Half-Bridge Circuits: Shunt Calibration

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Half-Bridge Circuits
In many stress analysis applications it is necessary (or at least advantageous) to employ two co-acting gages, connected as adjacent arms in the bridge circuit, to produce the required strain signal. A common example of this occurs when a second gage is installed on an unstressed specimen of the test material (and maintained in the same thermal environment as the test object) to provide temperature compensation for the active gage. In the special case of a purely uniaxial stress state, with the principal stress directions known, both gages can be mounted adjacent to each other, directly on the test part. One gage is aligned with the applied stress, and the other is installed in the perpendicular direction to sense the Poisson strain. This arrangement provides an augmented bridge output, along with excellent temperature compensation. Similar opportunities are offered by a beam in bending. One gage is mounted along the longitudinal centerline of the convex surface, with a mating gage at the corresponding point on the concave surface. When the two gages are connected as adjacent arms in the bridge circuit, and assuming uniform temperature through the thickness of the beam, the bridge output is doubled while maintaining temperature compensation.

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