8. A negative gain margin expressed in decibels means a/an __________ system. A. stable B. unstable

C. critically damped D. none of these

Explanation: The gain margin value should not be a negative value. Hence, it should be greater. This is according to bode stability criteria. (indiabix.com)

9. Thermistor, which has high temperature co-efficient of resistivity, is used as the sensing element in resistance thermometer. It is a/an A. insulatorB. conductor

C. solid semi-conductorD. liquid semi-conductor

Explanation: Thermistor is a device constructed of solid semiconductor material, whose electrical resistance decreases with an increase in temperature: used to measure temperature differences in body cells, microwave or infrared power, etc. (yourdictionary.com)

10. Flapper nozzle is used in a/an __________ controller.A. electronic B. hydraulic

C. pneumatic D. none of these

Explanation: It is converted into mechanical motion to pressure signal and also the displacement of flapper plate moving is proportional to the pressure due to the position of the flapper from the nozzle. (indiabix.com)

11. Typical specifications for design stipulates the gain margin and phase margin to be respectivelyA. > 1.7 and > 30°B. < 1.7 and > 30°

C. < 1.7 and < 30° D. > 1.7 and < 30°

Explanation: GM and PM both must be positive for a stable system. (indiabix.com)

12. Working principle of radiation pyrometer is based on the A. Wien's law B. Kirchoffs law

C. Stafan-Boltzman law D. Seebeck effect

Explanation: Stefan Boltzmann law states that the total energy radiated per unit surface area of a black body across all wavelengths per unit time (also known as the black-body radiant exitance or emissive power), j*, is directly proportional to the fourth power of the black body's thermodynamic temperature T. (indiabix.com)

13. Which of the following relates the emf generated in a single homogeneous wire to the temperature difference? A. Peltier effect B. Thomson effect

C. Seebeck effect D. none of these

Explanation: It states that the voltage produced in a thermocouple is proportional to the temperature between the two junctions. (indiabix.com)

14. Dilute wine was used as a thermometric liquid initially to develop temperature scale. First emperical temperature scale developed was the __________ scale. A. Kelvin C. Fahrenheit

B. Centigrade D. Reumer

Explanation: Centigrade scale was developed on 1742 while Fahrenheit scale was on 1714.

15. In a single tank system, the transfer function of level to inlet flow rate is

A. RTs

B. RTs+1

C. l(TS + l)

D. 1Ts

Explanation: In a single tank system, the transfer function of level to inlet flow rate isRTs+1

.

First, it is assumed the flow rate through resistance is related to the head linearly, as shown in

this equation qo=hR

. This is then incorporated in the mass balance in the tank giving an

equation of q−hR

=A dHdt. Deviation variables are then introduced by indicating a steady-state

value of the variable. Then taking the transform of this equation gives Q (s )=H (s)R

−AsH ( s).

Finally, rearranging into standard form gives H (s )Q(s )

= RTs+1

.

16. Which of the following is a desirable characteristic of an instrument? A. High drift B. High fidelity

C. High measuring lag D. Poor reproducibility

Explanation: Among the choices given, high fidelity appears to be a desirable characteristic of an instrument. Fidelity is defined as the degree to which an instrument indicates the changes in measured variable without dynamic error. This implies a faithful reproduction. On the other hand, the other choices are referred to as undesirable. For instance, high drift implies high dynamic error. High measuring lag represents delay in response while poor reproducibility means inefficient reproduction of the instrument.

17. The operation of a rotameter is based onA. variable flow area.B. rotation of a turbine.

C. pressure drop across a nozzle.D. pressure at a stagnation point.

Explanation: Rotameter’s operation is based on variable flow area since the fluid flowing through a slightly tapered tube causes a float, piston or vane to change position inside the tube, adjusting the area available for fluid to pass through. The greater the flow, the higher the float is raised. The height of the float is directly proportional to the flowrate.

18. The temperature of tempering oil baths maintained at 400°C during heat treatment of steel is measured by a/an __________ thermocouple. A. chromel-alumel B. iron-constantan C. platinum-platinum/rhodium

D. none of these.Explanation: The temperature of tempering oil baths maintained at 400°C during heat treatment of steel is measured by iron-constantan thermocouple. Both chromel-alumel and platinum-platinum/rhodium are recommended for use in oxidizing atmosphere. They are relatively easily contaminated in other atmosphere.

19. Instrumentation in a plant offers the advantage of A. greater safety of operation B. better quality of product C. greater operation economy D. all (a), (b) and (c)

Explanation: Instrumentation in a plant is advantageous. One of the advantages it offers is the greater safety of operation. An instrumented system takes automated action to keep a plant in a safe state, or to put it into a safe state when abnormal conditions are present. Also, this provides a better quality of product since instrumentation provides the best measuring instruments which then improve the quality of the product. Also, instrumentation provides a greater operation economy since it maximizes productivity, ensuring required quality and minimizes rejects, optimizes energy and resource consumption, and reduce emissions to meet local environmental directives in cost effective ways.

20. Which of the following temperature measuring instruments need not touch the object whose temperature is being measured? A. Radiation/infrared pyrometer B. Filled system thermometer C. Mercury in glass thermometer D. Thermo electric pyrometer

Explanation: By the name itself, radiation/infrared pyrometer is a temperature measuring instruments that does not need to touch the object whose temperature is being measured. There is no need for direct contact between the radiation thermometer and the object, thus this is suited especially to the measurement of moving objects or any surfaces that cannot be reached or cannot be touched. On the other hand, the other instruments basically need to provide an intimate contact with the to-be-measured system.

21. Thermal conductivity measurement comprises the working principle of aA. CO2 analyserB. polarimeter

C. spectrometerD. chromatograph

Explanation: According to Bala, Ponni M. and Krishinaswamy, K. in their book Power Plant Instrumentation 2nd edition, thermal conductivity principle is normally employed for measuring CO2. A thermal conductivity system measures concentrations of hydrogen purity and CO2 gas. Thermal Conductivity Analyzer uses the principles of thermal conductivity to provide a highly sensitive and accurate analysis of a binary mixture of gases and can also be calibrated to measure a single component of a multi-component gas mixture. The resulting thermal change is taken out as a change in electric resistance, according to which the concentration of measured gas is calculated.

22. Response of a system to a sinusoidal input is called __________ response.A. impulseB. unit step

C. frequencyD. none of these

Explanation: Sinusoidal input is a function represented mathematically by the equations x=0 where t<0 and X=Asinwt where t≥0 and where A is the amplitude and w is the radian frequency. The radian frequency w is related to the frequency f in cycles per unit time by w = 2~f. The transform is X(s) = Aw/(s2 + w2). This forcing function forms the basis of an important branch of control theory known as frequency response. (Coughanowr)

23. The closed loop pole of a stable second order system could beA. both real and positive.B. complex conjugate with positive real parts.C. both real and negative.D. one real positive and the other real negative.

Explanation: Poles are the roots of the characteristic equation of a closed-loop transfer function at controller gain, Kc = 0. For a second order system, the characteristic equation is

. At Solving the above quadratic equation, we get the roots which indicates that the roots of the characteristic equation may be real, imaginary, or complex, but having real parts for both the roots are negative. For any stable system, the real parts of the roots of the characteristic equation should be negative. (Chaudhuri, et al. Fundamentals of Automatic Process Control)

24. Smoke density of the flue gas going out of the chimney is measured by aA. polarographB. thermal conductivity meter

C. photo electric cellD. chromatograph

Explanation: Conventional means for detecting and measuring the density of smoke in a chimney or duct employ a light beam, which after traversing the flow of smoke excites a photo-electric cell, so that the density of the smoke is related to the output of the cell. A photo-electric cell measures the reduction in intensity of a beam of light passing through the chimney or duct – it can be indicating or recording.

25. Transfer function of transportation lag isA. eTS

B. e-TSC. D. none of these

Explanation: It can be seen from the figure that the relationship between y(t) and x(t) is y(t) = x(t - T). Introducing the deviation variables X = x - xs, and Y = y - ys give Y(r) = X(t - 7). If the Laplace transform of X(t) is X(s), the Laplace transform of X(t - 7) is e-STX(s). This result follows from the theorem on translation of a function, Y(s) = e-ST X(s) or Y(s)/X(s) = e-ST. Therefore, the transfer function of a transportation lag is e-ST. (Coughanowr)

26. Temperature measuring instruments are standardized mostly with __________ points of pure substances.

A. meltingB. boiling

C. both (a) & (b)D.neither (a) nor (b)

Explanation: Both melting and boiling points of pure substances are used to standardized temperature measuring instruments in order to create a “neutral” temperature standard.

27. Pick out the first order system from among the following.A. Damped vibrator.B. Mercury in glass thermometer kept in boiling water.C. Interacting system of two tanks in series.D. Non-interacting system of two tanks in series.

Explanation: A first order system is described by a first order differential equation. The system is defined by the single parameter τ, the system time constant, and f(t) is a forcing function. The time-constant τ, which has units of time, is the system parameter that establishes the time scale of system responses in a first-order system. Typical examples of a first order system are electric systems where energy is essentially stored in one component, incompressible fluid flow in a pipe, level control of a tank, pressure control in a gas tank, and temperature in a body with essentially uniform temperature distribution.

28. The maximum service temperature for fibre glass used as thermocouple wire insulation material is __________ °C.

A. 250B. 500C. 750D. 1000Explanation: Insulated thermocouple wire and thermocouple extension wire products are used to assist in monitoring and controlling temperatures in a wide and varied range of environments. The fiberglass wire insulation is designed to withstand a maximum continuous use at 900°F (482°C).

29. Which of the following controllers has the least maximum deviation?A. P-controllerB. P-I controllerC. P-I-D controllerD. P-D controller

Explanation: PD control results in the shortest time to reach steady state with the least oscillation at the smallest maximum deviation but at the expense of offset, and is very sensitive to measurement noises.

30. Volumetric expansion is the working principle of the __________ thermometers.A. mercury in glassB. constant volume gasC. vapor pressureD. bimetallic

Explanation: The Liquid in Glass thermometer utilizes the variation in volume of a liquid in temperature. They use the fact that most fluids expand on heating. Liquids commonly used include mercury and alcohol.

31. Which of the following measurements can be made by the measurement of emf?A. pH valueB. Degree of hydrolysisC. Composition of complex ionsD. All (a), (b) & (c)

Explanation: The electromotive force (EMF) is the maximum potential difference between two electrodes of a galvanic or voltaic cell. This quantity is related to the tendency for an element, a compound or an ion to acquire (gain) or release (loss) electrons. Applications of EMF measurement include the solubility of sparingly soluble salt, determination of pH, determination of ionic product of water, determination of degree of hydrolysis, and determination of formula and instability constant of complex ions.

32. A magnetic flowmeter isA. based on the principle of Faraday's law.B. capable of measuring the flow rate of slurries and electrolytes.C. based on the linear relationship between the fluid flow rate and the induced voltage.D. all (a), (b) and (c).

Explanation: Magnetic flowmeters use Faraday’s Law of Electromagnetic Induction to determine the flow of liquid in a pipe. In a magnetic flowmeter, a magnetic field is generated and channeled into the liquid flowing through the pipe. Following Faraday’s Law, flow of a

conductive liquid through the magnetic field will cause a voltage signal to be sensed by electrodes located on the flow tube walls. When the fluid moves faster, more voltage is generated. Faraday’s Law states that the voltage generated is proportional to the movement of the flowing liquid. Magnetic flowmeters measure the velocity of conductive liquids in pipes, such as water, acids, caustic, and slurries.

33. Zirconia probe is used for the continuous measurement of __________ flue gases going out of the furnace.A. oxygen inB. carbon dioxide inC. carbon monoxide inD. temperature of

ANSWER: Zirconia probe also known as Zirconia oxygen analyzer which is used to determine oxygen concentration. (Toray Engineering Co.,Ltd.)

34. Strain gage pressure transducers are used to measure __________ pressures.A. gauge as well as vacuumB. absolute as well as differentialC. both (a) and (b)D. neither (a) nor (b)

ANSWER: All transducers basically measure differential pressure. That is, all measurements are made with respect to a reference pressure. The gage pressure transducer, PSIG, measures pressure referenced to local atmospheric pressure and is vented to the atmosphere.The absolute pressure transducer, PSIA, measures pressure referenced to an absolute vacuum sealed within the transducer.The differential pressure transducer, PSID, measures the difference of two (2) pressures applied simultaneously to the transducer(Dynisco)

35. The transfer function for a PID controller is (where, τ i is the integral (reset) time and τD is the derivative time.)

ANSWER: PROPORTIONAL CONTROL. The proportional controller produces an output signal (pressure in the case of a pneumatic controller, current or voltage for an electronic controller) that is proportional to the error ϵ.PROPORTIONAL-INTEGRAL (PI) CONTROL. This mode of control is described by the

relationship p=K cϵ+K cτ I∫ ϵ dt+ ps .

To obtain the transfer function of the given equation, we introduce the deviation variable

P=p−ps and then take the transform to obtain P (s )ϵ (s)

=K c(1+ 1τ I s ).

Some manufacturers prefer to use the term reset rate, which is defined as the reciprocal of τ I. The integral adjustment knob on a controller may be marked in terms of integral time or reset rate. (Coughanowr, 1991)

36. Compositional analysis of __________ is done using mass spectrometer.A. an isotopeB. natural gasC. a solidD. an alloy

ANSWER: Gas source mass spectrometers are the principal instruments used for measuring isotopic ratios of light elements, including hydrogen, carbon, nitrogen, and oxygen. The sample is prepared in gaseous form, often hydrogen, nitrogen, or carbon dioxide, and inlet into the mass spectrometer for analysis. (Geochemical Instrumentation and Analysis)

37. The function of a transducer is toA. modify the input signal.B. amplify the input signal.C. convert the primary signal into a more useful quantity, usually an electric impulse.D. codify/decodify the input signal.

ANSWERS: A transducer is a device that is used to convert a physical quantity into its corresponding electrical signal. (Instrumentation-Electronics, 2011)

38. Nichol's chart deals withA. A.R. vs. phase lag of first order.B. A.R. vs. phase lag of second order.C. closed loop values vs. open loop values.D. frequency response values of controllers.

ANSWER: The chart consisting of constant-magnitude loci and constant phase-angle loci in the log-magnitude versus phase diagram is called Nichols chart. (Interactive Control Systems Tools System Analysis)We can combine the ease of sketching the open-loop response with the transient response information contained in the closed-loop response. (Engr. Muhammad Nasiruddin Mahyuddin)

39. Which of the following thermocouples will give the highest output for the same value of hot and cold junction temperature?A. Platinum-platinum + rhodiumB. Iron-constantanC. Chromel- constantanD. All will give the same output

Explanation: Thermocouples consist of two dissimilar conducting wires joined at one end. This, the hot junction, is placed with a good thermal contact at the point of measurement and the two free ends are maintained at the cold junction. An emf is generated in the circuit which can be related to the temperature of the hot junction. Chrome1-constantan thermocouples give the highest output at any given temperature.

40. A proportional controller with a gain of Kc is used to control a first order process. The offset will increase, ifA. Kc is reducedB. Kc is increasedC. Integral control action is introducedD. Derivative control action is introduced

Explanation: proportional controller output is proportional to the offset or error which at the same time proportional to Kc or the adjustable setting. As more error is produced, Kc increases, which means that the control action for such error gets bigger.

41. The symbol for “capillary line” in instrumentation diagram is A.B.C.D.Explanation: The first line symbol denotes electrical signal. The second denotes capillary line. While the third and fourth line symbols denote pneumatic and straight line pipe respectively.

42. __________ is undesirable in thermocouples used in industries,A. Linear relation of emf to temperatureB. Corrosion resistanceC. Oxidation resistanceD. Non-linear relation of emf to temperature

Explanation: Nonlinear relation of emf to temperature is undesirable in thermocouples because they require more complex expressions and measuring/controlling instrumentation.

43. Select the correct statement from the following.A. The frequency response of a pure capacity process is unbounded.B. The phase lag of a pure time delay system decreases with increasing frequency.C. The amplitude ratio of a pure capacity process is inversely proportional to frequency.D. The amplitude ratio of a pure time delay system increase with frequency.

Explanation: Among the choices, the third statement is considered as the correct one. The frequency response of a pure capacity process is bounded. The phase lag of a pure time delay system is directly proportional to frequency for a delay, thus increases with increasing frequency. The amplitude ratio of a pure time delay system normally decreases with frequency.

44. For an input forcing function, X(t) = 2t2, the Laplace transform of this function isA. 2/s2

B. 4/s2

C. 2/s3

D. 4/s3

Explanation: Taking the Laplace transform of X(t) = 2t2 gives 4/s3 based on the Laplace

transform of constant 2 and t2 into 2 and n!

sn+1= 2

s3 , respectively.

45. Continuous shell temperature measurement in a liquid-liquid heat exchanger is done by a

A. thermocoupleB. resistance thermometerC. mercury in glass thermometerD. vapor pressure thermometer

Explanation: According to Heat Exchangers Lab of the Dipartimento di Ingegneria Industriale, the following instruments are installed on liquid-liquid heat exchangers (shell and tube, plate heat exchangers)  : magnetic flow rate transducer, T-type thermocouples, T-type thermopiles and a differential pressure transducer.

46. The __________ of a vapor pressure thermometer is a secondary element.A. pointerB. Bourdon tubeC. bulbD. none of these

Explanation: According to http://www.cim.mcgill.ca/, a secondary transducer element is used to convert the deformation or deflection into a more convenient signal such as an electrical voltage and a mechanical position. Bourdon tube behaves similarly in this way and can be categorized as a secondary element for pressure metering.

47. Emf developed by a thermocouple, while measuring a temperature of 600°C is about 5.5 mV. The type of thermocouple used isA. chromel-alumelB. iron-constantanC. platinum-platinum+rhodiumD. either (a), (b) or (c)

Explanation: A Chromel-alumel thermocouple, has a range of -270 °C to 1260 °C and an output of -6.4 to 54.9 mV over maximum temperature range - A coupling of Chromel and Alumel wires, has a range of -270 °C to 1260 °C and an output of -6.4 to 54.9 mV over maximum temperature range. Type J or iron-constantan on the other hand is useable from 0 to 816°C, (32 to 1500°F) with higher sensitivity of about 55 µV/°C. Platinum-platinum+rhodium usable from (32° to 2700°F) or approximately 00C-15000C-http://www.thermometricscorp.com/

48. Which of the following relates the absorption & evolution of heat at the junctions of a thermocouple to th current flow in the circuit?A. Seebeck effectB. Peltier effectC. Joule heating effectD. Thomson effect

Explanation: The Peltier effect is the phenomenon that a potential difference applied across a thermocouple causes a temperature difference between the junctions of the different materials in the thermocouple- http://ffden-2.phys.uaf.edu

49. The second order system with the transfer function has a damping ratio ofA. 2.0B. 0.5C. 1.0D. 4.0

Explanation: -Ƭ < 1, for underdamped systems – Process System Analysis and Control by Coughanowr -An Introduction to System Dynamics - Second Order Systems - www.facstaff.bucknell.edu

50. In a shell and tube heat exchanger, the flow rate of heating/cooling fluid is the __________ variable.A. loadB. controlledC. manipulatedD. none of these

Explanation: Two fluids, of different starting temperatures, flow through the heat exchanger. One flows through the tubes (the tube side) and the other flows outside the tubes but inside the shell (the shell side). Heat is transferred from one fluid to the other through the tube walls, either from tube side to shell side or vice versa. The fluids can be either liquids or gases on either the shell or the tube side. In that case, flow rate is not a controlling factor but a manipulated variable to attain the desired temperature of either streams – Perry’s Chemical Engineers’ Handbook (8 th

edition)