HP / Agilent 34921A 40-Channel Armature Multiplexer for 34980A

The HP/Agilent 34921A is a 40-channel armature multiplexer module for the 34980A Multifunction Switch/Measure Unit. It delivers high-density signal routing with low thermal offset performance, supporting mixed 2-wire and 4-wire configurations for automated test and data acquisition systems. The module features latching armature relays with integrated relay life monitoring and direct AC/DC current measurement capability on four dedicated channels, eliminating the need for external shunts in standard current measurement applications.

## Technical Specifications

• **Channels:** 40 (2-wire configuration)
• **Switch Rating:** 300 V, 1 A
• **Carry Current:** 2 A maximum
• **Scan Rate:** 100 channels/second
• **Configuration:** Mixable 2-wire or 4-wire
• **Thermal Offset:** <3 µV
• **Relay Type:** Latching armature with integrated counter
• **Bandwidth:** Up to 45 MHz
• **Current Measurement Channels:** 4 channels (AC/DC, built-in; additional channels via optional shunts)

## Key Features

• Latching armature relays with integrated relay counter for life monitoring
• Low thermal offset (<3 µV) for precision low-level signal measurements
• Four direct AC/DC current measurement channels on channels 41–44
• Optional terminal blocks (such as 34921T) provide built-in thermocouple reference junctions for temperature measurements with minimal thermal error
• 50-pin D-sub connectors support standard cables, terminal blocks, and mass interconnect solutions
• Safety interlock prevents analog bus connections when not properly configured

## Typical Applications

General-purpose signal scanning, temperature measurement with thermocouple inputs, direct AC/DC current monitoring, and multi-channel data acquisition in automated test environments.

## Compatibility & Integration

Designed as a plug-in module for the Agilent 34980A mainframe. When combined with other 34980A modules, enables up to 560 2-wire or 640 1-wire channels across the system. Connects directly to mainframe analog buses for integrated measurement and switching operations.