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Interactive Guide
Tech Notes
TN-514
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Shunt Calibration of Strain Gage
Instrumentation
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Full-Bridge Circuits In strain-measurement (stress analysis) applications for which the half bridge is suitable, the output signal can be doubled by installing a full bridge, with four active strain gages on the test object. A representative circuit, including two supplementary leadwires for remote shunt calibration, is shown here. 
Remote shunt calibration of external full-bridge circuit. In practice, the calibration leadwires can be connected across any arm of the bridge, and will always produce the same signal magnitude, but the sign of the signal depends on which arm is shunted. It will be noticed, in the case of the full-bridge circuit, that the leadwire resistance is now in the bridge power and output leads rather than in the bridge arms. With the assumption of infinite impedance at the bridge output, the resistance in the latter leads has no effect. However, the resistance in the power leads reduces the voltage applied to the bridge proper, and attenuates the output signal accordingly. ( continued ... ) 
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