Brands     Vishay Measurements Group     Interactive Guide     Tech Notes     TN-514

Shunt Calibration of Strain Gage Instrumentation

( ... continued )

It is always necessary to maintain the distinction between instrument scaling and verification , both in selecting a calibration resistor and in interpreting the result of shunting. There are also several other factors to be considered in shunt calibration, some of which are especially important in scaling applications. The relationships needed to calculate calibration resistors for commonly occurring cases are given in the remaining sections of this publication as follows:

Basic Shunt Calibration     Derivation of fundamental shunt-calibration equations.

Instrument Scaling for Small Strains     Simple quarter-bridge circuit - downscale, upscale calibration. Half- and full-bridge circuits.

Wheatstone Bridge Nonlinearity     Basic considerations. Effects on strain measurement and shunt calibration.

Instrument Scaling for Large Strains     Quarter-bridge circuit - downscale, upscale calibration. Half- and full-bridge circuits.

Instrument Verification     Small strains. Large strains.

Accuracy Considerations     Maximum error. Probable error.
For a wide range of practical applications, the sections on Basic Shunt Calibration , Instrument Scaling for Small Strains , and Instrument Verification should provide the necessary information and relationships for routine shunt calibration at modest strain levels. When large strains are involved, however, reference should be made to the sections on Wheatstone Bridge Nonlinearity and Instrument Scaling for Large Strains . Limitations on the accuracy of shunt calibration are investigated in Accuracy Considerations section.



Page 5 of 50