1.5

Force, pressure and flow

1.5.1 Strain gauge

A strain gauge is a metal or semiconductor whose resistance changes markedly when it is deformed. The deformation is usually taken to be a measurement of strain, and hence force, applied to a structure.

The resistance of a specimen of material of length 1 and cross-sectional area A is given by:

image

A change in length or area with strain produces a change in resistance of a particular element.

If the resistance of a particular element is Ro with no strain, then the strain gauge factor G is given by:

Strain gauges typically carry only a small current (15 – 100 mA) to avoid self-heating changes in ...

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