Keysight 34921A - 34921 A 40-Channel Armature Multiplexer

Keysight 34921A-34925A Low Frequency Multiplexer Modules User’s Guide 15
Low Frequency Multiplexer Modules
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. Refer to the 34980A
Service Guide for specific information about these fuses.
This module also contains nine armature Analog Bus relays (channels 911-914,
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 on page 17.
Using program commands or the mainframe front panel, you can control each of
the channel switches individually, and thus configure the 34921A module in
these modes:
- two independent 20-channel 2-wire MUXes. This configuration requires
neither using external wiring nor connecting through the internal Analog
Buses.
- one 20-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+20 on Bank 2 (sense) to provide
these connections. Four-wire controls occur only when doing 4-wire
measurement operations through the internal DMM, such as
MEASure:FRESistance? or scanning a channel previously configured as
4-wire.
ABus1 consists of three wires that are used for current and
voltage measurements. A separate current bus on ABus1
connects to the internal DMM current measurement input
and this bus can be connected only to channels 41 through
44. The current channel low (L) signal path is common with
the ABus1 low (L) signal path.
You cannot measure current and voltage on ABus1
simultaneously.
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