Free Process Control and Instrumentation MCQs with Answers

• A. Electrical conductivity
• B. Polarimetry
• C. Emission spectroscopy
• D. Dielectric constant end loss factor

Explanation: Water changes the dielectric constant and dielectric loss factor of an organic liquid substantially, allowing small amounts to be detected…

• A. Stefan Boltzmann law
• B. Kirchoff's law
• C. Wien's law
• D. Seebeck effect

Explanation: A radiation pyrometer determines temperature from the thermal radiation emitted by a hot body, commonly using the Stefan-Boltzmann…

• A. P-I controller
• B. P-controller
• C. P-D controller
• D. P-I-D controller

Explanation: A proportional controller alone leaves a steady-state error, called offset, and its offset is not removed by derivative action.

• A. Mcleod gauge
• B. Alphatron
• C. Bourdon gauge
• D. Ionisation gauge

Explanation: An ionisation gauge is designed for very low pressures in the micron and sub-micron range by measuring ions produced in the gas.

• A. Non-linear relation of emf to temperature
• B. Corrosion resistance
• C. Oxidation resistance
• D. Linear relation of emf to temperature

Explanation: A useful industrial thermocouple should give an emf that changes nearly linearly with temperature, while resisting oxidation and…

• A. Seebeck effect
• B. Peltier effect
• C. Joule heating effect
• D. Thomson effect

Explanation: The Peltier effect is the absorption or liberation of heat at a junction when current passes through it.

• A. Chromatograph
• B. Polarograph
• C. Polarimeter
• D. Spectrometer

Explanation: A polarimeter measures optical rotation by passing polarized light through a sample and determining the angle of rotation.

• A. Kc(1 + ηis + ηD ). s
• B. None of these
• C. Kc(1 + ηis + (1/ηD . s)
• D. Kc[1 + (1/ηis) + ηD . s)

Explanation: The ideal PID controller is written as Kc[1 + 1/(ηi s) + ηD s], combining proportional, integral, and derivative actions.

• A. Thermal conductivity cell
• B. X-ray diffraction
• C. Mass spectrometer
• D. Emission spectrometer

Explanation: A thermal conductivity cell compares the thermal conductivity of a gas sample with a reference gas, making it useful for continuous gas…

• A. Weight
• B. Stress
• C. Strain
• D. Velocity

Explanation: A load cell converts the force produced by a load into an electrical signal, so it is commonly used to measure weight.

• A. Teflon
• B. Asbestos
• C. Ceramic fibre
• D. Fibre glass

Explanation: Ceramic fibre withstands much higher temperatures than Teflon, asbestos, or fibreglass, so it provides the highest temperature rating…

• A. Large area but small mass
• B. High thermal conductivity
• C. Small specific heat
• D. All A , B & C

Explanation: Fast thermometer response requires a large heat-transfer area, low bulb thermal mass, high thermal conductivity, and low specific heat.

• A. Differential float type manometer
• B. Simple float
• C. Glass gauge
• D. None of these

Explanation: An autoclave operates under pressure, so its liquid level is commonly inferred from the pressure difference across the liquid column using…

• A. Reproducibility
• B. Fidelity
• C. Dead zone
• D. Sensitivity

Explanation: Fidelity is a dynamic characteristic because it describes how closely an instrument reproduces a changing input over time.

• A. First order system
• B. Second order system
• C. Transportation lag
• D. None of these

Explanation: A pure transportation lag only delays a sinusoidal signal and does not change its amplitude, so its amplitude ratio is one.

• A. ∫0 ∞ |e| dt
• B. ∫0 ∞ |e2| dt
• C. None of these
• D. ∫0 ∞ e2 dt

Explanation: The integral of squared error, ISE, heavily penalises large errors and is a widely used criterion for controller tuning.

• A. Oxygen in
• B. Carbon dioxide in
• C. Carbon monoxide in
• D. Temperature of

Explanation: A zirconia probe measures oxygen by producing an electrical signal related to the oxygen partial-pressure difference across its…

• A. Specially designed thermocouple
• B. Optical pyrometer
• C. Radiation pyrometer
• D. None of these

Explanation: A radiation pyrometer determines high temperature from the thermal radiation emitted by the hot body, making it suitable for temperatures…

• A. Response
• B. Tine lag
• C. Dynamic error
• D. Drift

Explanation: Drift is a static characteristic because it describes a gradual change in instrument output when the measured input remains constant.

• A. The maximum
• B. The minimum
• C. Both maximum and the minimum
• D. Nothing about the

Explanation: The process degree of freedom gives the number of independent variables that can be controlled, so it sets the maximum number of…