Stanford Research SIM923 Diode Temperature Monitor

The Stanford Research Systems SIM923 is a single-wide modular temperature monitor designed for precision measurements with Platinum Resistance Temperature Detectors (Pt RTDs) within the SIM900 Mainframe. The module employs a ratiometric half-bridge measurement technique with four-wire configuration to eliminate lead resistance effects, delivering up to four readings per second across the 20 K to 873 K range.

– Technical Specifications

Measurement Architecture
• Sensor type: Platinum RTDs (Pt-100, DIN 43760)
• Four-wire circuit (±I excitation, ±V sense leads)
• Ratiometric half-bridge with internal reference resistor
• Input resistance range: 0 Ω to 1400 Ω
• Reading rate: 4 readings/second maximum
• Current reversal capability for offset testing

Excitation Source
• Selectable DC current sources: 10 µA and 1 mA
• 1 mA accuracy: ±0.1% with ±5 ppm/°C stability
• 10 µA accuracy: ±0.01% with ±5 ppm/°C stability
• Independent per-channel control with disable option

Outputs and Display
• 4-digit LED display (single-channel, K or Ω selectable)
• Linearized analog output proportional to temperature
• Buffered raw sensor voltage output
• Analog output range: ±10 V (full-scale 10 K to 1000 K)

Calibration
• Factory DIN 43760 curve pre-programmed
• Custom curve storage: up to 256 temperature-vs-resistance points in non-volatile memory
• Remote curve selection via command interface

– Key Features

• Four-wire topology minimizes lead resistance contribution to measurement error
• Dual current-source flexibility accommodates low-power and high-precision requirements
• Current reversal diagnostics detect systematic voltage offsets
• Excitation disable reduces power dissipation in battery or low-power applications
• On-board calibration storage eliminates external lookup tables

– Typical Applications

• Cryogenic temperature monitoring (20 K baseline)
• Materials characterization across wide thermal ranges
• Calibration and verification of secondary temperature standards
• Laboratory and industrial process monitoring

– Compatibility & Integration

The SIM923 integrates into the SIM900 Mainframe ecosystem, requiring clean, well-regulated ±5V and ±15 VDC supplies. Remote command interface enables automated measurement and curve selection in multi-channel systems.