Load Cell: Force can be measured easily from a load cell. Weigh bridge is one of the most common applications of load cell. Here two strain gauges are fixed so as to measure the longitudinal strain, while two other measuring the transverse strain, as shown in Figure 18.11. The strain gauges, measuring the similar strain (say, tensile) are placed in the opposite arms, while the adjacent arms in the bridge should measure opposite strains (one tensile, the other compression). If the strain gauges are identical in characteristics, this will provide not only the perfect temperature coefficient, but also maximum obtainable sensitivity from the bridge. The longitudinal strain developed in the load cell would be compression in nature and is given by,
Figure 18.11 Load Cell with Four Strain Gauges
where F is the force applied, A is the cross-sectional area, and Y is the Young’s modulus of elasticity.
The strain gauges 1 and 3 will experience this strain, while for 2 and 4 the strain will be
where v is Poisson’s ratio.
Leave a Reply