External)
In Single Reference and Dual Harmonic mode, the value of n sets the reference input
mode according to the following table:
n
0
1
2
Selection
INT (internal)
EXT TTL (external front panel REF input)
EXT ANALOG (external front panel REF input)
In Dual Reference mode, the value of n sets the External channel reference input
mode according to the following table:
n
1
2
Selection
EXT TTL (external front panel REF input)
EXT ANALOG (external front panel REF input)
E-13
Appendix E, ALPHABETICAL LISTING OF COMMANDS
IMODE [n]
Current/Voltage mode input selector
The value of n sets the input mode according to the following table
n
0
1
2
Input mode
Current mode off - voltage mode input enabled
High bandwidth current mode enabled - connect signal to B (I) input connector
Low noise current mode enabled - connect signal to B (I) input connector
If n = 0 then the input configuration is determined by the VMODE command.
If n > 0 then current mode is enabled irrespective of the VMODE setting.
INT [n]
Internal Reference Channel Selection
This command is functional only in Dual Reference mode. The value of n sets the
reference channel that is operated in internal reference mode, and hence also the
external reference channel, according to the following table
n
1
2
Reference channel
Reference Channel 1 = Internal; Reference Channel 2 = External
Reference Channel 2 = Internal; Reference Channel 1 = External
Use the IE command with parameter values of 1 or 2 to select which input type
(analog or TTL) is active for the external reference channel.
IPADDR [n1 n2 n3 n4]
Ethernet IP Address
When this command is sent without parameters, the instrument responds with the
current IP address e.g. 169.254.0.10
When sent with the four parameters, the command sets the IP address that will be
used when the model 7230 is set to static IP address mode (via the rear panel Config
Switch 2, see section 4.2.07)
The parameters are separated by a space character and not by a dot, e.g.
IPADDR 169 254 0 10
sets the IP address to 169.254.0.10 Based on the IP address, this command will also
generate a default subnet mask and gateway address so if values other than the
defaults are required set the IP address before setting the subnet mask and gateway
address otherwise they will be overwritten.
IPLOCK
Restrict Ethernet Access
When this command is sent via the Ethernet interface, subsequent connection
requests and hence commands will only be accepted if sent from the same IP address,
preventing unauthorized access to the instrument.
IPUNLOCK
Remove Ethernet Access Restrictions
When this command is sent via the Ethernet interface, subsequent connection
requests and hence commands will be accepted from any computer on the same
network as the instrument.
LEN [n]
Curve length control
The value of n sets the curve buffer length in effect for data acquisition. In fast curve
buffer mode the maximum allowed value is 100,000; in standard mode it depends on
the number of curves requested using the CBD command, and a parameter error
results if the value given is too large. For this reason, in standard mode if the number
E-14
Appendix E, ALPHABETICAL LISTING OF COMMANDS
of points is to be increased and the number of curves to be stored is to be reduced
using the CBD command, then the CBD command should be issued first.
LF [n1 n2]
Signal channel line frequency rejection filter control
The LF command sets the mode and frequency of the line frequency rejection (notch)
filter according to the following tables:
n1
0
1
2
3
Selection
Off
Enable 50 or 60 Hz notch filter
Enable 100 or 120 Hz notch filter
Enable both filters
n2 Notch Filter Center Frequencies
0 60 Hz (and/or 120 Hz)
1 50 Hz (and/or 100 Hz)
LOCK
System lock control
Updates all frequency-dependent gain and phase correction parameters.
LR[.]
Log Ratio output
In integer mode, the LR command reports a number equivalent to
1000×log(X/ADC1) where X is the value that would be returned by the X command
and ADC1 is the value that would be returned by the ADC1 command. The response
range is -3000 to +2079
In floating point mode, the LR. command reports a number equivalent to
log(X/ADC1). The response range is -3.000 to +2.079
M
Curve acquisition status monitor
Causes the lock-in amplifier to respond with four values that provide information
concerning data acquisition, as follows:
First value, Curve Acquisition Status: a number with five possible values, defined
by the following table:
First Value
0
1
2
5
6
Significance
No curve activity in progress.
Acquisition via TD command in progress and running.
Acquisition via TDC command in progress and running.
Acquisition via TD command in progress but halted by HC
command.
Acquisition via TDC command in progress but halted by
HC command.
Second value, Number of Sweeps Acquired: This number is incremented each
time a TD is completed and each time a full cycle is completed on a TDC acquisition.
It is zeroed by the NC command and also whenever a CBD or LEN command is
applied without parameters.
Third value, Status Byte: The same as the response to the ST command. The
number returned is the decimal equivalent of the status byte and refers to the
previously applied command.
Fourth value, Number of Points Acquired: This number is incremented each time a
point is taken. It is zeroed by the NC command and whenever CBD or LEN is
E-15
Appendix E, ALPHABETICAL LISTING OF COMMANDS
applied without parameters.
MAG[.]
Magnitude
In fixed point mode causes the lock-in amplifier to respond with the magnitude value
in the range 0 to 30000, full-scale being 10000.
In floating point mode causes the lock-in amplifier to respond with the magnitude
value in the range +3.000E0 to +0.001E-9 volts or +3.000E-6 to +0.001E-15 amps.
MENABLE [n]
Oscillator amplitude/frequency modulation enable command
The value of n enables the oscillator amplitude modulation function in accordance
with the following table:
n
0
1
2
Function
Oscillator amplitude/frequency modulation disabled
Oscillator amplitude modulation enabled
Oscillator frequency modulation enabled
MP[.]
Magnitude, phase
This returns the MAG and PHA outputs separated by the defined delimiter.
N
Report overload byte
Causes the lock-in amplifier to respond with the overload byte, an integer between 0
and 255, which is the decimal equivalent of a binary number with the following bitsignificance:
Bit 0
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Bit 6
Bit 7
NAME
X channel output overload (> ±300 %FS)
Y channel output overload (> ±300 %FS)
X2 channel output overload (> ±300 %FS)
Y2 channel output overload (> ±300 %FS)
CH1 output overload
CH2 output overload
CH3 output overload
CH4 output overload
Set/Read Instrument Name
The NAME command allows the user to store an ASCII text string as “name” to help
identify the instrument. This is especially useful when there are several instruments
connected to the same Ethernet network, since it can be used as a more convenient
alternative to the serial number as an aid to identification.
When sent with a string of up to 64 characters as a parameter, the string will be
stored. When sent without characters the instrument will respond with the stored
string. For example:
NAME Optical absorption lab lock-in amplifier
will set the name to “Optical absorption lab lock-in amplifier”; sending NAME with
no parameters will return:
Optical absorption lab lock-in amplifier
NC
New curve
Initializes the curve storage memory and status variables. All record of previously
taken curves is removed.
E-16
Appendix E, ALPHABETICAL LISTING OF COMMANDS
NHZ.
Causes the lock-in amplifier to respond with the square root of the noise spectral
density measured at the Y channel output, expressed in volt/√Hz or amps/√Hz
referred to the input. This measurement assumes that the Y channel output is
Gaussian with zero mean. (Section 3.3.20). The command is only available in
floating point mode.
NN[.]
Noise output
In fixed point mode causes the lock-in amplifier to respond with the mean absolute
value of the Y channel output in the range 0 to 12000, full-scale being 10000. If the
mean value of the Y channel output is zero, this is a measure of the output noise.
In floating point mode causes the lock-in amplifier to respond in volts.
NNBUF [n]
Noise Buffer Length control
The value of n sets the noise buffer length according to the following table:
n
0
1
2
3
4
Function
Noise buffer off
1 second noise buffer
2 second noise buffer
3 second noise buffer
4 second noise buffer
NOISEMODE [n] Noise Measurement Mode control
The value of n sets the noise measurement mode according to the following table:
n
0
1
Function
Noise measurement mode off
Noise measurement mode on.
When the noise measurement mode is turned on, the output filter time constant is
automatically adjusted until it lies in the range 500 µs to 10 ms inclusive, the
synchronous time constant control is turned off, the fast analog output mode is turned
on (FASTMODE 1), and the output filter slope is set to 12 dB/octave if it had
previously been 18 or 24 dB/octave.
OA[.] [n]
Oscillator amplitude control
microvolts rms. The range of n is 0 to 5000000 representing 0 V to 5 V rms.
In floating point mode n sets the amplitude in volts.
OF[.] [n]
Oscillator frequency control
In fixed point mode n sets the oscillator frequency in mHz. The range of n is 0 to
120000000 or 250000000 representing 0 to 120 kHz or 250 kHz.
In floating point mode n sets the oscillator frequency in Hz. The range of n is 0 to
1.2E5 or 2.5E5
PHA[.]
Signal phase
In fixed point mode causes the lock-in amplifier to respond with the signal phase in
centidegrees, in the range ±18000.
In floating point mode causes the lock-in amplifier to respond with the signal phase
in degrees.
E-17
Appendix E, ALPHABETICAL LISTING OF COMMANDS
PORTDIR [n]
Digital port direction control
The value of n determines which of the eight lines on the digital port are configured
as inputs and which as outputs. The parameter n is a decimal number whose bit-wise
interpretation defines whether the corresponding line is an input or output. The line is
an input if the corresponding bit is a “1”. For example:
n
0
1
2
4
8
16
32
64
128
255
status
All lines configured as inputs
D0 = output, D1 - D7 = inputs
D1 = output, D0 and D2 - D7 = inputs
D2 = output, D0 - D1 and D3 - D7 = inputs
D3 = output, D0 - D2 and D4 - D7 = inputs
D4 = output, D0 - D3 and D5 - D7 = inputs
D5 = output, D0 - D4 and D6 - D7 = inputs
D6 = output, D0 - D5 and D7 = inputs
D7 = output, D0 - D6 inputs
All lines configured as outputs
READBYTE
Read digital port input
The response to the READBYTE command is an integer between 0 and 255
representing the binary value of all eight lines of the instrument rear panel digital
port. Hence, for example, if PORTDIR = 0 and the response to READBYTE is 255,
then all lines are high, and if the response to READBYTE is 0, then all lines are low.
Note that because the command does not differentiate between whether a line is
configured as an input or output, it can be used as a single command to determine the
present status of all eight lines, both inputs and outputs, of the port.
REFMODE [n]
Reference mode selector
The value of n sets the reference mode of the instrument according to the following
table:
n
0
1
2
Mode
Single Reference / Virtual Reference mode
Dual Harmonic mode
Dual Reference mode
NOTE: When in either of the dual reference modes the command set changes to
accommodate the additional controls. These changes are detailed in section 6.7.14
REFMON [n]
Reference monitor control
The value of n sets the function of the rear panel TRIG OUT connector according to
the following table:
n
0
1
REFN [n]
Mode
Trig Out signal is generated by curve buffer triggering
Trig Out signal is a TTL signal at the reference frequency (i.e. it is a Reference
Monitor output)
Reference harmonic mode control
The value of n sets the reference channel to one of the NF modes, or restores it to the
default 1F mode. The value of n is in the range 1 to 127.
E-18
Appendix E, ALPHABETICAL LISTING OF COMMANDS
REFP[.] [n]
Reference phase control
In fixed point mode n sets the phase in millidegrees in the range ±360000.
In floating point mode n sets the phase in degrees.
RS [n1 [n2]]
n1
0
1
2
3
4
5
6
Set/read RS232 interface parameters
Baud rate (bits per second)
75
110
134.5
150
300
600
1200
n1
7
8
9
10
11
12
13
Baud rate (bits per second)
1800
2000
2400
4800
9600
19200
38400
The lowest five bits in n2 control the other RS232 parameters according to the
following table:
bit number
0
1
2
3
4
RT[.]
bit negated
data = 7 bits
no parity bit
even parity
echo disabled
prompt disabled
bit asserted
data = 8 bits
1 parity bit
odd parity
echo enabled
prompt enabled
Ratio output
In integer mode the RT command reports a number equivalent to 1000×X/ADC1
where X is the value that would be returned by the X command and ADC1 is the
value that would be returned by the ADC1 command.
In floating point mode the RT. command reports a number equivalent to X/ADC1.
SEN [n]
SEN.
Full-scale sensitivity control
The value of n sets the full-scale sensitivity according to the following table,
depending on the setting of the IMODE control:
n
3
4
5
6
7
8
9
10
11
12
13
14
15
16
full-scale sensitivity
IMODE=0
IMODE=1
10 nV
10 fA
20 nV
20 fA
50 nV
50 fA
100 nV
100 fA
200 nV
200 fA
500 nV
500 fA
1 µV
1 pA
2 µV
2 pA
5 µV
5 pA
10 µV
10 pA
20 µV
20 pA
50 µV
50 pA
100 µV
100 pA
200 µV
200 pA
IMODE=2
n/a
n/a
n/a
n/a
2 fA
5 fA
10 fA
20 fA
50 fA
100 fA
200 fA
500 fA
1 pA
2 pA
E-19
Appendix E, ALPHABETICAL LISTING OF COMMANDS
n
full-scale sensitivity
IMODE=0
IMODE=1
500 µV
500 pA
1 mV
1 nA
2 mV
2 nA
5 mV
5 nA
10 mV
10 nA
20 mV
20 nA
50 mV
50 nA
100 mV
100 nA
200 mV
200 nA
500 mV
500 nA
1V
1 µA
17
18
19
20
21
22
23
24
25
26
27
IMODE=2
5 pA
10 pA
20 pA
50 pA
100 pA
200 pA
500 pA
1 nA
2 nA
5 nA
10 nA
Floating point mode can only be used for reading the sensitivity, which is reported in
volts or amps. For example, if IMODE = 0 and the sensitivity is 1 mV the command
SEN would report 18 and the command SEN. would report +1.0E-03. If IMODE was
changed to 1, SEN would still report 18 but SEN. would report +1.0E-09
SLOPE [n]
Output low-pass filter slope (roll-off) control
When the fast analog output mode and noise measurement mode are turned off
(FASTMODE 0 and NOISEMODE 0), the selection is according to the following
table:
n
0
1
2
3
Slope
6 dB/octave
12 dB/octave
18 dB/octave
24 dB/octave
When:
a) The fast output filter mode is turned on, or
b) Noise measurement mode is turned ON (NOISEMODE 1)
the selection is according to the following table:
n
0
1
Slope
6 dB/octave
12 dB/octave
SNMASK [n1 n2 n3 n4] Ethernet Subnet Mask
When this command is sent without parameters, the instrument responds with the
current subnet mask e.g. 255.255.0.0
When sent with the four parameters, the command sets the subnet mask that will be
used when the model 7230 is set to static IP address mode (via the rear panel Config
Switch 2, see section 4.2.07)
The parameters are separated by a space character and not by a dot, e.g.
SNMASK 255 255 0 0
sets the subnet mask to 255.255.0.0
Note that the setting can be overridden if the IP address is set using the IPADDR
command.
E-20
Appendix E, ALPHABETICAL LISTING OF COMMANDS
SRATE[.] [n]
Oscillator frequency and amplitude sweep step rate
In fixed point mode, sets the sweep rate in milliseconds per step, and in floating point
mode sets the rate in seconds. The range of n is 1 to 1000000 (1 ms to 1000 s)
ST
Report status byte
Causes the lock-in amplifier to respond with the status byte, an integer between 0 and
255, which is the decimal equivalent of a binary number with the following bitsignificance:
Bit 0
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
Bit 6
Bit 7
STR [n]
Command complete
Invalid command
Command parameter error
Reference unlock
Output overload - read overload byte to determine location
New ADC values available after external trigger
Input overload
Data available
Storage interval control
Sets the time interval between successive points being acquired into the curve buffer.
n specifies the time interval in microseconds with a resolution of 1 µs. In fast curve
buffer mode, the shortest time that can be specified is 1 µs; in standard mode it is
1000 µs, or 1 ms
SWEEP [n]
n
0
1
2
3
5
6
7
9
10
11
Oscillator frequency and amplitude sweep control
Sweep status
Stop
Start/continue frequency sweep
Start/continue amplitude sweep
Start/continue frequency sweep and amplitude sweep
Pause frequency sweep
Pause amplitude sweep
Pause frequency sweep and amplitude sweep
Link frequency sweep to curve buffer acquisition
Link amplitude sweep to curve buffer acquisition
Link frequency and amplitude sweep to curve buffer acquisition
This command is used to start or stop the internal oscillator frequency or amplitude
sweep, or to specify that the sweep should be linked to the curve buffer data
acquisition.
In the normal mode, when a frequency and/or amplitude sweep has been defined,
applying SWEEP with a parameter of 1, 2, or 3 will start it. The sweep can be paused
using the command with the correct value of n for the sweep in progress. For
example, if a frequency sweep is started using SWEEP 1 then it can only be paused
by sending SWEEP 5. Similarly, it can only be continued by sending SWEEP 1. The
command SWEEP 0 will, however, stop either or both types of sweep.
When n is equal to 9, 10 or 11 the instrument is set to link the oscillator frequency
and/or amplitude sweeps to the curve buffer. The SWEEP command continues to
function as a write/read command except when the curve buffer acquisition is
actually running. In such cases, the SWEEP command changes to read-only and will
only report values of 9, 10 or 11, indicating what type of linking is active. The sweep
E-21
Appendix E, ALPHABETICAL LISTING OF COMMANDS
can then only be stopped by stopping the curve buffer, using the HC command.
However, the user can still determine the progress of the sweep using the curve
buffer monitor “M” command and the OF and/or OA (oscillator frequency and
amplitude) commands.
SYNC [n]
n
0
1
TADC [n]
Synchronous time constant control
Effect
Synchronous time constant disabled
Synchronous time constant enabled
Auxiliary analog-to-digital input trigger mode
The value of n sets the trigger modes for the auxiliary ADC inputs according to the
following table:
n
0
1
2
3
TC [n]
TC.
Trigger Mode
Internal (1 kHz)
External - apply trigger to ADC TRIG IN connector
Burst ADC1 (5 µs per point, only ADC1 is converted)
Burst ADC1 & ADC2
Filter time constant control
The value of n sets the output filter time constant in accordance with the following
table:
n
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
NOISEMODE
=0
NOISEMODE
=1
time constant
10 µs
20 µs
50 µs
100 µs
200 µs
500 µs
1 ms
2 ms
5 ms
10 ms
20 ms
50 ms
100 ms
200 ms
500 ms
1s
time constant
N/A
N/A
N/A
N/A
N/A
500 µs
1 ms
2 ms
5 ms
10 ms
N/A
N/A
N/A
N/A
N/A
N/A
n
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
NOISEMODE
=0
NOISEMODE
=1
time constant
2s
5s
10 s
20 s
50 s
100 s
200 s
500 s
1 ks
2 ks
5 ks
10 ks
20 ks
50 ks
100 ks
time constant
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A means that n is an illegal value under these conditions.
The TC. command is only used for reading the time constant, and reports the current
setting in seconds. Hence if a TC 12 command were sent and the noise measurement
mode was turned off, TC would report 12 and TC. would report 1.0E-01, i.e. 0.1 s or
100 ms.
E-22
Appendix E, ALPHABETICAL LISTING OF COMMANDS
TD
Take data
Initiates data acquisition. Acquisition starts at the current position in the curve buffer
and continues at the rate set by the STR command until the buffer is full. If an
oscillator frequency and/or amplitude sweep has been defined and linked to the curve
buffer using the SWEEP command with a parameter of 9, 10 or 11, then this sweep
will be started as well.
TDC n
Take data continuously
Initiates data acquisition. Acquisition starts at the current position in the curve buffer
and continues at the rate set by the STR command until halted by an HC command or
on receipt of a trigger at the TRIG in connector, in accordance with the following
table:
n
0
1
2
Start condition
On command
On command
On command
Stop condition
On HC command
Ext rising edge
Ext falling edge
Note also that if sent without a parameter the command functions as if TDT 0 had
been sent.
The buffer is circular in the sense that when it has been filled, new data overwrites
earlier points.
TDT n
Take data triggered
Sets the instrument so that data acquisition is initiated on receipt of various trigger
conditions at the TRIG connector on the rear panel. If an oscillator frequency and/or
amplitude sweep has been defined and linked to the curve buffer using the SWEEP
command with a parameter of 9, 10 or 11, then this sweep will be started as well.
There are two basic triggers. The Acquisition trigger is a "per curve" (start) or "per
point" (sample) trigger and can be active on either the rising or falling edge. The Stop
trigger sets the condition by which acquisition finishes. In normal operation this is
simply when the number of points specified by the LEN command parameter have
been acquired, but it is also possible to leave acquisition running until an HC
command is sent or until either a rising or falling edge occurs at the trigger input.
The trigger modes, set by the value of n, are as follows:
n
0
1
2
3
4
5
6
7
8
9
Start condition
Ext rising edge
On command
Ext falling edge
On command
Ext rising edge
On command
Ext falling edge
On command
Ext rising edge
Ext falling edge
Sample condition
Ext rising edge
Ext falling edge
Ext rising edge
Ext falling edge
-
Stop condition
Points = LEN
Points = LEN
Points = LEN
Points = LEN
On HC command
On HC command
On HC command
On HC command
Ext falling edge
Ext rising edge
Note that in modes 1, 3, 5 and 7 the maximum trigger rate is 1000 Hz and the storage
interval control setting has no effect.
E-23
Appendix E, ALPHABETICAL LISTING OF COMMANDS
TRIGOUT [n]
Curve buffer trigger output
The value of n defines the type of trigger output generated when a buffer acquisition
is run in accordance with the following table:
n
0
1
Trigger
Trigger generated once per curve, at start of curve
Trigger generated once per point
TRIGOUTPOL [n]
Curve buffer trigger output polarity
The value of n defines the polarity of the trigger output generated when a buffer
acquisition is run in accordance with the following table:
n
0
1
Trigger Output
Rising-edge
Falling edge
VER
Report firmware version
Causes the lock-in amplifier to respond with the firmware version number, as also
displayed on the Configuration menu.
VMODE [n]
Voltage input configuration
The value of n sets up the input configuration according to the following table:
n
0
1
2
3
Input configuration
Both inputs grounded (test mode)
A input only
-B input only
A-B differential mode
Note that the IMODE command takes precedence over the VMODE command.
VRLOCK [n]
Virtual reference mode lock
The Seek option of the frequency sweep mode must be used before issuing this
command, for which the value of n has the following significance:
n
0
1
Mode
Disables virtual reference mode
Enters virtual reference mode by enabling tracking of the signal frequency
X[.]
X channel output
In fixed point mode causes the lock-in amplifier to respond with the X demodulator
output in the range ±30000, full-scale being ±10000.
In floating point mode causes the lock-in amplifier to respond with the X
demodulator output in volts or amps.
XOF [n1 [n2]]
X channel output offset control
n1 Selection
0 Disables offset
1 Enables offset facility
The range of n2 is ±30000 corresponding to ±300% full-scale.
E-24
Appendix E, ALPHABETICAL LISTING OF COMMANDS
XY[.]
X, Y channel outputs
This returns the X and Y outputs separated by the defined delimiter.
Y[.]
Y channel output
In fixed point mode causes the lock-in amplifier to respond with the Y demodulator
output in the range ±30000, full-scale being ±10000.
In floating point mode causes the lock-in amplifier to respond with the Y
demodulator output in volts or amps.
YOF [n1 [n2]]
Y channel output offset control
n1 Selection
0
1
Disables offset facility
Enables offset facility
The range of n2 is ±30000 corresponding to ±300% full-scale.
E-25
Appendix E, ALPHABETICAL LISTING OF COMMANDS
E-26
Index
Index
? command 6-17, E-1
8-bit programmable output port 3-14
A input connector 4-1
AC Gain
and dynamic reserve 5-20
and full scale sensitivity 3-5
and input overload 3-5, 3-13
AUTOMATIC control 3-5
description of 3-4
Accuracy 3-16
ACGAIN [n] command 6-10, E-1
ADC
sampling frequency 3-6
trigger input 4-4
trigger output 4-5
ADC[.] n command 6-22, E-1
ADC1
auxiliary input 3-14
connector 4-5
ADC2
auxiliary input 3-14
connector 4-5
ADC3
auxiliary input 3-14
connector 4-5
ADC4
auxiliary input 3-14
connector 4-5
ADF n command 6-32, D-1, E-1
AMCENTERV[.] [n] command 6-19, E-1
AMDEPTH [n] command 6-19, E-1
AMFILTER [n] command 6-19, E-2
AMSOURCE [n] command 6-19, E-2
AMVSPAN[.] [n] command 6-19, E-2
Analog outputs (DACs) 3-14
Analog to digital converter (ADC) 3-7
Anti-aliasing filter 3-6
AQN command 6-12, E-2
AS command 6-10, E-2
ASM command 6-10, E-2
ASTART[.] [n] command 6-17, E-2
ASTEP[.] [n] command 6-17, E-2
ASTOP[.] [n] command 6-17, E-2
Auto functions
Auto-Offset 3-16
Auto-Phase 3-15
Auto-Sensitivity 3-15
introduction 3-14
AUTOMATIC [n] command 6-10, E-3
Auxiliary ADC's 4-5
AXO command 6-14, E-3
B (I) input connector 4-1
Block diagram 3-2
BYTE [n] command 6-22, E-3
C1 n1 [n2] command 6-17, E-3
C2 n1 [n2] command 6-17, E-3
CBD [n] command 6-23, E-3
CH n1 [n2] command 6-20, E-4
CMODE command 6-23, E-5
Command formats 6-7
Commands
alphabetical listing of E-1
compound commands 6-1
delimiters 6-3, 6-6, 6-7
floating point mode 6-8
for analog outputs 6-20
for Auto-Default function and calibration 6-32
for auxiliary inputs 6-22
for computer interfaces 6-30
for data curve buffer 6-23
for digital I/O 6-22
for dual harmonic mode 6-33
for dual reference mode 6-33
for instrument identification 6-32
for instrument outputs 6-14
for internal oscillator 6-17
for reference channel 6-10
for signal channel inputs 6-8
for signal channel output amplifiers 6-14
for signal channel output filters 6-12
Common mode rejection ratio (CMRR) 3-3
Computer control, sample programs 6-33
Computer operation,introduction 6-1
CONFIG 1 Switch 4-4, 5-38
CONFIG 2 Switch 4-4, 5-39
CONFIG 3 Switch 4-4, 5-39
CONFIG switches 4-4
Current/Voltage input mode selection 5-15
Curve buffer
fast mode 3-11
standard mode 3-13
Curve storage
commands for 6-23
programming examples 6-35
trigger output 4-5
DAC[.] n1 [n2] command 6-21, E-5
INDEX-1
INDEX
DAC1
and user equations 5-41
connector 4-5
control 5-31
DAC2
and user equations 5-41
connector 4-5
control 5-31
DAC3
and user equations 5-41
connector 4-5
control 5-31
DAC4
and user equations 5-41
connector 4-5
control 5-31
DATE command 6-32, E-6
DC[.] n command 6-27, E-6
DCB n command 6-27, E-7
DCCOUPLE [n] command 6-9, E-7
DCT n command 6-29, E-8
DD [n] command 6-30, E-9
DEFEQU [n1 n2 n3 n4 n5] command 6-16, E-9
Delimiters 6-3, 6-6, 6-7
DEMOD2SRC [n] command 6-8, E-10
Demodulator
Dual 5-24
gain 3-5
Single 5-24
Demodulators
described 3-9
output filters 3-10
Differential voltage input mode 3-3
DIGITAL I/O connector 4-3
Direct Connection to a Single Computer 5-1
Dual channel mode
described 5-24
Dual harmonic mode
described 3-1, 5-13, 5-24
signal channel restrictions 3-2
Dual reference mode
described 3-1, 5-13, 5-24
signal channel restrictions 3-1
Dynamic reserve
description of 3-4
ENBW[.] command 6-15, E-10
EQU n command 6-16, E-10
Equations
Auto Default 5-42
Command interface 5-42
Equation 1 and Equation 2 5-40
overview 5-40
INDEX-2
Ethernet Connection Methods 5-1
Ethernet interface
IP Address 6-6
main controls 6-6
Overload byte 6-6
sockets 6-6
Status byte 6-6
Terminator 6-6
Ethernet Operation 6-6
EVENT [n] command 6-26, E-10
EX [n] command 6-14, E-10
FET command 6-9, E-11
FET input device 3-3
FLOAT [n] command 6-9, E-11
FMCENTERF[.] [n] command 6-20, E-11
FMCENTERV[.] [n] command 6-20, E-11
FMFILTER [n] command 6-20, E-11
FMSPANF[.] [n] command 6-20, E-11
FMVSPAN[.] [n] command 6-20, E-12
Front Panel
layout 4-1
Operation 5-1
FRQ[.] command 6-12, E-12
FSTART[.] [n] command 6-18, E-12
FSTEP[.] [n1 n2] command 6-18, E-12
FSTOP[.] [n] command 6-18, E-13
GWADDR [n1 n2 n3 n4] command 6-31, E-13
HC command 6-26, E-13
ID command 6-32, E-13
IE [n] command 6-11, E-13
IMODE [n] command 6-8, E-14
Initial checks 2-1
Input
AC gain control 5-15
connector selection 3-3, 4-1
connector shell ground/float 3-4
coupling control 5-15
current/voltage mode control 5-15
current/voltage mode selection 3-4
Demod2 source control 5-16
device control 5-15
line filter control 5-16
overload indicators 4-1
shield control 5-16
Inspection 2-1
INT [n] command 6-11, E-14
IPADDR [n1 n2 n3 n4] command 6-31, E-14
IPLOCK command 6-32, E-14
IPUNLOCK command 6-32, E-14
Key specifications 1-3
LAN connector 4-3
LEN [n] command 6-24, E-14
INDEX
LF [n1 n2] command 6-10, E-15
Line cord 2-1
Line frequency rejection filter 3-4
Line voltage selection 2-1
LOCK command 6-12, E-15
Log ratio output 5-33
LR[.] command 6-15, E-15
M command 6-26, E-15
MAG[.] command 6-15, E-16
Main Controls
Demodulator Control 5-24
Display Indictors 5-13
Input 5-14
Oscillator 5-19
Output 1 5-19
Output 2 5-22
Output Filters 5-23
Overview 5-11
Reference 1 5-17
Reference 2 5-21
Status Indicators 5-25
Main output processor 3-11
MENABLE command 6-19, E-16
MP[.] command 6-15, E-16
N command 6-30, E-16
NAME command 6-32, E-16
NC command 6-24, E-16
NHZ. command 6-15, E-17
NN[.] command 6-16, E-17
NNBUF [n] command 6-12, E-17
Noise measurements 3-12
NOISEMODE [n] command 6-12, E-17
OA[.] [n] command 6-17, E-17
OF[.] [n] command 6-17, E-17
Operating environment 2-1
Operating Modes 3-1
OSC OUT connector 4-1
Oscillator
ADC1 as source control 5-29
Amplitude and Frequency Controls 5-30
Amplitude control 5-19, 5-30
amplitude modulation 3-9
Amplitude sweep Armed control 5-28
Center frequency control 5-28
Center voltage control 5-29
Enable AM control 5-29
Enable FM control 5-28
Ext ref as source control 5-29
Filter control 5-29
Frequency control 5-19, 5-30
frequency modulation 3-9
Frequency span control 5-28
Frequency sweep Armed control 5-27
frequency sweeps - general 3-9
Linear control 5-27
Logarithmic control 5-27
Modulation Control 5-28
Modulation depth control 5-29
output amplitude sweeps - general 3-9
output update rate 3-9
Overview 3-9, 5-26
Start amplitude control 5-27
Start button 5-27
Start frequency control 5-27
Step size control 5-27, 5-28
Stop amplitude control 5-27
Stop frequency control 5-27
Sweep control 5-26
Time/step control 5-27
Voltage span control 5-29
Output
output expansion 3-11
output offset 3-11
Output 1
Auto Offset control 5-20
Auto Sen control 5-20
Noise Buffer Length control 5-21
Noise Measurement control 5-21
Sensitivity control 5-19
Slope control 5-20
Time constant control 5-20
X Offset control 5-20
Y Offset control 5-20
Output 2
Auto Offset control 5-23
Auto Sen control 5-22
Sensitivity control 5-22
Slope control 5-23
Time constant control 5-23
X Offset control 5-23
Y Offset control 5-23
Output Filters
Fast mode control 5-23
Synchronous control 5-23
PHA[.] command 6-15, E-17
PORTDIR [n] command 6-22, E-18
Power input connector 4-3
Power switch 4-3
Power-up defaults 3-16
PS0110 power supply 2-1
Rack mounting 2-1
Ratio output 5-32
READBYTE command 6-22, E-18
Rear Panel
INDEX-3
INDEX
ADCs 5-35
Bind 5-37
DACs 5-31
Digital port 5-38
DIP switches 5-38
Expand 5-37
layout 4-3
Overview 5-30
Ref Mon 5-37
RS232 5-36
USB Status 5-39
REF IN connector 4-1
Reference 1
Auto-Phase 5-19
Reference 1
+90 Deg control 5-19
Frequency display 5-18
Harmonic control 5-19
Phase control 5-19
Source control 5-17
Reference 2
Auto-Phase 5-22
Reference 2
+90 Deg control 5-22
Frequency display 5-22
Harmonic control 5-22
Phase control 5-22
Source control 5-21
Reference channel inputs 3-7
Reference mode
external 3-2, 3-7
internal 3-2, 3-7
Reference phase shifter 3-8
REFMODE [n] command 6-10, E-18
REFMON [n] command 6-11, E-18
REFN [n] command 6-11, E-18
REFP[.] [n] command 6-11, E-19
RS [n1 [n2]] command 6-30, E-19
RS232 interface
baud rate control 5-36
choice of baud rate 6-2
choice of number of data bits 6-2
choice of parity check option 6-2
connector 4-3
delimiter control 5-36
echo on control 5-36
general features 6-1
handshaking and echoes 6-3
N (overload) command 6-4
number of data bits control 5-36
INDEX-4
parity control 5-36
prompt on control 5-36
prompts 6-4
ST (status) command 6-4
terminators 6-3
RS232 Operation 6-1
RT[.] command 6-15, E-19
SEN [n] command 6-9, E-19
SEN. command 6-9, E-19
SIG MON connector 4-4
Signal channel inputs 3-3
Signal phase 3-11
Single harmonic mode
described 3-1
Single reference mode
described 3-1, 5-12
SLOPE [n] command 6-13, E-20
SNMASK [n1 n2 n3 n4] command 6-31, E-20
Specifications
detailed listing of A-1
for analog outputs A-4
for auxiliary inputs A-3
for computer interfaces A-4
for data storage buffer A-4
for demodulators and output processing A-3
for internal oscillator A-3
for measurement modes A-1
for reference channel A-2
for reference input A-2
for signal channel A-1
weight and dimensions A-4
SRATE[.] [n] command 6-18, E-21
ST command 6-30, E-21
Status
Dynamic reserve 5-25
Input limit 5-25
Overload byte 5-25
Status byte 5-25
STATUS indicator 4-1
STR [n] command 6-24, E-21
SWEEP [n] command 6-18, E-21
SYNC [n] command 6-13, E-22
TADC [n] command 6-22, E-22
Tandem demodulation mode
described 3-1
Tandem demodulation mode
described 5-13, 5-24
Tandem demodulator mode 5-16
TC [n] command 6-12, E-22
TC. command 6-12, E-22
TD command 6-25, E-23
TDC n command 6-25, E-23
INDEX
TDT n command 6-25, E-23
Terminators 6-3
TRIG IN connector 4-4
TRIG OUT connector 4-5
TRIGOUT [n] command 6-26, E-24
TRIGOUTPOL [n] command 6-26, E-24
USB connector 4-4
USB interface
general features 6-5
Overload byte 6-5
Status byte 6-5
Terminator 6-5
USB Operation 6-5
Vector magnitude 3-11
VER command 6-32, E-24
Virtual reference
Search button 5-18
Start Freq control 5-18
Step size control 5-18
Stop Freq control 5-18
Time/Step Freq control 5-18
Virtual reference mode
described 3-2, 5-13
VMODE [n] command 6-8, E-24
VRLOCK [n] command 6-12, E-24
Web Control Panels 5-11
What is a lock-in amplifier? 1-2
Wired Connection to a Company or Corporate
Network Using a DHCP Allocated IP Address 5-9
Wired Connection to a Company or Corporate
Network Using a Static IP Address 5-5
Wireless Connection to an iPad, Laptop, or Netbook
Computer 5-1
X[.] command 6-14, E-24
X1 expand control 5-37
XOF [n1 [n2]] command 6-14, E-24
XY[.] command 6-15, E-25
Y[.] command 6-14, E-25
Y1 expand control 5-37
YOF [n1 [n2]] command 6-14, E-25
INDEX-5
INDEX
INDEX-6
WARRANTY
SIGNAL RECOVERY, a part of AMETEK Advanced Measurement Technology, Inc, warrants each instrument of its own
manufacture to be free of defects in material and workmanship for a period of ONE year from the date of delivery to the
original purchaser. Obligations under this Warranty shall be limited to replacing, repairing or giving credit for the purchase,
at our option, of any instruments returned, shipment prepaid, to our Service Department for that purpose, provided prior
authorization for such return has been given by an authorized representative of AMETEK Advanced Measurement
Technology, Inc.
This Warranty shall not apply to any instrument, which our inspection shall disclose to our satisfaction, to have become
defective or unusable due to abuse, mishandling, misuse, accident, alteration, negligence, improper installation, or other
causes beyond our control. This Warranty shall not apply to any instrument or component not manufactured by AMETEK
Advanced Measurement Technology, Inc. When products manufactured by others are included in AMETEK Advanced
Measurement Technology, Inc equipment, the original manufacturers Warranty is extended to AMETEK Advanced
Measurement Technology, Inc customers. AMETEK Advanced Measurement Technology, Inc reserves the right to make
changes in design at any time without incurring any obligation to install same on units previously purchased.
THERE ARE NO WARRANTIES WHICH EXTEND BEYOND THE DESCRIPTION ON THE FACE HEREOF. THIS
WARRANTY IS IN LIEU OF, AND EXCLUDES ANY AND ALL OTHER WARRANTIES OR REPRESENTATIONS,
EXPRESSED, IMPLIED OR STATUTORY, INCLUDING MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE, AS WELL AS ANY AND ALL OTHER OBLIGATIONS OR LIABILITIES OF AMETEK ADVANCED
MEASUREMENT TECHNOLOGY, INC, INCLUDING, BUT NOT LIMITED TO, SPECIAL OR CONSEQUENTIAL
DAMAGES. NO PERSON, FIRM OR CORPORATION IS AUTHORIZED TOASSUME FOR AMETEK ADVANCED
MEASUREMENT TECHNOLOGY, INC ANY ADDITIONAL OBLIGATION OR LIABILITY NOT EXPRESSLY
PROVIDED FOR HEREIN EXCEPT IN WRITING DULY EXECUTED BY AN OFFICER OF AMETEK ADVANCED
MEASUREMENT TECHNOLOGY, INC.
SHOULD YOUR EQUIPMENT REQUIRE SERVICE
A. Contact your local SIGNAL RECOVERY office, agent, representative or distributor to discuss the problem. In many
cases it may be possible to expedite servicing by localizing the problem to a particular unit or cable.
B. We will need the following information, a copy of which should also be attached to any equipment which is returned for
service.
1. Model number and serial number of instrument
6. Symptoms (in detail, including control settings)
2. Your name (instrument user)
3. Your address
4. Address to which the instrument should be returned
5. Your telephone number and extension
7. Your purchase order number for repair charges (does
not apply to repairs in warranty)
8. Shipping instructions (if you wish to authorize
shipment by any method other than normal surface
transportation)
C. If you experience any difficulties in obtaining service please contact:
SIGNAL RECOVERY Service
AMETEK Advanced Measurement Technology, Inc
801 South Illinois Avenue
Oak Ridge
TN 37831-2011, USA
Phone:
Fax:
E-mail:
+1 865 482 4411
+1 865 481 2410
info@signalrecovery.com
SIGNAL RECOVERY Service
AMETEK Advanced Measurement Technology
Phone:
Unit 1 Armstrong Mall, Southwood Business Park
Fax:
Farnborough, Hampshire, GU14 0NR, UNITED KINGDOM E-mail:
+44 (0) 1252 556 800
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