Q3. a) A potentiometer is used to detect the linear movement of a table. The circuitry is shown in Figure Q3a. Given VDc = 10 V, L= 500 mm. Displacement of table A R2 VDC Vt Potentiometer C Figure Q3a (i) If Vt= 3V, calculate the displacement of the table. (ii) If the displacement of the table is 120 mm, what will be Vt measured? (iii) Determine the resolution of this potentiometer (in mV/mm). (3 marks) (3 marks) (3 marks) (iv) If Vt is measured by a voltmeter with resolution of 50 mV, is this set up (4 marks) possible to measure the table displacement of 1 mm? Explain your answer. b) Table Q3b shows the specification of a strain gauge. Temperature compensation for Gauge length Gauge resistance (24C,50%RH) Gauge factor(24C,50%RH) Adoptable thermal expansion Transverse sensitivity(24C,50%RH) Application gauge cement Steel 2 mm 119.6 0.4 2 2.11 1.0 % 11.7 PPM/C 2.00 % -33, -34 Table Q3b When this strain gauge is used to measure the strain of a loaded steel bar, the resistance of the strain gauge is increased by 20 m2. Determine : (i) the electrical strain of the strain gauge; (ii) the mechanical strain of the strain gauge; (4 marks) (3 marks) (iii) the increased length of the stain gauge; and (3 marks) (iv) the ideal environmental temperature when the measurement is performed. (2 marks)