This Article shows Past Questions and Answer workings in Measurements and Control Engineering (also known as Electrical Measurement and Control) for Higher National Diploma (HND) Students of Electrical/ Electronics Engineering Auchi Polytechnic, Auchi.

This Past Questions and Answers is helpful to all students in the Department of Electrical/ Electronics Engineering offering this course; Measurements and Control Engineering (EEI 431). For those currently writing their on going exams in Electrical Engineering HND 2 Power Option. This is the past questions and answers for you to study.

N.B – These questions and answers are uploaded only as a guide and ease for your studies.

DEPARTMENT OF ELECTRICAL /ELECTRONIC ENGINEERING 

AUCHI POLYTECHNIC, AUCHI

FIRST SEMESTER EXAMINATION 2023/2024 ACADEMIC SESSION

CLASS: HND2 COURSE TITLE: MEASUREMENT & CONTROL

COURSE CODE: EEI 431 TIME ALLOWED: 3 HRS.

EXAMINER: ENGR. PIUS ISICHEI

INSTRUCTION: ATTEMPT ANY FIVE (5) QUESTIONS

QUESTION 1

(i)What is an earth electrode?

(ii) Briefly explain the importance of earth electrode in electrical system.

QUESTION 2

(i) Enumerate briefly the factors that influences the value of earth resistance.

(ii) On a 220 volts supply a fault of resistance 20 ohms occurred between unearthed end of the heater element of the frame, if the resistance of the substation’s earth electrode is 4 ohms and the resistance of the consumer’s earth electrode is 6 ohms. If a man of body resistance 2500 ohms is in contact with the live part at the consumer’s premises, determine the magnitude of current that will flow through the man to earth. 

QUESTION 3

(i) Explain concisely the causes of faults in underground cables

(ii) A twin cable has developed a short circuit fault along its length and varley loop test was made to locate the point of the fault. The ratio arm of the test are set at 10 ohms and 7 ohms respectively, the value of the variable resistance for position one is 16 ohms and that of two 10 ohms. If the sound and faulty cable are identical and have a length of 2.5 km each, determine the

loop resistance of the cable distance of faulty point from test end.

QUESTION 4

(i) A twin cable of length 800meters has developed a low resistance to earth on one core. A fall of potential test taken at P are V1 = 2.5V and I1 = 5A. The reading at Q are V2 = 5V and I2 = 7A. Find the Position of the fault.

(ii) Draw the diagram of open circuit capacitance test, for an open circuit in a cable, derive the expression to determine the position of fault.

QUESTION 5

(i) With the aid of an illustrative diagram explain how liquid level can be measured using sliding contact resistive transducer.

(ii) A potentiometer displacement transducer with 16mm travel has a resistance of 8 kilo-ohms. If it is connected to a 10Vdc sources of negligible output resistance, calculate the error in position if the output is measured as 5V (that is =8mm) on an instrument that has an input resistance of 20 kilo ohms.

QUESTION 6

(i) Define transducers and briefly explain the term active transducers and Passive transducer, give example of each

(ii) Why are Electrical transducers more popular than the non-electrical transducers.

QUESTION 7

(i) What is the use of dummy gauge in strain gauge device?. Discuss the operation of bounded strain gauge.

(ii) Explain the construction and working principles of thermocouples.

Study the Answers Available!.

ANSWER 1

(i) Definition of An Earth Electrode

 An earth electrode is a conductor through which electricity enters all lives and object, substance or region 

(ii) The Importance of Earth Electrodes

Earth electrodes arę provided for electrical of system because the following reasons:

– All parts of electrical equipment/installation such as circuit breakers, around cable, transformer tanks, casing of machine etc. That are to be at earth potential must be connected to earth through the electrodes.

– In the event of over-voltage on the system due to system fault or lighting discharge, the earth electrodes ensures that the parts of equipment/installation which are normally dead

as far as high voltages are concerned do not attain dangerously high potential.

– In a three-phase circuit the neutral of the system is earthed so as the stabilize or put at balance the potential of the circuit with respect to earth.

ANSWER 2

(i) FACTORS AFFECTING EARTH RESISTANCE

Factors affecting earth resistance are enumerated below.

1) The shape and type of material used for the earth electrode.

2) Depth of the electrode into the soil. The electrode resistance reduces as the depth increases.

3) Specific resistance, of the soil surrounding the neighbourhood of the electrode. The specific resistance or resistivity of the soil is not constant but varies from one type to another. The amount of moisture. also affect the resistivity. For this reason, earth electrode resistance is not a constant factor but undergo seasonal changes. Therefore, there is need for periodic testing to ensure that the earth system remain effective.