Engineering School of Bilbao 1 Industrial Electronics 19-DEC-2023

Apuntes

Engineering School of Bilbao – Industrial Electronics 19-DEC-2023 Surname Name Group EXERCISES: 60 % of the overall mark of the handwritten exam EXERCISE 1 (20/60 points) The circuit shown in the figure is common in electronic instrumentation, and is used to provide a voltage signal, Vs, proportional to the variation of a strain gauge. The strain gauge is a resistor of value R0, which when subjected to a mechanical stress (force, pressure, elongation or extension) causes its resistance to vary (factor X, 0≤X ≪ 1). In the circuit, R0=100 Ω and R1=1 kΩ. The circuit is to be solved by following the steps indicated below: a. Calculate the voltage V1 as a function of the voltage Vr. V + =0 and negative feedback so V - =0 too. Besides, a s Zin=∞ there will be no current into the operational amplifier, so current through first Ro and current through Ro(1-x) are equal. Then (Vr-0)/R0 = (0-V1)/[R0(1-x)]  V1=-Vr(1-x) b. Calculate the voltage V2 as a function of Vr and V1. All the currents entering that point must equal cero (Kirchoff). Current through resistor R0 between points V1 and V2 = (V1-V2)/R0 Current through resistor R0 between points Vr and V2 = (Vr-V2)/R0 So Vr-V2...