The Agilent/HP 34901A is a 20-channel multiplexer module for the 34970A and 34972A Data Acquisition/Switch Units. It delivers both 2-wire and 4-wire scanning capabilities with mixed-mode operation on a single module. The unit supports up to 60 channels/second module scan rate and 250 channels/second system scan rate to internal memory, with break-before-make switching that isolates one channel pair at a time during automated scanning. Two fused current input channels accept up to 1 A and connect directly to the mainframe DMM, eliminating external shunt resistors for AC and DC current measurements. A built-in thermocouple reference junction simplifies temperature measurement setups.
Technical Specifications
Multiplexing and Switching
• 20 multiplexer channels plus 2 fused current input channels (22 total)
• 2-wire and 4-wire selectable armature multiplexer
• Mixed 2-wire and 4-wire configuration on same module
• Maximum switching voltage: 300 V
• Maximum switching current: 1 A (dedicated current channels)
• Module scan rate: Up to 60 channels/second
• System scan rate: Up to 250 channels/second to internal memory
• Break-before-make scanning action
• Multiple simultaneous channel closures allowed in non-scanning mode
• Bandwidth: 10 MHz
• Built-in thermocouple reference junction
– Key Features
• Flexible dual-mode switching for impedance and low-voltage DC applications
• Direct current measurement via fused inputs without external components
• High-speed scanning for efficient data acquisition workflows
• Plug-in module design for 3-slot mainframes
– Typical Applications
• Automated voltage, current, and resistance measurement in multi-point systems
• Temperature monitoring via integrated thermocouple reference
• Signal routing in data logging and test automation
• Mixed signal environments requiring both resistance and current measurements
– Compatibility & Integration
Designed for the Agilent/HP 34970A Data Acquisition/Switch Unit and 34972A LXI Data Acquisition/Switch Unit.
