User`s guide

301
Chapter 7 Tutorial
Low-Level Signal Multiplexing and Switching
4
7
One-Wire (Single-Ended) Multiplexers
On the 34908A multiplexer, all of the 40 channels switch the HI input
only, with a common LO for the module. The module also provides a
thermocouple reference junction for making thermocouple
measurements (for more information on the purpose of an isothermal
block, see page 272).
Note: Only one channel can be closed at a time; closing one channel will open the previously
closed channel.
Two-Wire Multiplexers
The 34901A and 34902A multiplexers switch both HI and LO inputs,
thus providing fully isolated inputs to the internal DMM or an external
instrument. These modules also provide a thermocouple reference
junction for making thermocouple measurements (for more information
on the purpose of an isothermal block, see page 272).
Note: If any channels are configured to be part of the scan list, you cannot close multiple
channels; closing one channel will open the previously closed channel.
Channel 1
Channel 2
Channel 3
Channel 4
To D M M
To DMM
Channel 1
Channel 2
Channel 3
Channel 4
34970A Refresh UG.book Page 301 Wednesday, February 17, 2010 12:34 PM