Specifications

For a full bridge arrangement, strain gages comprise all four arms of the
Wheatstone Bridge (Figure 4-5). Note the position of the bridge selection
jumper required to configure the channel for full bridge measurements.
120Ω and 350Ω
Multiplexers
A 120Ω strain gage multiplexer is distinguished from a 350Ω multiplexer
by the value of the Wheatstone bridge completion resistor shown in Figure
4-3. When strain is measured with a
1
⁄
4
bridge arrangement, a 120Ω
strain gage multiplexer is required for 120Ω gages, and a 350Ω
multiplexer is required for 350Ω gages. In the
1
⁄
2
and full bridge
arrangements, the bridge completion resistor is replaced by a strain gage
(Figures 4-4, 4-5). Thus, any strain gage multiplexer can be used with
any value of gage resistance when measuring strain with a
1
⁄
2
or full
bridge arrangement.
Figure 4-5. Bridge Completion Circuitry - Full Bridge
Figure 4-4. Bridge Completion Circuitry - 1/2 Bridge
Chapter 4 Understanding the Strain Gage Multiplexers 55
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