a) The strain measurement system discussed in Question 1 is susceptible to surrounding temperature. How can the effect of surrounding temperature be avoided? Is the system above achieving that? Explain this, using equations of strain gauge resistance variation and output voltage from a Wheatstone bridge in Q1 b). [10 marks] b) Because the output signal from the bridge is not strong, you chose to use an amplifier circuit to amplify the signal as shown in Figure 4. Here, the amplification follows the equation below when R2/R1 = R./R3. R2 (V2 - V) =V, R2. Vamp = R1 Derive the equation to determine the strain e from Vamp, when the bridge is the same as in Q1 b) and assuming R1 R2/R1 = R4/R3 is satisfied. c) Now you want to use your experimental data below to estimate the strain measured when a certain constant load was applied. 1 2 3 4 Measurement Vamp [V] 9.8 9.7 9.9 10.1 10.3 10.2 Following the steps below, estimate the uncertainty expected in determining strain. The uncertainty of Vamp measurement is +2% and the resistances including their manufacturing tolerance are given R1 = 1 kn +1% and R2 = 400 kn +5%. Temperature dependency of the gauge can be ignored and the internal resistance of the meter can be assumed infinitely large. Uncertainty of the source voltage as well as that of gauge factor can be considered negligible. i) Calculate the uncertainty in Vamp measurement as an unbiased standard deviation. ii) Calculate the nominal strain e. iii) Calculate the uncertainty in %. iv) By looking through the RS-Component online catalogue below, discuss how much the uncertainty in calculation of strain can be improved by changing the resistors (make use of the filter function on the left of the page). https://uk.rs-online.com/web/c/passive-components/fixed-resistors/through-hole-fixed-resistors/?sra-p [20 marks] R From V, bridge R, Vamp Voo R + V2 R Figure 4. Amplifier circuit.