Question:

(a) With the help of a clearly labeled diagram explain the functioning of a basic thermocouple.

(b) Briefly explain the principle and operation of strain gauges. What is meant by gage factor "k" and give the equation to calculate the gage factor.

(c) Two strain gauges are mounted so that they sense axial strain on a steel member in uniaxial tension. The 120 Ω gauges form two legs of a Wheatstone bridge and are mounted on opposite arms. The gauge factor for each gauge is 2, the bridge constant is 2, and Em for steel is 200 MPa. For a bridge excitation voltage (Ei) of 4 V and a bridge output voltage (Eo) of 120 μV under load, estimate

          a) the maximum strain in the member, and

          b) the resistance change experienced by each gauge.

(d) Draw the block diagram of a simple frequency counter and explain how it operates