MIU EEG 383 Problem Set # 2 Measurement Errors Page 1 of 2

Misr International University Faculty of Engineering Term: Fall 2010 Department of Electronics and Communication Course: EEG 383 Electrical Measurements and Instrumentations Instructor: Prof. Fawzy Ibrahim TA: Eng. Waleed Elhalwagy

Problem Set #2 Measurement Errors

Question 2.1 Explain the difference between systematic and random errors. What are the typical sources of these two types of errors?

Question 2.2 In what ways can the act of measurement cause a disturbance in the system being measured?

Question 2.3 What procedures are normally taken to avoid measurement errors when using instruments that are subjected to changing ambient conditions?

Question 2.4 For the circuit given in fig.(1), if the instrument measuring the output voltage across 270 ohm resistance has resistance of 5000 ohm. What is the measurement error due to the loading effect of the instrument?

Question 2.5 For the circuit given in fig.(2), if the instrument measuring the output voltage across 500 ohm resistance has resistance of 4750 ohm. What is the measurement error due to the loading effect of the instrument?

Fig.(1) Fig. (2) Question 2.6 For the circuit given in fig.(3), the current flowing in the 500 ohm is to be measured using a 100 ohm ammeter. What is the loading effect of the measurement instrument?

Fig. (3)

MIU EEG 383 Problem Set # 2 Measurement Errors Page 2 of 2

Question 2.7 In a survey of 15 owners of a certain model of a car, the following figures for average petrol consumption were reported : 25.5 30.3 31.1 29.6 32.4 39.4 28.9 30 33.3 31.4 29.5 30.05 31.7 33 - 29.2 Calculate the mean value, the median and the standard deviation of the data set. Question 2.8 The following measurements were taken with analog meter, due to random errors: 21.5 mA 22.1 mA 21.3 mA 21.7 mA 22 mA 22.2 mA 21.8 mA 21.4 mA 21.9 mA 22.1 mA Calculate the mean value, the median and the standard deviation of the data set. Question 2.9 A 3 volt dc power source is obtained using two 1.5 V series batteries. If the error in each is 1%. Calculate the maximum possible error in the 3 V power source. Question 2.10 In order to calculate the heat loss through wall of building, the temperature difference was measured at both sides of the wall was 5 C and 20 C , by thermosters with a range 0 C to 50 C and th reading inaccuracy is 1% of full scale reading, calculate the maximum possible error in the calculated figure for the temperature difference. Question 2.11 The power dissipated in a load is measured as P = V.I, errors in measured voltage and current are 1% and 2% respectively. Calculate the maximum likely error in the power value. Question 2.12 In measuring R = V/I , the measured voltage was 10 0.1 V, current = 214 5 mA. Express the value of the resistance. Question 2.13 In measuring the density, d = m/ (a+b+c), error in a,b,c,m were 1% , 1% , 2% and 0.5% , determine the maximum possible error in the measured density.