SRS SIM922A Diode Monitor
- Single-channel LED display
- 1.4 K to 475 K with Si,
- GaAs or GaAlAs diodes
- 1.4 K to 873 K with RTDs
- Two analog outputs:
- Linearized V proportional to T
- Sensor voltage (buffered)
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The Stanford Research Systems SIM922A Diode Monitor continuously read a single sensor and provide both digital and analog outputs. Based on the modular SIM platform, they provide high performance capability in a small footprint.
The SRS SIM922A has a programmable, precision 10 µA current source to provide sensor excitation. Results can be displayed in either kelvins or volts.
The SIM922A employs four-wire measurement circuits (±I excitation leads, ±V sense leads), making readings insensitive to series lead resistance. Sensor excitations can be disabled to reduce power dissipation at sensitive cryogenic stages. Measurements are performed at five readings per second.
The scaled analog output (±10 V) produces a voltage proportional to measured temperature, with a full-scale range from 10 K to 1000 K. A relative-mode button subtracts the last absolute reading prior to scaling, to provide expanded resolution for temperature deviations. The second (monitor) output is the buffered, low-noise raw sensor voltage without any additional processing.
Either analog output may be coupled to the SIM960 Analog PID Controller for high-performance, closed-loop temperature control.
A factory-standard calibration curve is pre-programmed for each model. Non-volatile memory also permits storage of a 256-point custom calibration curve to convert sensor units (V or Ω) to temperature units (K).
Results are displayed on an easy-to-read, 4-digit LED display. Full remote operation is available over the serial interface.
| SIM922A | SIM923A | |
| Number of inputs | 1 | 1 |
| Sensor type | Si, GaAs, or GaAlAs diodes | Platinum and other RTDs |
| Measurement type | 4-wire | 4-wire |
| Excitation (constant current) | 10 µA ± 0.01 %, ±5 ppm/°C | 1.0 mA ± 0.1 %, ±5 ppm/°C 10 µA ± 0.1 %, ±5 ppm/°C |
| Sensor units | Volts | Ohms |
| Input range | 0 V to 7.5 V | 0 Ω to 1400 Ω (1 mA excitation) 0 Ω to 140 kΩ (10 µA excitation) (includes excitation lead resistance) |
| Calibration curves | 1 standard plus 1 user curve, 256 points | DIN 43760 plus 1 user curve, 256 points |
| Temperature range (sensor dependent) | 1.4 K to 475 K (typical) | 1.4 K to 873 K (typical) |
| Display resolution | 4 digits | 4 digits |
| Interface resolution | 1 µV | 1 mΩ / 100 mΩ (1 mA / 10 µA) |
| Measurement resolution (rms | 4 µV | 1.2 mΩ / 120 mΩ (1 mA / 10 µA) |
| Accuracy, (23 ± 1) °C | 20 µV + 0.01 % | 5 mΩ / 0.5 Ω + 0.01 % (1 mA / 10 µA) |
| Temperature coefficient | ±5 ppm/°C | ±5 ppm/°C |
| Common Specifications | ||
| Measurement rate | 5 readings per second | |
| Scaled analog output | ±10 VDC full-scale range | |
| Full scale | 10 K, 100 K or 1000 K | |
| Resolution | 300 µV | |
| Accuracy | 1 mV | |
| Monitor analog output | ||
| Offset | ||
| Bandwidth | 4 kHz | |
| Operating temperature | 0 °C to 40 °C, non-condensing | |
| Interface | Serial via SIM interface | |
| Connectors | ||
| Sensor | Two DB9 (female) | |
| SIM | DB15 (male) SIM interface | |
| Analog outputs | Two BNC (front panel) | |
| Power (max.) | Power supplied by the SIM900 Mainframe, or optionally by a user-supplied DC power supply (±15 V and +5 V) | |
| Dimensions | 1.5" × 3.6" × 7.0" (WHL) | |
| Weight | 1.4 lbs. | |
| Warranty | One year parts and labor on defects in materials and workmanship | |
Stanford Research Systems SIM922A datasheet 
