125 QUESTIONS ANSWERS TEMPERATURE INSTRUMENTATION_ENGINEERING

125 QUESTIONS & ANSWERS TEMPERATURE INSTRUMENTATION_ENGINEERING

1. Which of the following devices responds to temperature by producing a Action or movement?

1.   Bimetallic thermometer
2.   Thermocouple
3.   Resistance temperature detector
4.   Radiation pyrometer

2. One definition of temperature is based on the theory that: All molecules are in motion; motion is sensed as heat and measured as

1.  Temperature
2.   All matter contains heat
3.   Atomic particles are hot
4.   Radiation creates heat

3.  Definitions of temperature are based on:

1.    Molecular stability and energy non-transference
2.   Molecular motion and thermal energy transfer
3.   Molecular motion and molecular transfer
4.   Molecular stability and molecular cohesion

4. The four most commonly used scales to measure temperature are the:

1.  Fahrenheit, Celsius, Kelvin, and Newton scales
2.   Fahrenheit, Celsius, Galileo, and Rankine scales
3.   Fahrenheit, Celsius, Kelvin, and Rankine scales
4.   Fahrenheit, Galileo, Rankin, and Kelvin scales

5. The two general classes of temperature measuring devices are:

1.  Thermocouples and bulbs
2.  Bulb thermometers and temperature sensors
3.  Closed and open sensors and thermometers
4.  Temperature sensors and absolute thermometers

6. Two of the most common temperature sensors are

1. Thermocouples and resistance temperature detectors
2. Thermal transmitters and resistive couplers
3. Thermocouples and reactive detectors
4. Thermal transmitters and resistance temperature detectors

7. Temperature sensors are classified according to their

1.  Mounting
2.  Construction
3.  Application
4.  Configuration

8. Two examples of absolute thermometers are the:

1.   Resistance temperature detectors and the thermocouples
2.    Reactive detectors and thermocouples
3.   Radiation pyrometers and gas bulb thermometers
4.  Resistance temperature detectors and thermocouples

9. Mechanical temperature devices respond to temperature by producing

1.    An electrical signal that causes a mechanical action
2.    Light signals that radiate to a sensor
3.   A mechanical action or electrical signal
4.   A mechanical action or movement

10. What type of measurement error may result from surface mounted sensors?

•  Stem loss error
• Thermal shunting error
•  Radiation error
•  Line-of-sight error

11. What type of temperature measurement error may occur with high velocity fluids?

•   Response time error
•  Heat transfer lag error
•  Surface mounted sensor error
•  Frictional heating error

12. Stem loss errors can be reduced by using a:

•  Longer sensor
•  Cylindricalsensor
•  Shorter sensor
•   Sensor with a bulbous head

13. Thermal shunting can occur with surface mounted sensors if the lead wires are:

•    Too long
•   Not insulated correctly
•   Too short
•   Wrapped around a pipe

14. When temperature sensors are installed in gases, measurement errors can be caused by:

•  Reactance
•  Inductance
•  Radiation
•  Resistance

15. One way to solve the problem of radiation when measuring the temperature of gases is to install the sensor so that there is no direct line of sight between:

•   The sensor and the substance being measured that may be at a different temperature
•  The substance being measured and the sensor control
•  The sensor and the materials that may be at the same temperature
•  Materials that may be at a different temperature from the substance being measured and the sensor

16. Frictional heating errors may occur in:

•   High velocity fluids
•   Low velocity fluids
•   Thin fluids
•   Thick fluids

17. Kinetic energy is converted to heat when:

• Sensor shields are used
• The fluid impacts the tip of the sensor
• Fluid flow increases
• Friction between shield and sensor is minimized

18. To insure accuracy on surface mounted sensors, the sensor must be installed:

• Vertically in the center of the wall
• To the wall of the pipe
• With a tight interface between the sensor and the wall
• With the sensor in the center of the pipe

19. What is a major consideration when the temperature sensor is used for safety, process control, or data acquisition?

• The process being measured
• Material from which the sensor is made
• Sensor position
• Heat transfer lag

20. Which component of the liquid-in-glass thermometer serves to contain the fluid at high temperatures?

• Glass chamber
• Capillary tube
• Expansion chamber
• Contraction chamber

21. An identifying characteristic of the complete immersion thermometer is that it:

• Is immersed to the height of the fluid column
• Is the most accurate liquid-in-glass thermometer
• Has no immersion ring
• Is inserted to a fixed point

22. The type of thermometer that indicates temperature on a scale as the helix winds or unwinds is known as

• Gas-filled system thermometer
• Mercury filled system thermometer
• Vapor system thermometer
• Bimetallic thermometer

23. The components of a liquid-in-glass thermometer include:

• The bulb, the stem, and the capillary tube
• The stem, the bulb, and the capsule
• The ball, the shaft, and the piping
• The stem, the liquid cell, and the capillary tube

24. The component of a liquid-in-glass thermometer that increases the volume to contain fluid at low temperatures is called the:

• Capillary tube
• Contraction chamber
• Bulb
• Expansion chamber

25. The expansion chamber is located:

• Between the bulb and the capillary tube
• At the bottom of the thermometer
• Above the main capillary
• Between the bulb and the scale

26. The operation of a liquid-in-glass thermometer depends on:

• Viscosity of the fluid used
• The material or process that is being measured
• Composition of the bulb
• The coefficient of the liquid expansion being greater than that of  the bulb

27. The thermometer that is inserted to a fixed point indicated by the immersion ring is the:

• Partial immersion thermometer
• Total immersion thermometer
• Complete immersion thermometer
• Liquid-in-glass thermometer

28. The thermometer that is designed to be immersed to the height of the fluid column is the:

• Partial immersion thermometer
• Total immersion thermometer
• Complete immersion thermometer
• Liquid-in-glass thermometer

29. The thermometer that is designed to be totally submerged in the fluid to be measured is the:

• Partial immersion thermometer
• Total immersion thermometer
• Complete immersion thermometer
• Liquid-in-glass thermometer

30. The thermometer that is the most accurate of the three liquid-in-glass thermometers is the:

• Partial immersion thermometer
• Total immersion thermometer
• Non-immersion thermometer
• Complete immersion thermometer

 

31. One of the common liquids used because of its rapid response and ability to transfer heat efficiently is:

• Mercury
• Water with dye
• Saline with dye
• Alcohol with dye

32. Mercury is the preferred liquid in a filled thermometer because:

• It is more readily visible
• It expands uniformly with temperature changes
• It has the lowest surface tension of all liquids
• It is the least expensive and most readily available

33. The vapor filled system is filled with:

• Mercury vapor
• Nonvolatile vapor
• Volatile liquid and its vapor
• Volatile vapor

34. The gas-filled system is based on the ideal gas law, which states that:

• Gas expands to fill the space
• Gas and pressure are inversely proportional
• Every action has an equal and opposite reaction
• Gas will expand with an increase in temperature, thus increasing pressure

35. The bimetallic thermometer is made of:

• Two metals that have different expansion coefficients
• Two pieces of the same metal
• Metal spirals that are attached at both ends
• Two metal strips of different lengths

36. What is a bimetallic thermometer made of?

• Metal spirals that are attached at both ends
• Two metals that have different expansion coefficients
• Two metal strips of different lengths
• Two pieces of the same metal

37. Compared to liquid-in-glass thermometers, bimetallic thermometers are:

• More accurate
• More stable
• More durable
• More fragile

38. The thermometer that can be read directly and is the most accurate is the:

• Bimetallic thermometer
• Gas-filled thermometer
• Vapor filled thermometer
• Liquid-in-glass thermometer

39. Refractory metal thermocouples can be used to approximately:

• 1000 degrees centigrade
• 1600 degrees centigrade
• 2600 degrees centigrade
• 3400 degrees centigrade

40. Wires typically insulated with a crushed mineral oxide are known as:

• Bare
• Insulated
• Sheathed
• Ceramics

41. The thin-walled metal or ceramic cylinder of a thermocouple used in low pressure application is known as the:

• Thermowell
• Terminal block
• Connection head
• Protecting tube

42. When installing a thermocouple, you should consider the following EXCEPT:

• Location of thermocouple placement
• Depth of immersion
• Density of liquid being measure
• Use of a conduit

43. One type of an electrical temperature sensing device is the:

• Thermocouple
• Thermometer
• Fluid-filled pyrometer
• Liquid-in-glass thermometer

44. Thermocouples are used to measure temperature in:

• Molten metal applications only
• Many different industrial applications
• Gases and liquids only
• Highly specialized medical applications requiring extreme accuracy

     45.  A thermocouple is constructed of:

• Two wires connected to a ceramic disk
• Two wires of similar metals or alloys connected together at one   end
• Two wires of dissimilar metals or alloys connected together at one   end
• Two flat metal ribbons of metal in a helical shape

46. In a thermocouple, when the junctions of the two wires are at different temperatures, the electromotive force generated will:

• Create an alternating current
• Shut down the thermocouple
• Bond the two wires
• Induce a continuous electric current

47. Wires that are used as the extension wires connecting the thermocouple to the measuring instrument must have:

• The same thermoelectric characteristics
• The same number of strands
• The same type of insulation
• The same metal makeup

48. At the thermocouple reference junction, the signal is measured in:

• Milliamps
• Millivolts
• Milliohms
• Microvolts

49. When the thermocouples are not connected to transducers designed to automatically convert the signal to a temperature reading, a reference table is used to convert:

• Milliamp readings to temperature readings
• Milliohm readings to temperature readings
• Millivolt readings to temperature readings
• Microvolt readings to temperature readings

50. When a transducer is not available, what must you use to convert the millivolt readings of a thermocouple to temperature?

• A voltmeter
• A thermometer
• The Seeback equation
• A conversion table

51. The three classes of thermocouples are:

• Base metal, Noble metal, and Refractory metal
• Base metal, Type J, and Type T
• Bimetal, Noble metal, and Refraction Metal
• Base Metal, Noble metal, and Type T

52. Type J, Type K, Type T and Type E thermocouples are in the base metal class and can measure temperatures up to about:

• 500 degrees centigrade
• 1,000 degrees centigrade
• 1,500 degrees centigrade
• 2,000 degrees centigrade

53. The Noble metal thermocouples are made up of:

• Types S, T and E and can measure temperatures up to about   2,600 degrees centigrade
• Types J, T, and E and can measure temperatures up to about   2,000 degrees centigrade
• Types S, R, and B and can measure temperatures up to about   2,000 degrees centigrade
• Tungsten-Rhenium thermocouples and can measure temperatures up to about 2,600 degrees centigrade

54. The Refractory metal thermocouples are made of:

• Aluminum and nickel
• Platinum and iridium
• Copper and iron
• Tantalum and Molybdenum

55. When thermocouples are made on site, which of the following criteria must be considered?

• Grade of wire
• Length of the insulation
• Material construction of the insulation
• Diameter of the wire

56. The wire that will give a quicker response time is:

• Thick and short
• Smaller in diameter
• Shorter in length
• Thin and long

57. Thermocouples that are made of bare wires are typically insulated with:

• Aluminum oxide
• Braided glass
• Hard fired ceramic insulators
• Crushed mineral oxide

58. Thermocouple wires are similar to battery cables in that they are color coded and:

• The positive cable is normally white
• The positive cable is normally red
• The negative cable is normally black
• The negative is cable is normally red

59. On a thermocouple, the terminal block is:

• The insulating block that joins the terminations of the extension wires
• The part of the thermocouple that is used to mount the measuring instrument
• The housing that encloses the measuring instrument
• The protecting tube

60. What is the purpose of the connection head in a thermocouple?

• It is used as the insulating block that joins the terminations of the   extension wires
• It is the housing that encloses the terminal block
• It is the device that protects the thermocouple from contamination
• It is the device that provides mechanical protection and support   for the thermocouple

61. The protecting tube is used in a thermocouple:

• To house and enclose the terminal block
• To insulate and support the terminations of the extension wires
• To protect the thermocouple from contamination
• To make a pressure tight attachment to the vessel

62. What is the purpose of the thermowell in a thermocouple assembly?

• It insulates the wires
• It is the enclosure for the terminal block
• It protects the thermocouple from contamination
• It makes a pressure tight attachment to the vessel

63. When installing a thermocouple, other than location, what is an important consideration?

• The depth of immersion
• The method of mounting
• The type of thermocouple used
• The length of extension wires

64. Extending the thermowell beyond the outer end of the vessel or equipment in high temperature applications is done in order that:

• The thermocouple can sample the ambient temperature outside the vessel or equipment
• The temperature of the connection head is close to the ambient atmospheric temperature
• The depth of the installed thermocouple is properly achieved
• A multiple point application can be achieved and provide a way to get a high output for a small change

65. When thermocouples are connected in parallel, they:

• Produce a high output from a small change in temperature
• Create a low output from a large change in temperature
• Provide a way to get an average measure of temperature
• Form a thermopile

66. When thermocouples are connected in series, they:

• Provide a way to get the average of temperatures measured
• Extend beyond the equipment to sample the ambient air
• Create a low output from a large change in temperature
• Form a thermopile

67. When checking the accuracy of an installed thermocouple, the advantage of leaving the first thermocouple installed and installing a second is:

• The second sensor is subjected to the same temperatures
• Backup, in case the first one fails
• The second sensor checks the current temperature
• The first one can then be recalibrated

68. The disadvantage of installing a second thermocouple while leaving the first is:

• The second sensor is subject to the same temperature normally encountered in the
  process
• That it can only be checked at the current process temperatures
• The second sensor is used in the processes with steady temperatures
• The second sensor is installed in the same location to read the process
  temperatures

69. The disadvantage of installing a new thermocouple into the same location as the one to be checked is:

• The second sensor is subjected to the same temperatures
• That it can only be checked at the current process temperatures
• That it should only be used in process with steady temperatures
• That it can be installed in the same location to read the process temperatures

70. The three most important considerations to keep in mind when installing a thermocouple are:

• Where it will be installed, the materials it will measure, and its accuracy
• How it will be installed, the materials it will measure, and its accuracy
• Where it will be installed, the materials it is made with, and the temperature scale it uses
• Where it will be installed, the materials it is made with, and its accuracy

71. Which type of RTD mounting device uses ceramic disks to separate and prevent wires from touching?

• Sensor
• Birdcage
• Film element
• Fully supported

72. When a high degree of accuracy is required and you must measure a slight variation in temperature, it is best to use a:

• One-wire sensor
• Two-wire sensor
• Three-wire sensor
• Four-wire sensor

73. What type of thermistor design is important to use where high power dissipate ion is a primary requirement?

•  Rod
•  Washer
•  Disk
•  Bead

74. What affect will surface contamination have on the accuracy of a thermistor?

• Friction heating error
• False high temperature
• Shorting
• Heat transfer lag

75. RTDs operate when temperature variations cause changes in electrical:

• Resistance
• Current
• Voltage
• Wattage

76.  RTD stands for:

• Resistive temperature deflection
• Resistance temperature detector
• Responsive temperature deflection
• Reostatic temperature detector

77.  How many wires are there in the most common industrial RTDs?

• None
• One
• Three
• Five

78. Why is platinum preferred in the making of RTD elements?

• Because of its tensile strength and durability
• Because of its resistance to corrosion
• Its properties will not adversely effect the readings of the RTD
• Its relationship between resistance and temperature is linear

79. The manner in which a RTD is mounted important because:

• The strain on the detector can change the resistance of the detector
• The metal’s make up will determine how long the sensor lasts
• The metal of the mount can also transfer heat that could interfere with the
  sensor’s readings
• The strength of the RTD will determine the amount of vibrations that it can sustain

80.  The commonly used type of mounting system for RTDs in laboratory applications is the:

• Fully supported
• Birdcage design
• Partially supported
• Shaft design

81. The disks in a Birdcage mounted RTD are used for:

• Keeping the wires free to move
• To ensure that the temperature being measured is done so equally by both wires
• To keep the wires from touching one another
• To hold the wires steady

82. The RTD mount design used where the most strain can be tolerated is the:

• Birdcage design
• Partially supported
• Shaft design
• Fully supported

83. When connecting to a Wheatstone bridge, an RTD must have compensation for:

• Lead resistance
• Stress
• Fluid flow
• Free-moving wires

84. A two-wire sensor connected to a bridge allows for:

• No lead wire accuracy, but good compensation with short leads
• No lead wire compensation, but good accuracy with short leads
• No lead wire accuracy, but good compensation with long leads
• No lead wire compensation, but good accuracy with long leads

85. In a three-wire sensor, two leads are:

• In the same branch of the bridge
• In opposite branches of the bridge connected
• in series with the input voltage  Connected
• in parallel with the input voltage

86.  In a three-wire RTD, the third wire provides:

• A way to identify the type of RTD
• Structural stability to protect the measuring film in the birdcage
• A ground path for the reference signal
• Compensation for the voltage resistance loss of the two measuring wires

87. Thermistors read temperature variations by sensing changes in:

• Resistance
• Voltage
• Power
• Wattage

88. The ratio of output produced to temperature changes sensed by thermistors is:

• Higher output with greater temperature changes
• Higher output with smaller temperature changes
• Lower output with smaller temperature changes
• Lower output with greater temperature changes

89. What is the relationship between thermistor resistance and temperature changes?

• Resistance increases as temperature increases
• Resistance decreases as temperature decreases
• Resistance decreases as temperature increases
• Resistance increases as temperature decreases

90.  Some of the products that make up the composition of thermistors are:

• Analog devices and wire coils
• CRTs, tubes, and transformers
• Solid state devices and mechanical drivers
• Solid state devices and semi-conductors

91. The type of thermistor that is made with a small bit of thermistor material to which a pair of leads are attached is a:

• Bead type
• Disk type
• Washer type
• Rod type

92. The type of thermistor that is used where a moderate degree of power dissipation is required is:

• The bead type
• The disk type
• The washer type
• The rod type

93. The type of thermistor that is used where high power dissipation is a primary requirement is the:

• Bead type
• Disk type
• Washer type
• Rod type

94. The type of thermistor that is used where power dissipation is not a major concern is the:

• Bead type
• Disk type
• Washer type
• Rod type

95. Thermistors are generally made with how many leads?

• Two
• Three
• Four
• Five

96. The reason that only two lead wires are used with thermistors is:

• Lead wire resistance causes major concerns
• Large resistance values for thermistors reduces concerns about lead wire resistance
• Lead wire resistance has no effect and causes no concerns
• Small resistance values for thermistors increases concerns about lead wire resistance

97. Which of the following is a true statement concerning the accuracy of thermistors?

• Surface cleanliness has no effect on the accuracy of thermistors
• Major damage to thermistors has an effect on the accuracy, but a small chip has no effect
• Surface contamination may cause shorting of the thermistor
• If surface contamination is minor, no damage will occur and a thermistor will
  retain its accuracy

98. Which of the following is a true statement concerning how stress affects thermistors?

• Stress has no effect on the wires, terminals, or the thermistor itself
• Stress has no effect on the resistance and therefore has no effect on thermistor
  accuracy
• Stress has no effect on the resistance in the lead wires
• Stress can increase the connection resistance between the lead wires and the
  thermistor

99. Noncontact temperature measurement can be performed using:

• Radiation Pyrometers
• Thermistors  Resistance
• Temperature Detectors
• Thermocouples

100. In an automatic pyrometer a photomultiplier tube is used to:

• Compare radiation from a target
• Detect light from a heated target
• Adjust current flow
• Match brightness with the filament

101. What is the function of a thermopile in a total radiation pyrometer?

• It is a detector
• It amplifies pulses
• It is an oscillating device
• It senses incident energy

102. One of the reasons that pyrometers are used is that they:

• Do not have to be in direct contact with the product being measured
• Do not have to be mounted in the bird cage thus saving room
• Have greater sensitivity for lower temperatures
• Are able to measure temperatures in smaller increments of change

103. Measuring temperatures without direct physical contact is called:

• Relevant measurement
• Radiation pyrometry
• Virtual measurement
• Pyrometrical synthesis

104. Radiation pyrometers can measure light in the:

• Radio spectrum
• Sonar spectrum
• Infrared light spectrum
• Spectrum

105. When calibrating a radiation pyrometer a black body is used because it:

• Reflects radiation but passes light
• Reflects and passes radiation
• Reflects light but passes radiation
• Does not reflect or pass radiation

106. Corrections must be made to obtain the true temperature of an object because optical pyrometers:

• Are limited to a narrow band of the spectrum
• Are not limited to a narrow band of the spectrum
• Have no limits the range of light that they can sense
• Are able to sense a wide band of the spectrum

107. Corrections that must be made are made by:

• Spectrum matching
• Brightness matching
• Light matching

108. The corrections are made by adjusting the filament:

• Voltage
• Resistance
• Current
• Wattage

109. What is one way of improving the performance of an optical pyrometer?

• Move the target closer to the optics
• Nothing can be done to improve the performance
• Move the target further from the optics
• Drill a hole in the target

110. The detector in an automatic optical pyrometer is:

• A photomultiplier tube
• A multicurrent detector
• A photo sensing multiplier
• A photographic tube

111. In an automatic optical pyrometer, the light from the target enters through the:

• Refractive lens
• Objective lens
• Reflective lens
• Optical lens

112. The device that passes light from the target and the lamp is:

• The multiplexer
• The diplexer
• The modulator
• The duplexer

113. So that the radiation of the filament and the target is the same:

• The filament voltage is adjusted
• The filament wattage is adjusted
• The filament resistance is adjusted
• The filament current is adjusted

114. The radiation that passes through the lens of a total radiation pyrometer is:

• Both visual and infrared
• Visual only
• Both visual and ultraviolet
• Infrared only

115. The detector in a total radiation pyrometer is often:

• An optical sensor
• A thermopile
• A multisensor
• A photomultiplier

116. For measuring medium temperatures with a total radiation pyrometer, the lens is made of:

• Germanium
• Quartz
• Glass
• Mirrors

117. The lens used on a total radiation pyrometer is determined by:

• The target material
• The radiation emitted
• The size of the target
• The temperature of the target

118. The detector in a ratio pyrometer is used to detect:

• Incident energy
• Radiant light
• Infrared light spectrum
• Thermal energy

119. The ratio pyrometer measures the radiation falling on its detector at:

• Four different wavelengths
• Two different wavelengths
• Three different wavelengths
• One wavelength

120. In a ratio pyrometer, the pulses are amplified and separated by:

• Duration
• Spacing
• Wavelength
• Pulse slope

121. Which pyrometer is the most accurate, where the emmitance at the filter wavelength is constant or changes slowly?

• The optical pyrometer
• The automatic optical pyrometer
• The total radiation pyrometer
• The ratio pyrometer

122. The pyrometer that has good sensitivity and a high output signal level is:

• The total radiat ion pyrometer
• The automatic optical pyrometer
• The optical pyrometer
• The ratio pyrometer

123. The pyrometer that is simple to use and is moderate in cost is the:

• Total radiation pyrometer
• Optical pyrometer
• Comparison pyrometer
• Ratio pyrometer

124. The pyrometer that has good sensitivity, fast response, and the ability to be sighted on a small target is:

• The optical pyrometer
• The automatic optical pyrometer
• The ratio pyrometer
• The total radiation pyrometer

125. The pyrometer used depends on: