Agilent Technologies Switch/Measure manual 34923A 40/80-Channel Reed Multiplexer, Two-Wire Mode

4Low Frequency Multiplexer Switch Modules

34923A 40/80-Channel Reed Multiplexer

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. Refer to the simplified schematics on page 114 and page 118.

If you are using an optional Agilent 349xxT terminal block to connect your DUT to this module be sure to use the terminal block that corresponds to your module configuration. Use the 34923T- 001 terminal block for 2- wire or 4- wire configuration. Use the 34923T- 002 terminal block for 1- wire configuration. Refer to drawings on page 117 and page 120.

You can confirm the mode in which your module is configured by using the SYSTem:CTYPe? <slot number> program command. This command returns the identity of the plug- in module in the specified slot.

NOTE	Whenever you change from 2- or 4-wire mode to 1-wire mode, or the
	reverse, you must cycle power on the 34980A for the configuration
	to take effect.

Two-Wire Mode

•two independent 20- channel 2- wire MUXes. This configuration requires neither using external wiring nor connecting through the internal Analog Buses.

•one 40- channel, 2- wire MUX. You must use external wiring or connect through the internal Analog Buses for this configuration.

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.

112 34980A User’s Guide