Model 7265

SIGNAL RECOVERY
Model 7265
DSP Lock-in Amplifier
FEATURES
0.001 Hz to 250 kHz
operation
Voltage and current mode
inputs
Direct digital demodulation
without down-conversion
10 µs to 100 ks output time
constants
Quartz crystal stabilized
internal oscillator
Synchronous oscillator
output for input offset
reduction
Harmonic measurements to
65,536F
Dual reference, Dual
Harmonic and Virtual
Reference modes
Spectral display mode
Built-in experiments
APPLICATIONS
Scanned probe microscopy
Optical measurements
Audio studies
AC impedance studies
Atomic force microscopy
CatIss7Web:0411UK
DESCRIPTION
The SIGNAL RECOVERY model 7265 uses the latest digital signal processing (DSP)
technology to extend the operating capabilities of the lock-in amplifier to provide the
researcher with a very versatile unit suitable both for measurement and control of
experiments. At the same time due consideration has been given to the needs of those
users wishing only to make a simple measurement quickly and easily.
Operating over a frequency range of 1 mHz to 250 kHz, the model 7265 offers full-scale
voltage sensitivities down to 2 nV and current sensitivities to 2 fA. The instrument has a
choice of operating modes, signal recovery or vector voltmeter, for optimum
measurement accuracy under different conditions, and the use of DSP techniques
ensures exceptional performance.
The instrument performs all of the normal measurements of a dual phase lock-in
amplifier, measuring the in-phase and quadrature components, vector magnitude, phase
angle and noise of the input signal.
Several novel modes of operation are also include to give greater levels of versatility
than ever before, for example:
Virtual Reference™
Under suitable conditions, this mode allows measurements to be made in the absence
of a reference signal
Dual Reference
In this mode the instrument can make simultaneous measurements on two signals at
different reference frequencies, which is ideal, for example, for use in source
compensated optical experiments
Spectral Display
This allows the spectrum of the
signals present at the input to be
calculated and displayed, which can
help when choosing the reference
frequency
Spectral Display
Transient Recorder
In this mode, the auxiliary ADC inputs can be used as a 40 kSa/s (25 µs/point) transient
recorder, with the captured transient being displayed graphically
Frequency Response
This built-in experiment allows the internal oscillator frequency to be swept between
preset frequencies, while simultaneously measuring the input signal magnitude and
phase. The mode is ideal for determining the frequency and phase response of external
networks
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Lock-in Amplifiers
Harmonic Analysis
Most lock-in amplifiers will measure signals at the applied
reference frequency or its second harmonic. In the 7265,
operation is possible at harmonics up the 65,536th, and in Dual
Harmonic mode, simultaneous measurements can be made on
two harmonics
Three auxiliary ADC inputs, one of which is a special integrating
converter, four DAC outputs and eight output logic lines are
provided. These can be used to record the magnitude of external
signals associated with the experiment, such as temperature or
pressure, or to generate voltages to control or switch other
equipment. Information from the ADCs together with the lock-in
amplifier's output data can be stored in the 32k point buffer
memory, and even displayed graphically on screen.
Pop-up Keypad to set Controls
used when setting controls that need adjusting to a large number
of significant figures.
Control selection and adjustment is aided by the logical structure
of on-screen menus and sub-menus, supported by a series of
context-sensitive help screens. A number of built-in automatic
functions are also provided to simplify instrument operation.
External control of the unit is via either the RS232 or GPIB
interfaces, using simple mnemonic-type ASCII commands. A
second RS232 port allows up to sixteen 7265 or compatible
instruments to be operated from a single RS232 computer port
by connecting them in a “daisy-chain” configuration.
Graphical Display
The model 7265 is extremely easy to use. All instrument controls
are adjusted using soft-touch, front panel push-buttons, with the
present settings and measured outputs being displayed on the
centrally located, cold fluorescent backlit dot-matrix LCD. A
particularly convenient feature is the pop-up keypad which is
Compatible software is available in the form of a LabVIEW driver
supporting all instrument functions, and the Acquire lock-in
amplifier applications software. The driver and a free
demonstration version of the software, DemoAcquire, are
available for download from our website at
www.signalrecovery.com
Specifications
General
Dual-phase DSP lock-in amplifier operating
over a reference frequency range of 0.001 Hz
to 250 kHz.
Wide range of extended measuring modes and
auxiliary inputs and outputs.
User-upgradeable firmware.
Measurement Modes
The instrument can simultaneously show any
four of these outputs on the front panel display:
X
In-phase
Y
Quadrature
R
Magnitude
θ
Phase Angle
Noise
Harmonic
nF, n ≤ 65,536
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 is the external and F2 the internal
reference
Frequency Range for Dual Harmonic and Dual
Reference Modes:
F1 and F2 ≤ 20 kHz
Virtual Reference
Locks to and detects a signal without a
reference (100 Hz ≤ F ≤ 250 kHz)
Noise
Measures noise in a given bandwidth
centered at the reference frequency F
Spectral Display
Gives a visual indication of the spectral
power distribution of the input signal in a
user-selected frequency range lying
between 1 Hz and 60 kHz. Note that
although the display is calibrated in terms
of frequency, it is not calibrated for
amplitude. Hence it is only intended to
assist in choosing the optimum reference
frequency
Display
240 × 64 pixel cold fluorescent backlit
LCD panel giving digital, analog bar-graph
and graphical indication of measured
signals. Menu system with dynamic key
function allocation. On-screen context
sensitive help
Signal Channel
Voltage Input
Modes
A only, -B only or
Differential (A-B)
Full-scale Sensitivity
2 nV to 1 V in a
1-2-5 sequence
Max. Dynamic Reserve > 100 dB
Impedance
FET Input
10 MΩ // 30 pF
Bipolar Input
10 kΩ // 30 pF
Maximum Safe Input
20 V pk-pk
Voltage Noise
FET Input
5 nV/√Hz @ 1 kHz
Bipolar Input
2 nV/√Hz @ 1 kHz
C.M.R.R.
> 100 dB @ 1 kHz
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Frequency Response
Gain Accuracy
Distortion
Line Filter
Grounding
Current Input
Mode
0.001 Hz to 250 kHz
±0.2% typ
-90 dB THD (60 dB
AC gain, 1 kHz)
attenuates 50, 60,
100, 120 Hz
BNC shields can be
grounded or floated
via 1 kΩ to ground
Low Noise or Wide
Bandwidth
Full-scale Sensitivity
Low Noise
2 fA to 10 nA in a
1-2-5 sequence
Wide Bandwidth
2 fA to 1 µA in a
1-2-5 sequence
Max. Dynamic Reserve > 100 dB
Frequency Response (-3 dB)
Low Noise
≥ 500 Hz
Wide Bandwidth
≥ 50 kHz
Impedance
Low Noise
< 2.5 kΩ @ 100 Hz
Wide Bandwidth
< 250 Ω @ 1 kHz
Noise
Low Noise
13 fA/√Hz @ 500 Hz
Wide Bandwidth
1.3 pA/√Hz @ 1 kHz
Gain Accuracy
± 0.6% typ, midband
Line Filter
attenuates 50, 60,
100, 120 Hz
Grounding
BNC shield can be
grounded or floated
via 1 kΩ to ground
CatIss7Web:0411UK
Lock-in Amplifiers
Model 7265 Specifications
(continued)
Reference Channel
TTL Input (rear panel)
Frequency Range 0.001 Hz to 250 kHz
Analog Input (front panel)
Impedance
1 MΩ // 30 pF
Sinusoidal Input
Level
1.0 V rms*
Frequency Range 0.3 Hz to 250 kHz
Squarewave Input
Level
250 mV rms*
Frequency Range 2 Hz to 250 kHz
*Note: Lower levels can be used with the
analog input at the expense of increased
phase errors
Phase Set Resolution
0.001° increments
Phase Noise at 100 ms TC, 12 dB/octave slope
Internal Reference < 0.0001° rms
External Reference < 0.01° rms @ 1 kHz
Orthogonality
90° ±0.0001°
Acquisition Time
Internal Reference instantaneous
acquisition
External Reference 2 cycles + 50 ms
Reference Frequency Meter Resolution
1 ppm or 1 mHz,
whichever is the
greater
Demodulator and Output Processing
Output Zero Stability
Digital Outputs
No zero drift on all
settings
Displays
No zero drift on all
settings
Analog Outputs
< 5 ppm/°C
Harmonic Rejection
-90 dB
Output Filters
X, Y and R outputs only
Time Constant
10 µs to 640 µs in a
binary sequence
Slope (roll-off)
6 dB/octave
All outputs
Time Constant
5 msto 100 ks in a
1-2-5 sequence
Slope
6, 12, 18 and 24 dB/
octave
Synchronous Filter
Available for F <
20 Hz
Offset
Auto and Manual on X
and/or Y: ±300% fullscale
Absolute Phase Measurement Accuracy
≤ 0.01°
Oscillator
Frequency
Range
0.001 Hz to 250 kHz
Setting Resolution
1 mHz ≤ F ≤ 900 Hz 1 mHz
F > 900 Hz
4 mHz
Absolute Accuracy ± 50 ppm
Distortion (THD)
-80 dB @ 1 kHz and
100 mV rms
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Amplitude (rms)
Range
Setting Resolution
1 µV to 4 mV
4 mV to 500 mV
500 mV to 2 V
2 V to 5 V
Accuracy
> 1 mV
100 µV - 1 mV
Stability
Output Impedance
Sweep
Amplitude Sweep
Output Range
Law
Step Rate
Frequency Sweep
Output Range
Law
Step Rate
Auxiliary Inputs
ADC 1 & 2
Maximum Input
Resolution
Accuracy
Input Impedance
Sample Rate
ADC 1 only
ADC 1 and 2
Trigger Mode
Trigger Input
ADC 3
Maximum Input
Resolution
Input Impedance
Sampling Time
1 µV to 5 V rms
1 µV
125 µV
500 µV
1.25 mV
±0.3%, F ≤ 60 kHz,
±0.5%, F > 60 kHz
±1%, F ≤ 60 kHz
±3%, F > 60 kHz
50 ppm/°C
50 Ω
0.000 to 5.000 V rms
Linear
20 Hz maximum
(50 ms/step)
0.001 Hz to 250 kHz
Linear or Logarithmic
20 Hz maximum
(50 ms/step)
Auxiliary D/A Outputs 1, 2, 3 and 4
Maximum Output
±10 V
Resolution
1 mV
Accuracy
±10 mV
Output Impedance 1 kΩ
8-bit Digital Output Port
8 TTL-compatible lines that can be
independently set high or low to activate
external equipment
Reference Output
Waveform
0 to 5 V rectangular
wave
Impedance
TTL-compatible
Power - Low Voltage
±15 V at 100 mA rear
panel 5-pin 180° DIN
connector for
powering
SIGNAL RECOVERY
preamplifiers
Data Storage Buffer
Size
Max Storage Rate
From LIA
±10 V
1 mV
±20 mV
1 MΩ // 30 pF
40 kHz max.
17.8 kHz max.
Internal, External or
burst
TTL compatible
±10 V
12 to 20 bit,
depending on
sampling time
1 MΩ // 30 pF
10 ms to 2 s, variable
Outputs
Fast Outputs
Function
Amplitude
X and Y or X and Mag
±2.5 V full-scale;
linear to ±300% fullscale
Impedance
1 kΩ
Update Rate
166 kHz
Main Analog (CH1 and CH2) Outputs
Function
X, Y, R, θ, Noise,
Ratio, Log Ratio and
User Equations 1 & 2.
Amplitude
±10.0 V full-scale;
linear to ±120% fullscale
Impedance
1 kΩ
Update Rate
200 Hz
Signal Monitor
Amplitude
±10 V FS
Impedance
1 kΩ
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From ADC1
32k × 16-bit data
points, may be
organized as 1×32k,
2×16k, 3×10.6k, 4×8k,
etc.
up to 1000 16-bit
values per second
up to 40,000 16-bit
values per second
User Settings
Up to 8 complete instrument settings
can be saved or recalled from
non-volatile memory
Interfaces
RS232 and GPIB (IEEE-488). A second
RS232 port is provided to allow “daisychain” connection and control of up to 16
compatible instruments from a single
RS232 computer port
General
Power Requirements
Voltage
Frequency
Power
Dimensions
Width
Depth
Height
With feet
Without feet
Weight
110/120/220/240 VAC
50/60 Hz
40 VA max
13¼" (350 mm)
16½" (415 mm)
4¼" (105 mm)
3½" (90mm)
18 lb (8.1 kg)
Lock-in Amplifiers
LabVIEW Driver Software
A LabVIEW driver for the instrument is available from the
www.signalrecovery.com website, offering example VIs for all
its controls and outputs, as well as the usual Getting Started and
Utility VIs. It also includes example soft-front panels built using
these VIs, demonstrating how you can incorporate them in more
complex LabVIEW programs.
SIGNAL RECOVERY Acquire Software
(see page 56)
Users who do not wish to write their own control code but who
still want to record the instrument’s outputs to a computer file will
find the SIGNAL RECOVERY Instruments Acquire Lock-in
Amplifier Applications Software, available at a small extra cost,
useful. This 32-bit package, suitable for Windows XP/Vista,
extends the capabilities of the instrument by, for example,
adding the ability to record swept frequency measurements. It
also supports the internal curve buffer, allowing acquisition
rates of up to 1000 points per second independent of the
computer's processor speed.
SRInstComms Software
(see page 59)
Control up to ten SIGNAL RECOVERY instruments directly from Visual Basic, Visual
C++, LabVIEW, Visual Basic for Applications (included in Word, Excel, Outlook,
Access and other Microsoft products) and VBScript (supported by Internet Explorer 3
and later) without having to worry about low-level communications routines. The
SRInstComms control handles all the communications between your software and the
instrument(s) via the RS232 and/or GPIB interfaces, leaving you free to develop the
code to run your experiment.
Ordering Information
Each model 7265 is supplied complete with a comprehensive instruction manual. Users may download the instrument's LabVIEW
driver software and a free demonstration copy, DemoAcquire, of the SIGNAL RECOVERY lock-in amplifier applications software
package, from the www.signalrecovery.com website.
Optional Accessories
Model K02003
Rack mount to mount one model
7265 in a 19" rack
Model K02003 Rack Mount Kit
Model 7265 Rear Panel Layout
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CatIss7Web:0411UK