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4
Troubleshooting and Diagnostics
34921A 40-Channel Armature Multiplexer with Low Thermal Offset
The 34921A 40- Channel Armature Multiplexer (40- Ch Arm MUX) is
divided into two banks with 20 latching armature switches (channels 1- 20
and 21- 40) in each. This module also offers four additional fused relays
(channels 41- 44) for making AC and DC current measurements with the
internal DMM with no external shunts needed. These current channels
feature “make- before- break” connections to ensure continuous current flow
when switching from one current channel to another. The current fuses
are replaceable.
This module also contains nine armature Analog Bus relays (channels 911914, 921- 924, and 931), four on each bank that can connect the bank
relays to the system Analog Buses and one that connects the current
relays to the current input of the DMM. Through ABus1 and ABus2 you
can connect any of the channels to the internal DMM for voltage or
resistance measurements. Refer to the simplified schematic below.
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34980A Service Guide