120 34980A User’s Guide
4 Low Frequency Multiplexer Switch Modules
Low Frequency Multiplexer Switch Modules
All low frequency multiplexer (MUX) switch modules feature two banks
of channels that provide broad multiplexing and measuring capabilities.
You can connect a MUX to an external instrument, and/or switch
multiple analog signals to the internal DMM. With the 34921A, 34922A,
34923A, and the 34924A modules, you can close more than one channel
in each bank simultaneously (N:1 configuration). As the 34925A module
is protected with overvoltage circuitry, you can close only one channel in
each bank at one time (1:N configuration).
And, you can connect multiple MUXes to the built- in Analog Buses,
which allow you to scan as many as 560 2- wire (differential) channels or
640 1- wire (single- ended) channels in one 34980A mainframe.
NOTE
Safety Interlock The Analog Buses of the 34980A are capable of
carrying 300V signals. The MUX and matrix modules have a
hardware Safety Interlock feature that automatically opens the
Analog Bus relays when the associated interlock pins on the D-sub
connectors (faceplate) lose continuity. This prevents signals on the
Analog Buses from being present on the D-sub connector pins.
Optional terminal blocks available from Agilent automatically
provide continuity for these interlock pins. If cables are used,
you must provide continuity for the interlock pins in your DUT
assembly. See the pinout information later in this chapter for the
location of interlock pins on each module.
The MUX modules have Analog Bus relays on each of their two
banks. Therefore, the interlock pins are present on both the Bank 1
and Bank 2 D-sub connectors on the MUX modules.
Normally, if you attempt to connect to the Analog Buses without
a terminal block or cable connected, an error is generated.
The SYSTem:ABUS:INTerlock:SIMulate command
allows you to temporarily disable errors generated by the Safety
Interlock feature and enables the simulation mode. Although Safety
Interlock errors are suppressed in this mode, the actual Analog Bus
relays affected by the Safety Interlock are disabled as long as no
terminal block or cable is connected to the module.
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