Features and Functions 4
Keysight 34970A/34972A User’s Guide 227
34908A 40-Channel Single-Ended Multiplexer
The module is divided into two banks of 20 channels each. All of the 40 channels
switch HI only, with a common LO for the module. The module has a built-in
thermocouple reference junction to minimize errors due to thermal gradients
when measuring thermocouples.
Bank Switch
Channel Switches
Backplane
Internal
DMM Input
Reference
Junction
Sensor
01
20
Com
21
40
98
99
Switch
Com
– Refer to the diagrams on page 38 to connect wiring to the module.
– Only one channel can be closed at a time; closing one channel will open the
previously closed channel.
– This module cannot be used to directly measure current or any 4-wire
measurements.
– When connecting thermocouples to the screw terminals on this module (not
recommended due to the common LO configuration), be sure to provide
electrical isolation between thermocouples to avoid current loops and
subsequent measurement errors.
– Connections to AC line are not recommended unless you provide external
transient
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