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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
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
• one 20- channel 4- wire MUX. This configuration requires neither using
• one 40- channel 2- wire MUX. You must use external wiring or connect
Agilent 34921A-34925A Low Frequency Multiplexer Modules User's Guide
ABus1 consists of three wires that are used for current and voltage
N O T E
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.
neither using external wiring nor connecting through the internal
Analog Buses.
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.
through the internal Analog Bus relays for this configuration. For
example, closing Analog Bus channels 913 and 923 connects Bank 1 and
Bank 2 through ABus3. Or, externally you can connect COM1 to COM2
to create this configuration.
34921A 40-Channel Armature Multiplexer with Low Thermal Offset
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