Keysight / Agilent / HP 44422A Relay Multiplexer Thermocouple Compensation Terminal Block (Terminal Block Only)

The Keysight 44422A is a relay multiplexer thermocouple compensation terminal block designed as a plug-in assembly for the HP 3497A Data Acquisition/Control Unit. This detachable terminal card assembly provides isothermal reference junction compensation to eliminate measurement errors in thermocouple-based temperature acquisition systems. It supports both hardware and software compensation techniques, enabling flexible deployment across single or mixed thermocouple type configurations.

## Technical Specifications

• **Maximum Input Voltage:** Less than 170 V peak between any two input terminals
• **Maximum Current:** 50 mA per channel (non-inductive)
• **Maximum Power:** 0.5 VA per channel
• **Reference Junction Compensation Accuracy:** 1°C
• **Thermal Offset (Direct Switched):** Less than 1 µV differential
• **Thermal Offset (Tree Switched):** Less than 2 µV differential
• **Closed Channel Resistance (Series):** 100 Ω ±10% in High, Lo, and Guard
• **Relay Contact Resistance:** Less than 1 Ω per contact

## Key Features

• Isothermal connector block eliminates unwanted thermocouple measurement errors
• **Hardware Compensation Mode:** Supports up to 20 thermocouples per assembly; single thermocouple type (B, E, J, K, R, S, or T)
• **Software Compensation Mode:** Supports up to 19 thermocouples per assembly; mixed thermocouple types with programmatic voltage-to-temperature conversion
• Capable of voltage and resistance measurements in addition to thermocouple temperature acquisition
• Modular design with detachable relay card and terminal card components

## Typical Applications

Multi-channel thermocouple temperature monitoring in data acquisition systems requiring reference junction compensation. Applicable to systems needing either homogeneous or heterogeneous thermocouple arrays with software-based calibration.

## Compatibility & Integration

**Host System:** HP/Agilent/Keysight 3497A Data Acquisition/Control Unit (Option 020 plug-in assembly)

**Supported Thermocouple Types (Hardware Mode):** B, E, J, K, R, S, T