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Chapter 8 Tutorial
Low-Level Signal Multiplexing and Switching
The HP 34901A and HP 34902A multiplexers have an additional relay,
called a bank switch or tree switch, which helps reduce channel-to-
channel noise (C
). The multiplexer channels are divided into two banks.
adj
The bank switch isolates one bank of channels from the other, effectively
removing any parallel adjacent capacitance from the isolated bank.
During a scan, the instrument automatically controls the bank switches.
Bank Switch
DMM
If you are not using all of the channels on the multiplexer, divide the
input signals equally between Bank 1 and Bank 2. For example, if you
are multiplexing eight channels using the 16-channel multiplexer,
use four channels in the lower bank and four channels in the upper
bank. For even better noise immunity, leave one unused, grounded
channel between each input channel.
Module
Bank 1
HP 34901A
Channels 1 through 10
HP 34902A
Channels 1 through 8
HP 34908A
Channels 1 through 20
Bank Switch
Channel
Switch
C
adj
Channel
Source
Switch
Source
Bank 2
Channels 11 through 20
Channels 9 through 16
Channels 21 through 40
C
adj
Bank 1
Source
Source
Bank 2
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8
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