What is the difference between the 34901A and 34902A multiplexer modules?

The 34901A uses armature latching relays, offering up to 20 2-wire channels (plus 2 current channels) and a scan speed of up to 60 channels per second. The 34902A uses reed relays, providing 16 2-wire channels with a faster scan speed of up to 250 channels per second.

Which mainframe supports the 34922A high-density multiplexer?

The 34922A is designed specifically for the Keysight 34980A Multifunction Switch/Measure Unit. It is not compatible with the 34970A or 34972A mainframes.

Does the 34905A RF multiplexer module require an external power supply?

No, the 34905A is powered directly via the backplane of the compatible 34970A or 34972A mainframe.

Keysight Technologies (Agilent HP) Multiplexers

5 models with full specifications in Multiplexers.

Keysight Technologies (formerly Agilent and HP) offers a wide selection of plug-in multiplexer modules designed for use with its dedicated data acquisition and switch control mainframes. These modules act as multi-channel routing cards, allowing engineers to connect multiple measurement points to internal or external instruments like digital multimeters. Depending on the system architecture—such as the legacy HP 3488A, the widely used 34970A and 34972A systems, or the high-density 34980A platform—users can choose from various relay technologies, channel configurations, and signal types. This guide explains the differences between standard armature, high-speed reed, RF, and high-density multiplexers within the Keysight product portfolio, helping technical buyers choose the correct module for their switching and scanning requirements.

Mainframe Compatibility: Agilent 34970A, 34972A, 34980A, HP 3488A
Relay Types: Armature latching, reed, electromechanical
Maximum Frequency Range: DC to 2 GHz (RF modules)
Maximum Density: Up to 70 channels (2-wire) on a single module

All models

Model	Type	Power Supply	Number of Channels	Operating Temperature
34902A	Multiplexers	Powered by 34970A mainframe (internal)	—	—
34901A	Multiplexers	Powered directly from mainframe backplane	20 (configured as 2-wire) or 10 (configured as 4-wire)	0 °C to 55 °C
34905A	Multiplexers	Powered via mainframe backplane	8 (arranged as two independent 1x4 multiplexers)	0°C to 55°C
44470A	Multiplexers	Powered directly by HP 3488A mainframe	10	0 to 55 °C
34922A	Multiplexers	Powered directly via the Keysight 34980A mainframe backplane	70 (2-wire) or 35 (4-wire)	0 °C to 55 °C

Relay Technologies and Scan Rates

The choice of switching element directly affects scanning speed and relay lifespan. The 34901A uses armature latching relays, providing up to 20 channels of 2-wire routing (or 10 channels of 4-wire routing) and 2 dedicated fused current channels. It features a maximum scan rate of 60 channels per second and can switch up to 300 V.

For higher speed scanning applications, the 34902A employs reed relays. This module provides 16 channels of 2-wire routing and achieves scanning rates up to 250 channels per second. Both the 34901A and 34902A include integrated thermocouple reference junctions on the module to support temperature measurements directly through their compatible mainframes.

High-Density and Legacy Platforms

For high-channel-count automated test systems, the 34922A provides high-density routing for the Keysight 34980A Multifunction Switch/Measure Unit. It features 70 channels configured for 2-wire measurements (or 35 channels for 4-wire measurements) arranged in two banks of 35 channels. It utilizes low-thermal armature latching relays with a scan rate of up to 120 channels per second and handles up to 300 V.

For older systems, the legacy 44470A is a 10-channel, 2-wire electromechanical multiplexer designed specifically for the HP 3488A Switch/Control Unit. It operates as a double-pole, single-throw (DPST) latching switch and supports up to 250 V switching.

RF and High-Frequency Routing

Standard multiplexers are not designed for high-frequency signal integrity. For RF and pulsed signals in 50 Ohm systems, the 34905A is a dual 4-channel RF multiplexer module compatible with the 34970A and 34972A mainframes. Operating from DC up to 2 GHz, this module uses SMB connectors and maintains low insertion loss (under 1.00 dB at 2 GHz) and high isolation properties (greater than 60 dB at 100 MHz).