Measurement and Instrumentation

Daffodil International University Department of Electrical and Electronic Engineering Faculty of Engineering Midterm Examination, Fall – 2026 Course Code: 0713-325 Course Title: Measurement and Instrumentation Section: A, B, C & D Level-Term: L3-T2 Teacher's Initial: NH, BS Full Marks: 25 Exam Date: October 28, 2026 Time: 1.5 Hours Answer all the question. The number on the rightmost side of the question indicates the marks. Q1. Illustrate the block diagram of a basic measurement system, label each functional element, and explain briefly the role of each block in the measurement process. CO-1 C(2) 5 Q2. The Schering bridge balances under the following conditions: R1 = 10 kΩ, R2 = 1 kΩ, C1 = 100 pF, C3 = 400 pF. The bridge is driven by a 1 kHz sinusoidal source. CO-2 C(3) 5 a) Determine the values of Rs, Cs, and Dissipation factor. b) If the series combination of Rs and Cs is to be replaced by a parallel combination Rp and Cp, Prove that Cp = Cs / (1 + D^2), Rp = Rs(1 + Q^2) Q3. [Figure: Circuit diagram of a Wheatstone bridge connected for a Varley loop test] a) A Wheatstone bridge is connected for a Varley loop test as shown in the Fig. above. When the switch is in position a, the bridge is balanced with R1 = 1000 Ω, R2 = 100 Ω, R3 = 53 Ω. When switch S is in position b, the bridge is balanced with R1 = 1000 Ω, R2 = 100 Ω and R3 = 52.9 Ω. If the resistance of the shorted wire is 0.015 Ω/m. Determine the distance between the place of fault and the bridge? CO-2 C(3) 3 b) A Wheatstone bridge has ratio arms R1 = 1.2 kΩ and R2 = 120 Ω. It measures an unknown Rx = 40 Ω. At balance, the third arm is R3. Two galvanometers are available: G1: Rg = 40 Ω, S = 180mm/μA, G2: Rg = 450 Ω, S = 420mm/μA. Which Galvanometer is more sensitive to a small unbalance? Comment on the result. What shunt across G2 would make it as sensitive as G1? CO-2 C(4) 3 Q4. Explain the piezoresistive effect in materials. Develop the expression for the gauge factor when a tensile stress S is applied to the wire in figure 1. (The change in resistivity due to strain is negligible) CO-3 C(3) 4 [Figure: Change in dimensions of a strain gauge element when subjected to a tensile force] Figure 1: Change in dimensions of a strain gauge element when subjected to a tensile force. Q5. a) Construct the output of the Capacitive displacement sensor shown in the figure 2 and comment on its linearity. CO-3 C(3) 3 [Figure: Capacitive displacement sensor with plates and dielectric] Figure 2: Capacitive Displacement sensor b) Suppose you are given two sensors, one is an RTD and the other is a thermistor. Investigate out of these two, which one will you use for temperature compensation for circuit network application and why? CO-3 C(4) 2