This Portion of Electrical and Electronic Instrumentation contains Primary Sensing Elements and Transducers MCQs (Multiple Choice Questions and Answers) / Objective Type Questions and Answers.

**This Section covers below lists of topics.**

- Mechanical Devices as Primary Detectors
- Mechanical Spring Devices
- Pressure Sensitive Primary Devices
- Flow Rate Sensing Elements
- Transducers
- Electric Transducers
- Classification of Transducers
- Characteristics and Choice of Transducers
- Resistive Transducers
- Potentiometers
- Non-linear Potentiometers Function Generators
- Materials used for Potentiometers
- Strain Gauges
- Rosettes
- Resistance Thermometers
- Thermistors
- Thermocouples
- Integrated Circuit Temperature Transducers
- Variable inductance Transducers
- Linear Variable Differential Transformer (RVDT)
- Synchros
- Resolvers
- Capacitive Transducers
- Piezo-Electric Transducers
- Hall Effect Transducers
- Magneto resistors
- Magneto-Elastic and Magneto-Strictive Transducers
- Opto-Electronic Transducers
- Digital Encoding Transducers
- Classification of Encoders
- Shaft Encoders
- Photo Optic Transducers

#### 1. A transducer converts

- Mechanical energy into electrical energy
- Mechanical displacement into electrical signal
- One form of energy into another form of energy
- Electrical energy into mechanical form

C. One form of energy into another form of energy

#### 2. An inverse transducer converts

- Electrical energy into any other form of energy
- Electrical energy to light energy
- Mechanical displacement into electrical signal
- Electrical energy to mechanical form.

A. Electrical energy into any other form of energy

#### 3. One of the following can act as an inverse transducer

- Electrical resistance potentiometer
- L.V.D.T
- Capacitive transducer
- Piezo electric crystals

D. Piezo electric crystals

#### 4. One of the following is an active transducer

- Strain gauge
- Selsyn
- Photovoltaic cell
- Photo-emissive cell.

C. Photovoltaic cell

#### 5. A strip chart recorder is

- An active transducer
- An inverse transducer
- An output transducer
- (b) and (c)

D. (b) and (c)

#### 6. In a transducer, the experimentally obtained transfer function is different from the theoretical transfer function, the errors result from this difference are called

- Zero errors
- Sensitivity errors
- Non-conformity errors
- Dynamic errors

C. Non-conformity errors

#### 7. In a transducer, the observed output deviates from the correct value by a constant factor the resulting error is called

- Zero Error
- Sensitivity Error
- Non-conformity Error
- Hysteresis Error.

B. Sensitivity Error

#### 8. A transducer has an output impedance of 1 kΩ and the load resistance is 1 MΩ, the transducer behaves as

- A constant current source
- A constant voltage source
- A constant power source
- None of the above.

B. A constant voltage source

#### 9. A transducer has an output impedance of 1 Ω and the load resistance is 1 kΩ, the transducer behaves as

- A constant current source
- A constant voltage source
- A constant impedance source
- None of the above.

A. A constant current source

#### 10. The power limit of useful working range of a transducer is determined by

- Minimum useful input level
- By transducer error and noise
- Cross sensitivity
- Dynamic response.

B. By transducer error and noise

#### 11. While selecting a transducer for a particular application

- Only the input characteristics should be considered
- Only the output characteristics should be considered
- Only the transfer characteristics should be considered
- Input, output, transfer characteristics should be considered

D. Input, output, transfer characteristics should be considered

#### 12. A cantilever is used as a primary sensing element for measurement of force. The measured deflection 0.5 mm for a particular set up. Suppose each of the dimensions i.e length, width, and thickness of the cantilever of the cantilever are doubled with the force and material of cantilever remaining the same, the deflection is

- 1 mm
- 2 mm
- 0.251 mm
- 0.125 mm

C. 0.251 mm

#### 13. A closed coil spring has a stiffness of 20 × 10^{-6 }N/m. Suppose the diameter of the wire is doubled, its outer diameter is made two times and its number of turns are made 2 times, the stiffness of new spring would be

- 20 × 10
^{-6 }N/m - 80 × 10
^{-6 }N/m - 10 × 10
^{-6 }N/m - 160 × 10
^{-6 }N/m

A. 20 × 10

^{-6 }N/m#### 14. A diaphragm has a natural frequency of 30 kHz. If both its diameter and thickness are halved, the natural frequency is

- 15 kHz
- 240 kHz
- 60 kHz
- 120 kHz

C. 60 kHz

#### 15. A pressure of 256 kN/m^{2 }acting on a diaphragm produces a deflection of 0.2 mm at the center. What pressure would produce the same deflection if the diameter is 2 times the earlier one and the thickness is 1/2 of the earlier one

- 2 kN/m
^{2} - 128 kN/m
^{2} - 64 kN/m
^{2} - 0.5 kN/m
^{2}

A. 2 kN/m

^{2}#### 16. A pressure applied to a bellows element produces a linear displacement of 2 mm. supposes the number of bellows elements is made 3 times and the thickness of bellows element is halved, what would be the displacement of the element for the same applied pressure?

- 24 mm
- 12 mm
- 48 mm
- 3 mm

C. 48 mm

#### 17. A torsion bar of 30 mm diameter produces a twist of 1 minute when torque of 200 Nm is applied supposing the diameter of torsion bar is reduced to 15 mm, what would be the angle of twist for the same torque?

- 4 minute
- 8 minute
- 2 minute
- 0.125 minute.

B. 8 minute

#### 18. A Reynold’s number of 1000 indicates

- Turbulent flow
- Laminar flow
- A flow which can be either turbulent or laminar
- None of the above.

B. Laminar flow

#### 19. In a venture meter the flow is 0.15 m^{3}/s when the differential pressure is 30 kN/m^{2}

- 0.212 m
^{3}/s - 0.106 m
^{3}/s - 0.3 m
^{3}/s - 0.075 m
^{3}/s

A. 0.212 m

^{3}/s#### 20. Pilot tubes are useful

- For industrial applications
- For laboratory experimental purposes
- For both industrial and laboratory applications
- None of the above.

B. For laboratory experimental purposes

#### 21. Water is flowing with a depth of 0.9 m over a rectangular notch 1.2 m wide. Find the depth of flow over a right angle notch if the same were to pass over it. Assume that both the notches have the same co-efficient of discharge

- 0.91 n
- 1.1 m
- 2.2 m
- 0.45 m.

B. 1.1 m

#### 22. A resistance potentiometer is a

- First order instrument
- Zero order instruments
- Second order instrument
- None of the above.

B. Zero order instruments

#### 23. In a resistance potentiometer, the non-linearity

- Increases with increase of load to potentiometer resistance
- Decreases with increase of load to potentiometer resistance
- It not dependent upon load to potentiometer resistance
- None of the above.

B. Decreases with increase of load to potentiometer resistance

#### 24. In a resistance potentiometer high value of resistance of POT leads to

- High value of sensitivity
- Low value of sensitivity
- Low value of non-linearity
- Low value of error.

A. High value of sensitivity

#### 25. A 100 Ω resistive potentiometer is used with an input supply voltage of 10 V. the temperature of the POT is of the thermal resistance 30°C/W and the ambient temperature is 40°C

- 60°C
- 80°C
- 70°C
- 100°C

C. 70°C

#### 26. A heliport is used for measurement of linear displacement of 0.1 m. it uses a 10 turn potentiometer (3000 of movement full scale) with a total of 5000 turns of wire. Its resolution is

- 0.1 mm
- 0.2 mm
- 0.01 mm
- 0.02 mm.

D. 0.02 mm.

#### 27. In a wire wound strain gauges, the change in resistance on application of strain is mainly due to

- Change in length of wire
- Change in diameter of wire
- Change in both diameter and length of wire
- Change in resistivity.

C. Change in both diameter and length of wire

#### 28. Unbonded strain gauges are

- Exclusively used for transducer application
- Exclusively used for stress analysis
- Commonly used for both transducer applications as well as for stress analysis
- None of the above.

A. Exclusively used for transducer application

#### 29. The gauge factor is defined as______________ Where L, D,ρ and R are respectively the length, diameter, resistivity and resistance of strain gauge

- (∆L/L)/(∆R/R)
- (∆R/R)/(∆L/L)
- (∆R/R)/(∆D/D)
- (∆R/R)/(∆ρ/ρ)

B. (∆R/R)/(∆L/L)

#### 30. For wire wound strain gauges the approximate value of gauge factor is__________ Where ρ,R,v and D are respectively resistivity, resistance, poisson’s ratio and diameter?

- 1 + 2∆ρ / ρ
- 1 + 2∆R / R
- 1 + 2v
- 1 + 2∆D / D

C. 1 + 2v