Midterm

Question 1

The manipulated variable and controlled variable are synonymous terms in a closed-loop system.

Answer 1

False

Question 2

The triac is capable of handling more current than the SCR.

Answer 2

False

Question 3

In a typical process control system, the set point is constantly changing.

Answer 3

False

Question 4

The two classifications of industrial control systems are____ controls and____ controls.

Answer 4

process; motion

Question 5

A closed-loop industrial system typically uses____ feedback.

Answer 5

negative

Question 6

The control method used in____ control applications is to sustain a constant condition of the controlled variable.

Answer 6

process

Question 7

An open-loop system does not have a____.

Answer 7

feedback loop

Question 8

The difference between the setpoint and feedback signal is referred to as the____ signal, and is produced by the____ detector.

Answer 8

error; error

Question 9

Altering the____ variable causes the condition of the____ variable to change.

Answer 9

manipulated; control

Question 10

The devicethat provides the muscle to perform work in the closed-loop system is referred to as the____.

Answer 10

actuator

Question 11

The____ is sent to the final control element.

Answer 11

control signal

Question 12

Which of the following influences causes a controlled variable to change?

Answer 12

all the above

Question 13

Which of the following factors contributes to the dynamic response of a single control loop?

Answer 13

all the above

Question 14

The objective of____ control is to prevent the controlled variable from deviating from the setpoint.

Answer 14

feed forward

Question 15

Thyristors are primarily used as____ devices.

Answer 15

switching

Question 16

When the holding current drops below its minimum value, the thyristor will____.

Answer 16

turn off

Question 17

The term trigger refers to turning____ a thyristor device.

Answer 17

on

Question 18

The SCR has____ semiconductor layers and ____ junctions.

Answer 18

4;3

Question 19

The SCR is triggered on by a ____ voltage applied to its gate.

Answer 19

positive

Question 20

The gate lead of an SCR is used to turn it____.

Answer 20

on

Question 21

A ____ voltage can be applied across an SCR.

Answer 21

AC;DC(both)

Question 22

Once the SCR is triggered on, it can be turned off in a DC circuit when a ____

Answer 22

holding current falls below the minimum point

Question 23

The____ is a bidirectional device.

Answer 23

diac

Question 24

The voltage on the emitter of a UJT just before it fires is called the____.

Answer 24

peak voltage

Question 25

The____ is primarily used to turn on a triac.

Answer 25

diac

Question 26

If the voltage applied to an inverting op amp is 3 volts, the feedback resistor is 20k ohms and Rin is 10k ohms,the output voltage is ____.

Answer 26

-6 volts

Question 27

The output of the measurement device is the ____.

Answer 27

feedback signal

Question 28

Which elements and signals of a control system do not exist in an open-loop configuration?

Answer 28

all the above

Question 29

An error signal develops when which of the following conditions occur?

Answer 29

all the above

Question 30

The ____ is tge difference between the condition of the controlled variable and the set point.

Answer 30

error signal

Question 31

The final control element is positioned by a signal from the____.

Answer 31

controller

Question 32

____ is the elapsed time between the instant a deviation of the controlled variable occurs, and the corrective action begins.

Answer 32

Deadtime

Question 33

The setpoint typically remains unchanged in a ____ control system.

Answer 33

process

Question 34

A ____ is an example of an unintentional factor that causes the condition of the controlled variable to become different from the setpoint.

Answer 34

disturbance

Question 35

If +2 volts is applied to the inverting input of an op amp comparator, and -2 volts is applied to the non inverting input, the output will be at a ____ volt saturation.

Answer 35

negative

Question 36

What are the four control modes used by the controller section?

Answer 36

bang bang; PID; PIC; P

Question 37

What is the controlled variable in this process?

Answer 37

gas pressure

Question 38

What is the manipulated variable in this process?

Answer 38

steam flow

Question 39

What is the setpoint?

Answer 39

325 psi

Question 40

What is the measured variable?

Answer 40

pressure

Question 41

positive

Question 42

zero

Answer 42

=

Question 43

negative

Answer 43

>