In general, the shunt-calibration relationships appearing in this section are limited in application to the simulation of low strain magnitudes, since nonlinearity effects in the Wheatstone bridge circuit have been ignored. The equations given here are intended primarily for scaling the output of an instrument to register the same strain magnitude that it would if the selected gage were subjected to an actual strain equal to the simulated strain. This mode of shunt calibration offers a simple, convenient means for eliminating the effects of leadwire desensitization and accounting for more than one active gage ( > 1) in the bridge circuit.

For calibration at strain levels higher than about 2000 microstrain or for precise evaluation of instrument accuracy, it is ordinarily necessary to incorporate the effects of Wheatstone bridge nonlinearity in the shunt-calibration relationships. Nonlinearity considerations are treated in the next section, and application examples given in the section beyond that.

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