Agilent/Keysight 34908A

The Keysight 34908A is a 40-channel single-ended multiplexer module for the 34970A and 34972A Data Acquisition/Switch Units. It routes signals from multiple sources to test instruments using break-before-make relays optimized for common-low configurations. The module's isolated low connection floats up to 300 V, enabling flexible test setups for battery characterization, component testing, and benchtop applications without earth-ground constraints.

Technical Specifications

• Channel Configuration: 40 single-ended, one-wire inputs


• Switching Architecture: Break-before-make relays; single-wire switching


• Scanning Speed: Up to 60 channels per second


• Module Low Isolation: Isolated from earth; capable of floating up to 300 V


• Supported Measurements: All two-wire internal measurements except current


• Built-in Reference: Thermocouple reference junction


• Signal Routing: Internal analog bus connects low-frequency multiplexers directly to internal DMM

Key Features

• On-module screw-terminal connectors for direct wiring


• High-density channel count in compact form factor via surface mount construction


• Isolated floating low enables measurements above ground potential


• Integrated thermocouple reference eliminates external compensation circuits


• Break-before-make relay action prevents transient cross-connection during channel switching

Operating Conditions

• Temperature: 0 °C to 55 °C


• Humidity: 20% to 80% at 40 °C or less (non-condensing)


• Altitude: Up to 2000 meters


• Installation Category: II


• Pollution Degree: 2


• Shipping Weight: 4 lb

Compatibility & Integration The 34908A plugs directly into Keysight 34970A or 34972A mainframes. Internal signal routing eliminates need for external cabling between the module and host unit's analog measurement engine. Screw-terminal connections accept standard 22–16 AWG instrumentation wire. Product Status: Discontinued; actively supported.