Measurements And Instrumentation - 550 Words

Measurements And Instrumentation (Math Problem Sample) Content: Name: Instructor: Course Title: Electrical And Electronic Engineering Unit Title: Measurements And Instrumentation Date: QUESTION 1 A resistance is determined by voltmeter - ammeter method. The voltmeter reads 160V with a probable error of  ±10V and ammeter reads 10A with probable error of  ±1A. Find the probable error in the computed value of resistance. SOLUTION R=VI Voltage, V=160 ±10V Current, I=10 ±1A Probable error, e=102x12=10.0499ÃŽÂ © error, e=a2xb2=101602+1102=0.1179 Resistance=160V10A=16ÃŽÂ © Probable error in resistance= ±16x0.1179ÃŽÂ ©= ±1.88679 QUESTION 2 During the measurement of a low resistance using a potentiometer the following readings were obtained. * Voltage drop across the low resistance under test is 0.4221V * Voltage across the 0.1à ¢Ã¢â‚¬Å¾Ã‚ ¦ standard resistance is 1.0235V Calculate the value of the unknown resistance, current through it and power lost in it. SOLUTION Let Voltage drop across the low resistance be VL=0.4221V Voltage drop across the 0.1ÃŽÂ © standard resistor be V0=1.0235V Let also Rs be standard resistor and Rx be the unknown resistor. VL=RSRS+RXxVin 1.0235=0.10.1+RXx(0.4221+1.0235) RX=0.14456-0.102351.0235=0.04124ÃŽÂ © Current through the unknown resistor: I=VSRT=0.4221+1.02350.04124+0.1=10.2351A Power lost through the resistor: P=I2R=10.23512x0.04124ÃŽÂ ©=4.3201899W QUESTION 3 A thermocouple circuit uses a chromel-alumel thermocouple which gives an e.m.f. of 33.3mV when measuring a temperature of 8000C with reference temperature of 00C. The resistance of the meter coil, Rm is 50à ¢Ã¢â‚¬Å¾Ã‚ ¦ and a current of 0.1mA gives full scale deflection. The resistance of junction and leads, Re is 12à ¢Ã¢â‚¬Å¾Ã‚ ¦. Calculate: * Resistance of the series resistance if a temperature of 8000C is to give full scale deflection. V=IR emf=I(Re+Rm+Rs) Rs=33.3x10-31x10-4-12+50ÃŽÂ ©=271ÃŽÂ © * The approximate error due to a rise in 100C in the copper coil of the meter, given the resistance temperature co-efficient of the coil is 0.00426/0C. à ¢Ã¢â‚¬â€œÃ‚ ³R=10ÃŽÂ © à ¢Ã‹â€ Ã¢â‚¬  R=50x0.00426x10ÃŽÂ ©=2.13ÃŽÂ © Current in the circuit, I=emfRm+Re+Rs+à ¢Ã‹â€ Ã¢â‚¬  R=33.3x10-3V50+2.13+271+12=0.09936mA Approximate error in temperature, e=0.09936-0.10.1x800=-5.12 0C QUESTION 4 A Barium Titanate pickup has the dimensions of 4mm by 4.5mm by 1.0mm. The force acting on it is 10N. The charge sensitivity of Barium Titanite is 145pC/...