Question

Explain working of resistance strain gauge

Answer 1

Principle working: Strain gauge is a passive, versatile transducer and it is often used for measuring weight, pressure, force and displacement .They sense the strain produced in a wire due to applied force. The strain changes resistance of wire. By measuring this resistance variation strain in a material is calculated. At constant temperature, R= ρ*L/A. when tensile force is applied to a wire it increases it length and reduces cross-sectional area. Hence resistance of wire changes. Gauge factor of a strain gauge is called strain sensitivity factor. Thus knowing gauge factor, original resistance and change of resistance strain can be calculated. The resistive strain gauge element is one such device that plays the role of a secondary transducer in sensing the tensile or compressive strain in a particulardirection at point on the surface of a body or structure. If the modulus of elasticity (Young’s modulus) E of the material of the body is known, the stress can be calculated and utilized to identify the magnitude of quantities affecting the stress. Strain gauge pressure transducers and strain-gauge accelerometers are such transducer systems employing the strain gauges as the secondary electrical transducer along with a suitable primary mechanical transducer for converting the basic quantity under measurement into stress. In certain cases, the strain—gauge element may be stressed directly, allowing the strain measured to be related to the applied stress and hence the force applied.