Small Instrumentation Modules SIM922 and SIM923 — Diode and platinum RTD temperature monitors · Four channels · 1.4 K to 475 K with silicon diodes · 20 K to 873 K with platinum RTDs · Memory for 4 calibration curves plus standard curve SIM922 and SIM923 Temperature Monitors The SIM922 Diode Temperature Monitor and the SIM923 Platinum RTD Monitor are designed to measure four sensors simultaneously. Based on the modular SIM platform, they provide high-performance and multiple-channel capability in a small footprint. SIM922 Each of the four channels in the SIM922 has an independent, precision 10 µA current source to provide sensor excitation. Measurement results can be displayed in kelvin or volts. SIM923 The four channels in the SIM923 have independent, stable 1 mA current sources to provide sensor excitation. Sensor resistance is determined ratiometrically with a half-bridge circuit consisting of the sensor and an internal reference Stanford Research Systems resistor. The current to the sensor can be reversed by the user to test for any offset. Results are displayed in kelvin or ohms. Common Features Both the SIM922 and SIM923 employ four-wire measurement circuits (±I excitation leads, ±V sense leads) making the measurements insensitive to series lead resistance. The four channel excitations are independently controlled and do not switch on or off when the readout is advancing between channels. Sensor excitations can be disabled to reduce power dissipation at sensitive cryogenic stages. This also accelerates readings in the remaining enabled channels. Measurements are performed at rates up to four readings per second. A factory-standard calibration curve is built in for each model. In addition, each channel has non-volatile memory to store a 256-point custom calibration curve to convert sensor units (V or Ω) to temperature units (K).

Number of inputs 4 4 Sensor type Silicon diode Platinum and other RTDs Measurement type 4-wire 4-wire Excitation 4 constant current sources 4 constant current sources 10 µA ± 0.01 %, ±5 ppm/°C 1.0 mA ± 0.1 %, ±5 ppm/°C Sensor units Volts Ohms Input range 0 to 2.5 V 0 Ω to 1400 Ω (includes excitation lead resistance) Calibration curves 1 std., 4 user-defined curves DIN 43760, 4 user-defined curves 256 points each 256 points each Temperature range Sensor dependent Sensor dependent 1.4 K to 475 K (typ.) 20 K to 873 K (typ.) Display resolution 4 digits 4 digits Interface resolution 1 µV 1 mΩ Measurement...