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  • Instrumentation and Control Lab

    strain gauge

    Ex 2: Measurement of Strain Using Strain Gage

    1.1 Objective:

    Measurement of strain in a cantilever beam using strain gage.

    Strain guage balance circuit

    1.2 Apparatus:

    (i) Cantilever beam (ii) strain gage (iii) OP AMP (v) multimeter etc.

    1.3 Procedure and Experimental Results:

    (i) Measure the resistance of the strain gage with multimeter. Now deform the cantilever beam and note down the resistance of the strain gauges for maximum possible deformation.

    (ii) Now set up the experiment using single strain gage as shown in fig. 1. Set the micrometer such that there is no deformation of the beam but the micrometer is just touching the rod located to deform the beam.

    (iii) Set the wheatstone bridge resistance R1 and R2 as 1K. Set the amplifier gain as 100, vary the value of R3 such that zero (or nearest to zero) is obtained on the output of the amplifier. To obtain zero voltage at the amplifier output corresponding to zero deflection; you may external offset balancing technique.

    (iv) Now in step vary the slider up to 6mm in micrometer screw gage and note down the output voltage, micrometer and dial gage readings. Also move the micrometer in reverse order and note down the same parameters.

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