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
