Agilent/Keysight 34521A

The Keysight 34521A is a multiplexer module for the 34980A Multifunction Switch/Measure Unit, delivering dense multi-function switching across 40 2-wire channels. It combines low thermal offset design with integrated thermocouple reference capability, enabling direct temperature measurements through the internal DMM. The module scans at up to 100 channels per second and supports mixed 2-wire and 4-wire configurations with 300 V, 1 A switch rating and 2 A carry current capacity.

Four dedicated fused inputs route current measurements directly to the internal DMM, supporting both AC and DC current analysis without external shunt resistors.

Technical Specifications

• 40 2-wire channels


• 300 V, 1 A switch rating


• 2 A carry current capability


• Scanning rate: up to 100 channels per second


• Latching armature relay design Current Measurement


• Four fused inputs for direct current routing


• AC and DC current measurement support


• Direct connection to internal DMM Thermal Measurement


• Built-in thermocouple reference junction


• Low thermal offset characteristics


• Direct internal DMM integration for temperature readings Interface


• Standard 50-pin D-sub connectors

Key Features

• Mixed 2-wire and 4-wire configuration flexibility


• High-speed acquisition at 100 channels per second


• Integrated current sensing eliminates external shunt resistor requirement


• Minimal thermal transient effects for precision temperature work


• Latching relay technology reduces power consumption during hold states

Typical Applications

• Multi-channel data acquisition with temperature compensation


• Automated thermal testing and profiling


• High-speed current monitoring across distributed measurement points


• Mixed analog signal routing with integrated measurement capability

Compatibility & Integration The 34521A operates exclusively as a plug-in module within the Keysight 34980A Multifunction Switch/Measure Unit, where it leverages the mainframe's internal DMM resources for voltage, current, and resistance measurements alongside integrated switching functions.