Principle of Strain Measurement

Strain initiated resistance change is extremely small.Thus, for strain measurement a Wheatstone bridge isformed to convert the resistance change to a voltagechange. Suppose in Fig. 3 resistances (?) are R1,R2, R3 and R4 and the bridge voltage (V) is E.

Then,the output voltage e o (V) is obtained by the followingequation:

Suppose the resistance R1 is a strain gage andit changes by ? R due to strain. Then, the outputvoltage is,

f R1 = R2 = R3 = R4 = R in the online casino initial condition,

Since R may be regarded extremely larger than DR,

Thus obtained is an output voltage that isproportional to a change in resistance, i.e. a changein strain. This microscopic output voltage is amplifiedfor analog recording or digitial indication for strainmeasurement.