Stanford Research SIM921
Stanford Research Systems Laboratory Measurement Instruments.
- Model
- Stanford Research Systems SIM921
- Calibration
- Available on request
- Price
- $1,750
- Status
- In stock
- RFQ ref
- SIM921
This unit
The Stanford Research Systems SIM921 is a precision AC resistance bridge module engineered for cryogenic thermometry with ultra-low excitation power. Operating as a 4-wire bridge with a single input channel, it measures resistances from 1 mΩ to 100 MΩ across a variable excitation frequency range of 2 Hz to 60 Hz. The instrument delivers excitation power below 100 aW, enabling accurate thermistor measurements at temperatures below 50 mK with negligible self-heating errors.
The SIM921 features a 32-bit demodulator with user-selectable time constants from 0.3 s to 300 s and a reading rate of 2 updates/s. Measurement accuracy within the 2 Ω to 200 kΩ range is ±(0.05% of reading + 0.05% of range), with input impedance exceeding 10 GΩ. Internal reference resistors span 1 Ω to 10 MΩ, supplemented by two expanded scales at 200 mΩ and 20 mΩ implemented via additional gain stages.
Maximum permissible lead resistance is 100 Ω plus 25% of range. The module supports both constant current and constant voltage excitation modes. Constant voltage operation reduces power dissipation in NTC thermistors as temperature decreases - essential for cryogenic applications.
A linearized DC analog output provides voltage proportional to resistance or temperature with user-adjustable scale and offset parameters.
Technical Specifications
- Measurement type: 4-wire AC bridge
- Resistance range: 1 mΩ to 100 MΩ
- Excitation frequency: 2 Hz to 60 Hz (variable)
- Excitation power: 10 GΩ (typical)
- Maximum lead resistance: 100 Ω + 25% of range
Key Features
- Constant current and constant voltage excitation modes
- Linearized DC analog output with user-controlled scale and offset
- Support for up to four user-calibration curves (ohm to kelvin) with 200 data points each
- Double-wide SIM module format for SIM900 Mainframe integration
- Remote operation and data querying via computer interface
Compatibility & Integration The SIM921 operates with NTC sensors (germanium, Carbon-Glass, carbon-composition, Cernox, ruthenium oxide) and PTC sensors (rhodium-iron RTD, platinum RTD). Integration with the SIM900 Mainframe provides power, serial communications, and clock synchronization. For closed-loop temperature control, the module pairs with the SIM960 Analog PID Controller.
Specifications
| Parameter | Value |
|---|---|
| Frequency Range | 2 Hz to 60 Hz | Voltage / Current Range: ±15 V and +5 V |
Stanford Research Systems SIM921 — Repair & Calibration Service
Aumictech offers NIST-traceable calibration and repair for the Stanford Research Systems SIM921. Calibration covers calibration scope varies by instrument type: vacuum gauges are verified at multiple pressure points against NIST-traceable pressure standards; spectrophotometers at wavelength accuracy and photometric accuracy points; strain gauge indicators at bridge excitation accuracy and full-scale output accuracy; pH meters against certified buffer solutions at pH 4, 7, and 10.. All calibrations ship with a NIST-traceable certificate. Turnaround is typically 1–3 business days after receipt.
Common Stanford Research Systems SIM921 faults: vacuum gauge filament failure (ionization gauges), spectrophotometer D2 lamp end-of-life, wavelength motor failure, strain indicator front-panel binding post corrosion, pH electrode conditioning failure. Most specialty laboratory instruments fail at their electromechanical interfaces first — vacuum gauge connectors and filament assemblies, spectrophotometer lamp housings and motor drives, strain indicator binding post corrosion. Component-level repair is standard; manufacturer support for legacy instruments is often limited, making third-party bench repair the practical path.
Stanford Research Systems SIM921 price
This Stanford Research Systems SIM921 is listed at $1,750. Calibration is available separately from $450. Contact us for volume pricing or if you need multiple units.
Stanford Research Systems SIM921 calibration cost
NIST-traceable calibration for the Stanford Research Systems SIM921 is $450 (standard — pass/fail certificate and calibration sticker) or $650 (full measured data at every test point, reference standards documented, traceability chain included). Calibration for this instrument covers calibration scope varies by instrument type: vacuum gauges are verified at multiple pressure points against NIST-traceable pressure standards; spectrophotometers at wavelength accuracy and photometric accuracy points; strain gauge indicators at bridge excitation accuracy and full-scale output accuracy; pH meters against certified buffer solutions at pH 4, 7, and 10.. Turnaround is 1 to 3 business days after receipt. See full calibration details →
