This set of Process Control Multiple Choice Questions & Answers (MCQs) focuses on “Use and Working Principles of Instruments “.
1. Which of the following instrument is used to measure the composition of LPG?
a) Radiation thermometer
b) Thermocouple
c) Gas chromatograph
d) Spectrophotometer
View Answer
Explanation: Radiation thermometer is used for measuring the temperature of the flame. Thermocouple is used to measure the fluid temperature. Spectrophotometer is used to measure the number of photons. Gas chromatograph is used to measure the composition of LPG.
2. Which of the following thermometer is used to measure the temperature in case of radiation process?
a) Pyrometer
b) J type thermocouple
c) Flare thermometer
d) RTD
View Answer
Explanation: Typically, for temperature in case of radiation process where the temperature of the process is as high as 1800°C, pyrometers are used. A pyrometer measures the temperature of the system by measuring the intensity of radiation emitted. Optical systems and detectors present in pyrometers are used to measure the surface temperature of the object.
3. Which of the following process variables is measured by Bourden tube element?
a) Temperature
b) Concentration
c) Flow
d) Pressure
View Answer
Explanation: When a bourden tube element is pressurized, a flattened tube tends to straighten or regain its circular form in cross-section. With the increase in the pressure, the bourden tube element needs to be stiffer. That’s how a bourden tube element measure pressure.
4. Which of the following instruments measure the flow of a system?
a) Infrared analyser
b) Orifice meter
c) Displacer device
d) Pressure gauge
View Answer
Explanation: Flow of a system is measure by orifice meter. Infrared analyser is used to measure composition. Displacer device are used to measure the liquid level. Pressure gauge is used to measure the pressure of a system.
5. Which of the following pairs correctly represent the instruments used to measure flow of a system?
a) Venturi meter and orifice meter
b) Bourden element and RTD
c) Pitot tube and strain gauge
d) Chromatographic analyser and orifice meter
View Answer
Explanation: Following table is the list of instruments with their respective measured variable
| Instrument | Measured variable |
| Venturi meter | Flow |
| Orifice meter | Flow |
| Bourden element | Pressure |
| RTD | Temperature |
| Pitot tube | Static velocity |
| Strain gauge | Pressure |
| Chromatographic analyser | Composition |
6. Which of the following instrument is used to measure small and positive pressure?
a) Bourden tube
b) Piezometer
c) Spectrometer
d) Anemometer
View Answer
Explanation: Spectrometer is used to measure the concentration. Anemometer is used to measure the velocity. Piezometer is used to measure small and positive pressure.
7. What is the normal range of temperature measured by pyrometers?
a) (20 to 50)°C
b) (-10 to 0)°C
c) (800 – 1600)°C
d) upto 150°C
View Answer
Explanation: Pyrometers measure temperature depending upon high radiation. Temperature ranging -10°C upto 150°C does not have high radiation. At a range of (800 – 1600)°C, high radiation is generally observed.
8. Which of the following options correctly represent the working principle of mercury glass thermometer?
a) Surface area expansion of air with increase in temperature
b) Volume expansion of air with increase in temperature
c) Volume expansion of mercury with increase in temperature
d) Surface area expansion of mercury with increase in temperature
View Answer
Explanation: In a mercury glass thermometer, as the temperature increases, the volume of the mercury inside expands. This expanded mercury, with upper meniscus, gives the reading of temperature of the system.
9. Which of the following law is followed in pyrometer’s working principle?
a) Charles law
b) Fick’s law
c) Stefan-Boltzmann law
d) Reynolds law
View Answer
Explanation: Fick’s law is used in mass transfer diffusion. Reynolds law is applicable in fluid flow. Charles law is applicable in gas law. Stefan-Boltzmann law is applicable in high temperature radiation region.
10. Which of the following instrument is used to measure the liquid level of a tank?
a) Strain gauge
b) Manometer
c) Thermocouple
d) Capacitance probe
View Answer
Explanation: Strain gauge and manometer are used to measure the pressure. Thermocouple is also used to measure temperature. Capacitance probe is used to measure the liquid level of a tank.
Sanfoundry Global Education & Learning Series – Process Control.
To practice all areas of Process Control, here is complete set of Multiple Choice Questions and Answers.
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