(a) A user is building an instrument that can indicate if the loaded mass of a caravan exceeds its limit of 1330 kg when

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A A User Is Building An Instrument That Can Indicate If The Loaded Mass Of A Caravan Exceeds Its Limit Of 1330 Kg When 1 (149.75 KiB) Viewed 28 times

(a) A user is building an instrument that can indicate if the loaded mass of a caravan exceeds its limit of 1330 kg when towed horizontally at constant speed. Four identical strain gauges are available, and the user attaches one of them at the centre of a 5 cm diameter steel tow bar as shown in Figure A1-1. The strain gauge has a gauge factor of 2 and is connected in a Wheatstone bridge with an input dc voltage of 5 V. To complete the instrument, the user needs to buy a voltmeter to measure the Wheatstone bridge output accurately. Strain gauge Car Caravan Tow bar Figure A1-1 i. Consider a suitable coefficient of rolling friction of your choice, what maximum noise level is allowed for the voltmeter? Show relevant calculations to support your answer. (6 marks) ii. The user can only afford a cheaper voltmeter with higher noise level. What design modification to the instrument can the user make to allow such a voltmeter to be used? What is the maximum noise level required for the cheaper voltmeter? (2 marks) iii. With the aid of a three-dimensional sketch, explain how you would mount a strain gauge on the tow bar to measure the effect of twisting around its outer diameter. (2 marks)