The Wheatstone
Bridge
The Wheatstone Bridge Circuit shown in Figure 4-2 is the fundamental
strain measuring circuit.
When a strain gage is wired to a bridge completion channel, it completes the
Wheatstone Bridge circuit as indicated in Figure 4-3. This circuit represents
a
1
⁄
4
bridge arrangement where only one arm contains an active element
(strain gage). The other arms are fixed value resistors (as shown) or they
may represent unstrained gages.
In a
1
⁄
2
bridge arrangement, the 120
Ω
or 350
Ω
bridge completion resistor is
replaced by a strain gage when the gages are connected to the terminals as
indicated in Figure 4-4.
Figure 4-2. The Wheatstone Bridge
Figure 4-3. Bridge Completion Circuitry - 1/4 Bridge
54 Understanding the Strain Gage Multiplexers
Chapter 4
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