The high-density 34922A 70-Channel Armature Multiplexer (70-Ch Arm MUX) is divided into two banks with 35 latching armature switches (channels 1-35 and 36-70) in each. This module also contains eight armature Analog Bus relays (channels 911-914 and 921-924), four on each bank that can connect the bank relays to the system Analog Buses. Through ABus1 and ABus2 you can connect any of the channels to the internal DMM for voltage or resistance measurements.

Using program commands or the mainframe front panel, you can control each of the channel switches individually, and thus configure the 34922A in these modes:

• Two independent 35-channel 2-wire MUXes. This configuration requires neither using external wiring nor connecting through the internal Analog Buses
• One 35-channel 4-wire MUX. This configuration requires neither using external wiring nor connecting through the internal Analog Buses. For 4-wire resistance measurements, the instrument automatically pairs channel n on Bank 1 (source) with channel n+35 on Bank 2 (sense) to provide these connections. Four-wire controls occur only when doing 4-wire measurement operations through the internal DMM, or scanning a channel previously configured as 4-wire
• One 70-channel 2-wire MUX. You must use external wiring or connect through the internal Analog Bus relays for this configuration. For example, closing Analog Bus channels 913 and 923 connects Bank 1 and Bank 2 through ABus3. Or, externally you can connect COM1 to COM2 to create this configuration.

This module has capability to scan as many as 100 channels/second using the internal DMM. With the automatic “break-before-make” connection operation, you are assured that no two signals are connected to each other during a scan. When using the module in a non-scanning mode, you can close as many channels as you wish.

This module is interlock protected, which means whenever the D-sub connector end of the modules is exposed, the Analog Bus relays automatically open and disconnect from the Analog Bus.

When the power is off, all channel relays maintain state, and the Analog Bus relays open.

Two terminal blocks are available to facilitate wiring connections to the 34922A module:

• 34922T-001 (Option 001) Terminal block with solder connectors
• 34922T-002 (Option 002) Terminal block with screw connectors

For additional information on the 34922A, please see the document linked here beginning on page 25.

The chart below provides a brief overview of multiplexer modules for the 34980A.