1

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Philadelphia University Student Name:

Faculty of Engineering Student Number:

Dept. of Electrical Engineering

Final Exam, Second Semester: 2014/2015

Course Title: Instrumentation and Measurement Date: 15/6/2015

Course No: (610332) Time Allowed: 2 Hours

Lecturer: Dr. Mohammad Abu-Naser No. of Pages: 4

Question 1: (10Mark)

Objectives: This question is related to analog indicating instruments

1) Design a series type ohmmeter. The basic PMMC movement has internal

resistance Rm=50Ω and requires a current of Im=1mA for full-scale deflection.

If the battery has a voltage of E=3V and the desired value of half-scale

position resistance Rh=2000Ω.

a) Calculate the values of resistances R1 and R2.

b) Draw the circuit diagram of the series type ohmmeter and indicate all

components’ values.

2) Explain the advantages and disadvantages of electrodynamometer type

instruments.

3) Calculate the percentage error for the following wattmeter connection.

Question 2: (5Mark)

Objectives: This question is related to bridge measurement

a) A 1000 Hz bridge has the following constants: Arm1: R1 = 1000 Ω in parallel

with C1 = 0.5 µF. Arm3: R3 = 1000 Ω in series with C3 = 0.5 µF. Arm 4: R4 =

200 Ω in series with L4 = 30 mH. Find the constants of Arm 2 to balance the

bridge. Express the result as a resistance in series with capacitance or

inductance.

Form No. T611

Form 1

2

Question 3: (5Mark)

Objectives: This question is related to temperature transducers

1) A platinum thermometer has resistance of 150 Ω at 0°C.

a) Calculate the resistance when the temperature is 200°C?

b) Calculate the temperature when the resistance of the thermometer is 400 Ω.

Note: The resistance temperature coefficient of platinum is 0.0039/°C.

2) Explain the design of a Wheatstone bridge to measure temperature using RTD

connected to one of its arms.

Question 4: (5Mark)

Objectives: This question is related to capacitive transducers

A capacitive transducer is used for measurement of linear displacement by

changing the distance between the plates.

1) Derive an expression for the sensitivity of the transducer.

2) If the transducer Cx is used in the following op-amp circuit. Derive the

expression of Vo.

3) What is the main advantage achieved by using the capacitive transducer in

the op-amp circuit?

Question 5: (5Mark)

Objectives: This question is related to photoelectric transducers

A relay is to be controlled by a photoconductive cell with the characteristics shown in

the following figure. The circuit delivers 5 mA at a 20-V setting when the cell is

illuminated with 400 lm/m2. The circuit becomes de-energized when the cell is dark.

Find:

a) The value of R1

b) Dark current

3

Question 6: (10Mark)

Objectives: This question is related to multiple choices

1) An 0-10 A ammeter has a guaranteed accuracy of 1 % of full scale

deflection. The limiting error while reading 2.5 A is:

a) 1 % b) 2 % c) 4 % d) none of the above.

2) In a permanent magnet moving coil ammeter the deflection of the pointer

is proportional to the magnetic flux density produced by the permanent

magnet. If the strength of the permanent magnet becomes 95% of the

original, the meter gives erroneous reading. This error is classified as:

a) Gross error b) Systematic error c) Random error d) None of

the above

3) A 1 mA PMMC movement has a resistance of 100 Ω. It is to be converted

to a 1 A ammeter. The value of the shunt resistance is:

a) 0.001 Ω b) 0.1001 Ω c) 100000 Ω d) 100 Ω

4) A PMMC movement is rated at 100 µA. Its sensitivity is:

a) 1000 Ω/V b) 10000 Ω/V c) 100 Ω/V d) none of the above

5) Capacitive transducers can be used for measurement of liquid level. The

principle of operation used in this case is:

a) Change of capacitance with change of distance between plates

b) Change of area of plates

c) Change of dielectric constant (relative permittivity)

d) None of the above

6) A photoconductive cell is useful for

a) Low frequency applications

b) Medium frequency applications

c) High frequency applications

d) All of the above

7) What device is similar to an RTD but has a negative temperature

coefficient?

a) Thermistor

b) Strain gauge

c) Negative-type RTD

d) Thermocouple

4

8) For the following square-wave pattern, the frequency is:

a) 12.5 MHz b) 12.5 kHz c) 25 MHz d) 25 kHz

9) For the following square-wave pattern, the peak to peak voltage is

a) 3V b) 6V c) 12 V d) 24 V

Vertical sensitivity = 1V/div

Horizontal sensitivity = 10µs/div

10) In the following Lissajous figure, the phase angle is:

a) 0° b) 30° c) 45° d) 60°

Good luck

1

de

Philadelphia University Student Name:

Faculty of Engineering Student Number:

Dept. of Electrical Engineering

Final Exam, Second Semester: 2014/2015

Course Title: Instrumentation and Measurement Date: 15/6/2015

Course No: (610332) Time Allowed: 2 Hours

Lecturer: Dr. Mohammad Abu-Naser No. of Pages: 4

Question 1: (10Mark)

Objectives: This question is related to analog indicating instruments

1) Design a series type ohmmeter. The basic PMMC movement has internal

resistance Rm=50Ω and requires a current of Im=1mA for full-scale deflection.

If the battery has a voltage of E=3V and the desired value of half-scale

position resistance Rh=2000Ω.

a) Calculate the values of resistances R1 and R2.

b) Draw the circuit diagram of the series type ohmmeter and indicate all

components’ values.

2) Explain the advantages and disadvantages of electrodynamometer type

instruments.

3) Calculate the percentage error for the following wattmeter connection.

Question 2: (5Mark)

Objectives: This question is related to bridge measurement

a) A 1000 Hz bridge has the following constants: Arm1: R1 = 1000 Ω in parallel

with C1 = 0.5 µF. Arm3: R3 = 1000 Ω in series with C3 = 0.5 µF. Arm 4: R4 =

200 Ω in series with L4 = 30 mH. Find the constants of Arm 2 to balance the

bridge. Express the result as a resistance in series with capacitance or

inductance.

Form No. T611

Form 2

2

Question 3: (5Mark)

Objectives: This question is related to temperature transducers

1) A platinum thermometer has resistance of 150 Ω at 0°C.

a) Calculate the resistance when the temperature is 200°C?

b) Calculate the temperature when the resistance of the thermometer is 400 Ω.

Note: The resistance temperature coefficient of platinum is 0.0039/°C.

2) Explain the design of a Wheatstone bridge to measure temperature using RTD

connected to one of its arms.

Question 4: (5Mark)

Objectives: This question is related to capacitive transducers

A capacitive transducer is used for measurement of linear displacement by

changing the distance between the plates.

1) Derive an expression for the sensitivity of the transducer.

2) If the transducer Cx is used in the following op-amp circuit. Derive the

expression of Vo.

3) What is the main advantage achieved by using the capacitive transducer in

the op-amp circuit?

Question 5: (5Mark)

Objectives: This question is related to photoelectric transducers

A relay is to be controlled by a photoconductive cell with the characteristics shown in

the following figure. The circuit delivers 5 mA at a 20-V setting when the cell is

illuminated with 400 lm/m2. The circuit becomes de-energized when the cell is dark.

Find:

a) The value of R1

b) Dark current

3

Question 6: (10Mark)

Objectives: This question is related to multiple choices

1) An 0-10 A ammeter has a guaranteed accuracy of 1 % of full scale

deflection. The limiting error while reading 5 A is:

a) 1 % b) 2 % c) 4 % d) none of the above.

2) A set of readings has a wide range, and therefore it has

a) Low precision

b) high precision

c) low accuracy

d) high accuracy

3) A 1 mA PMMC movement has a resistance of 100 Ω. It is to be converted

to a 10 V voltmeter. The value of the multiplier resistance is:

a) 999 Ω b) 9999 Ω c) 9900 Ω d) 990 Ω

4) A PMMC movement is rated at 50 µA. Its sensitivity is:

a) 20000 Ω/V b) 200000 Ω/V c) 200 Ω/V d) none of the above

5) What is the order of minimum displacement that can be measured with

capacitive transducers:

a) 1 cm b) 1 mm c) 1 µm d) 10-12 m

6) A photoconductive cell is useful for

a) High frequency applications

b) Medium frequency applications

c) Low frequency applications

d) All of the above

7) What device is similar to an RTD but has a negative temperature

coefficient?

a) Strain gauge

b) Negative-type RTD

c) Thermistor

d) Thermocouple

4

8) For the following square-wave pattern, the frequency is:

a) 12.5 MHz b) 12.5 kHz c) 25 MHz d) 25 kHz

9) For the following square-wave pattern, the peak to peak voltage is

a) 3V b) 6V c) 12 V d) 24 V

Vertical sensitivity = 2V/div

Horizontal sensitivity = 20µs/div

10) In the following Lissajous figure, the phase angle is:

a) 0° b) 30° c) 45° d) 60°

Good luck

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