Question

In strain gauge bridge configuration for measurement of torque, the strain gauge must be precisely mounted at
1. 0° with the shaft axis
2. 45° with the shaft axis
3. 90° with the shaft axis
4. 60° with the shaft axis

Answer 1

Correct Answer - Option 2 : 45° with the shaft axis

Strain gauge bridge measurement of torque:

• A strain gauge converts torque into an electrical signal. The sensor is bonded to a rotating shaft that deforms when a torque is applied.
• Generally, four strain gauges are attached to the rotating shaft in the form of a Wheatstone bridge circuit. They are placed precisely at 45 degrees with the shaft axis with gauge 1 and 3 being diametrically opposite, as must gauge 2 and 4.
• When torque is applied to the shaft, the shaft gets twisted to the direction of rotation, thereby producing shear strain.
• This causes elongation in gauges 1 and 3 and compression in gauges 2 and 4. These changes in the strain gauges lead to an increase in the circuit resistance due to tensile strain generated by one pair of gauges and a decrease in the circuit resistance due to the compression strain generated by the other pair.
• This results in an unbalanced bridge, which produces an electrical output corresponding to the applied torque.