(3) Process Control instrumentation Flashcards
Which of the following is an undesirable dynamic characteristic of an instrument ?
-Reproducibility
-Dead zone
-Time lag
-Static error
-Time lag
Which of the following is not the triple point of water ?
32°R
273°K
492°R
32°F
32°R
Pick out the one which is a first order instrument.
-Mercury in glass thermometer (without any covering or air gap).
-Bare metallic thermometer.
-Bare vapor pressure thermometer.
-All (a), (b) and (c).
-All (a), (b) and (c).
Load cells are used for the measurement of
-stress
-weight
-strain
-velocity
weight
Which of the following is the dynamic characteristics of an instrument ?
-Reproducibility
-Sensitivity
-Dead zone
-Fidelity
Fidelity
Pick out the wrong statement.
-O2, NO and NO2 exhibit paramagnetic properties as a result of unpaired electrons.
-CO2 is the strongest paramagnetic gas.
-Paramagnetic susceptibility of gases decreases with temperature.
-Paramagnetic susceptibility of gases permits the measurement of their concentration.
-CO2 is the strongest paramagnetic gas.
The __________ of a vapor pressure thermometer is a functioning element.
-pointer
-bourdon tube
-bulb
-none of these
pointer
A negative gain margin expressed in decibels means a/an __________ system.
-stable
-unstable
-critically damped
-none of these
unstable
Thermistor, which has high temperature co-efficient of resistivity, is used as the sensing element in resistance thermometer. It is a/an
-insulator
-conductor
-solid semi-conductor
-liquid semi-conductor
-solid semi-conductor
Flapper nozzle is used in a/an __________ controller.
-electronic
-hydraulic
-pneumatic
-none of these
pneumatic
Typical specifications for design stipulates the gain margin and phase margin to be respectively
> 1.7 and > 30°
< 1.7 and > 30°
< 1.7 and < 30°
> 1.7 and < 30°
> 1.7 and > 30°
Working principle of radiation pyrometer is based on the
-Wien’s law
-Kirchoffs law
-Stafan-Boltzman law
-Seebeck effect
Stafan-Boltzman law
Which of the following relates the emf. generated in a single homogeneous wire to the temperature difference ?
-Peltier effect
-Thomson effect
-Seebeck effect
-none of these
-Thomson effect
Dilute wine was used as a thermometric liquid initially to develop temperature scale. First emperical temperature scale developed was the __________ scale.
-Kelvin
-Centigrade
-Fahrenheit
-Reaumer
Fahrenheit
In a single tank system, the transfer function of level to inlet flow rate is
-R/TS
-R/(TS + 1)
-l(TS + l)
-1/TS
R/(TS + 1)
Which of the following is a desirable characteristic of an instrument ?
-High drift
-High fidelity
-High measuring lag
-Poor reproducibility
-High fidelity
The operation of a rotameter is based on
-variable flow area.
-rotation of a turbine.
-pressure drop across a nozzle.
-pressure at a stagnation point.
-variable flow area.
The temperature of tempering oil baths maintained at 400°C during heat treatment of steel is measured by a/an __________ thermocouple.
-chromel-alumel
-iron-constantan
-platinum-platinum/rhodium
-none of these.
-iron-constantan
Instrumentation in a plant offers the advantage of
-greater safety of operation
-better quality of product
-greater operation economy
-all (a), (b) and (c)
all (a), (b) and (c)
Which of the following temperature measuring instruments need not touch the object whose temperature is being measured ?
-Radiation/infrared pyrometer
-Filled system thermometer
-Mercury in glass thermometer
-Thermo electric pyrometer
-Radiation/infrared pyrometer
Thermal conductivity measurement comprises the working principle of a
-CO2 analyser
-polarimeter
-spectrometer
-chromatograph
-CO2 analyser
Response of a system to a sinusoidal input is called __________ response.
-impluse
-unit step
-frequency
-none of these
frequency
The closed loop pole of a stable second order system could be
-both real and positive.
-complex conjugate with positive real parts.
-both real and negative.
-one real positive and the other real negative.
-both real and negative.
Smoke density of the flue gas going out of the chimney is measured by a
-polarograph
-thermal conductivity meter
-photo electric cell
-chromatograph
-photo electric cell
Transfer function of transportation lag is
a. eTS
b. e-TS
c. 1/TS+1
d. none of these
b. e-TS
Temperature measuring instruments are standardised mostly with __________ points of pure substances.
-melting
-boiling
-both (a) & (b)
-neither (a) nor (b)
both (a) & (b)
Pick out the first order system from among the following.
-Damped vibrator.
-Mercury in glass thermometer kept in boiling water.
-Interacting system of two tanks in series.
-Non-interacting system of two tanks in series.
-Mercury in glass thermometer kept in boiling water.
The maximum service temperature for fibre glass used as thermocouple wire insulation material is __________ °C.
250
500
750
1000
500
Which of the following controllers has the least maximum deviation ?
-P-controller
-P-I controller
-P-I-D controller
-P-D controller
-P-D controller
Volumetric expansion is the working principle of the __________ thermometers.
-mercury in glass
-constant volume gas
-vapor pressure
-bimetallic
-mercury in glass
A magnetic flowmeter is
-based on the principle of Faraday’s law.
-capable of measuring the flow rate of slurries and electrolytes.
-based on the linear relationship between the fluid flow rate and the induced voltage.
-all (a), (b) and (c).
-all (a), (b) and (c).
Which of the following measurements can be made by the measurement of emf ?
-pH value
-Degree of hydrolysis
-Composition of complex ions
-All (a), (b) & (c)
All (a), (b) & (c)
Zirconia probe is used for the continuous measurment of __________ flue gases going out of the furnace.
-oxygen in
-carbon dioxide in
-carbon monoxide in
-temperature of
-oxygen in
The transfer function for a PID controller is (where, τ i is the integral (reset) time and τD is the derivative time.)
Kc(1 + τis + τD ). s
τD * s (last)
Strain gage pressure transducers are used to measure __________ pressures.
-gage as well as vacuum
-absolute as well as differential
-both (a) and (b)
-neither (a) nor (b)
both (a) and (b)
Compositional analysis of __________ is done using mass spectrometer.
-an isotope
-natural gas
-a solid
-an alloy
an isotope
The function of a transducer is to
-modify the input signal.
-amplify the input signal.
-convert the primary signal into a more useful quantity, usually an electric impulse.
-codify/decodify the input signal.
-convert the primary signal into a more useful quantity, usually an electric impulse.
Which of the following thermocouples will give the highest output for the same value of hot and cold junction temperature ?
-Platinum-platinum + rhodium.
-Iron-constantan.
-Chromel-constantan.
-All will give the same output.
-Chromel-constantan.
A proportional controller with a gain of Kc is used to control a first order process. The offset will increase, if
-Kc is reduced.
-Kc is increased.
-integral control action is introduced.
-derivative control action is introduced.
-Kc is reduced.
The symbol for “capillary line” in instrumentation diagram is
-.-.-.-.–
–x—x—x
–//—//–//
—————
—x—x—-x
Select the correct statement from the following.
-The frequency response of a pure capacity process is unbounded.
-The phase lag of a pure time delay system decreases with increasing frequency.
-The amplitude ratio of a pure capacity process is inversely proportional to frequency.
-The amplitude ratio of a pure time delay system increases with frequency.
-The amplitude ratio of a pure capacity process is inversely proportional to frequency.
Nichol’s chart deals with
-A.R.vs. phase lag of first order.
-A.R. vs. phase lag of second order.
-closed loop values vs. open loop values.
-frequency response values of controllers.
-closed loop values vs. open loop values.
The transfer function for an ideal proportional plus reset controller (reset time T) is
Kc(1 + 1/TS)
Continuous shell temperature measurement in a liquid-liquid heat exchanger is done by a
-thermocouple
-reistance thermometer
-mercury in glass thermometer
-vapor pressure thermometer
-thermocouple
__________ is undesirable in thermocouples used in industries,
-Linear relation of emf to temperature
-Corrosion resistance
-Oxidation resistance
-Non-linear relation of emf to temperature
-Non-linear relation of emf to temperature
The frequency response of a first order system, has a phase shift with lower and upper bounds given by
- ∞, π/2
-π/2, π/2
-π/2, 0
0, π/2
0, π/2
For an input forcing function, X(t) = 2t2, the Laplace transform of this function is
2/s2
4/s2
2/s3
4/s3
4/s3
The __________ of a vapor pressure thermometer is a secondary element.
-pointer
-Bourdon tube
-bulb
-none ofthese
Bourdon tube
Emf developed by a thermocouple, while measuring a temperature of 600°C is about 5.5 mV. The type of thermocouple used is
-chromel-alumel
-iron-constantan
-platinum-platinum+rhodium
-either (a), (b) or (c)
-platinum-platinum+rhodium
Which of the following relates the absorption & evolution of heat at the junctions of a thermocouple to the current flow in the circuit?
-Seebeck effect
-Peltier effect
-Joule heating effect
-Thomson effect
Peltier effect
A non-linear chemical system is exemplified by a/an
-isothermal CSTR
-mixer
-non-isothermal CSTR
-none of these
-non-isothermal CSTR
In a shell and tube heat exchanger, the flow rate of heating/cooling fluid is the __________ variable.
-load
-controlled
-manipulated
-none of these
manipulated
The second order system with the transfer function 4/s2+2s+4 has a damping ratio of
2.0
0.5
1.0
4.0
0.5
Liquid flow rate in a small channel is best measured by a/an
-weir
-pitot tube
-vane meter
-venturimeter
-pitot tube
__________ temperature scale assigns 0° to the ‘ice point’ and 80° to the ‘steam point’.
-Celcius
-Rankine
-Reumur
-Farenhite
Reumur
Gas chromatography is used for the measurement of
-temperature
-pressure
-concentration
-flow rate
concentration
Which of the following thermocouples can measure the maximum temperature ?
-Platinum-rhodium
-Tungsten-molybdenum
-Chromel-alumel
-Iron-constantan
-Tungsten-molybdenum
Radiation pyrometers as compared to thermocouples
-has a slower speed of response.
-can measure higher temperature.
-can’t measure the temperature of moving objects.
-is more affected by corrosive atmosphere.
-can measure higher temperature.
Specific gravity of a liquid can not be measured by a/an
-anemometer
-specific gravity bottle
-pycnometer
-hydrometer
-anemometer
Dead zone is the
-same as time constant.
-same as transportation lag.
-maximum change in the variable that does not change the reading of the instrument.
-none of these.
-maximum change in the variable that does not change the reading of the instrument.
Which of the following thermometers is not suitable for distant reading upto 60 metres?
-Vapor pressure thermometer
-Mercury in glass thermometer
-Constant volume gas thermometer
-Resistance thermometer
-Mercury in glass thermometer
Degree to which an instrument indicates the changes in measured variable without dynamic error is called its
-speed of response
-reproducibility
-fidielity
-static characteristics
fidielity
Thermistors are made of
-ultra pure metals
-metal oxides
-iron-copper alloys
-nickel-chromium alloys
-metal oxides
A barometer measures the __________ pressure.
-absolute
-gauge
-absolute as well as gauge
-dynamic
-absolute
Humidity of air can be determined by a
-chromatograph
-sling psychrometer
-mass spectrometer
-polarimeter
-sling psychrometer
