Top Most Process Instrumentation & Control Objective Questions
1.Which of the following does not pertain to timing device :
charging of a condenser
flow of oil through a dash pot
release of air through a nozzle
flow of sand through an opening
piezoelectric crystal.
ANSWER : : piezoelectric crystal.
2.The smallest change in measured value to which the instrument will respond is called
accuracy
precision
amplification
resolution
sensitivity.
ANSWER : : resolution
3.Pick up the appropriate word for A pointer moving over a scale :
instrument
indicator
transducer
gauge
recorder.
ANSWER : : indicator
4.Motion of fast-moving systems may be timed and studied by means of a :
stroboscope
piezoelectric crystal
electronic timer
chronometer
photovoltaic cell.
ANSWER : : stroboscope
5.Which of the following may be measured by the deflection of an elastic element, by balancing against a known force, by the acceleration produced in an object of known mass :
force
pressure
temperature
level
displacement.
ANSWER : : force
6.Pick up false statement about pressure measurements :
low pressure is normally measured by manometers
medium pressure by diaphragms or bellows
medium and high pressure by Bourdon gauge
all pressures by transducers
absolute pressure by piezoelectric crystal.
ANSWER : : absolute pressure by piezoelectric crystal.
7.Which gauge can be used to measure pressure below 1 |xm :
dead weight tester
pirani gauge
ionization gauge
McLeod gauge
absolute pressure sensor.
ANSWER : : ionization gauge
8.Which is not correct statement about selection of tube material for a Bourdon gauge:
Have high creep strength to withstand high temperature
Be stable enough to maintain its calibration indefinitely
Be immune to corrosion from the fluid inside the tube, and from the atmosphere outside it
Be hard enough to withstand the applied pressure without any part of it being stressed above the limit of proportionality
Be easy to fabricate.
ANSWER : : Have high creep strength to withstand high temperature
9.The condition of how much successive readings differ from one another for a fixed value of the variable is called :
accuracy
error
sensitivity
resolution
precision.
ANSWER : : precision.
10.Which of the following device is used as a standard for calibrating pressure gauges :
manometer
diaphragm
bellows
dead weight pressure tester
piezoelectric crystal.
ANSWER : : dead weight pressure tester
11.Errors due to assignable causes are called :
static errors
systematic errors
calibration errors
random errors
known errors.
ANSWER : : systematic errors
12.The sensitivity of reading of manometer can be increased by :
inclining the manometer rube
using low specific gravity fluid
application of optical magnification
use of level sensing device
all of the above.
ANSWER : : inclining the manometer rube
13.Which effect is useful in measuring rapidly varying forces :
piezoelectric
strain gauge
photovoltaic
pneumatic gauging
change of capacitance.
ANSWER : : piezoelectric
14.Hysteresis error in Bourdon tube can be minimized by :
using proper tube material
using proper diameter and thickness of tube
avoiding temperature cycling
using it well within the designed pressure range
using separating diaphragm and avoid direct ingress of hot. fluid to tube
ANSWER : : using it well within the designed pressure range
15.In which device the input motion changes the inductive coupling between primary and secondary coils :
potentiometer
synchro
collimator
protractor
dial gauge.
ANSWER : : synchro
16.Pick up the appropriate word for A reading obtained from the motion of a pointer on a scale :
analog
digital
display
indicator
instrument.
ANSWER : : analog
17.Determining moisture in steam by measuring the temperature in a throttling calorimeter is an example of :
direct measurement
indirect measurement
measurement by comparison
measurement by calibration
automatic measurement.
ANSWER : : indirect measurement
18.The closeness with which the reading of an instrument approaches the true value of the variable being measured is called :
accuracy
precision
sensitivity
resolution
discrimination.
ANSWER : : accuracy
19.The ratio of output signal or response of the instrument'” to a change in input or measured variable is called :
sensitivity
precision
resolution
threshold
accuracy.
ANSWER : : sensitivity
20.Which of the following is used to count the number of brass items passing on a conveyor line, when no contact is permitted with the object:
event counter
mechanical counter
magnetic pick up
photoelectric cell
electronic counter.
ANSWER : : photoelectric cell
21.For studying detailed variations with time, one uses :
indicator
digital indicator
recorder
integrator
analog indicator.
ANSWER : : recorder
22.It responds directly to the measured quantity, producing a related motion or signal :
sensing element
transducer
transmitter
indicator
measuring device.
ANSWER : : sensing element
23.Pressure measuring devices are not based on:
measure of an equivalent height of liquid column
measure of the force exerted on a fixed area
measure of some change in electrical or physical characteristics of the fluid
area measurement by polar planimeter
all of the above.
ANSWER : : area measurement by polar planimeter
24.Pick up the appropriate word for The reading displayed as a number, a series of holes on a punched card, or a sequence of pulses on magnetic tape :
pulse train
digital
analog
numeral
recording.
ANSWER : : digital
25.Which is not correct about load cells used to measure weight/force :
accuracy of the order of 0.01 to 1%
rugged and compact construction
no moving parts and negligible deflection under load
low resistance to side load and low overload withstand
hermetically sealed and thermal compensation.
ANSWER : : low resistance to side load and low overload withstand
26.Which type of device is suitable for dynamic force measurement:
lever balance
spring balance
proving ring
piezo-electric transducer
all of the above.
ANSWER : : piezo-electric transducer
27.When the pressure medium to be measured is air or gas, the pipe is made to rise continuously to the gauge, so that:
no air or vapour can collect in pipe
any moisture can be drained ‘
moisture does not come in contact with elements of sensor/gauge
moisture can condense to form seal of water
static head error due to moisture is eliminated.
ANSWER : : any moisture can be drained ‘
28.Thermal expansion of a solid is employed in :
thermocouple
resistance thermometer
bulb thermometer
bimetal element
zener diode.
ANSWER : : bimetal element
29.Pick up false statement about liquid-in-metal thermometers :
remote indication of temperature can’t be given
error is produced if capillary passes through hot zone
error also occurs if instrument base is at high ambient temperature
error can also creep in by the head of the liquid if the bulb is installed either above or below the Bourdon
these are used for industrial applica-tions where accuracy is not so impor-tant.
ANSWER : : remote indication of temperature can’t be given
30.For measuring temperature in the range of 200 to 30�C, following liquid is used in glass thermometer:
mercury
alcohol
toluene
pentane
creosote.
ANSWER : : pentane
31.Which gauge is based on the change of heat conductivity of a gas with pressure and the change of electrical resistance of a wire with temperature :
thermocouple gauge
Bourdon gauge
Ionization gauge
nuitating disk gauge
Pirani gauge.
ANSWER : : Pirani gauge.
32.The development of following element has improved the reliability and the response action of low pressure gauges :
diaphragm
capsule
bourdon
ring balance
all of the above.
ANSWER : : capsule
33.The deflection of center of capsule (formed by circumferential welding of two diaphragms) is proportional to :
active diameter of diaphragm (D)
D
D2
D3
D4
ANSWER : : D4
34.The resistance of strain gauge grid used in pressure transducers is of the order of :
0.1 to 1 ohm
1 to 10 ohm
10 to 100 ohm
100 to 2000 ohm
2000 to 105 ohm
ANSWER : : 100 to 2000 ohm
35.Which of the following have relatively large and negative temperature coefficients of resistance :
radiation pyrometers
optical pyrometers
thermistors
platinum resistance detectors
thermocouples.
ANSWER : : thermistors
36.Protective coating by a suitable cover are applied over strain gauge in order to protect it against:
temperature rise
dust and dirt
moisture
ageing
shorting by conductive contact.
ANSWER : : moisture
37.Which of the following glass is used for 00-600�C temperature measurement by mercury-in-glass thermometer :
lead glass
normal grade
borosilicate
supermax
any one of the above.
ANSWER : : supermax
38.Cold junction compensation is needed in ase of measurement of temperature by :
thermocouple
thermopile
thermistor
zener diode
resistance thermometer.
ANSWER : : thermocouple
39.Which of the following consists of a very thin strip of nickel or platinum foil which responds to temperature in the same manner as the resistance thermometer :
thermo pile
bolometer
radiation pyrometer
thermistor
optical pyrometer.
ANSWER : : bolometer
40.Twisting the thermocouple wires together and heat welding them :
is the standard practice of making junction
would result in noise generation
cause small errors due to local e.m.f. which may arise if the junction is too long
would slow down the response
result in inaccuracies.
ANSWER : : cause small errors due to local e.m.f. which may arise if the junction is too long
41.Proving rings are used to measure :
displacement
force
velocity
acceleration
shock.
ANSWER : : force
42.A siphon or loop in the connecting pipe is interposed as close as possible to the pressure gauge so that:
steam can condense to form a seal of water to fill the tube or bellows at the pressure being measured
air or vapour collection is avoided
moisture formed in pipe can be drained
static head errors are eliminated
it acts as dampener and does not pass on pressure variations to sensor.
ANSWER : : steam can condense to form a seal of water to fill the tube or bellows at the pressure being measured
43.Which of the following thermocouple generates highest e.m.f. for a given temperature :
copper-constantan
iron-constantan
chromel-alumel
platinum-rhodium platinum
silver-palladium.
ANSWER : : iron-constantan
44.For measuring temperature in the range of 20 to 600�C, following liquid is used in glass thermometer :
mercury
alcohol
toluene
pentane
creosote.
ANSWER : : mercury
45.In case of strain gauge transducers, several strain cycles, and temperature cycles are carried out before making measurements, in order to :
increase life
enable high repeatable readings
eliminate premature failures
increase accuracy
avoid drift.
ANSWER : : enable high repeatable readings
46.Ring balance gauge is used for measurement of:
absolute pressure
vacuum
differential pressure
temperature
gauge pressure.
ANSWER : : differential pressure
47.Accuracy of standard pressure gauges, used for testing and calibration purposes is of the order of :
� 1.5%
� 1%
� 0.5%
� 0.25%
�0.1%.
ANSWER : : � 0.25%
48.Target meter is concerned with measure-ment of:
flow
pressure
viscosity
density
level.
ANSWER : : flow
49.Flange taps in case of orifice plate are installed :
25 mm from each side of the orfice plate
D (pipe diameter) upstream and D/2 downstream
just at surface of orifice plate
2.5 D upstream and 8 D downstream
any one of the above.
ANSWER : : 25 mm from each side of the orfice plate
50.Dall tube is another variation of :
orifice plate
nozzle
venturi tube
rotameter
pitot-tube.
ANSWER : : venturi tube
51.Which of the following flow meter maintains a constant pressure differential but varies the orifice area with flow :
Ledoux bell
variable area
straightening vane
variable head
vane-type.
ANSWER : : variable area
52.Pick up correct statement about calibration of temperature sensors by comparison method using liquid bath :
water is used for temperatures from 0 to I00�C
special grade of paraffin oil is used for temperatures between 100 and 200�C
For temperature between 200 and 600�C, a mixture of sodium nitrate and potassium nitrate is used
all of above are true
none of above is true.
ANSWER : : all of above are true
53.Flow in open channels is measured by using :
nozzle
orifice plate
propeller
weir
vortex-shedding meter.
ANSWER : : weir
54.The flow error in case of normal nozzles is of the order of :
0.1%
0.2%
0.5%
1%
2%.
ANSWER : : 1%
55.Local velocity is measured by a :
pitot tube
venturi tube
orifice plate
vena contracta device
nozzle.
ANSWER : : pitot tube
56.Automatic cold junction compensation in thermocouple is provided by :
connecting thermocouple wires, in op-position
a nickel wire resistance in series with a manganin resistance
maintaining cold junction temperature constant by a cooling unit
using a photovoltaic cell
connecting a dry battery cell in opposi�tion.
ANSWER : : a nickel wire resistance in series with a manganin resistance
57.Pick out the odd flow measuring device among the following :
positive displacement type
nutating disc type
sliding vane type
turbine type
hydraulic flume.
ANSWER : : hydraulic flume.
58.In calibration of temperature sensors by fixed point method, the device is calibrated at:
ice point (0�C)
steam point (100�C)
sulphur point (444.6�C)
all of the above
none of the above.
ANSWER : : all of the above
59.Pick out false statement about advantages of orifice plates, used for flow measurement :
no moving parts
long-term reliability
highturn-down ratio
inexpensive
inherently simple in operation.
ANSWER : : highturn-down ratio
60.Pick out false statement about disadvantages of orifice plates :
square root relationship
poor turn-down ratio
critical installation requirements
short-term reliability
high irrecoverable pressure loss.
ANSWER : : short-term reliability
61.Vena-contracta taps are employed :
D upstream and D downstream from the plate
D upstream and at vena contracta
2 D upstream and at vena contracta
just at surface of plate upstream and at vena contracta
any one of the above.
ANSWER : : D upstream and at vena contracta
62.To prevent self-heating errors becoming too great, the current through platinum element (100 ohm) is kept at a very small value :
0.1 raA
1 mA
5 mA
20 mA
50 mA.
ANSWER : : 5 mA
63.In some measurements, in order to increase the sensitivity, two measuring and two reference cells are often used. This arrange ment is usually referred to as :
wheatstone bridge
katharometer
attenuator
amplifier
Kelvin bridge.
ANSWER : : katharometer
64.In which flow device the pressure loss is minimum :
orifice plate
nozzle
variable orifice meter
venturi tube
Dall tube.
ANSWER : : Dall tube.
65.Laser droppler anemometer is used to measure :
pressure
velocity
level
density
temperature.
ANSWER : : velocity
66.The material used for resistance temperature sensor is :
copper
nickel
platinum
any one of above
none of above.
ANSWER : : any one of above
67.15� taper venturi tube causes loss of following % of the differential pressure :
5%
10%
20%
30%
40%.
ANSWER : : 10%
68.For an orfice plate having ratio of inside and pipe diameter as 0.5, the pressure loss in comparison to differential pressure created is of the order of :
5%
10%
20%
35%
50%.
ANSWER : : 50%.
69.Dynamometers are :
force measuring devices
torque measuring devices
power measuring devices
energy measuring devices
displacement measuring devices.
ANSWER : : power measuring devices
70.For measuring air flow, following meter is often used :
vane-type or anemometer
electro magnetic flow meter
vortex-shedding meter
ultrasonic flow meter
pitot tube.
ANSWER : : vane-type or anemometer
71.Pick up false statement:
copper-constantan thermocouple is a stable couple resistant to both oxidis�ing and reducing atmosphere, but needs protection from acidic vapours
Iron-constantan thermocouple suffers from oxidation attack on iron wire, if exposed
iron-constantant couple can be made stable by using enamelled iron
Both wires of chromel-alumel ther-mocouples are prone to damage by sulphurous gases
copper-constantan thermocouple is used as a reference standard for calibration purposes.
ANSWER : : copper-constantan thermocouple is used as a reference standard for calibration purposes.
72.An operation which, in the presence of a disturbing influence, tends to reduce the difference between the actual state of a system and an arbitrarily varied desired state and which does so on the basis of this difference, is called :
automatic control
feedback control
open feed back control
closed feed back control
self regulation.
ANSWER : : closed feed back control
73.The orsat apparatus is used for measuring:
chemical analysis of flue gases
moisture in air
composition of alloys
colour spectrum
molecular configuration.
ANSWER : : chemical analysis of flue gases
74.The density can be measured using :
weight
buoyancy
hydrostatic head
resonant elements
all of above.
ANSWER : : all of above.
75.Spectrophotometer is used to :
measure surface hardness
measure surface characteristics
measure chemical composition of al-loys
analyse colour spectrum
analyse gas composition.
ANSWER : : analyse colour spectrum
76.Which measurement is a good guide to the quality of the water :
conductivity
pH
dissolved 02 content
turbidity
all of the above.
ANSWER : : conductivity
77.Electrode potential is concerned with measurement of:
density
viscosity
chemical analysis
PH
all of above.
ANSWER : : PH
78.Almost all pH measurements are best made with a:
glass electrode
solid state electrode
liquid ion exchange electrode
redox electrode
heterogeneous membrane electrode.
ANSWER : : glass electrode
79.The Ringelmann chart is associated with measurement of:
smoke density
S02 and S03
NO,
CO
dust concentration.
ANSWER : : smoke density
80.The commonly used unit of conductivity is:
mho
mho/m
n mho/cm
ohm/m
m mho/mm.
ANSWER : : n mho/cm
81.The operating characteristic which inherently assists the establishment of equilibrium is called :
corrective action
self regulation
automatic regulation
proportional control action
floating controller action.
ANSWER : : self regulation
82.An apparatus which measures the value of a quantity or condition which is subject to change with time, and operates to maintain within limits this measured value, is called
automatic regulator
self controller
feedback controller
two-position controller
floating regulator.
ANSWER : : automatic regulator
83.Machine health monitoring is mainly based on measurement of:
lub oil pressure
vibrations at strategic points
bearing temperature measurement
efficiency and losses of machine
all of above.
ANSWER : : vibrations at strategic points
84.Continuous analysers for measuring following are based on the chemiluminescent flameless reaction with ethylene :
oxygen
ozone
sulphur oxides
nitrogen oxides
pollutants.
ANSWER : : ozone
85.The time required for the controlled variable to reach a specified value after the application of a step input is called :
rise time
settling time
response time
peak time
proportional time.
ANSWER : : response time
86.The error caused in vibration measuring equipment due to non compliance (not stiff) of bond made between sensor and the surface it is mounted is called :
cross-coupling
coupling compliance
influence error
subject loading by sensor
spurious variation in capacitance.
ANSWER : : coupling compliance
87.The change in length of humidity sensitive elements is measured by :
hydrometer
hygrometer
psychrometer
photometer
all of the above.
ANSWER : : hygrometer
89.The quantity or condition of the controlled system which is directly, measured or controlled :
set point
deviation
controlled variable
command signal
control agent.
ANSWER : : controlled variable
90.Industrial flow meters are based on :
rotational devices
flow through restrictions
flow around obstructions
all of above
none of above.
ANSWER : : all of above
91.Mass-spring seismic sensors measure directly the :
displacement
velocity
acceleration
shock
force.
ANSWER : : acceleration
92.Chromatographic analyser is used to measure the :
02 content in flue gases
C02 content in flue gases
CO content in flue gases
amount of individual gases in a mix�ture
amount of elements in an alloy.
ANSWER : : amount of individual gases in a mix�ture
93.Pure water has pH value of 7. This means that pure water has :
7 g of ionized hydrogen per litre
10 g of ionized hydrogen in/m
1CT7 % of ionized hydrogen
10″7 g of ionized hydrogen per litre
none of the above.
ANSWER : : 10″7 g of ionized hydrogen per litre
95.The range of values through which the variable must change to cause the final control element to move from one extreme position to the other :
throttling range
disturbance
proportional band
response
deviation.
ANSWER : : throttling range
96.The pH value is a measure of hydrogen ionin a solution. The letters pH stand for :
percentage of H2 in solution
power of the hydrogen ion concentra-tion
presence of hydrogen ions
purity of H20
none of the above.
ANSWER : : power of the hydrogen ion concentra-tion
97.In capillary viscometer, viscosity is proportional to :
flow
1/flow
Vflow
1/Vfl ow
1/flow3/2.
ANSWER : : 1/flow