Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Instrumentation > Module 2- The Feedback Control Loop and its Dynamics > Flashcards

Module 2- The Feedback Control Loop and its Dynamics Flashcards

1
Q

What are the two types of controllers

A

On-Off controller
Proportional Controller

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the other name for the on-off controller

A

Two Position Controller

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Explain how the on- off controller works

A

It has two extremes/ position of operation. It is either totally on or totally off ( fully opened or fully closed)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Explain how the Proportional controller works

A

It opens or closes in proportion to the difference between the Setpoint and the PV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Define Feedback Control

A

measuring the controlled variable after a change has occurred, then signaling an additional corrective change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is critical in determining the type of control strategy used

A

The type of process and its speed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Control Loop Four Basic Functional Blocks

A

Process
Measurement
Automatic Controller
The Final Control Element

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the additional control loop functional block

A

Transmission Media

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Define Transmission Media

A

technology used for transmitting signals from 1 loop device to another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the purpose of the process block

A

to make a product of a desired quality and or quantity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

For the purpose of control theory define the process

A

an action in which material and or energy is modified to a different form

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

In majority of control loops what dictates the behavior of the loop and as a result it is important to….

A

the process functional block, this is why it is important to include the characteristics of the processes in process control theory

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Measurement block purpose

A

to measure the value of the
process output variable (in the case of the feedback loop), and to convey the value to the automatic controller.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

The measurement block is an interface between

A

the process and the controller
and
the process and human operator

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Measurement block usually comprises of… state its purpose as well

A

a transmitter
transmits an analog or a digital signal whose value is indicative
of the magnitude of the process’s output variable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Some times measurement may require more than one device to… give an example

A

measure a single variable
Flow rate is measured with head type flow element such as an orifice plate, differential pressure transmitter and a square root extractor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What does the square root extractor do

A

linearize the measurement wrt to flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

The square root extractor can be in what two places

A

the transmitter itself ie the measurement block (smart transmitter) or the mounted in the control room (automatic controller) despite the location it is still considered part of the measurement block

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Define local controller

A

A controller located in the process area and does need the value of the pv to be transmitted to the control room

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

When may transmitters not be necessary

A

when low level electronic signal generating devices are used such as Thermocouples

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Define Final Actuator

A

the device that regulates the supply of material and/or energy to affect the desired value of the controlled variable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

The primary function of the automatic controller is to

A

continually compare the measurement signal to the desired value or setpoint, of
the controlled variable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What doe the controller do if there is a difference in the SP and measurement signal

A

he controller takes corrective action by changing its output,
which in turn adjusts the final actuator

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What does the final actuator change and why

A

The final actuator changes the supply of material and/or energy to
the process, in order to bring the controlled variable closer to the
setpoint

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

The automatic controller can sometimes be made up of two different blocks they are

A

a summer
and
a control modes block

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Another name for summer

A

error detector
deviation detector
offset detector

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Function of error detector

A

compares the setpoint to the measured value

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

The summer must have… for the loop to function properly since…

A

algebraic signs included since the algebraic sign of the error is important

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

The error detector in a pneumatic controller is

A

a mechanical flapper nozzle mechanism

30
Q

The error detector in a electronic controller is an

A

electronic solid state amplifier

31
Q

In a microprocessor-based the error is developed by

A

the numerical difference between the sp and the measurement signal

32
Q

what does the controller mode block do

A

it acts on the error signal to determine the behavior of the controller’s output signal

33
Q

What is executed in the controller mode block

A

the on-off or proportional control with its integral (reset) and derivate(rate) modes are executed

34
Q

What does the derivative / rate mode handles

A

how frequent the error occurs
rate of change of the error

35
Q

integral in addition to proportional mode deals with

A

duration of error

36
Q

PID Control

A

Proportional Integral Derivative

37
Q

Proportional mode deals with

A

the magnitude of the error

38
Q

PI Control

A

Proportional control and integral control

39
Q

Why is it important to have calibrated measurement devices

A

to maintain the efficiency of the process

40
Q

Other not commonly used, 4 types of transmission media

A

Sonic, hydraulic, capillary and electromagnetic

41
Q

A pneumatic signal is transmitted over a distance through….,
using a range….

A

cubing
using a range of 20-100KPa (3-15 psig )

42
Q

In pneumatics the air/gas is

A

filtered and compressed to be at the required pressure and and cooled, therefore it is conditioned for this purpose

43
Q

In pneumatics sometimes the signal range is often changed to… in order

A

a multiple of the standard 20-100 kPa range
eg 40-200kPa or 60-300kPa
in order to increase the forces applied to the valve actuator

44
Q

How is pneumatic response time increased

A

by a valve positioner/air amplifier supplying a larger volume of air

45
Q

The electronic media often uses a…for which a signal range …. is used

A

current loop
of 4-20mA

46
Q

The most common voltage range used is … and how is it obtained

A

1-5V
he 1 - 5 V range is developed by passing 4 - 20 mA through a 250 ohm resistor.

47
Q

What magnitude of electronic signals are referred to as high level signals

A

1-5 V
4-20mA
0-10V

48
Q

Another form of signal, which can be considered electronic is

A

the transmission of values in the form of digital codes

49
Q

define fibre optics

A

Light beams, modulated with digital codes, are used as the carrier
frequency.

50
Q

Whatever the transmission medium, it has two design features which enhance the dynamics of the feedback control loop:

A

It must be instantaneous. or very nearly so.
* It must be compatible with the controller, transmitter and valve type

51
Q

Ti

A

Temperature indicator

52
Q

TiT

A

Temperature indicating Transmitter

53
Q

TiC

A

Temperature indicating Controller

54
Q

TV

A

Temperature valve

55
Q

TY

A

current to pneumatic transducer

56
Q

Control loop signals designations
b=

A

measurement signal

57
Q

Control loop signals designations
c=

A

controlled variable

58
Q

Control loop signals designations
e=

A

error, deviation or offset

59
Q

Control loop signals designations
m =

A

manipulated variable

60
Q

Control loop signals designations
m꜀=

A

controller output

61
Q

Control loop signals designations
r=

A

setpoint or desired value

62
Q

Control loop signals designations
q=

A

load variable

63
Q

the success of the controller to maintain the efficiency of the process depends on

A

how accurately it can reduce
error to zero and maintain the controlled variable at the desired value aka sp

64
Q

What four factors determine the loop dynamics

A
  • Response time of the process
  • Dead time of the process
  • Single capacity/single resistance process
  • Multiple capacity/multiple resistance process
65
Q

why does the control strategy of a control loop need to consider response time

A

The control strategy of any feedback loop has to consider the response time of the process to make changes to itself

66
Q

Define response time of a process

A

the total process time delay

67
Q

When it comes to response time what does the controller have to consider

A

the time delay by the manipulated variable

68
Q

If the response time is not consider what can happen

A

the loop will be poorly designed and can oscillate out of control and the controller will over correct making things worse

69
Q

How can lo0ps be designed to be stable in regards to the response time

A

by mathematically determining their response time, to aloe
the valve and controller characteristics to minimize effects of response time.

loops can be designed so they are stable and their response time mathematically
determined to allow valve and controller characteristics to minimize the effects of
response time.

70
Q

Define Dead time

A

the duration of time where nothing happens
the amount of time after a change is made in the input to the process before there is any change in the process output measurement

Instrumentation (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions