Process Control and Instrumentation Flashcards
1
Q
Pick out the one which is a first order instrument.
A
All (a), (b) and (c)
2
Q
Load cells are used for the measurement of
A
Weight
3
Q
Which of the following is the dynamic characteristics of an instrument ?
A
Fidelity
4
Q
Pick out the wrong statement.
A
CO2 is the strongest paramagnetic gas.
5
Q
The __________ of a vapor pressure thermometer is a functioning element.
A
Pointer
6
Q
A negative gain margin expressed in decibels means a/an __________ system.
A
Unstable
7
Q
Thermistor, which has high temperature co-efficient of resistivity, is used as the sensing element in resistance thermometer. It is a/an
A
solid semi-conductor
8
Q
Flapper nozzle is used in a/an __________ controller.
A
pneumatic
9
Q
Typical specifications for design stipulates the gain margin and phase margin to be respectively
A
> 1.7 and > 30°
10
Q
Working principle of radiation pyrometer is based on the
A
Stafan-Boltzman law
11
Q
Which of the following relates the emf. generated in a single homogeneous wire to the temperature difference ?
A
Thomson effect
12
Q
Dilute wine was used as a thermometric liquid initially to develop temperature scale. First emperical temperature scale developed was the __________ scale.
A
Fahrenheit
13
Q
In a single tank system, the transfer function of level to inlet flow rate is
A
R/(TS + 1)
14
Q
Which of the following is a desirable characteristic of an instrument ?
A
High fidelity
15
Q
The operation of a rotameter is based on
A
variable flow area
16
Q
The temperature of tempering oil baths maintained at 400°C during heat treatment of steel is measured by a/an __________ thermocouple.
A
iron-constantan
17
Q
Instrumentation in a plant offers the advantage of
A
all (a), (b) and (c)
(greater safety of operation
better quality of product
greater operation economy)
18
Q
Which of the following temperature measuring instruments need not touch the object whose temperature is being measured ?
A
Radiation/infrared pyrometer
19
Q
Thermal conductivity measurement com-prises the working principle of a _________.
A
CO2 analyser
20
Q
Response of a system to a sinusoidal input is called __________ response.
A
frequency
21
Q
The closed loop pole of a stable second order system could be
A
both real and negative.
22
Q
Smoke density of the flue gas going out of the chimney is measured by a
A
photo electric cell
23
Q
Transfer function of transportation lag is
A
e-TS
24
Q
Temperature measuring instruments are standardised mostly with __________ points of pure substances.
A
both (a) & (b)
(melting
boiling)
25
Pick out the first order system from among the following.
Mercury in glass thermometer kept in boiling water.
26
The maximum service temperature for fibre glass used as thermocouple wire insulation material is __________ °C.
500 °C
27
Which of the following controllers has the least maximum deviation ?
P-D controller
28
Volumetric expansion is the working principle of the __________ thermometers.
mercury in glass
29
A magnetic flowmeter is
all (a), (b) and (c)
30
Zirconia probe is used for the continuous measurment of __________ flue gases going out of the furnace.
oxygen in
31
Strain gage pressure transducers are used to measure __________ pressures.
both (a) and (b)
(gage as well as vacuum
absolute as well as differential)
32
The transfer function for a PID controller is (where, τ i is the integral (reset) time and τD is the derivative time.)
Kc(1 + 1/τis + τD. s)
33
Compositional analysis of __________ is done using mass spectrometer.
an isotope
34
The function of a transducer is to
convert the primary signal into a more useful quantity, usually an electric impulse.
35
Nichol's chart deals with
closed loop values vs. open loop values
36
Which of the following thermocouples will give the highest output for the same value of hot and cold junction temperature ?
Chromel-constantan
37
A proportional controller with a gain of Kc is used to control a first order process. The offset will increase, if
Kc is reduced
38
The symbol for "capillary line" in instrumentation diagram is
------*-------*------
39
__________ is undesirable in thermocouples used in industries,
Non-linear relation of emf to temperature
40
Select the correct statement from the following.
The amplitude ratio of a pure capacity process is inversely proportional to frequency.
41
Continuous shell temperature measurement in a liquid-liquid heat exchanger is done by a
thermocouple
42
The __________ of a vapor pressure thermometer is a secondary element.
Bourdon tube
43
Emf developed by a thermocouple, while measuring a temperature of 600°C is about 5.5 mV. The type of thermocouple used is
platinum-platinum+rhodium
44
Which of the following relates the absorption & evolution of heat at the junctions of a thermocouple to the current flow in the circuit?
Peltier effect
45
The second order system with the transfer function has a damping ratio of
46
In a shell and tube heat exchanger, the flow rate of heating/cooling fluid is the __________ variable.
manipulated
47
The second order system with the transfer function has a damping ratio of
0.5
48
A non-linear chemical system is exemplified by a/an
non-isothermal CSTR
49
The transfer function for an ideal proportional plus reset controller (reset time T) is
Kc(1 + 1/TS)
50
The frequency response of a first order system, has a phase shift with lower and upper bounds given by
0, π/2
51
Gas chromatography is used for the measurement of
concentration
52
Which of the following thermocouples can measure the maximum temperature ?
Tungsten-molybdenum
53
Radiation pyrometers as compared to thermocouples
can measure higher temperature
54
Liquid flow rate in a small channel is best measured by a/an
pitot tube
55
Specific gravity of a liquid can not be measured by a/an
anemometer
56
__________ temperature scale assigns 0° to the 'ice point' and 80° to the 'steam point'.
Reumur
57
Dead zone is the
maximum change in the variable that does not change the reading of the instrument.
58
Which of the following thermometers is not suitable for distant reading upto 60 metres?
Mercury in glass thermometer
59
Degree to which an instrument indicates the changes in measured variable without dynamic error is called its
fidelity
60
Thermistors are made of
metal oxides
61
A barometer measures the __________ pressure.
absolute
62
Humidity of air can be determined by a
sling psychrometer
63
Thermocouple in a thermal well behaves as a true
multiple first order system
64
The transfer function for a P-D controller is
Kc(1+τD s)
65
Bode diagram is a plot of
log (AR) vs. log (f) and (Φ) vs. log (f)
66
Working principle of disappearing filament type optical pyrometer is based on the
Wien's law
67
Strain gage uses an electrical conductor wire, which when elastically stretched increases in length and reduces in diameter. Both these dimensional changes result in __________ in the electrical resistance of the wire.
increase
68
Pick out the wrong statement
CSTR can be considered as a distributed parameter system
69
Range of hydrogen gas constant volume themometer is __________ °C.
0 to 100
70
The __________ of a vapor pressure thermometer is a primary element.
bulb
71
The time constant of a first order process with resistance R and capacitance C is
RC
72
A sinusoidal variation in the input passing through a linear first order system
gets attenuated (magnitude decreases)
73
Nitrogen gas constant volume thermometer is suitable for measuring a temperature of __________ °C.
> 100
74
Pick out the most suitable instrument for measuring temperature in the range of-40 to 425°C.
bimetallic thermometer
75
Accurate temperature measurement performance of a radiation pyrometer can not be affected, if the
object and surrounding are at almost the same temperature.
76
Relationship between absorption/evolution of heat at the thermocouple junctions and the current flow in the circuit is given by __________ effect.
Peltier
77
Configuration of Bourdon spring tube is never made of __________ shape.
circular
78
Thermodynamic celcius scale of temperature measurement is
both (b) and (c)
(defined on the basis of melting point of ice and condensation temperature of water vapor.
having an interval of 100° between ice point to steam point.)
79
According to Bode stability criterian, a system is unstable, if the open loop frequency response exhibits an amplitude ratio exceeding unity at frequency for which phase lag is
180°
80
In a closed loop system, the process to be controlled is an integrating process with transfer function l/2s. The controller proposed to be used in an integral controller with transfer function 1/T1s. When a step change in set point is applied to such a closed loop system, the controlled variable will exhibit
underdamped response
81
Resistance of a gas in a vessel is given by (where, P = pressure, V = volume of the vessel, n = no. of moles of the gas, R = gas constant)
V/nRT
82
Measurement of pressure in ammonia reactor is done by
Bourdon gauge
83
The fluid used in hydraulic controller is
oil
84
Flow rate of a river is measured by a/an
vane meter
85
Which of the following thermocouple materials does not contain nickel ?
None of these.
86
Flow rate of those fluids which are insensitive to changes in their density, viscosity or flow velocity profile can be best measured by a
magnetic flowmeter
87
"A control system is unstable, if the open loop frequency response exhibits an amplitude ratio exceeding unity at the crossover frequency." This is __________ criterion.
Bode stability
88
Feed forward controller accounts for the __________ changes.
load
89
Which thermocouple can be used to measure a temperature of around 1400°C ?
Platinum-platinum+rhodium
90
Which of the following filled system expansion thermometer has the capability to measure the lowest temperature ?
Alcohol in glass thermometer
91
Concentration of sugar solution can be determined by the
polarimetry
92
In a single tank system, the transfer function of __________ to inlet flow rate is 1/TS+1.
outlet flow rate
93
Which of the following can not measure a temperature of 1600°C ?
Platinum resistance thermometer
94
The temperature range for which copper resistance thermometer can be used is __________ °C
-200 to 150
95
Paramagnetism method is not used for the composition determination of __________ in gases.
carbon dioxide
96
An amplitude ratio of 0.1 corresponds to __________ decibels.
20
-20
97
For increased speed of response of an expansion pressure spring thermometer, the thermometer bulb should have a
all'a', 'b' & 'c'
(large area but small mass.
high thermal conductivity.
small specific heat.)
98
Pressure of 0.0001 absolute psi can be measured by __________ gauge.
Mcloid
99
Pirani gauge is used for the measurement of
high vacuum
100
The __________ of the fluid contained in the temperature sensing element (i.e., bulb) of filled system thermometers changes with change in temperature.
all (a), (b) and (c)
(pressure
volume
viscosity)
101
__________ thermometer can not measure sub-zero (< 0° C) temperature,
Bimetallic
102
The characteristic equation for the control system with a closed loop transfer function G1/1 + G2 is given by 1 + G2 = 0. The characteristic equation for the control system
all 'a', 'b' & 'c'
(depends only upon the open loop transfer function.
determines its stability.
is the same for set point or load changes.)
103
Starting temperature of optical radiation pyrometer is __________ °C.
800
104
Liquid argon level in a pressurised storage tank (at 3 kg/cm2 ) is measured by a/an
differential pressure gage
105
An ideal PID controller has the transfer function . The frequency at which the magnitude ratio of the controller is 1, is
1/<<(0.2 x 0.5)
106
The deflection of the free end of the bimetallic strips in a bimetallic thermometer with temperature is nearly
linear
107
Alphatron measures pressure __________ microns.
> 3
108
What is the ratio of output amplitude to input amplitude for a sinusoidal forcing function in a first order system ?
< 1
109
The unit step response of the transfer functionreaches its final steady state assymptotically after
a monotonic increase
110
The term analogous to the electrical current in a thermal system is the
heat flow rate
111
Reset rate is the another term used for __________ time.
integral
112
Continuous measurement of moisture in paper is done by
high resistance Wheatstone's bridge circuit
113
Psychrometer determines the
humidity of gases
114
A mercury barometer measures the __________ pressure.
atmospheric
115
Positioning controllers are used for
high loads
116
The amplitude ratio for the sinusoidal response of a __________ is 1.
transportation lag
117
The response of two tanks of same size and resistance in series is
critically damped
118
The amplitude ratio for the sinusoidal response of __________ is < 1.
first order system
119
Which of the following is a 'contact' pyrometer ?
resistance pyrometer
120
Which of the following is not a speed measuring instrument ?
Psychrometer
121
Measurement of sub-zero Celcius temperature in industry is done most commonly by
resistance thermometers
122
Use of I-control along with P-control facilitates
elimination of offset
123
Turbine flow meters are suitable for
both
(cryogenic flow measurements.
aerospace and in air borne applications.)
124
Liquid discharge from a tank or reservoir can not be measured by
orificemeters
125
Which of the following is not a mechanical pressure sensing element ?
U-tube
126
__________ are analysed using a polarograph.
Solids
127
Which of the following judges the accuracy of an instrument ?
Static error
128
On-off controllers are normally used for
low loads
129
Magnetic flowmeters are generally not used for the velocity/flow measurement of hydrocarbons due to their
low electrical conductivity.
130
Which of the following controllers has maximum offset ?
P-controller
131
Pressure of 0.01 psi (absolute) can be measured by __________ gauge.
Mcloid
132
High temperature of around 2000°C of incandescent gas mantles is measured by a/an
radiation pyrometer
133
The unit step response of the transfer function 1/(s2 + 2s + 3)
has a damped oscillatory characteristics
