The 34923A 40/80-Channel Reed Multiplexer (40/80-Ch Reed MUX) is divided into two equal banks of non-latching reed switches. 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. You can connect any of the channels to the internal DMM through ABus1 and ABus2 for voltage or resistance measurements.
Using program commands or the mainframe front panel, you can control each of the channel switches individually, and configure this module for differential (2-wire or 4-wire) or single-ended (1-wire) mode.
In all modes, this module has capability to scan as many as 500 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.
This module is interlock protected, which means whenever the D-sub connector end of the modules is exposed, the Analog Bus relays immediately open and disconnect from the Analog Bus.
Terminal blocks
If you are using an Keysight 34923T-00x terminal block to connect your DUT to this module, be sure to use the terminal block that corresponds to your module configuration mode.
- 34923T-001 (Option 001) Terminal block for differential (two- or four-wire) mode
- 34923T-002 (Option 002) Terminal block for single-ended (1-wire) mode
Two wire mode
You may configure the 34923A as:
- Two independent 20-channel 2-wire MUXes. This configuration requires neither the use of external wiring nor connection through the internal Analog Buses
- One 40-channel, 2-wire MUX. For this configuration, you must use external wiring or connect through the internal Analog Buses
In 2-wire mode, you can close no more than 20 channels simultaneously due to power dissipation. These 20 channels are split 10 to a bank. However, note that Analog Bus relays count half as much as channel relays in that total. For example, with one Analog Bus relay closed, you can close up to a maximum of 19 channel relays. If you try to close more than the allowed number of channels, you will receive an error message.
Four wire mode
You may configure the 34923A as a 20-channel 4-wire MUX. This configuration requires neither external wiring nor connection through the Analog Buses.
For 4-wire resistance measurements, the instrument automatically pairs channel n on Bank 1 (source) with channel n+20 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 wire mode
You may configure the 34923A as:
- Two independent 40-channel 1-wire MUXes. This configuration requires neither external wiring nor connection through the internal Analog Buses
- One 80-channel 1-wire MUX. You must use external wiring or connect through the internal Analog Bus for this configuration
In 1-wire mode, you can close no more than 40 channels simultaneously due to power dissipation. These channels are split 20 to a bank. For example, with one Analog Bus relay closed you can close up to a maximum of 39 channel relays. If you try to close more than the allowed number of channels, you will receive an error message.