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Eme Lang > Instrumentation and Process Control > Flashcards

Instrumentation and Process Control Flashcards

1
Q

```

what is the laplace transform of sin t?

A

1/s^2+1

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2
Q

The transfer function of the first order system is

A

1/Ts+1

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3
Q

Pick out the first order system from among the following

A

mercury in glass thermometer kept in boiling water

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4
Q

Response of a system to a sinusoidal input called

A

frequency response

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5
Q

What is the ratio of output amplitude to input amplitude for a sinusoidal forcing function in a first order system?

A

none of these
(a) 1
(c) < 1
(b) > 1

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6
Q

Phase lag of the sinusoidal response of a first order system is

A

120 degree

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7
Q

Conversion formula for converting amplitude ratio (AR) into decibels is

A

Decibel=20 log10 (AR)

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8
Q

“A control system is unstable if the open loop frequency response exhibits an amplitude ratio exceeding unity at the cross-over frequency.” This is

A

Bode stability criterion

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9
Q

Typical specifications for design stipulates the gain margin and phase margin to be respectively

A

> 1.7 and > 30°

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10
Q

The frequency at which maximum amplitude ratio is attained is called

A

resonant frequency

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11
Q

A negative gain margin expressed in decibels means

A

unstable system

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12
Q

Bode diagram is a plot of

A

log (AR) vs. log (f) and Ø vs. log (1)

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13
Q

For measuring the temperature of a furnace, which is the most suitable instrument?

A

Optical pyrometer

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14
Q

Degree to which an instrument indicates the changes in measured variable without dynamic error is called

A

fidelity

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15
Q

Which of the following is a desirable characteristic of an instrument?

A

high fidelity

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16
Q

Which of the following shows maximum dip affect
(indicating reverse direction of temperature change)?

A

mercury thermometer

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17
Q

Pick out the most suitable instrument for measuring temperature in the range of -40 to 800°F.

A

bimetallic thermometer

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18
Q

Thermocouple is suitable for measuring

A

both high and low temperature

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19
Q

Which of the following relates the absorption and evolution of heat at the junctions of a thermocouple to the current flow in the circuit?

A

Peltier effect

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20
Q

Thermal wells are used in temperature measurement to

A

guard against corrosive and oxidizing action on thermocouple materials

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21
Q

Gas analysis is commonly done using

A

thermal conductivity cell

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22
Q

Psychrometer determines

A

humidity of gases

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23
Q

Continuous measurement of moisture done by measuring

A

electrical resistance through the paper

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24
Q

Optimal activity of a solution can be determined using a

A

polarimeter

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25
Q

A simple pitot tube measures

A

Static pressure

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26
Q

Pirani gauge also known as thermal conductivity gauges is used for

A

measurement of high vacuum

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27
Q

A barometer measures

A

absolute pressure

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28
Q

The level of a liquid under pressure can be determined using

A

Differential pressure manometer

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29
Q

Continuous measurement of specific gravity of a liquid is done by

A

Hydrometer and displacement meter

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30
Q

Hot wire anemometer is used for the measurement of

A

flow rates of fluid

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31
Q

Flow rate through an orifice is

A

proportional to the square root of pressure

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32
Q

Which of the following flow-metering instruments is an area meter?

A

rotameter

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33
Q

Continuous measurement of flow rates of dry granular fertilizer is done using

A

weighing meters

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34
Q

Pick out the symbol for “locally mounted instrument” in instrumentation diagram

A

O

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35
Q

Which is the symbol for “pneumatic control valve”

A
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36
Q

The symbol for “capillary line” in instrumentation diagram is

A
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36
Q

Instrumentation in a plant offers the advantage of

A

greater safety of operation
better quality of product
greater operation economy

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37
Q

Dilatometer is used to measure

A

contraction/expansion due to changes

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38
Q

Stalagmometer is used for the measurement of

A

surface tension

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39
Q

Stroboscope is used for the measurement of

A

rpm of a flywheel

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40
Q

Minute depression of freezing point of a liquid solvent or addition of a solid solute

A

Beckman thermometer

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41
Q

Gain margin is equal to the

A

Reciprocal of amplitude ratio

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42
Q

Phase margin is equal to

A

180° - phase lag

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43
Q

A system with a transfer function 2s is of 4s+1

A

1st order

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44
Q

Bode stability method uses

A

open loop transfer function

45
Q

Routh stability method uses

A

closed loop transfer function

46
Q

Nichel’s chart deals with

A

closed loop values vs. open loop value

47
Q

The fluid used in hydraulic controller is

A

oil

48
Q

Number of poles in a system with transfer function 1/s^2 + 2s^2 + 1 is

A

3

49
Q

Which of the following controllers has maximum offset?

A

P-controller

50
Q

Process degrees of freedom

A

indicates the maximum number of controllers to be used

51
Q

Resistance of a gas in a vessel is

A

V/NRT

52
Q

In an exothermic chemical reactor, the manipulated variable is the flow rate of

A

coolant

53
Q

Which of the following error integral is considered as the best criterion in controller settings?

A

Integral from 0 to infinity | e |dt

54
Q

Cascade control means

A

more than one feed-back loop

55
Q

Which of the following controllers has the least maximum deviation?

A

P-D controller

56
Q

Measurement of pressure in ammonia reactor is done by

A

Bourdon gauge

57
Q

Pressure of 0.01 psi (absolute) can be measured by

A

Mcleoid gauge

58
Q

Continuous measurement of moisture in paper is done by

A

high resistance
Wheatstone’s bridge circuit (strain gauge)

59
Q

Pressure of 0.0001 absolute psi can be measured by

A

Meloid gauge

60
Q

E.m.f. generated by thermocouples is of the order of

A

millivolts

61
Q

Measurement of sub-zero Celsius temperature in industry is done by

A

resistance thermometers

62
Q

Starting temperature of optical radiation pyrometer is

A

800°C

63
Q

Which thermocouple can be used to measure temperature around 1400°C?

A

platinum-platinum+rhodium

64
Q

pH meter has

A

Two cells

65
Q

Maximum differential pressure in liquid manometer is

A

30psi

66
Q

Interfacial level in pressure vessel is measured by

A

manometers of float type

67
Q

Flow rate of sludge is measured by

A

Kennison nozzle

68
Q

Composition of natural gas can be determined by

A

chromatograph

69
Q

Bellows are made of

A

Thin copper

70
Q

Flapper nozzle is a

A

pneumatic controller

71
Q

Weir valve is used for

A

slurries

72
Q

Valve used to supply oil to burner is

A

rotary plug valve

73
Q

Mode used for transmitting signal for one kilometer distance is

A

electronic

74
Q

Use of pilot in transmission (pneumatic) is to

A

Change the flow of air

75
Q

Final control element is a

A

valve

76
Q

Example of a second order instrument is a

A

mercury-glass thermometer with covering

77
Q

does not vary with time

A

Offset

78
Q

Regulator problem means that

A

set point is constant

79
Q

Servo problem means that

A

load is constant

80
Q

Critically damped system means that the damping coefficient is

A

1

81
Q

In Bode stability criterion, amplitude ratio at 180° should be

A

< 1

82
Q

Phase plane method is used for

A

nonlinear-behavior

83
Q

Laplace transform method is used for

A

linear behavior

84
Q

Phase lag of first order system is

A

tan^-1 (w T)

85
Q

P-I controller as compared to P-controller has a

A

higher maximum deviation
longer period of oscillation
longer response time

86
Q

Difference at any instant between the value of controlled variable and the set point is called

A

deviation

87
Q

The time difference by which the output of a P-D controller leads the input when theinput changes linearly with time is called

A

derivative time

88
Q

Steady state deviation resulting from a change in the value of the load variable is called

A

offset

89
Q

Time required for the output of a first order system to change from a given value to within 36.8% of the final value when a step change of input is made is called

A

time constant

90
Q

A controller action in which there is a continuous linear relation between value of the controlled variable and rate of change of controlled output signal is called

A

integral action

91
Q

A controller action in which there is a continuous relation between value of the controlled variable and the value of the output signal of the controller is called

A

Proportional action

92
Q

Steady state ratio of the change of proportional controller output variable and the change in actuating signal is called

A

proportional sensitivity

93
Q

In case of flow measurement by an orifice, the pressure difference signal is proportional to

A

Q^2

94
Q

Thermistor is a

A

semiconductor whose resistance decreases with temperature rise

95
Q

Which of the following factors does not influence measurement accuracy?

A

(none) : static and dynamic error, dead zone and reproducibility

96
Q

Which of the following is suitable for measuring the temperature of a red hot moving object (e.g. steel ingots on roller table)?

A

radiation pyrometer

97
Q

need cold junction compensation

A

Thermocouples

98
Q

Selection of material for thermocouple depends on the

A

minimum and maximum temperature

99
Q

Radiation pyrometers

A

none of these :

(a) have very low speed of response
(b) need not “see” the temperature source; it is measuring
(c) can’t measure temperature of objects without making physical contact

100
Q

V-notch is used to measure flow rate of a liquid in

A

an open channel

101
Q

Which of the following is not a head flowmeter?

A

rotameter

102
Q

Use of I-control along with P-control facilitates

A

elimination of offset

103
Q

Flow rate of a liquid containing heavy solids (e.g. sand) can be best measured by

A

eccentric orifice

104
Q

has poor accuracy on high orifice ratios (above 0.75)

A

Orifice plates for flow measurement

105
Q

Pitot tube is used

A

line is large
velocity is high

106
Q

In an area meter (e.g. rotameter), the flow rate is

A

inferred from the change in area of an orifice in the flow line across which the pressure differential is constant zero

107
Q

incurs constant and small permanent pressure drop

A

A rotameter

108
Q

is a two position (fully open or fully closed) control adequate to control a process with slow reaction rate and minimum dead time or transfer lag

A

On-off control

109
Q

moves the final control element at constant speed in either direction in response to an error signal

A

Floating control action

110
Q

All:
(a) the continuous adjustment of the set point index of an automatic control loop by a primary (master) controller
(b) used when changes in process conditions cause serious upsets
in controlled variable
(c) useful to control flow from temperature

A

Cascade control

Eme Lang (2 decks)

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