Chapter 11: Control Loops and Strategies

Question 1

In analog instrument loops, ______ convert physical quantities into electrical signals that represent those quantities.
Select one:

a.
Controllers

b.
Amplifiers

c.
Transmitters

d.
Analog switches

e.
Transducers

Answer 1

c.
Transmitters

Question 2

In on-off control, the controller signal to the final control element is either _____ positive or _____ negative.
Select one:

a.
0%, 100%

b.
0%, 50%

c.
50%, 100%

d.
100%, 50%

e.
100%, 100%

Answer 2

e.
100%, 100%

Question 3

_____ control operates to prevent errors from occurring in the first place.
Select one:

a.
Feedback

b.
Feedforward

c.
Proportional

d.
Proportional plus reset

e.
Proportional plus reset plus derivative

Answer 3

b.
Feedforward

Question 4

Cascade control uses two controllers, but only one:
Select one:

a.
Sensing point

b.
Process variable

c.
Set point

d.
Transmitter

e.
Final control element

Answer 4

e.
Final control element

Question 5

Flow rate is often measured with a(n):
Select one:

a.
Pedometer

b.
Ultrasonic meter

c.
Speedometer

d.
Velocity meter

e.
Orifice plate

Answer 5

e.
Orifice plate

Question 6

Loop alarms:
Select one:

a.
Are acknowledged and ignored until they activate for a second time

b.
Are visual only

c.
Are displayed only on a computer screen

d.
May be audible and visible

e.
Are only displayed on an annunciator panel

Answer 6

d.
May be audible and visible

Question 7

Which of the following main devices are used as final control elements?
1. Control valves
2. Variable speed motor drives
3. Steam flow
4. Speed governors
5. Level switches
6. Damper positioners
Select one:

A.
1, 6

B.
1, 2, 6

C.
4, 5, 6

D.
1, 2, 4, 6

E.
1, 2, 3, 4, 5, 6

Answer 7

D.
1, 2, 4, 6

Question 8

Digital computer systems use a binary number system of:
Select one:

A.
Zeros and tens

B.
Ones and zeros

C.
Tens and one hundreds

D.
Ones and one hundreds

E.
Zero and one hundred percentages

Answer 8

B.
Ones and zeros

Question 9

In a proportional-plus-reset controller, the reset time can be varied by manipulating the _____ adjustment value.
Select one:

a.
Integral

b.
Proportional

c.
Derivative

d.
Gain

e.
Set point

Answer 9

a.
Integral

Question 10

Fail-safe means that the end devices will be _______ once their source of power is removed.
Select one:

a.
Fully open

b.
Fully closed

c.
Manually locked

d.
Held in current position

e.
Either fully open or fully closed

Answer 10

e.
Either fully open or fully closed

Question 11

Control valves create process changes by manipulating the process variable. They are the devices that the controller uses to effect corrective action and are called:
Select one:

a.
Process amplifiers

b.
Final control elements

c.
Signal transducers

d.
Process cyclers

e.
Control variables

Answer 11

b.
Final control elements

Question 12

Emergency shutdown (ESD) devices are operated by:
1. Air
2. Hydraulics
3. Solar energy
4. Nitrogen
5. Electricity
6. Natural gas
Select one:

a.
1, 2, 3

b.
3, 4, 5

c.
2, 3, 6

d.
3, 5, 6

e.
1, 2, 5

Answer 12

e.
1, 2, 5

Question 13

The percent of the process variable range that causes _____ change in controller output is often called the proportional band.
Select one:

a.
20%

b.
25%

c.
50%

d.
75%

e.
100%

Answer 13

e.
100%

Question 14

A controller compares the input signal, representing a ________, with a set point established by operations personnel.
Select one:

a.
Process variable

b.
Controlled variable

c.
Process temperature

d.
Process pressure

e.
Cascade variable

Answer 14

b.
Controlled variable

Question 15

The smart transmitter is a digital device, containing an on-board _____ complete with memory.
Select one:

a.
Microprocessor

b.
Calibrator

c.
Video

d.
Process variable

e.
Modem

Answer 15

a.
Microprocessor

Question 16

The difference between the set point and the actual process variable is known as offset. Offset is an inherent characteristic of __________ controllers:
Select one:

a.
All

b.
Proportional only

c.
Proportional plus integral

d.
Proportional plus integral plus derivative

e.
Integral only

Answer 16

b.
Proportional only

Question 17

In a closed-loop control configuration, a measurement is made of the controlled variable, and this is compared with the desired:
Select one:

a.
Output signal

b.
Set point

c.
Valve position

d.
Product

e.
Controller reset

Answer 17

b.
Set point

Question 18

Two typical modes for ESD systems are to:
1. Shutdown and isolate equipment
2. Regulate pressure to flare
3. Shutdown, isolate, and de-pressure
4. Start critical pumps
Select one:

a.
1, 2

b.
2, 3

c.
3, 4

d.
1, 3

e.
2, 4

Answer 18

c.
3, 4

Question 19

The control system that continuously mixes two or more streams together in order to maintain a consistent mixture is known as:
Select one:

a.
Ratio control

b.
Feed-forward control

c.
Proportional control

d.
Split control

e.
Select control

Answer 19

a.
Ratio control

Question 20

A simple controller station allows the operator to do which of the following?
1. View and change the setpoint.
2. View feed forward settings.
3. View the process variable.
4. Switch from auto to manual.
5. View process history.
Select one:

A.
1, 2

B.
2, 3, 5

C.
1, 3, 4

D.
1, 2, 3, 4

E.
1, 2, 3, 4, 5

Answer 20

C.
1, 3, 4

Question 21

Integral control, often called reset, responds to both the _____ and _____ duration of the deviation.
Select one:

a.
Offset, span

b.
Speed, magnitude

c.
Amount, time

d.
Error, reset

e.
Rate, derivative

Answer 21

c.
Amount, time

Question 22

Feed forward control:
Select one:

a.
Sends outputs to demand loads

b.
Does not accept feedback

c.
Does not accept an operator set point

d.
Adjusts the manipulated variable in response to changes in demand load

e.
Is not facilitated by modern controllers

Answer 22

d.
Adjusts the manipulated variable in response to changes in demand load

Question 23

Transmitters can convert a process physical quantity such as level, pressure, flow, or temperature into a representative pneumatic analog signal, usually:
Select one:

a.
0 kPa–25 kPa

b.
20 kPa–100 kPa

c.
4 mA–20 mA

d.
1%–100%

e.
0 kPa–103 kPa

Answer 23

b.
20 kPa–100 kPa

Question 24

The two process conditions that can make the overall effectiveness of feedback control unsatisfactory are:
1. Closed system
2. Open system
3. Large disturbances
4. Large amounts of lag
Select one:

a.
1, 2

b.
2, 3

c.
3, 4

d.
1, 3

e.
2, 4

Answer 24

c.
3, 4

Question 25

Process parameters may require recording in real time. Such recording may be captured using:
1. Circular charts
2. Enunciator panels
3. Luminated indicators
4. Strip charts
5. DCS trends
Select one:

a.
1, 2

b.
2, 3, 4

c.
3, 4

d.
1, 3, 5

e.
1, 4, 5

Answer 25

e.
1, 4, 5

Question 26

Pneumatic switches are available for _____ sensing.
1. Level
2. Pressure
3. Viscosity
4. Temperature
5. Density
6. Flow
Select one:

a.
1

b.
1, 2, 3

c.
1, 4, 5, 6

d.
1, 2, 4, 6

e.
1, 2, 3, 4, 5, 6

Answer 26

d.
1, 2, 4, 6

Question 27

The percent of the process variable range that causes _____ change in controller output is often called the proportional band.
Select one:

a.
20%

b.
25%

c.
50%

d.
75%

e.
100%

Answer 27

e.
100%

Question 28

In analog instrument loops, ______ convert physical quantities into electrical signals that represent those quantities.
Select one:

a.
Controllers

b.
Amplifiers

c.
Transmitters

d.
Analog switches

e.
Transducers

Answer 28

c.
Transmitters

Question 29

In a proportional-plus-reset controller, the reset time can be varied by manipulating the _____ adjustment value.
Select one:

a.
Integral

b.
Proportional

c.
Derivative

d.
Gain

e.
Set point

Answer 29

a.
Integral

Question 30

The smart transmitter is a digital device, containing an on-board _____ complete with memory.
Select one:

a.
Microprocessor

b.
Calibrator

c.
Video

d.
Process variable

e.
Modem

Answer 30

a.
Microprocessor