Describe strain gauge with labelled diagram.

1 Answer

Answer :

A Strain gauge is a sensor whose resistance varies with applied force. It converts force, pressure, tension, weight, etc., into a change in electrical resistance which can then be measured. When external forces are applied to a stationary object, stress and strain are the result. 

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* The foil type strain gauges are very common in which a resistive foil is mounted on a backing material. Metal foil gauges use similar materials to wire strain gauges. 
* The sensing elements of foil gauges are formed from sheets less than 0.005 mm thick by photo etching processes, which allows greater flexibility with regards to shape. 
* The resistance of the foil changes as the material to which the gauge is attached undergoes tension or compression due to change in its length and diameter. This change in resistance is proportional to the applied strain. As this change in resistance is very small in magnitude so its effect can be only sensed by a Wheatstone bridge. 
* When strain is applied to the strain gauge, the resistance of the strain gauge sensor changes, the Wheatstone bridge becomes unbalanced, a current flows through the voltmeter. Since the net change in the resistance is proportional to the applied strain, therefore, resultant current flow through the voltmeter is proportional to the applied strain. So, the voltmeter can be calibrated in terms of strain or force. 

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