Strain Gauge Transducer
1. It is a force or pressure transducer. It converts the force or pressure to a proportional electrical signal.
2. Strain gauge is small resistor, whose value changes when its length is changed.
3. It may be made of thin wire, thin foil semiconductor material.
4. When strain gauge is stretched, it's resistance increases, whereas change in resistance is proportional to applied force.
5. If current is passed through strain gauge then change in voltage across strain gauge occurs.
6. Change is voltage is already proportional to applied force.
Unfortunately resistance of strain gauge element also changes with temperature. To compensate, two strain gauge elements must be mounted at right angles, so that will change resistance with temperature but only one element will change resistance with applied force.
So it needs to connect in bridge form which cancel out effect of temperature on the positive strain gauge. Full scale differential output voltage is typically 2 or 3 mv/v of applied voltage.