Full Bridge
Measurements
In a full bridge arrangement, strain gages are used in all four legs of the
Wheatstone Bridge circuit (Figure 4-13). The full bridge arrangement has
the highest sensitivity and accuracy of any bridge arrangement, and it
provides complete temperature compensation for temperature induced
apparent strain. The full bridge strain measurements available based on
gage positioning are described in the following sections.
Bending Full Bridge
(FBENding)
The maximum sensitivity achieved with a full bridge arrangement is when
the strain gages are mounted to the specimen as indicated in Figure 4-14.
When the beam is strained, gages Rg1 and Rg2 are strained in tension and
gages Rg3 and Rg4 are strained in compression. When all gages are
strained the same amount simultaneously, the bridge sensitivity is increased
by a factor of four. Since the gages undergoing tensile and compressive
strain are adjacent legs in the Wheatstone Bridge circuit, any temperature
induced strain is cancelled.
Figure 4-13. Full Bridge Arrangement
Figure 4-14. Bending Full Bridge
Chapter 4
Understanding the Strain Gage Multiplexers 61
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