SRS Labs SIM923 Operation manual

Operation and Service Manual
Pt RTD Monitor
SIM923
Stanford Research Systems
Revision 1.7 •May 8, 2007

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 workman-
ship 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.
Copyright c Stanford Research Systems, Inc., 2003, 2007. All rights reserved.
Stanford Research Systems, Inc.
1290–D Reamwood Avenue
Sunnyvale, CA 94089 USA
Phone: [phone] •Fax: [phone]
www.thinkSRS.com •e-mail: [email protected]
Printed in U.S.A. Document number 9-01557-903
SIM923 Pt RTD Monitor

Contents
General Information iii
Service .............................. iii
Symbols ............................. iv
Notation ............................. v
Specifications .......................... vi
1 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 SIMInterface........................ 1–6
2 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 StatusModel........................ 2–17
i

ii Contents
SIM923 Pt RTD Monitor

General Information
The SIM923 Pt RTD Monitor, part of Stanford Research Systems’
Small Instrumentation Modules family, consists of four channels of
sensor excitation and readout for precision low-noise resistive ther-
mometry. Independent 1 mA DC current sources provide sensor
excitations to the four-wire measurement circuits.
Service
Do not install substitute parts or perform any unauthorized modifi-
cations to this instrument.
The SIM923 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)
SIM923 Pt RTD 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.
SIM923 Pt RTD Monitor

vi General Information
Specifications
Performance Characteristics
Min Typ Max Units
Inputs Number of inputs 4
Sensor type Platinum RTD, other RTDs
Measurement type 4–wire
Excitation 4 constant current sources
0.999 1 1.001 mA DC
Sensor Characteristics Sensor units Ohms
Input Range 0 1400 Ω
sensor+lead resistance 1400 Ω
Calibration curves DIN 43760
4 user defined curves
Curve size (each) 256 points
Temperature range 20 873 K (typical)
sensor dependent
Measurement Display resolution 4 digits
Interface resolution 1 mΩ
1 mK
Measurement resolution 1.2 mΩrms
Measurement accuracy, (23 ±1)◦C 5 mΩ
Temperature coefficient −5+5 ppm/◦C
Operating Temperature 0 40 ◦C
Power ±15,+5 V DC
Supply current 50 (±15 V), 250 (+5 V) mA
General Characteristics
Interface Serial (RS-232) through SIM interface
Connectors 2 DB–9 (female)
4–wire measurement +ground (Ch 1 & 2)
4–wire measurement +ground (Ch 3 & 4)
DB–15 (male) SIM interface
Weight 1.4 lbs
Dimensions 1.500 W×3.600 H×7.000 D
SIM923 Pt RTD Monitor

1 Getting Started
This chapter gives you the necessary information to get started
quickly with the SIM923 Pt RTD Monitor.
In This Chapter
1.1 Introduction to the Instrument . . . . . . . . . . . . . 1 – 2
1.1.1 Overview ..................... 1–2
1.2 Front-Panel Operation . . . . . . . . . . . . . . . . . . 1 – 2
1.2.1 Excitation ..................... 1–2
1.2.2 Units........................ 1–2
1.2.3 Current reversal . . . . . . . . . . . . . . . . . . 1 – 3
1.3 Sensor Interface . . . . . . . . . . . . . . . . . . . . . . 1 – 4
1.3.1 Four-wire measurement . . . . . . . . . . . . . 1 – 4
1.3.2 Two-wire measurement . . . . . . . . . . . . . 1 – 5
1.4 SIMInterface ....................... 1–6
1.4.1 SIM interface connector . . . . . . . . . . . . . 1 – 6
1.4.2 Direct interfacing . . . . . . . . . . . . . . . . . 1 – 6
1–1

1–2 Getting Started
1.1 Introduction to the Instrument
The SIM923 Pt RTD Monitor monitors up to four (4) resistive tem-
perature detectors (RTDs) using a stable 1 mA DC current excitation.
1.1.1 Overview
The SIM923 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 calculates 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.
Each channel has an independent current source and reference re-
sistor, so the excitation to the user’s sensor remains steady as the
SIM923 cycles between measurements. Disabling a channel switches
that channel’s current source off.
A precision 24–bit analog-to-digital converter is cycled between the
channels with a rate of 4 conversions per second. With all channels
enabled, a complete cycle is completed every second; disabling some
channels yields a corresponding increase in overall cycle rate.
1.2 Front-Panel Operation
The front panel of the SIM923(see Figure 1.1) provides a simple op-
erator interface.
1.2.1 Excitation
The four channels of the SIM923 Pt RTD Monitor can be indepen-
dently enabled or disabled from the front panel. Disabling a channel
turns offthe 1 mA excitation current to that sensor, and speeds the
readout rate for the remaining (enabled) channels.
To toggle the excitation for a channel, first briefly press [Excitation].
One of the four channel displays will appear highlighted, indicating
which channel is selected. Briefly tap [Excitation] to advance the
highlighted selection until the desired channel is selected. Then
depress and hold [Excitation] until the display switches between the
numerical value and the word .
1.2.2 Units
The SIM923 displays the sensor results either as resistance (in ohms)
or temperature (in kelvin). Pressing [Units] toggles between these
two modes; the active units are indicated by the illuminated Kor Ω.
SIM923 Pt RTD Monitor

1.2 Front-Panel Operation 1–3
Figure 1.1: The SIM923 front and rear panels.
When temperature units are selected, a sensor calibration curve is re-
quired. The SIM923 is preprogrammed with the DIN-43760 standard
curve for Pt–100 RTD sensors. Each channel also has non-volatile
memory to store a separate sensor curve with up to 256 temperature-
vs-resistance points. The actual curve to use is selected with the
remote interface CURV command.
1.2.3 Current reversal
To test for any voltage offsets in the measurement, the user may
command the SIM923 to reverse the excitation current. Any ther-
moelectric or amplifier offsets will remain unchanged under current
reversal, while the true resistive signal will be inverted.
To reverse the excitation current, press [Reverse]. When the current
is reversed (i.e., flowing from the I−pin to the I+pin), REVERSE is
illuminated.
To estimate the magnitude of any offset errors, take the difference
in results before and after current reversal. The best-estimate of the
actual sensor resistance is the average of these two values.
SIM923 Pt RTD Monitor

1–4 Getting Started
1.3 Sensor Interface
The sensor interface on the SIM923 consists of two rear-panel DB–9/F
connectors, labeled “CHANNELS 1 & 2” and “CHANNELS 3 & 4”
(see Figure 1.1). Both connectors follow the same pinout, given in
Table 1.1
Pin Signal
1 I+, Ch 1(3)
2 I−, Ch 1(3)
3 ground
4 I+, Ch 2(4)
5 I−, Ch 2(4)
6 V+, Ch 1(3)
7 V−, Ch 1(3)
8 V+, Ch 2(4)
9 V−, Ch 2(4)
Table 1.1: SIM923 Sensor Interface Connector Pin Assignments, DB–9
1.3.1 Four-wire measurement
To avoid sensitivity to wiring lead resistance, the SIM923 is config-
ured for four-wire measurements. The basic circuit for this wiring
scheme is shown in Figure 1.2.
V+
Sensor
V–
I–
I+
Figure 1.2: Wiring diagram for four-wire readout.
SIM923 Pt RTD Monitor

1.3 Sensor Interface 1–5
1.3.2 Two-wire measurement
If application-specific constraints limit the number of leads to the
sensor, the SIM923 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.
V+
Sensor
V–
I–
I+
Figure 1.3: Wiring diagram for two-wire readout.
SIM923 Pt RTD Monitor

1–6 Getting Started
1.4 SIM Interface
The primary connection to the SIM923 Pt RTD Monitor is the rear-
panel DB–15 SIM interface connector. Typically, the SIM923 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 SIM923 directly, without using the
SIM900 Mainframe. This section provides details on the interface.
The SIM923 has no internal protection against reverse polarity, missing
CAUTION supply, or overvoltage on the power supply pins. Misapplication of power
may cause circuit damage. SRS recommends using the SIM923 together
with the SIM900 Mainframe for most applications.
1.4.1 SIM interface connector
The DB–15 SIM interface connector carries all the power and commu-
nications lines to the instrument. The connector signals are specified
in Table 1.2
Direction
Pin Signal Src ⇒Dest Description
1 SIGNAL GND MF ⇒SIM Ground reference for signal
2−STATUS SIM ⇒MF Status/service request (GND=asserted, +5V=idle)
3 RTS MF ⇒SIM HW Handshake (+5 V=talk; GND=stop)
4 CTS SIM ⇒MF HW Handshake (+5 V=talk; GND=stop)
5−REF 10MHZ MF ⇒SIM 10 MHz reference (optional connection)
6−5V MF ⇒SIM Power supply (No connection in SIM923)
7−15V MF ⇒SIM Power supply (analog circuitry)
8 PS RTN MF ⇒SIM Power supply return
9 CHASSIS GND Chassis ground
10 TXD MF ⇒SIM Async data (start bit=“0”=+5 V; “1”=GND)
11 RXD SIM ⇒MF Async data (start bit=“0”=+5 V; “1”=GND)
12 +REF 10MHz MF ⇒SIM 10 MHz reference (optional connection)
13 +5V MF ⇒SIM Power supply (digital circuitry)
14 +15V MF ⇒SIM Power supply (analog circuitry)
15 +24V MF ⇒SIM Power supply (No connection in SIM923)
Table 1.2: SIM Interface Connector Pin Assignments, DB-15
1.4.2 Direct interfacing
The SIM923 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.
SIM923 Pt RTD Monitor

1.4 SIM Interface 1–7
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,
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.
1.4.2.1 Direct interface cabling
If the user intends to directly wire the SIM923 independent of the
SIM900 Mainframe, communication is usually possible by directly
connecting the appropriate interface lines from the SIM923 DB–15
plug to the RS-232 serial port of a personal computer.1Connect RXD
from the SIM923 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 SIM923, 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 SIM923 Name
DB–9/F
3→ 7 RTS
4→ 8 CTS
10 → 3 TxD
11 → 2 RxD
5 Computer Ground
to P/S
7→ −15 VDC
14 → +15 VDC
13 → +5 VDC
8,9 → Ground (P/S return current)
1→ Signal Ground (separate wire to Ground)
Table 1.3: SIM923 Direct Interface Cable Pin Assignments
1Although 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
SIM923 Pt RTD Monitor

1–8 Getting Started
1.4.2.2 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 SIM923 supports is 38400.
The minimum baud rate is 110. Above 38400, the SIM923 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 SIM923 and
the SIM900 Mainframe.
SIM923 Pt RTD Monitor

2 Remote Operation
This chapter describes operating the SIM923 over the serial interface.
In This Chapter
2.1 Index of Common Commands . . . . . . . . . . . . . 2 – 2
2.2 Alphabetic List of Commands . . . . . . . . . . . . . 2 – 4
2.3 Introduction........................ 2–6
2.3.1 Power-on configuration . . . . . . . . . . . . . 2 – 6
2.3.2 Buffers ....................... 2–6
2.3.3 Device Clear . . . . . . . . . . . . . . . . . . . . 2 – 6
2.4 Commands ........................ 2–7
2.4.1 Command syntax . . . . . . . . . . . . . . . . . 2 – 7
2.4.2 Notation...................... 2–8
2.4.3 Readout commands . . . . . . . . . . . . . . . 2 – 9
2.4.4 Excitation commands . . . . . . . . . . . . . . 2 – 9
2.4.5 Display & configuration commands . . . . . . 2 – 10
2.4.6 Sensor calibration commands . . . . . . . . . . 2 – 10
2.4.7 Serial communication commands . . . . . . . 2 – 11
2.4.8 Status commands . . . . . . . . . . . . . . . . . 2 – 12
2.4.9 Interface commands . . . . . . . . . . . . . . . 2 – 13
2.5 StatusModel ....................... 2–17
2.5.1 Status Byte (SB) . . . . . . . . . . . . . . . . . . 2 – 18
2.5.2 Service Request Enable (SRE) . . . . . . . . . . 2 – 19
2.5.3 Standard Event Status (ESR) . . . . . . . . . . 2 – 19
2.5.4 Standard Event Status Enable (ESE) . . . . . . 2 – 20
2.5.5 Communication Error Status (CESR) . . . . . . 2 – 20
2.5.6 Communication Error Status Enable (CESE) . 2 – 21
2.5.7 Overload Status (OVSR) . . . . . . . . . . . . . 2 – 21
2.5.8 Channel Status Enable (OVSE) . . . . . . . . . 2 – 21
2–1

2–2 Remote Operation
2.1 Index of Common Commands
symbol definition
i,jIntegers
f,gFloating-point values
cChannel number (0–4); c=0 means “all”
zLiteral token
sArbitrary character sequence (no “,” or “;”)
(?) Required for queries; illegal for set commands
var Parameter always required
{var}Required parameter for set commands; illegal for queries
[var] Optional parameter for both set and query forms
Readout
RVAL? c[,n]2 – 9 Resistance Value
TVAL? c[,n]2 – 9 Temperature Value
SOUT 2 – 9 Stop Streaming
Excitation
EXON(?) c{,z}2 – 9 Excitation On/Off
IPOL(?) {z}2 – 9 Current Polarity
Display& Configuration
DISX(?) {z}2 – 10 Display Enable/Disable
DTEM(?) {z}2 – 10 Display Temperature
FPLC(?) {i}2 – 10 Frequency of Power Line Cycle
Sensor Calibration
CINI(?) c{,z,s}2 – 10 Initialize Sensor Calibration
CAPT c,f,g 2 – 11 Add User Curve Point
CAPT? c,j 2 – 11 Query User Curve Point
CURV(?) c{,z}2 – 11 Select Sensor Curve
Serial Communications
BAUD(?) {i}2 – 11 Baud Rate
FLOW(?) {z}2 – 12 Flow Control
PARI(?) {z}2 – 12 Parity
Status
*CLS 2 – 12 Clear Status
*STB? [i]2 – 12 Status Byte
*SRE(?) [i,]{j}2 – 12 Service Request Enable
*ESR? [i]2 – 12 Standard Event Status
SIM923 Pt RTD Monitor

2.1 Index of Common Commands 2–3
*ESE(?) [i,]{j}2 – 12 Standard Event Status Enable
CESR? [i]2 – 13 Communication Error Status
CESE(?) [i,]{j}2 – 13 Communication Error Status Enable
OVSR? [i]2 – 13 Overload Status
OVSE(?) [i,]{j}2 – 13 Overload Status Enable
PSTA(?) {z}2 – 13 Pulse −STATUS Mode
Interface
*RST 2 – 13 Reset
CONS(?) {z}2 – 14 Console Mode
*IDN? 2 – 14 Identify
*OPC(?) 2 – 14 Operation Complete
LEXE? 2 – 14 Execution Error
LCME? 2 – 15 Device Error
LDDE? 2 – 15 Device Error
LBTN? 2 – 15 Button
TOKN(?) {z}2 – 15 Token Mode
TERM(?) {z}2 – 16 Response Termination
SIM923 Pt RTD Monitor

2–4 Remote Operation
2.2 Alphabetic List of Commands
?
*CLS 2 – 12 Clear Status
*ESE(?) [i,]{j}2 – 12 Standard Event Status Enable
*ESR? [i]2 – 12 Standard Event Status
*IDN? 2 – 14 Identify
*OPC(?) 2 – 14 Operation Complete
*RST 2 – 13 Reset
*SRE(?) [i,]{j}2 – 12 Service Request Enable
*STB? [i]2 – 12 Status Byte
B
BAUD(?) {i}2 – 11 Baud Rate
C
CAPT c,f,g 2 – 11 Add User Curve Point
CAPT? c,j 2 – 11 Query User Curve Point
CESE(?) [i,]{j}2 – 13 Communication Error Status Enable
CESR? [i]2 – 13 Communication Error Status
CINI(?) c{,z,s}2 – 10 Initialize Sensor Calibration
CONS(?) {z}2 – 14 Console Mode
CURV(?) c{,z}2 – 11 Select Sensor Curve
D
DISX(?) {z}2 – 10 Display Enable/Disable
DTEM(?) {z}2 – 10 Display Temperature
E
EXON(?) c{,z}2 – 9 Excitation On/Off
F
FLOW(?) {z}2 – 12 Flow Control
FPLC(?) {i}2 – 10 Frequency of Power Line Cycle
I
IPOL(?) {z}2 – 9 Current Polarity
L
LBTN? 2 – 15 Button
LCME? 2 – 15 Device Error
LDDE? 2 – 15 Device Error
LEXE? 2 – 14 Execution Error
SIM923 Pt RTD Monitor