Temperature Monitor
Operation and Service Manual
RTD Temperature Monitor
SIM923A
Stanford Research Systems
Revision 1.2 • February 15, 2005
Certification
Stanford Research Systems certifies that this product met its published specifications at the time
of shipment.
Warranty
This Stanford Research Systems product is warranted against defects in materials and workmanship for a period of one (1) year from the date of shipment.
Service
For warranty service or repair, this product must be returned to a Stanford Research Systems
authorized service facility. Contact Stanford Research Systems or an authorized representative
before returning this product for repair.
Information in this document is subject to change without notice.
c Stanford Research Systems, Inc., 2004, 2005. All rights reserved.
Copyright Stanford Research Systems, Inc.
1290–C Reamwood Avenue
Sunnyvale, CA 94089 USA
Phone: (408) 744-9040 • Fax: (408) 744-9049
www.thinkSRS.com • e-mail: info@thinkSRS.com
Printed in U.S.A.
SIM923A
RTD Temperature Monitor
Contents
General Information
1
2
iii
Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
iii
Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
iv
Notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
v
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . .
vi
Getting Started
1–1
1.1
Introduction to the Instrument . . . . . . . . . . . . . 1 – 2
1.2
Front-Panel Operation . . . . . . . . . . . . . . . . . . 1 – 2
1.3
Sensor Interface . . . . . . . . . . . . . . . . . . . . . . 1 – 4
1.4
SIM Interface . . . . . . . . . . . . . . . . . . . . . . . . 1 – 6
Remote Operation
2–1
2.1
Index of Common Commands . . . . . . . . . . . . . . 2 – 2
2.2
Alphabetic List of Commands . . . . . . . . . . . . . . 2 – 4
2.3
Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 – 6
2.4
Commands . . . . . . . . . . . . . . . . . . . . . . . . . 2 – 7
2.5
Status Model . . . . . . . . . . . . . . . . . . . . . . . . 2 – 19
i
ii
Contents
SIM923A
RTD Temperature Monitor
General Information
The SIM923A RTD Temperature Monitor, part of Stanford Research
Systems’ Small Instrumentation Modules family, consists of a singlechannel sensor excitation and readout for precision low-noise resistive thermometry. Front-panel analog outputs provide both scaled
(linear voltage proportional to temperature) and raw (buffered sensor
voltage) signals. Two reversable DC current sources (10 µA & 1 mA)
provide sensor excitation to the four-wire measurement circuit.
Service
Do not install substitute parts or perform any unauthorized modifications to this instrument.
The SIM923A is a single-wide module designed to be used inside the
SIM900 Mainframe. Do not turn on the power until the module is
completely inserted into the mainframe and locked in place.
iii
iv
General Information
Symbols you may Find on SRS Products
Symbol
Description
Alternating current
Caution - risk of electric shock
Frame or chassis terminal
Caution - refer to accompanying documents
Earth (ground) terminal
Battery
Fuse
On (supply)
Off (supply)
SIM923A
RTD Temperature Monitor
General Information
v
Notation
The following notation will be used throughout this manual:
• Front-panel buttons are set as [Button];
[Adjust ] is shorthand for “[Adjust ] & [Adjust ]”.
• Front-panel indicators are set as Overload.
• Remote command names are set as *IDN?.
• Literal text other than command names is set as OFF.
SIM923A
RTD Temperature Monitor
vi
General Information
Specifications
Performance Characteristics
Min
Inputs
Number of inputs
Sensor type
Measurement type
Excitation
(10 µA setting)
(1 mA setting)
Sensor Characteristics
Calibration curves
Measurement
Measurement Rate
Display resolution
Interface resolution
Measurement resolution
Accuracy, (23 ± 1)◦ C
Temperature coefficient
Operating
Temperature
Power
Supply current
Max
Units
1
Platinum RTD or other resistive
sensor (either PTC or NTC)
4–wire
constant current
9.999
10 10.001 µA DC
±15
ppm/◦ C
0.9999 1.0 1.0001 mA DC
±15
ppm/◦ C
Sensor units
sensor+lead resistance
Curve size
Temperature range
Typ
1.4
Ohms
1400
Ω (1 mA exc.)
140
kΩ (10 µA exc.)
built-in: IEC 751/DIN 43760
1 user defined curve
1024
points
873
K (typical)
sensor dependent
5 readings per second
4
digits
7
digits
1.2
mΩ rms (1 mA exc.)
120
mΩ rms (10 µA exc.)
5 mΩ + 0.01 %
(1 mA exc.)
0.5 Ω + 0.01 %
(10 µA exc.)
−5
+5
ppm/◦ C
0
40
±15, +5
50 (±15 V), 250 (+5 V)
◦C
V DC
mA
General Characteristics
Interface
Connectors
Weight
Dimensions
Serial (RS-232) through SIM interface
DB–9 (female)
4–wire measurement + ground
DB–15 (male) SIM interface
1.4 lbs
1.500 W × 3.600 H × 7.000 D
SIM923A
RTD Temperature Monitor
1
Getting Started
This chapter gives you the necessary information to get started
quickly with the SIM923A RTD Temperature Monitor.
In This Chapter
1.1
1.2
1.3
1.4
Introduction to the Instrument
1.1.1 Overview . . . . . . . .
Front-Panel Operation . . . . .
1.2.1 Excitation . . . . . . . .
1.2.2 Units . . . . . . . . . . .
1.2.3 Reverse . . . . . . . . . .
1.2.4 Setpoint . . . . . . . . .
1.2.5 Scaled Output . . . . . .
Sensor Interface . . . . . . . . .
1.3.1 Four-wire measurement
1.3.2 Two-wire measurement
SIM Interface . . . . . . . . . .
1.4.1 SIM interface connector
1.4.2 Direct interfacing . . . .
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1–2
1–2
1–2
1–2
1–2
1–3
1–4
1–4
1–4
1–4
1–5
1–6
1–6
1–6
1–1
1–2
1.1
Getting Started
Introduction to the Instrument
The SIM923A RTD Temperature Monitor provides excitation and
readout for a single resistive temperature detector (RTD). Analog
outputs, both proportional to temperature and the buffered sensor
voltage, are available on the front panel.
1.1.1
Overview
The SIM923A uses a ratiometric design, where the excitation current
is passed through both an internal, stable reference resistor and the
user’s resistive thermometer. The instrument measures the ratio
of the voltage across the user’s resistor to the voltage across the
reference resistor, multiplied by the (known) value of the reference
resistor, to obtain the user result.
Two separate excitation and reference circuits are included in the
SIM923A, a 1 mA excitation appropriate for ∼1 kΩ full-scale measurements, and a 10 µA excitation useable for up to ∼100 kΩ fullscale measurements. The excitation is also reversable, permitting the
user to test for potential offset voltages in the setup.
A precision 24–bit analog-to-digital converter records the results.
New sensor measurements are available at a rate of 5 conversions
per second.
1.2
Front-Panel Operation
The front panel of the SIM923A(see Figure 1.1) provides a simple
operator interface.
1.2.1
Excitation
The current source of the SIM923A RTD Temperature Monitor can
be fully controlled from the front panel.
To select between 10 µA and 1 mA briefly tap [Excitation]. To toggle
the current on and off, hold [Excitation] for about 1 second, until the
display switches between the numerical result and the word
.
The excitation can also be controlled with the EXCI and EXON remote
interface commands.
1.2.2
Units
The SIM923A displays results either as raw sensor units (in ohms) or
temperature (in kelvin). Pressing [Units] toggles between these two
modes; the active units are indicated by the illuminated K, or Ω (or
SIM923A
RTD Temperature Monitor
1.2
Front-Panel Operation
1–3
Figure 1.1: The SIM923A front and rear panels.
kΩ). The display mode can also be controlled with the DISP remote
interface command.
When temperature units are selected, a sensor calibration curve is
required. The SIM923A is programmed with a standard curve for
100 Ω, 0.00385 alpha Pt RTD sensors (IEC 751). The SIM923A also
has non-volatile memory to store a separate sensor curve with up to
1024 temperature-vs-resistance points. Which curve to use is set by
the remote interface CURV command.
1.2.3
Reverse
The excitation current produced by the SIM923A can be reversed
to check for possible offset potentials. Pressing [Reverse] toggles
the current direction; when REVERSE is lit, the current is reversed
(i.e., positive current flows from the I− terminal to the I+ terminal).
Note that when reversed, the raw sensor monitor output will also
reverse, but the scaled analog output (and display result) will not.
The current direction can also be controlled with the IPOL remote
interface command.
SIM923A
RTD Temperature Monitor
1–4
1.2.4
Getting Started
Setpoint
The scaled analog output can produce a voltage proportional to either absolute temperature, or temperature deviation around some
setpoint. [Setpoint] is used to review or set the setpoint temperature.
Briefly tapping [Setpoint] toggles the display between showing the
latest reading, and showing the setpoint temperature (indicated by
the SETPOINT lamp).
Holding [Setpoint] for longer than ∼1 second will update the setpoint
temperature, as indicated by the word
flashing on the display.
There are two different behaviors that can occur, depending on the
state of the numeric display.
• If the display is presently showing the setpoint (the SETPOINT
lamp is lit), then long presses of [Setpoint] will toggle between
commanding the setpoint temperature to 273.15 K and the most
recent measurement result.
• If the display is presently showing the measurement result
(the SETPOINT lamp is not lit), then long presses of [Setpoint]
simply update the setpoint to the most recent measurement
result.
To configure the SIM923A for an arbitrary setpoint, see the TSET
remote interface command.
1.2.5
Scaled Output
[Scale] controls the gain for the scaled analog output. Gain is indicated by the temperature span corresponding to a full-scale output voltage (10 V). Three scales are available from the front panel,
10 K (1 V/K), 100 K (0.1 V/K), and 1000 K (0.01 V/K). To configure the
SIM923A for an arbitrary analog scale, see the VKEL remote interface
command.
[Rel] toggles the scaled output between two modes: absolute (V ∝ T),
and relative (V ∝ T−Tset ). Relative mode can also be controlled with
the AMOD remote interface command.
1.3
Sensor Interface
The sensor interface on the SIM923A consists of a rear-panel DB–9/F
connector (see Figure 1.1). The connector pinout is given in Table 1.1
1.3.1
Four-wire measurement
To avoid sensitivity to wiring lead resistance, the SIM923A is configured for four-wire measurements. The basic circuit for this wiring
SIM923A
RTD Temperature Monitor
1.3
Sensor Interface
1–5
Pin
1
2
3
4
5
6–9
Signal
I+
I−
ground
V+
V−
ground
Table 1.1: SIM923A Sensor Interface Connector Pin Assignments,
DB–9
scheme is shown in Figure 1.2.
I+
V+
Sensor
V–
I–
Figure 1.2: Wiring diagram for four-wire readout.
1.3.2
Two-wire measurement
If application-specific constraints limit the number of leads to the
sensor, the SIM923A can be wired to measure the sensor resistance
with a simple two-wire circuit, shown in Figure 1.3. Note that the
lead resistance (past the junction points of the current and voltage
leads) will add as a direct resistance error when measuring the sensor.
I+
V+
Sensor
V–
I–
Figure 1.3: Wiring diagram for two-wire readout.
SIM923A
RTD Temperature Monitor
1–6
1.4
Getting Started
SIM Interface
The primary connection to the SIM923A RTD Temperature Monitor is the rear-panel DB–15 SIM interface connector. Typically, the
SIM923A is mated to a SIM900 Mainframe via this connection, either through one of the internal Mainframe slots, or the remote cable
interface.
It is also possible to operate the SIM923A directly, without using the
SIM900 Mainframe. This section provides details on the interface.
1.4.1
SIM interface connector
The DB–15 SIM interface connector carries all the power and communications lines to the instrument. The connector signals are specified
in Table 1.2
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Direction
Src ⇒ Dest
Signal
SIGNAL GND
−STATUS
RTS
CTS
−REF 10MHZ
−5V
−15V
PS RTN
CHASSIS GND
TXD
RXD
+REF 10MHz
+5V
+15V
+24V
MF ⇒ SIM
SIM ⇒ MF
MF ⇒ SIM
SIM ⇒ MF
MF ⇒ SIM
MF ⇒ SIM
MF ⇒ SIM
MF ⇒ SIM
MF ⇒ SIM
SIM ⇒ MF
MF ⇒ SIM
MF ⇒ SIM
MF ⇒ SIM
MF ⇒ SIM
Description
Ground reference for signal
Status/service request (GND=asserted, +5V=idle)
HW Handshake (+5 V=talk; GND=stop)
HW Handshake (+5 V=talk; GND=stop)
10 MHz reference (optional connection)
Power supply (No connection in SIM923A)
Power supply (analog circuitry)
Power supply return
Chassis ground
Async data (start bit=“0”=+5 V; “1”=GND)
Async data (start bit=“0”=+5 V; “1”=GND)
10 MHz reference (optional connection)
Power supply (digital circuitry)
Power supply (analog circuitry)
Power supply (No connection in SIM923A)
Table 1.2: SIM Interface Connector Pin Assignments, DB-15
1.4.2
Direct interfacing
The SIM923A is intended for operation in the SIM900 Mainframe,
but users may wish to directly interface the module to their own
systems without the use of additional hardware.
The mating connector needed is a standard DB–15 receptacle, such as
Amp part # 747909-2 (or equivalent). Clean, well-regulated supply
voltages of +5, ±15 VDC must be provided, following the pin-out
specified in Table 1.2. Ground must be provided on pins 1 and 8,
SIM923A
RTD Temperature Monitor
1.4
SIM Interface
1–7
with chassis ground on pin 9. The −STATUS signal may be monitored
on pin 2 for a low-going TTL-compatible output indicating a status
message.
The SIM923A has no internal protection against reverse polarity, missing
supply, or overvoltage on the power supply pins.
1.4.2.1
Direct interface cabling
If the user intends to directly wire the SIM923A independent of the
SIM900 Mainframe, communication is usually possible by directly
connecting the appropriate interface lines from the SIM923A DB–15
plug to the RS-232 serial port of a personal computer.1 Connect RXD
from the SIM923A directly to RD on the PC, TXD directly to TD, and
similarly RTS→RTS and CTS→CTS. In other words, a null-modem
style cable is not needed.
To interface directly to the DB–9 male (DTE) RS-232 port typically
found on contemporary personal computers, a cable must be made
with a female DB–15 socket to mate with the SIM923A, and a female
DB–9 socket to mate with the PC’s serial port. Separate leads from
the DB–15 need to go to the power supply, making what is sometimes
know as a “hydra” cable. The pin-connections are given in Table 1.3.
DB–15/F to SIM923A
Name
DB–9/F
3 ←→ 7
4 ←→ 8
10 ←→ 3
11 ←→ 2
5
7 ←→
14 ←→
13 ←→
8,9 ←→
1 ←→
RTS
CTS
TxD
RxD
Computer Ground
to P/S
−15 VDC
+15 VDC
+5 VDC
Ground (P/S return current)
Signal Ground (separate wire to Ground)
Table 1.3: SIM923A Direct Interface Cable Pin Assignments
1
SIM923A
Although the serial interface lines on the DB-15 do not satisfy the minimum
voltage levels of the RS-232 standard, they are typically compatible with desktop
personal computers
RTD Temperature Monitor
1–8
1.4.2.2
Getting Started
Serial settings
The initial serial port settings at power-on are: 9600 Baud, 8–bits, no
parity, 1 stop bit, and RTS/CTS flow control. These may be changed
with the BAUD, FLOW, or PARI commands.
The maximum standard baud rate that the SIM923A supports is 38400.
The minimum baud rate is 110. Above 38400, the SIM923A can be
set to the following (non-RS-232-standard) baud rates: 62500, 78125,
104167, 156250. Note that these rates are typically not accessible on a
standard PC RS-232 port, but can be used between the SIM923A and
the SIM900 Mainframe.
SIM923A
RTD Temperature Monitor
2
Remote Operation
This chapter describes operating the SIM923A over the serial interface.
In This Chapter
2.1
2.2
2.3
2.4
2.5
Index of Common Commands . . . . . . . . . . . .
Alphabetic List of Commands . . . . . . . . . . . .
Introduction . . . . . . . . . . . . . . . . . . . . . . .
2.3.1 Power-on configuration . . . . . . . . . . . .
2.3.2 Buffers . . . . . . . . . . . . . . . . . . . . . .
2.3.3 Device Clear . . . . . . . . . . . . . . . . . . .
Commands . . . . . . . . . . . . . . . . . . . . . . .
2.4.1 Command syntax . . . . . . . . . . . . . . . .
2.4.2 Notation . . . . . . . . . . . . . . . . . . . . .
2.4.3 Readout commands . . . . . . . . . . . . . .
2.4.4 Setpoint and analog output commands . . .
2.4.5 Excitation commands . . . . . . . . . . . . .
2.4.6 Display & configuration commands . . . . .
2.4.7 Sensor calibration commands . . . . . . . . .
2.4.8 Serial communication commands . . . . . .
2.4.9 Status commands . . . . . . . . . . . . . . . .
2.4.10 Interface commands . . . . . . . . . . . . . .
Status Model . . . . . . . . . . . . . . . . . . . . . .
2.5.1 Status Byte (SB) . . . . . . . . . . . . . . . . .
2.5.2 Service Request Enable (SRE) . . . . . . . . .
2.5.3 Standard Event Status (ESR) . . . . . . . . .
2.5.4 Standard Event Status Enable (ESE) . . . . .
2.5.5 Communication Error Status (CESR) . . . . .
2.5.6 Communication Error Status Enable (CESE)
2.5.7 Overload Status (OVCR) . . . . . . . . . . . .
2.5.8 Overload Status (OVSR) . . . . . . . . . . . .
2.5.9 Overload Status Enable (OVSE) . . . . . . . .
2–2
2–4
2–6
2–6
2–6
2–6
2–7
2–7
2–8
2–9
2 – 10
2 – 11
2 – 11
2 – 12
2 – 13
2 – 14
2 – 15
2 – 19
2 – 20
2 – 21
2 – 21
2 – 21
2 – 22
2 – 22
2 – 23
2 – 23
2 – 23
2–1
2–2
2.1
Remote Operation
Index of Common Commands
symbol
i,j
f ,g
z
s
definition
Integers
Floating-point values
Literal token
Arbitrary character sequence (no “,” or “;”)
(?)
var
{var}
[var]
Required for queries; illegal for set commands
Parameter always required
Required parameter for set commands; illegal for queries
Optional parameter for both set and query forms
Readout
RVAL? [n]
TVAL? [n]
TDEV? [n]
SOUT
2–9
2–9
2–9
2–9
Setpoint/Analog Output
TSET(?) {f }
2 – 10
VKEL(?) {f }
2 – 10
AMOD(?) {z}
2 – 10
AOUT(?) {f }
2 – 10
Excitation
EXON(?) {z}
EXCI(?) {z}
IPOL(?) {z}
Resistance Value
Temperature Value
Temperature Deviation Value
Stop Streaming
Temperature Setpoint
Temperature Scale Factor
Analog Output Mode
Analog Output Voltage
2 – 11 Excitation On/Off
2 – 11 Current Source High/Low
2 – 11 Current Source Polarity
Display& Configuration
DISX(?) {z}
2 – 11 Display Enable/Disable
DISP(?) {z}
2 – 11 Display Mode
FPLC(?) {i}
2 – 11 Frequency of Power Line Cycle
Sensor Calibration
CINI(?) {z,s}
2 – 12
CAPT f,g
2 – 12
CAPT? j
2 – 13
CURV(?) {z}
2 – 13
Initialize Sensor Calibration
Add User Curve Point
Query User Curve Point
Select Sensor Curve
Serial Communications
BAUD(?) {i}
2 – 13 Baud Rate
FLOW(?) {z}
2 – 13 Flow Control
SIM923A
RTD Temperature Monitor
2.1
Index of Common Commands
SIM923A
2–3
PARI(?) {z}
2 – 13 Parity
Status
*CLS
*STB? [i]
*SRE(?) [i,] {j}
*ESR? [i]
*ESE(?) [i,] {j}
CESR? [i]
CESE(?) [i,]{j}
OVCR? [i]
OVSR? [i]
OVSE(?) [i,]{j}
PSTA(?) {z}
2 – 14
2 – 14
2 – 14
2 – 14
2 – 14
2 – 14
2 – 14
2 – 14
2 – 15
2 – 15
2 – 15
Clear Status
Status Byte
Service Request Enable
Standard Event Status
Standard Event Status Enable
Communication Error Status
Communication Error Status Enable
Overload Condition
Overload Status
Overload Status Enable
Pulse −STATUS Mode
Interface
*RST
CONS(?) {z}
*IDN?
*OPC(?)
LEXE?
LCME?
LBTN?
TOKN(?) {z}
TERM(?) {z}
2 – 15
2 – 16
2 – 16
2 – 16
2 – 16
2 – 17
2 – 17
2 – 17
2 – 18
Reset
Console Mode
Identify
Operation Complete
Execution Error
Device Error
Button
Token Mode
Response Termination
RTD Temperature Monitor
2–4
2.2
Remote Operation
Alphabetic List of Commands
?
*CLS
*ESE(?) [i,] {j}
*ESR? [i]
*IDN?
*OPC(?)
*RST
*SRE(?) [i,] {j}
*STB? [i]
2 – 14
2 – 14
2 – 14
2 – 16
2 – 16
2 – 15
2 – 14
2 – 14
Clear Status
Standard Event Status Enable
Standard Event Status
Identify
Operation Complete
Reset
Service Request Enable
Status Byte
A
AMOD(?) {z}
AOUT(?) {f }
2 – 10 Analog Output Mode
2 – 10 Analog Output Voltage
B
BAUD(?) {i}
2 – 13 Baud Rate
C
CAPT f,g
CAPT? j
CESE(?) [i,]{j}
CESR? [i]
CINI(?) {z,s}
CONS(?) {z}
CURV(?) {z}
2 – 12
2 – 13
2 – 14
2 – 14
2 – 12
2 – 16
2 – 13
Add User Curve Point
Query User Curve Point
Communication Error Status Enable
Communication Error Status
Initialize Sensor Calibration
Console Mode
Select Sensor Curve
D
DISP(?) {z}
DISX(?) {z}
2 – 11 Display Mode
2 – 11 Display Enable/Disable
E
EXCI(?) {z}
EXON(?) {z}
2 – 11 Current Source High/Low
2 – 11 Excitation On/Off
F
FLOW(?) {z}
FPLC(?) {i}
2 – 13 Flow Control
2 – 11 Frequency of Power Line Cycle
I
IPOL(?) {z}
2 – 11 Current Source Polarity
SIM923A
RTD Temperature Monitor
2.2
Alphabetic List of Commands
2–5
L
LBTN?
LCME?
LEXE?
2 – 17 Button
2 – 17 Device Error
2 – 16 Execution Error
O
OVCR? [i]
OVSE(?) [i,]{j}
OVSR? [i]
2 – 14 Overload Condition
2 – 15 Overload Status Enable
2 – 15 Overload Status
P
PARI(?) {z}
PSTA(?) {z}
2 – 13 Parity
2 – 15 Pulse −STATUS Mode
R
RVAL? [n]
2 – 9 Resistance Value
S
SOUT
2 – 9 Stop Streaming
T
TDEV? [n]
TERM(?) {z}
TOKN(?) {z}
TSET(?) {f }
TVAL? [n]
2–9
2 – 18
2 – 17
2 – 10
2–9
Temperature Deviation Value
Response Termination
Token Mode
Temperature Setpoint
Temperature Value
V
VKEL(?) {f }
SIM923A
RTD Temperature Monitor
2 – 10 Temperature Scale Factor
2–6
2.3
Remote Operation
Introduction
Remote operation of the SIM923A is through a simple command language documented in this chapter. Both set and query forms of most
commands are supported, allowing the user complete control of the
amplifier from a remote computer, either through the SIM900 Mainframe or directly via RS-232 (see Section 1.4.2.1).
See Table 1.2 for specification of the DB–15 SIM interface connector.
2.3.1
Power-on configuration
The settings for the remote interface are 9600 baud with no parity
and hardware flow control, and local echo disabled (CONS OFF).
Most of the SIM923A instrument settings are stored in non-volatile
memory, and at power-on the instrument returns to the state it was
last in when power was removed. Exceptions are noted in the command descriptions.
Reset values of parameters are shown in boldface.
2.3.2
Buffers
Incoming data from the host interface is stored in a 32-byte input
buffer. Characters accumulate in the input buffer until a command
terminator (either hCRi or hLFi) is received, at which point the message is parsed and executed. Query responses from the SIM923A are
buffered in a 32-byte output queue.
If the input buffer overflows, then all data in both the input buffer
and the output queue are discarded, and an error is recorded in the
CESR and ESR status registers.
2.3.3
Device Clear
The SIM923A host interface can be asynchronously reset to its poweron configuration by sending an RS-232-style hbreaki signal. From the
SIM900 Mainframe, this is accomplished with the SRST command;
if directly interfacing via RS-232, then use a serial break signal. After
receiving the Device Clear, the interface is reset to 9600 baud and
CONS mode is turned OFF. Note that this only resets the communication interface; the basic function of the SIM923A is left unchanged;
to reset the instrument, see *RST.
The Device Clear signal will also terminate any streaming outputs
from the SIM923A due to a TVAL?, TDEV?, or RVAL? query of multiple conversions.
SIM923A
RTD Temperature Monitor
2.4
2.4
Commands
2–7
Commands
This section provides syntax and operational descriptions for remote
commands.
2.4.1
Command syntax
The four letter mnemonic (shown in CAPS) in each command sequence specifies the command. The rest of the sequence consists of
parameters.
Commands may take either set or query form, depending on whether
the “?” character follows the mnemonic. Set only commands are
listed without the “?”, query only commands show the “?” after the
mnemonic, and optionally query commands are marked with a “(?)”.
Parameters shown in { } and [ ] are not always required. Parameters in
{ } are required to set a value, and are omitted for queries. Parameters
in [ ] are optional in both set and query commands. Parameters listed
without any surrounding characters are always required.
Do not send ( ) or { } or [ ] as part of the command.
Multiple parameters are separated by commas. Multiple commands
may be sent on one command line by separating them with semicolons (;) so long as the input buffer does not overflow. Commands
are terminated by either hCRi or hLFi characters. Null commands
and whitespace are ignored. Execution of command(s) does not
begin until the command terminator is received.
tokens Token parameters (generically shown as z in the command de-
scriptions) can be specified either as a keyword or integer value.
Command descriptions list the valid keyword options, with each
keyword followed by its corresponding integer value. For example,
to set the response termination sequence to hCRi+hLFi, the following
two commands are equivalent:
TERM CRLF
—or—
TERM 3
For queries that return token values, the return format (keyword or
integer) is specified with the TOKN command.
SIM923A
RTD Temperature Monitor
2–8
2.4.2
Remote Operation
Notation
The following table summarizes the notation used in the command
descriptions:
symbol
i,j
f ,g
z
s
definition
Integers
Floating-point values
Literal token
Arbitrary character sequence (no “,” or “;”)
(?)
var
{var}
[var]
Required for queries; illegal for set commands
Parameter always required
Required parameter for set commands; illegal for queries
Optional parameter for both set and query forms
SIM923A
RTD Temperature Monitor
2.4
Commands
2.4.3
2–9
Readout commands
RVAL? [n]
Resistance Value
Query the sensor resistance.
The result is formatted as +#.######E+##, where + indicates sign (“+”
or “−”), and the value following E is a power-of-ten that multiplies
the preceeding value. The value is always in ohms.
If the optional parameter n is provided, then n sequential conversion
results are returned to the host. If n=0, the conversion results continue indefinitely. To terminate the stream before n results (or when
n=0), issue the SOUT command.
Note that omitting n is equivalent to n=1.
TVAL? [n]
Temperature Value
Query the sensor temperature value.
The result is formatted identically to RVAL, above.
If the optional parameter n is provided, then n sequential conversion
results are returned to the host. If n=0, the conversion results continue indefinitely. To terminate the stream before n results (or when
n=0), issue the SOUT command.
Note that omitting n is equivalent to n=1.
TDEV? [n]
Temperature Deviation Value
Query the sensor temperature minus setpoint value.
The result is formatted identically to RVAL, above.
If the optional parameter n is provided, then n sequential conversion
results are returned to the host. If n=0, the conversion results continue indefinitely. To terminate the stream before n results (or when
n=0), issue the SOUT command.
Note that omitting n is equivalent to n=1.
SOUT
Stop Streaming
Turn off streaming output.
SIM923A
RTD Temperature Monitor
2 – 10
2.4.4
Remote Operation
Setpoint and analog output commands
TSET(?) {f }
Temperature Setpoint
Set (query) the temperature setpoint {to f kelvin}. This is the “offset”
value used for the scaled analog output when in AMOD REL mode.
Temperature values must be in the range 1 mK ≤ T ≤ 9999.499 K.
VKEL(?) {f }
Temperature Scale Factor
Set (query) the temperature scale factor {to f }, in volts per kelvin.
When set to 1.0, 0.1, or 0.01, the corresponding front panel scale
indicator (10 V = 10 K, 100 K, or 1000 K) is lit; when set to any other
value, all three indicators are dark.
AMOD(?) {z}
Analog Output Mode
Set (query) the analog output mode {to z=(ABS 0, REL 1, MAN 2)}.
In AMOD ABS, the scaled output is given by
V = T × VKEL.
In AMOD REL, the output is given by
V = (T − Tset ) × VKEL.
In AMOD MAN, the output is controlled by AOUT.
AOUT(?) {f }
Analog Output Voltage
Set (query) the manual analog output {to f }, in volts.
SIM923A
RTD Temperature Monitor
2.4
2.4.5
Commands
2 – 11
Excitation commands
EXON(?) {z}
Excitation On/Off
Set (query) the excitation current {to z=(OFF 0, ON 1)}.
EXCI(?) {z}
Current Source High/Low
Set (query) the excitation current {to z=(LOW 0, HIGH 1)}.
Setting EXCI LOW commands the current source to 10 µA, while
EXCI HIGH sets it to 1 mA. Note that the EXCI setting does not alter the EXON setting; if the current source is off, switching between
10 µA and 1 mA still leaves the source off.
IPOL(?) {z}
Current Source Polarity
Set (query) the excitation current polarity {to z=(POSITIVE 0,
NEGATIVE 1)}.
Setting IPOL NEGATIVE reverses the excitation; IPOL POSITIVE sets it
to nominal.
2.4.6
Display & configuration commands
DISX(?) {z}
Display Enable/Disable
Set (query) the front panel display {to z=(OFF 0, ON 1)}.
The DISX setting is not stored in non-volatile memory. At power-on,
the SIM923A returns to DISX ON.
DISP(?) {z}
Display Mode
Set (query) the display mode {to z=(OHMS 0, TEMP 1, or TSET 2)}.
If DISP OHMS, then results are displayed in ohms or milliohms; if
DISP TEMP, results are displayed in kelvin. If DISP TSET, the display
shows the setpoint temperature.
FPLC(?) {i}
Frequency of Power Line Cycle
Set (query) the power line rejection frequency {to j=(50, 60)}, in Hz.
SIM923A
RTD Temperature Monitor
2 – 12
2.4.7
Remote Operation
Sensor calibration commands
In addition to the built-in curve, the SIM923A has a dedicated 1024point non-volatile memory for storing user calibration data. Once
loaded, this curve is retained by the SIM923A though power cycles.
CINI(?) {z,s}
Initialize Sensor Calibration
Initialize sensor calibration curve.
The set form of the command, CINI z,s, erases the old curve. The
parameter zspecifies the curve format, as one of:
z meaning
LINEAR 0 ohms, kelvin
SEMILOGT 1 ohms, log10 (kelvin)
SEMILOGR 2 log10 (ohms), kelvin
LOGLOG 3 log10 (ohms), log10 (kelvin)
The second parameter s is an arbitrary identification string for this
sensor calibration curve. This string can consist of any non-blank
characters except the comma “,” or semicolon “;”, and can be up to
15 characters in length.
If CURV USER was active when CINI is executed, the SIM923A reverts
to CURV STAN, and records an execution error (EXE bit in the ESR)
of “uninitialized curve.”
The query form of the command, CINI?, returns the following response:
hformati, hseriali, n
where hformati is the calibration curve format (same as z above),
hseriali is the identification string (s above), and n is the number of
points currently stored in the curve.
CAPT f,g
Add User Curve Point
Add a new point to the user curve. f is the raw sensor value (in
either ohms or log10 (ohms), depending on curve format), and g is the
corresponding temperature value (in either kelvin or log10 (kelvin),
again depending on curve format).
Note that curve points must be added in increasing order of sensor
value f .
Temperature values must be in the range 1 mK ≤ T ≤ 9999.499 K.
SIM923A
RTD Temperature Monitor
2.4
Commands
CAPT? j
2 – 13
Query User Curve Point
Query the value of the user curve, entry point j.
The response is
hsensori,htemperaturei,
where hsensori is the raw sensor value (in either ohms or log10 (ohms),
depending on curve format), and htemperaturei is the corresponding
temperature value (in either kelvin or log10 (kelvin), again depending
on curve format).
CURV(?) {z}
Select Sensor Curve
Set (query) the sensor curve selection {to z=(STAN 0, USER 1)}.
The built-in standard curve for Pt RTDs (IEC 751) is selected by
z=STAN. When CURV USER is selected, the user calibration curve
(previously loaded with CINI and CAPT) is used.
2.4.8
Serial communication commands
For further discussion of serial communications, including limitations on settings, see Section 1.4.2.2.
BAUD(?) {i}
Baud Rate
Set (query) the baud rate {to i}.
At power-on, the baud rate defaults to 9600.
Actual baud rate settings depend on implementation details of the
SIM923A, and are limited to values of 312500/n, where n is a positive
integer. As a result, queries of BAUD? will in general be slightly
different from the set values. For example, after setting BAUD 9600,
the query BAUD? will respond 9470. The functional requirement
for successful asynchronous serial communication is no greater than
∼ 5 % mismatch in baud rates.
FLOW(?) {z}
Flow Control
Set (query) flow control {to z=(NONE 0, RTS 1, XON 2)}.
At power-on, the SIM923A defaults to FLOW RTS flow control.
PARI(?) {z}
Parity
Set (query) parity {to z = (NONE 0, ODD 1, EVEN 2, MARK 3, SPACE 4)}.
At power-on, the SIM923A defaults to PARI NONE.
SIM923A
RTD Temperature Monitor
2 – 14
2.4.9
Remote Operation
Status commands
The Status commands query and configure registers associated with
status reporting of the SIM923A. See Section 2.5 for more details.
*CLS
Clear Status
*CLS immediately clears the ESR, CESR, and the OVSR.
*STB? [i]
Status Byte
Reads the Status Byte register [bit i].
Execution of the *STB? query (without the optional bit i) always
causes the −STATUS signal to be deasserted. Note that *STB? i will
not clear −STATUS, even if bit i is the only bit presently causing the
−STATUS signal.
*SRE(?) [i,] {j}
Service Request Enable
Set (query) the Service Request Enable register [bit i] {to j}.
*ESR? [i]
Standard Event Status
Reads the Standard Event Status Register [bit i].
Upon executing *ESR?, the returned bit(s) of the ESR register are
cleared.
*ESE(?) [i,] {j}
Standard Event Status Enable
Set (query) the Standard Event Status Enable Register [bit i] {to j}.
CESR? [i]
Communication Error Status
Query Communication Error Status Register [for bit i].
Upon executing a CESR? query, the returned bit(s) of the CESR
register are cleared.
CESE(?) [i,]{j}
Communication Error Status Enable
Set (query) Communication Error Status Enable Register [bit i] {to j}.
OVCR? [i]
Overload Condition
Query Overload Condition Register [for bit i].
SIM923A
RTD Temperature Monitor
2.4
Commands
OVSR? [i]
2 – 15
Overload Status
Query Overload Status Register [for bit i].
Upon executing a OVSR? query, the returned bit(s) of the OVSR
register are cleared.
OVSE(?) [i,]{j}
Overload Status Enable
Set (query) Overload Status Enable Register [bit i] {to j}.
PSTA(?) {z}
Pulse −STATUS Mode
Set (query) the Pulse −STATUS Mode {to z=(OFF 0, ON 1)}.
When PSTA ON is set, any new service request will only pulse the
−STATUS signal low (for a minimum of 1 µs). The default behavior
is to latch −STATUS low until a *STB? query is received.
At power-on, PSTA is set to OFF.
2.4.10
Interface commands
*RST
Reset
Reset the SIM923A to default configuration.
The following commands are internally executed upon *RST:
• DISX ON
• EXON ON
• EXCI LOW
• CURV STAN
• DISP TEMP
• AMOD ABS
• VKEL 1
• IPOL POSITIVE
• SOUT
SIM923A
RTD Temperature Monitor
2 – 16
CONS(?) {z}
Remote Operation
Console Mode
Set (query) the Console mode {to z=(OFF 0, ON 1)}.
CONS causes each character received at the Input Buffer to be copied
to the Output Queue.
At power-on and Device-Clear, CONS is set to OFF.
*IDN?
Identify
Read the device identification string.
The identification string is formatted as:
Stanford Research Systems,SIM923A,s/n******,ver#.##
where ****** is the 6-digit serial number, and #.## is the firmware
revision level.
*OPC(?)
Operation Complete
Operation Complete. Sets the OPC flag in the ESR register.
The query form *OPC? writes a 1 in the output queue when complete,
but does not affect the ESR register.
LEXE?
Execution Error
Query the last execution error code. Valid codes are:
Value
0
1
2
3
16
17
18
19
20
Definition
No execution error since last LEXE?
Illegal value
Wrong token
Invalid bit
Uninitialized curve
Curve full
Curve point out-of-order
Illegal temperature value
No Excitation
SIM923A
RTD Temperature Monitor
2.4
Commands
LCME?
2 – 17
Device Error
Query the last command error code. Valid codes are:
Value
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
LBTN?
Definition
No command error since last LCME?
Illegal command
Undefined command
Illegal query
Illegal set
Missing parameter(s)
Extra parameter(s)
Null parameter(s)
Parameter buffer overflow
Bad floating-point
Bad integer
Bad integer token
Bad token value
Bad hex block
Unknown token
Button
Query the last button-press code. Valid codes are:
Value
0
1
2
3
4
5
6
TOKN(?) {z}
Definition
no button pressed since last query
[Rel]
[Scale]
[Setpoint]
[Units]
[Reverse]
[Excitation]
Token Mode
Set (query) the Token Query mode {to z=(OFF 0, ON 1)}.
If TOKN ON is set, then queries to the SIM923A that return tokens will
return the text keyword; otherwise they return the decimal integer
value.
Thus, the only possible responses to the TOKN? query are ON and 0.
At power-on, TOKN OFF is set.
SIM923A
RTD Temperature Monitor
2 – 18
TERM(?) {z}
Remote Operation
Response Termination
Set (query) the htermi sequence {to z=(NONE 0, CR 1, LF 2, CRLF 3,
LFCR 4)}.
The htermi sequence is appended to all query responses sent by the
module, and is constructed of ASCII character(s) 13 (carriage return)
and/or 10 (line feed).
At power-on, TERM CRLF is set.
SIM923A
RTD Temperature Monitor
2.5
2.5
Status Model
2 – 19
Status Model
The SIM923A status registers follow the hierarchical IEEE–488.2 format. A block diagram of the status register array is given in Figure 2.1.
There are three categories of registers in the SIM923A status model:
Condition Registers : These read-only registers correspond to the real-time condition of some underlying physical property being monitored.
Queries return the latest value of the property, and have no
other effect. Condition register names end with CR.
Event Registers : These read-only registers record the occurrence of defined
events. When the event occurs, the corresponding bit is set
to 1. Upon querying an event register, any set bits within it
are cleared. These are sometimes known as “sticky bits,” since
once set, a bit can only be cleared by reading its value. Event
register names end with SR.
Enable Registers : These read/write registers define a bitwise mask for their corresponding event register. If any bit position is set in an event
register while the same bit position is also set in the enable
register, then the corresponding summary bit message is set.
Enable register names end with SE.
Communication Error Status
Standard Event Status
DCAS: Device Clear 7
CTSH: CTS Halted 6
7
RTSH: RTS Halted 5
OVR: Input Buffer Overrun 4
5
HWOVRN: Hardware Overrun 3
NOISE: Noise Error 2
3
FRAME: Framing Error 1
PARITY: Parity Error 0
1
6
4
PON: Power On 7
URQ: User Request 6
7
CME: Command Error 5
EXE: Execution Error 4
5
DDE: Device Error 3
QYE: Query Error 2
3
2
7
7 CESB
INP: Input Buffer Error 1
OPC: Operation Complete 0
1
6
X MSS
0
5
5 ESB
ESE
4
4 IDLE
3
3 undef
ESR
6
4
CESR
Overload Status
2
0
CESE
Status Byte
2
2 undef
undef (0) X
undef (0) X
X
X
1
1 undef
X
X
undef (0) X
undef (0) X
X
X
0
SB
0 OVSB
SRE
X
X
undef (0) X
OVERT 2
X
2
2
UNDERT 1
ADC 0
1
1
0
0
OVCR
-STATUS
X
OVSR OVSE
Figure 2.1: Status Register Model for the SIM923A RTD Temperature
Monitor.
SIM923A
RTD Temperature Monitor
2 – 20
2.5.1
Remote Operation
Status Byte (SB)
The Status Byte is the top-level summary of the SIM923A status
model. When masked by the Service Request Enable register, a bit
set in the Status Byte causes the −STATUS signal to be asserted on
the rear-panel SIM interface connector.
Typically, −STATUS remains asserted (low) until a *STB? query is
received, at which time −STATUS is deasserted (raised)1 . After clearing the −STATUS signal, it will only be re-asserted in response to a
new status-generating condition.
Weight
Bit
1
2
4
8
16
32
64
128
0
1
2
3
4
5
6
7
Flag
OVSB
undef (0)
undef (0)
undef (0)
IDLE
ESB
MSS
CESB
OVSB : Overload Status Summary Bit. Indicates whether one or more
of the enabled flags in the Overload Status Register has become
true.
IDLE : Indicates that the Input Buffer is empty and the command
parser is idle. Can be used to help synchronize SIM923A query
responses.
ESB : Event Status Bit. Indicates whether one or more of the enabled
events in the Standard Event Status Register is true.
MSS : Master Summary Status. Indicates whether one or more of
the enabled status messages in the Status Byte register is true.
Note that while −STATUS is released by the *STB? query, MSS
is only cleared when the underlying enabled bit message(s) are
cleared.
CESB : Communication Error Summary Bit. Indicates whether one or
more of the enabled flags in the Communication Error Status
Register has become true.
Bits in the Status Byte are not cleared by the *STB? query. These
bits are only cleared by reading the underlying event registers, or by
clearing the corresponding enable registers.
1
but see the PSTA command
SIM923A
RTD Temperature Monitor
2.5
2.5.2
Status Model
2 – 21
Service Request Enable (SRE)
Each bit in the SRE corresponds one-to-one with a bit in the SB
register, and acts as a bitwise AND of the SB flags to generate the
MSS bit in the SB and the −STATUS signal. Bit 6 of the SRE is
undefined—setting it has no effect, and reading it always returns 0.
This register is set and queried with the *SRE(?) command.
This register is cleared at power-on.
2.5.3
Standard Event Status (ESR)
The Standard Event Status register consists of 8 event flags. These
event flags are all “sticky bits” that are set by the corresponding event,
and cleared only by reading or with the *CLS command. Reading a
single bit (with the *ESR? i query) clears only bit i.
Weight
Bit
1
2
4
8
16
32
64
128
0
1
2
3
4
5
6
7
Flag
OPC
INP
QYE
DDE
EXE
CME
URQ
PON
OPC : Operation Complete. Set by the *OPC command.
INP : Input Buffer Error. Indicates data has been discarded from the
Input Buffer.
QYE : Query Error. Indicates data in the Output Queue has been lost.
DDE : Device Dependent Error. Not used in the SIM923A.
EXE : Execution Error. Indicates an error in a command that was
successfully parsed. Out-of-range parameters are an example.
The error code can be queried with LEXE?.
CME : Command Error. Indicates a parser-detected error. The error
code can be queried with LCME?.
URQ : User Request. Indicates a front-panel button was pressed.
PON : Power On. Indicates that an off-to-on transition has occurred
2.5.4
Standard Event Status Enable (ESE)
The ESE acts as a bitwise AND with the ESR register to produce the
single bit ESB message in the Status Byte Register (SB). It can be set
and queried with the *ESE(?) command.
SIM923A
RTD Temperature Monitor
2 – 22
Remote Operation
This register is cleared at power-on.
2.5.5
Communication Error Status (CESR)
The Communication Error Status register consists of 8 event flags;
each of which is set by the corresponding event, and cleared only by
reading or with the *CLS command. Reading a single bit (with the
CESR? i query) clears only bit i.
Weight
Bit
1
2
4
8
16
32
64
128
0
1
2
3
4
5
6
7
Flag
PARITY
FRAME
NOISE
HWOVRN
OVR
RTSH
CTSH
DCAS
PARITY : Parity Error. Set by serial parity mismatch on incoming data
byte.
FRAME : Framing Error. Set when an incoming serial data byte is missing
the STOP bit.
NOISE : Noise Error. Set when an incoming serial data byte does not
present a steady logic level during each asynchronous bitperiod window.
HWOVRN : Hardware Overrun. Set when an incoming serial data byte is
lost due to internal processor latency. Causes the Input Buffer
to be flushed, and resets the command parser.
OVR : Input Buffer Overrun. Set when the Input Buffer is overrun
by incoming data. Causes the Input Buffer to be flushed, and
resets the command parser.
RTSH : RTS holdoff. The host asserted the RTS hardware flow control
line to stop the SIM923A from sending more data.
CTSH : CTS holdoff. The SIM923A asserted the CTS hardware flow
control line to stop the host from sending more data.
DCAS : Device Clear. Indicates the SIM923A received the Device Clear
signal (an RS-232 hbreaki). Clears the Input Buffer and Output
Queue, and resets the command parser.
2.5.6
Communication Error Status Enable (CESE)
The CESE acts as a bitwise AND with the CESR register to produce
the single bit CESB message in the Status Byte Register (SB). It can
SIM923A
RTD Temperature Monitor
2.5
Status Model
2 – 23
be set and queried with the CESE(?) command.
This register is cleared at power-on.
2.5.7
Overload Status (OVCR)
The Overload Condition Register consists of 7 single-bit monitors of
condition events within the SIM923A. Bits in the OVCR reflect the
real-time values of their corresponding signals. Reading the entire
register, or individual bits within it, does not affect the OVCR.
Weight
Bit
1
2
4
8
16
32
64
128
0
1
2
3
4
5
6
7
Flag
ADC
UNDERT
OVERT
undef (0)
undef (0)
undef (0)
undef (0)
undef (0)
ADC : Analog-to-Digital overload.
loaded.
The digitizer input was over-
UNDERT : Calibration curve underflow (R < Rmin ).
OVERT : Calibration curve overflow (R > Rmax ).
2.5.8
Overload Status (OVSR)
The Overload Status Register consists of (latching) event flags that
correspond one-to-one with the bits of the OVCR (see above). Upon
the transition 0 → 1 of any bit within the OVCR, the corresponding
bit in the OVSR becomes set.
Bits in the OVSR are unaffected by the 1 → 0 transitions in the OVCR,
and are cleared only by reading or with the *CLS command. Reading
a single bit (with the OVSR? i query) clears only bit i.
2.5.9
Overload Status Enable (OVSE)
The OVSE acts as a bitwise AND with the OVSR register to produce
the single bit OVSB message in the Status Byte Register (SB). It can
be set and queried with the OVSE(?) command.
This register is cleared at power-on.
SIM923A
RTD Temperature Monitor
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