100 Temperature Measurements Objective Questions and Answers

1. Temperature is defined as:
a) Measure of heat content
b) Measure of average kinetic energy of particles
c) Amount of thermal resistance
d) Heat transfer rate
Answer: b

2. Which device is most commonly used for temperature measurement in industries?
a) Pressure gauge
b) Thermocouple
c) Orifice plate
d) Flow nozzle
Answer: b

3. The Seebeck effect is the basis of which temperature sensor?
a) RTD
b) Thermistor
c) Thermocouple
d) Bimetallic thermometer
Answer: c

4. The resistance of a platinum RTD increases:
a) Linearly with pressure
b) Linearly with temperature
c) Exponentially with time
d) Inversely with current
Answer: b

5. A thermistor is mainly used for:
a) High-temperature measurement
b) Low-temperature, high-sensitivity applications
c) Pressure measurement
d) Flow measurement
Answer: b

6. The commonly used material for RTDs is:
a) Copper
b) Nickel
c) Platinum
d) Silver
Answer: c

7. Which type of thermometer uses two different metals bonded together?
a) Thermocouple
b) RTD
c) Bimetallic thermometer
d) Mercury thermometer
Answer: c

8. The accuracy of thermocouples is usually:
a) ±0.1 °C
b) ±1–2 °C
c) ±10 °C
d) ±0.01 °C
Answer: b

9. Which thermocouple type is suitable for very high temperature (>1600 °C)?
a) Type J
b) Type K
c) Type R/S
d) Type T
Answer: c

10. The output of a thermocouple is:
a) Resistance change
b) Voltage (millivolts)
c) Current (amps)
d) Frequency signal
Answer: b

11. Cold junction compensation is required for:
a) RTDs
b) Thermistors
c) Thermocouples
d) Bimetallic thermometers
Answer: c

12. Which temperature scale is absolute (starts from 0 = no molecular motion)?
a) Celsius
b) Fahrenheit
c) Kelvin
d) Rankine
Answer: c

13. Pyrometers are used to measure:
a) Low temperatures
b) Extremely high temperatures (furnaces, kilns)
c) Pressure only
d) Ambient air temperature
Answer: b

14. Which instrument measures temperature using radiation from a hot body?
a) Infrared thermometer
b) Thermocouple
c) RTD
d) Bimetallic strip
Answer: a

15. The thermal well (thermowell) is used for:
a) Enhancing accuracy
b) Protecting temperature sensors from process fluid
c) Converting signals
d) Lowering sensor cost
Answer: b

16. The temperature coefficient of resistance of platinum is approximately:
a) 0.00385 Ω/°C
b) 0.0385 Ω/°C
c) 0.000385 Ω/°C
d) 0.385 Ω/°C
Answer: a

17. Which type of thermometer is filled with mercury or alcohol?
a) Thermistor
b) Liquid-in-glass thermometer
c) RTD
d) Infrared thermometer
Answer: b

18. Thermocouples generate EMF because of:
a) Magnetic induction
b) Difference in temperature between junctions
c) Voltage supply
d) Resistance change
Answer: b

19. Which temperature sensor has the fastest response time?
a) Thermocouple (small junction)
b) RTD
c) Thermistor
d) Bimetallic thermometer
Answer: a

20. The range of thermistors is usually limited to:
a) −200 to 850 °C
b) −50 to 150 °C
c) 0 to 2000 °C
d) 100 to 500 °C
Answer: b

21. Which is more linear in response to temperature?
a) Thermistor
b) RTD
c) Thermocouple
d) Infrared thermometer
Answer: b

22. A bimetallic thermometer works on the principle of:
a) Electrical resistance change
b) Differential expansion of metals with temperature
c) Electromagnetic induction
d) Capacitance change
Answer: b

23. The accuracy of a standard industrial platinum RTD can be up to:
a) ±0.5 °C
b) ±0.2 °C
c) ±2 °C
d) ±1 °C
Answer: b

24. Which thermocouple is best suited for cryogenic applications?
a) Type J
b) Type T
c) Type K
d) Type R
Answer: b

25. A thermowell reduces:
a) Sensor life
b) Sensor exposure to fluid and mechanical damage
c) Sensor accuracy
d) Heat conduction losses
Answer: b

26. Which thermocouple is widely used for general-purpose industrial applications?
a) Type B
b) Type K
c) Type S
d) Type C
Answer: b

27. The Stefan-Boltzmann law relates to:
a) Radiation pyrometry
b) RTD response
c) Thermocouple EMF
d) Thermal conductivity
Answer: a

28. Which is the most suitable sensor for measuring temperature in moving machinery parts?
a) RTD
b) Infrared thermometer
c) Thermistor
d) Bimetallic strip
Answer: b

29. Which of these has the highest sensitivity to small temperature changes?
a) RTD
b) Thermocouple
c) Thermistor
d) Infrared pyrometer
Answer: c

30. Which thermocouple types are made of platinum and rhodium?
a) Type J
b) Type K
c) Type R/S
d) Type T
Answer: c

31. The principle of liquid-in-glass thermometers is based on:
a) Thermal expansion of liquids
b) Seebeck effect
c) Differential expansion of metals
d) Resistance change
Answer: a

32. For high accuracy, temperature measurement in laboratories often uses:
a) RTDs (Platinum)
b) Thermocouples
c) Thermistors
d) Bimetallic strips
Answer: a

33. Which thermocouple is suitable for oxidizing environments?
a) Type J
b) Type K
c) Type T
d) Type E
Answer: b

34. The time constant of a temperature sensor refers to:
a) The time required to reach 63.2% of final response to a step change
b) The total lifespan of the sensor
c) The calibration period
d) The cooling rate
Answer: a

35. Which factor most affects RTD accuracy?
a) Lead wire resistance
b) Pressure in process
c) Electromagnetic interference
d) Flow velocity
Answer: a

36. Optical pyrometers work on:
a) Comparing brightness of hot object with filament lamp
b) Resistance change
c) Capacitance variation
d) Bimetal expansion
Answer: a

37. Thermocouples are standardized by:
a) ASTM and IEC standards
b) Local codes only
c) No standardization
d) Manufacturer-specific rules
Answer: a

38. Which device is non-contact and suitable for high-temperature rotating furnaces?
a) Infrared pyrometer
b) RTD
c) Thermistor
d) Bimetallic thermometer
Answer: a

39. The main disadvantage of thermistors is:
a) Limited temperature range (−50 to 150 °C)
b) Poor sensitivity
c) High cost
d) Need for cold junction compensation
Answer: a

40. Type B thermocouple (Pt30Rh-Pt6Rh) is suitable for:
a) Low-temperature refrigeration
b) High-temperature furnaces up to 1700 °C
c) Room temperature monitoring
d) Water heating
Answer: b

41. Which type of RTD has better stability and accuracy?
a) Copper
b) Nickel
c) Platinum
d) Aluminum
Answer: c

42. Which thermocouple has the lowest temperature range?
a) Type T (Copper–Constantan)
b) Type K (Chromel–Alumel)
c) Type R (Platinum–Rhodium)
d) Type B (Platinum–Rhodium)
Answer: a

43. What is the main use of cold junction compensation in thermocouples?
a) Eliminate lead resistance
b) Correct EMF reading by accounting for reference temperature
c) Prevent oxidation
d) Improve sensitivity
Answer: b

44. The Curie point is related to which type of temperature sensor?
a) RTD
b) Thermocouple
c) Magnetic temperature sensors
d) Bimetallic strip
Answer: c

45. Which device uses change in electrical resistance to measure temperature?
a) RTD
b) Thermocouple
c) Infrared pyrometer
d) Liquid-in-glass thermometer
Answer: a

46. Which temperature measurement device requires no contact with the object?
a) RTD
b) Infrared thermometer
c) Thermocouple
d) Thermistor
Answer: b

47. Which thermocouple has the widest operating temperature range?
a) Type K
b) Type R
c) Type B
d) Type C (Tungsten-Rhenium)
Answer: d

48. The resistance of a typical 100Ω platinum RTD at 0 °C is:
a) 10 Ω
b) 50 Ω
c) 100 Ω
d) 200 Ω
Answer: c

49. The emissivity factor is important in which type of measurement?
a) Infrared and radiation pyrometry
b) RTD measurement
c) Thermistor response
d) Bimetallic thermometer
Answer: a

50. Which thermocouple is least affected by oxidation at high temperatures?
a) Type J
b) Type K
c) Type N
d) Type T
Answer: c

51. Which thermometer is widely used in laboratories for calibration standards?
a) Thermistor
b) Platinum RTD
c) Infrared thermometer
d) Thermocouple
Answer: b

52. Which factor most affects the response time of a thermocouple?
a) Junction size and placement
b) Wire color code
c) Length of extension wires
d) Calibration frequency
Answer: a

53. The unit of thermal conductivity used in heat flow-based temperature sensors is:
a) W/m·K
b) N/m²
c) Ω/°C
d) J/kg·K
Answer: a

54. For food and pharmaceutical industries, the preferred temperature sensors are:
a) Infrared pyrometers
b) Sanitary RTDs with hygienic thermowells
c) Thermocouples only
d) Bimetallic thermometers
Answer: b

55. The ice point method is used for:
a) Calibration of thermocouples
b) Testing thermowell material
c) Zero adjustment of RTDs
d) Verifying bimetallic strips
Answer: a

56. The sensitivity of a Type K thermocouple is approximately:
a) 10 µV/°C
b) 41 µV/°C
c) 5 mV/°C
d) 0.1 V/°C
Answer: b

57. Which factor influences thermistor performance the most?
a) Pressure
b) Humidity
c) Non-linear resistance–temperature relationship
d) Radiation
Answer: c

58. What is the main drawback of bimetallic thermometers?
a) Slow response and limited accuracy
b) High cost
c) Non-linear response
d) Requires power supply
Answer: a

59. Which sensor type is commonly used in electronic devices for overheat protection?
a) Thermistor
b) RTD
c) Thermocouple
d) Pyrometer
Answer: a

60. Which thermocouple is suitable for vacuum furnaces at high temperatures?
a) Type K
b) Type B
c) Type C
d) Type T
Answer: c

61. Which law states that EMF generated in a thermocouple is proportional to temperature difference between junctions?
a) Ohm’s Law
b) Seebeck’s Law
c) Joule’s Law
d) Stefan’s Law
Answer: b

62. Which RTD element material gives the best long-term stability?
a) Nickel
b) Copper
c) Platinum
d) Iron
Answer: c

63. Which thermometer uses expansion of a gas at constant volume?
a) Resistance thermometer
b) Gas thermometer
c) Liquid-in-glass thermometer
d) Infrared thermometer
Answer: b

64. Which thermocouple is commonly used in nuclear reactors?
a) Type K
b) Type N
c) Type T
d) Type C
Answer: b

65. The emissivity of a blackbody is:
a) 0
b) 0.5
c) 1
d) Variable
Answer: c

66. Which method is best for measuring surface temperature of moving objects?
a) RTD
b) Infrared thermometer
c) Thermistor
d) Bimetallic strip
Answer: b

67. The maximum operating temperature for platinum RTDs is about:
a) 150 °C
b) 400 °C
c) 850 °C
d) 1600 °C
Answer: c

68. Which factor most affects thermocouple drift at high temperature?
a) Oxidation and contamination of wires
b) Junction size
c) Extension wire length
d) Cold junction compensation
Answer: a

69. Which type of thermometer is most rugged and maintenance-free?
a) RTD
b) Bimetallic strip thermometer
c) Infrared thermometer
d) Thermistor
Answer: b

70. Which thermocouple type is most commonly used in food industry for freezers and refrigeration?
a) Type K
b) Type T
c) Type J
d) Type R
Answer: b

71. In temperature measurement, The main advantage of radiation pyrometers is:
a) Contact measurement
b) Fast, non-contact measurement of very high temperatures
c) Low cost
d) Extremely linear response
Answer: b

72. Which gas is often used in gas thermometers for accurate low-temperature measurement?
a) Nitrogen
b) Hydrogen or Helium
c) Oxygen
d) Carbon dioxide
Answer: b

73. The main purpose of using 4-wire RTD connections is to:
a) Reduce cost
b) Eliminate lead resistance effect
c) Increase range
d) Improve sensitivity
Answer: b

74. Which thermocouple has the highest EMF output per degree Celsius?
a) Type K
b) Type E
c) Type J
d) Type T
Answer: b

75. Which sensor is best suited for applications requiring very high precision (<0.1 °C) in temperature measurement?
a) Thermocouple
b) RTD
c) Thermistor
d) Bimetallic strip
Answer: b

76. Which temperature sensor has the lowest cost and simplest design?
a) Thermistor
b) Thermocouple
c) RTD
d) Infrared thermometer
Answer: b

77. Which thermocouple color code represents Type K in IEC standard?
a) Black (+), Red (–)
b) Green (+), White (–)
c) Yellow (+), Red (–)
d) Blue (+), Red (–)
Answer: c

78. Which principle is used in fiber optic temperature sensors?
a) Capacitance
b) Optical signal change with temperature
c) Resistance change
d) Seebeck effect
Answer: b

79. Which thermocouple can withstand temperatures above 2000 °C?
a) Type B
b) Type K
c) Type C (Tungsten-Rhenium)
d) Type T
Answer: c

80. Which instrument is often used for calibration of high-accuracy temperature sensors?
a) Dry block calibrator
b) Mercury thermometer
c) Bimetallic thermometer
d) Pressure gauge
Answer: a

81. Which is the most common industrial standard RTD element resistance?
a) 50 Ω
b) 100 Ω
c) 200 Ω
d) 1000 Ω
Answer: b

82. Which thermocouple type is best for vacuum and reducing atmospheres in temperature measurement?
a) Type B
b) Type C
c) Type T
d) Type K
Answer: b

83. The main advantage of thermistors over RTDs is:
a) Lower cost and higher sensitivity in narrow ranges
b) Wider temperature range
c) Higher accuracy at high temperatures
d) Better linearity
Answer: a

84. A pyrometer is generally used when temperature is above:
a) 100 °C
b) 300 °C
c) 600 °C
d) 1200 °C
Answer: c

85. Which thermocouple is recommended for oxidizing and inert environments up to 1260 °C?
a) Type J
b) Type K
c) Type T
d) Type S
Answer: b

86. A drawback of RTDs compared to thermocouples is:
a) Slower response and higher cost
b) Limited accuracy
c) Non-repeatability
d) Lack of standardization
Answer: a

87. Which device is used for calibrating thermocouples at very high temperatures?
a) Dry block calibrator
b) Standard platinum resistance thermometer (SPRT)
c) Blackbody furnace
d) Ice bath
Answer: c

88. The sensitivity of a thermistor is highest in which temperature range?
a) −200 to −50 °C
b) −50 to 150 °C
c) 200 to 800 °C
d) Above 1000 °C
Answer: b

89. Which is the safest temperature sensor for explosive environments?
a) Thermocouple with intrinsic safety barrier
b) RTD with thermowell
c) Mercury thermometer
d) Thermistor
Answer: a

90. Which factor determines the emissivity correction in infrared thermometers?
a) Color and surface finish of object
b) Object shape only
c) Ambient pressure
d) Cable length
Answer: a

91. Which instrument is known as the “primary standard” for temperature measurement?
a) Platinum RTD
b) Gas thermometer
c) Thermistor
d) Pyrometer
Answer: b

92. Which thermocouple is most commonly used in petrochemical industries?
a) Type T
b) Type K
c) Type R
d) Type N
Answer: b

93. Which sensor is most suitable for semiconductor chip temperature monitoring?
a) RTD
b) Thermistor
c) Thermocouple
d) Infrared thermometer
Answer: b

94. What is the output signal of a resistance thermometer?
a) Voltage
b) Resistance change
c) Frequency
d) Current
Answer: b

95. Which is the fastest temperature measurement method?
a) Bare junction thermocouple
b) RTD
c) Thermistor
d) Bimetallic strip
Answer: a

96. Which thermocouple is recommended for cryogenic applications down to −200 °C?
a) Type J
b) Type T
c) Type K
d) Type R
Answer: b

97. Which type of thermometer is not affected by electromagnetic interference (EMI)?
a) RTD
b) Thermocouple
c) Infrared thermometer
d) Thermistor
Answer: c

98. What is the resistance of a Pt1000 RTD at 0 °C?
a) 100 Ω
b) 500 Ω
c) 1000 Ω
d) 2000 Ω
Answer: c

99. Which sensor uses negative temperature coefficient (NTC) behavior?
a) Thermistor
b) RTD
c) Thermocouple
d) Pyrometer
Answer: a

100. The triple point of water (0.01 °C, 611 Pa) is used for:
a) RTD calibration
b) Defining the Kelvin scale
c) Thermistor range setting
d) Pyrometer adjustment
Answer: b