a. (15 marks) A 120 ? strain gauge bridge consists of four identical 120 ? resistors arranged in a Wheatstone bridge. When the gauge experiences a positive strain of 0.5%, the resistances of the individual resistor elements change as shown in Figure 5. The op-amp circuit shown has been designed to amplify these small changes in resistance into a larger change in voltage for measurement. i. (3 marks) Calculate the voltages v_a and v_b at the output of the strain gauge. ii. (10 marks) Derive an expression for the op-amp output voltage v_out in terms of the input voltages v_a and v_b to demonstrate that it is a difference amplifier. Note: DO NOT substitute the values of v_a and v_b from part (i) so that you can find a general expression rather than a voltage value. iii. (2 marks) Substitute the values of v_a and v_b from part (i) to calculate the voltage value at the output of the op-amp. b. (15 marks) Calculate the steady-state value for v_out in the circuit shown in Figure 6 if v_g = 25cos(50000t) V.
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When the gauge experiences a positive strain of 0.5%, the resistances of the individual resistor elements change as shown in Figure 5. The op-amp circuit shown has been designed to amplify these small changes in resistance into a larger change in voltage for Show more…
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