SRS SIM923A Platinum RTD Temperature Monitors

The SRS SIM923A is a precision Platinum RTD temperature monitor designed for simultaneous measurement of up to four independent RTD sensors using 4-wire measurement circuits. Part of the SIM modular platform, it delivers both digital and analog outputs for flexible data acquisition and closed-loop control integration. The unit operates from 20 K to 873 K, measuring resistance up to 1400 Ω with factory-calibrated curves for standard Pt-100 sensors and user-programmable custom calibration tables supporting up to 256 points per channel.

Technical Specifications

• Channels: 4 independent RTD channels


• Measurement Type: 4-wire circuit eliminating lead resistance effects


• Excitation Current: Selectable 10 µA or 1 mA DC per channel; current reversal capability for offset testing


• Temperature Range: 20 K to 873 K (Platinum RTD)


• Resistance Range: 0 to 1400 Ω (sensor + leads)


• Measurement Rate: Up to 4 readings per second


• Calibration: Factory DIN 43760 curve; non-volatile memory for custom curves (256 points per channel); remote selection via serial interface


• Data Display: 4-digit LED; selectable Kelvins or Ohms readout


• Analog Outputs: Scaled ±10 V (10 K to 1000 K full-scale); buffered monitor output (raw sensor voltage)


• Power Supply: ±15 V DC, +5 V DC


• Supply Current: 50 mA (±15 V), 250 mA (+5 V)


• Serial Interface: RS-232 at 9600 to 38400 Baud standard; supports non-standard rates to 156250 Baud for mainframe integration

Key Features

• Independent stable current sources with reversible polarity for diagnostic testing


• Ratiometric half-bridge measurement principle for temperature conversion


• Relative mode for expanded resolution of temperature deviations


• Excitation disable function reduces power dissipation in cryogenic applications


• Full remote control via RS-232 (8-bit, no parity, 1 stop bit, RTS/CTS flow control)

Typical Applications

• Cryogenic temperature monitoring (20 K minimum)


• Multi-point thermal mapping in laboratory and industrial systems


• Closed-loop control via SIM960 Analog PID Controller integration

Compatibility & Integration The SIM923A integrates into the SIM mainframe platform for modular system expansion and operates standalone. Analog outputs directly couple to SIM960 PID controllers for automated temperature regulation.