Stanford Research SIM922

The Stanford Research Systems SIM922 is a four-channel diode temperature monitor module for precision cryogenic and low-temperature measurements. It employs four-wire sensing circuits on each channel to eliminate lead resistance errors, paired with independent 10 µA ± 0.01% constant current sources for sensor excitation. The module accepts silicon, GaAs, and GaAlAs diodes across a typical range of 1.4 K to 475 K and outputs measurements as either voltage (millivolts) or temperature (Kelvin) at up to four readings per second.

Factory-standard and user-defined calibration curves - up to four custom 256-point curves stored in non-volatile memory - enable direct sensor-to-temperature conversion. Four-digit display resolution and 1 µV interface resolution support high-precision data acquisition. Selectable excitation current can be disabled to minimize sensor power dissipation in sensitive cryogenic applications.

Remote operation is available via RS-232 serial interface with configurable baud rates and flow control. The SIM922 integrates within the SIM900 Mainframe ecosystem and can operate standalone with external ±5 V and ±15 VDC supplies and a DB-15 connector.

Technical Specifications

• Channels: 4 independent, four-wire measurement circuits


• Sensor Type: Silicon diode (Si, GaAs, GaAlAs compatible)


• Temperature Range: 1.4 K to 475 K (typical)


• Input Range: 0 to 2.5 V


• Measurement Rate: Up to 4 readings per second


• Display Resolution: 4 digits


• Interface Resolution: 1 µV


• Measurement Resolution: 1.2 µVrms


• Excitation Current: 10 µA ± 0.01%, ±5 ppm/°C


• Calibration Memory: 1 factory curve + up to 4 user-defined curves (256 points each)

Key Features

• Four-wire measurement eliminates lead resistance artifacts


• Independent precision current sources per channel; excitation disable option for low-power operation


• Non-volatile memory for custom calibration curves


• Selectable output: voltage (mV) or temperature (K)


• RS-232 remote interface; configurable baud rates (9600 to 156250 supported)


• Operates within SIM900 Mainframe or standalone with external power

Compatibility & Integration

• Platform: SIM900 Mainframe (Small Instrumentation Modules)


• Standalone Operation: Requires external ±5 V and ±15 VDC supplies; DB-15 connector interfacing


• Control: Serial RS-232 (default 9600 baud, 8-bit, no parity, 1 stop bit, RTS/CTS flow control)


• SIM922A Variant: Includes scaled analog output (±10 V) proportional to measured temperature