Assignment_3_on_precision_rectifiers_and_wheatstone_bridge_1550241303714335075c66ce1766a5a.pdf

Electrical & Electronic Instrumentation – Assignment 3 1. Sketch and label the VTC of the circuit given below if R1 = R2 = 10 kΩ, and a third resistance R3 = 150 kΩ is connected between the +15V supply and the inverting-input pin of the op amp. (b) Repeat, but with the diode polarities reversed.

2. Suitably modify the FWR given below so that, when fed with a triangular wave of ±5 V peak values, it gives a triangular wave of ±5V peak values, but twice the frequency.

3. Assuming R1 = R2 = R4 = 10 kΩ and R3 = 20 kΩ in the FWR given below, find all node voltages for 𝑣𝐼 = 10 mV, 1 V, and −1 V. For a forward-biased diode, assume 𝑣𝐷 = (26 mV) ln[𝑖𝐷 /(20 fA)].

4. Find the VTC of the given circuit. Assuming ±Vsat = ± 13 V and VD(on) = 0.7 V, show all node voltages for 𝑣𝐼 = +3 V and 𝑣𝐼 = − 5 V.

5. A DC Wheatstone bridge contains a resistance temperature detector (RTD) whose resistance around 25°C is approximated by R(T) = R25 [1 + α(T − 25)]. The smallest ΔVo the detector can resolve is 100 nV. VS = 3.1 V, R = R25 = 300 Ω, and α = 0.004. Find the just-resolvable ΔT under these conditions

6. A DSBSCM signal is generated in many sensor systems. A DSBSCM signal is basically the product of two sine waves with different frequencies. In the Wheatstone bridge circuit, two strain gauges are subject to an LF sinusoidal strain such that δR(t) = ΔR sin(2t). ΔR = 0.03 Ω, R = 300 Ω, vb(t) = VB sin(1000t), and VB = 5 Vpk. The DA’s gain is 103. Find an expression for vo(t) and show that it can be resolved into the algebraic sum of sum and difference frequencies.

7. A Wheatstone bridge is powered with a 1 V rms, 200 Hz sinusoidal source. Fixed resistors A and B are 1000 Ω, with LEs of 10 ppm. The value of variable resistor, D, is known to be 100 ppm. At null, D = 100 Ω. (a) Find the nominal value of X (b) The AC null detector can just resolve ΔVo = 1 μV rms. The DA is ideal with gain = 1. Calculate the LE in X, considering the LEs in A, B, D, and Vo.

X

D