Instrumentation and Process Control

Question 1

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what is the laplace transform of sin t?

Answer 1

1/s^2+1

Question 2

The transfer function of the first order system is

Answer 2

1/Ts+1

Question 3

Pick out the first order system from among the following

Answer 3

mercury in glass thermometer kept in boiling water

Question 4

Response of a system to a sinusoidal input called

Answer 4

frequency response

Question 5

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

Answer 5

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

Question 6

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

Answer 6

120 degree

Question 7

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

Answer 7

Decibel=20 log10 (AR)

Question 8

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

Answer 8

Bode stability criterion

Question 9

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

Answer 9

> 1.7 and > 30°

Question 10

The frequency at which maximum amplitude ratio is attained is called

Answer 10

resonant frequency

Question 11

A negative gain margin expressed in decibels means

Answer 11

unstable system

Question 12

Bode diagram is a plot of

Answer 12

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

Question 13

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

Answer 13

Optical pyrometer

Question 14

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

Answer 14

fidelity

Question 15

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

Answer 15

high fidelity

Question 16

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

Answer 16

mercury thermometer

Question 17

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

Answer 17

bimetallic thermometer

Question 18

Thermocouple is suitable for measuring

Answer 18

both high and low temperature

Question 19

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

Answer 19

Peltier effect

Question 20

Thermal wells are used in temperature measurement to

Answer 20

guard against corrosive and oxidizing action on thermocouple materials

Question 21

Gas analysis is commonly done using

Answer 21

thermal conductivity cell

Question 22

Psychrometer determines

Answer 22

humidity of gases

Question 23

Continuous measurement of moisture done by measuring

Answer 23

electrical resistance through the paper

Question 24

Optimal activity of a solution can be determined using a

Answer 24

polarimeter

Question 25

A **simple pitot tube** measures

Answer 25

Static pressure

Question 26

**Pirani gauge** *also known as thermal conductivity gauges* is used for

Answer 26

measurement of **high vacuum**

Question 27

A **barometer** measures

Answer 27

absolute pressure

Question 28

The **level of a liquid under pressure** can be determined using

Answer 28

Differential pressure manometer

Question 29

**Continuous** measurement of **specific gravity** of a liquid is done by

Answer 29

Hydrometer and displacement meter

Question 30

**Hot wire anemometer** is used for the measurement of

Answer 30

flow rates of fluid

Question 31

**Flow rate** through an orifice is

Answer 31

proportional to the **square root of pressure**

Question 32

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

Answer 32

rotameter

Question 33

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

Answer 33

weighing meters

Question 34

Pick out the symbol for "locally mounted instrument" in instrumentation diagram

Answer 34

O

Question 35

Which is the symbol for "pneumatic control valve"

Question 36

The symbol for "capillary line" in instrumentation diagram is

Question 36

Instrumentation in a plant offers the advantage of

Answer 36

greater safety of operation better quality of product greater operation economy

Question 37

**Dilatometer** is used to measure

Answer 37

**contraction/expansion** due to changes

Question 38

**Stalagmometer** is used for the measurement of

Answer 38

surface tension

Question 39

**Stroboscope** is used for the measurement of

Answer 39

rpm of a flywheel

Question 40

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

Answer 40

Beckman thermometer

Question 41

**Gain margin** is equal to the

Answer 41

Reciprocal of amplitude ratio

Question 42

**Phase margin** is equal to

Answer 42

180° - phase lag

Question 43

A system with a transfer function _2s_ is of 4s+1

Answer 43

1st order

Question 44

***Bode stability*** method uses

Answer 44

open loop transfer function

Question 45

**Routh stability** method uses

Answer 45

closed loop transfer function

Question 46

Nichel's chart deals with

Answer 46

closed loop values vs. open loop value

Question 47

The fluid used in **hydraulic controller** is

Answer 47

oil

Question 48

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

Answer 48

3

Question 49

Which of the following controllers has **maximum offset**?

Answer 49

P-controller

Question 50

**Process degrees** of freedom

Answer 50

indicates the **maximum number of controllers** to be used

Question 51

**Resistance** of a gas in a vessel is

Answer 51

V/NRT

Question 52

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

Answer 52

coolant

Question 53

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

Answer 53

Integral from 0 to infinity | e |dt

Question 54

**Cascade** control means

Answer 54

**more than one** feed-back loop

Question 55

Which of the following controllers has the **least maximum deviation**?

Answer 55

P-D controller

Question 56

Measurement of **pressure in ammonia reactor** is done by

Answer 56

Bourdon gauge

Question 57

Pressure of **0.01 psi (absolute)** can be measured by

Answer 57

Mcleoid gauge

Question 58

**Continuous** measurement of **moisture in paper** is done by

Answer 58

high resistance Wheatstone's bridge circuit (strain gauge)

Question 59

Pressure of **0.0001 absolute psi** can be measured by

Answer 59

Meloid gauge

Question 60

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

Answer 60

millivolts

Question 61

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

Answer 61

resistance thermometers

Question 62

Starting temperature of **optical radiation pyrometer** is

Answer 62

800°C

Question 63

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

Answer 63

platinum-platinum+rhodium

Question 64

**pH meter** has

Answer 64

Two cells

Question 65

**Maximum differential pressure** in liquid manometer is

Answer 65

30psi

Question 66

**Interfacial level** in pressure vessel is measured by

Answer 66

manometers of float type

Question 67

**Flow rate of sludge** is measured by

Answer 67

Kennison nozzle

Question 68

**Composition** of **natural gas** can be determined by

Answer 68

chromatograph

Question 69

**Bellows** are made of

Answer 69

Thin copper

Question 70

**Flapper nozzle** is a

Answer 70

pneumatic controller

Question 71

**Weir valve** is used for

Answer 71

slurries

Question 72

Valve used to **supply oil to burner** is

Answer 72

rotary plug valve

Question 73

**Mode** used for transmitting signal for **one kilometer distance** is

Answer 73

electronic

Question 74

Use of **pilot in transmission (pneumatic)** is to

Answer 74

Change the flow of air

Question 75

Final control element is a

Answer 75

valve

Question 76

Example of a **second order instrument** is a

Answer 76

mercury-glass thermometer with covering

Question 77

does not vary with time

Answer 77

Offset

Question 78

**Regulator problem** means that

Answer 78

set point is constant

Question 79

**Servo problem** means that

Answer 79

load is constant

Question 80

**Critically damped system** means that the damping coefficient is

Answer 80

1

Question 81

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

Answer 81

< 1

Question 82

**Phase plane** method is used for

Answer 82

nonlinear-behavior

Question 83

**Laplace transform** method is used for

Answer 83

linear behavior

Question 84

**Phase lag of first order** system is

Answer 84

tan^-1 (w T)

Question 85

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

Answer 85

higher maximum deviation longer period of oscillation longer response time

Question 86

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

Answer 86

deviation

Question 87

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

Answer 87

derivative time

Question 88

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

Answer 88

offset

Question 89

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

Answer 89

time constant

Question 90

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

Answer 90

integral action

Question 91

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

Answer 91

Proportional action

Question 92

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

Answer 92

proportional sensitivity

Question 93

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

Answer 93

Q^2

Question 94

Thermistor is a

Answer 94

semiconductor whose resistance decreases with temperature rise

Question 95

Which of the following factors **does not influence measurement accuracy**?

Answer 95

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

Question 96

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

Answer 96

radiation pyrometer

Question 97

need cold junction compensation

Answer 97

Thermocouples

Question 98

Selection of material for thermocouple depends on the

Answer 98

minimum and maximum temperature

Question 99

Radiation pyrometers

Answer 99

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

Question 100

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

Answer 100

an open channel

Question 101

Which of the following is not a **head flowmeter**?

Answer 101

rotameter

Question 102

Use of I-control along with P-control facilitates

Answer 102

elimination of offset

Question 103

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

Answer 103

eccentric orifice

Question 104

has **poor accuracy on high orifice ratios** (above 0.75)

Answer 104

**Orifice** plates for flow measurement

Question 105

Pitot tube is used

Answer 105

line is large velocity is high

Question 106

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

Answer 106

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

Question 107

**incurs constant** and **small permanent pressure drop**

Answer 107

A rotameter

Question 108

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

Answer 108

On-off control

Question 109

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

Answer 109

Floating control action

Question 110

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

Answer 110

Cascade control