Brainscape's Knowledge GenomeTM

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


See full index

automatic controls test study > ac study > Flashcards

ac study Flashcards

1
Q

Hydraulic actuators generally operate at lower pressures than pneumatic actuators

A

False

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

In thermocouple circuits, cold junction compensation is used to eliminate errors due to the effects of

A

ambient temperatures

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

The coefficient of __________ expansion is the amount a unit volume of a material expands or contracts with temperature changes

A

volumetric

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

____________ are commonly used in industry to identify equipment that is running hotter than normal

A

Thermal imagers

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

RTD’s, thermistors and strain gauges are essentially resistors T/F

A

True

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

Feedback Control is commonly implemented using digital computers. T/F

A

true

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

Which of following input transducers would function by a change in resistance ?

  • Thermistor
  • RTD
  • Strain Gauge
A

all of them

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

In a closed loop automated system the error signal is determined from the sensor feedback signal and the _________ signal.

A

Set point

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

What is an actuator?

A

A device that adjusts the process variable

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

Modern _________ contain instruments that can use inputs from many types of devices and combine digital and analog output signals to a controller.

A

control loops

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

The letter designation for thermocouple wires specifies a _______________.

A

voltage-temperature relationship

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

In batch production applications, ____ are the two most common process variables that must be regulated to control the rate of reaction.

A

temperature and pressure

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

A transmitter __________.

a)

converts a signal from the sensor into a standardized signal

b)

is used to boost and send signals to a remote location

A

Both a and b

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

A new steady-state condition occurs ____ time constant(s) after a controlled variable is exposed to an energy change.

A

5

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

I operate by sending sound waves toward the target & measuring the time it takes for the pulses to bounce back.

A

Ultrasonic Sensor

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

If a pressure gauge displays a reading of 50 psig, what is the absolute pressure?

A

about 65 psia

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

Which of the following devices is used for sensing the position of an object by measuring the time it takes for a transmitted pulse to be echoed back?

A

Ultrasonic Transducer

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

Some open-loop automatic control systems are self-regulating. T/F

A

False

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

A sensor is usually a transducer. T/F

A

True

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

The hydrostatic pressure created by a liquid in an open container __________ when its temperature increases.

A

stays the same

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

What is the primary function of an “actuator”?

A

Alter the process variable

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

What name is usually given to the system element that is described in the diagram below as a “Summer ”?

A

Comparator

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

The psia pressure reading of an inflated tire is the pressure __________.

A

above a vacuum

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

Feedback Control is always implemented using digital computers. T/F

A

False

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

In a time of flight ultrasonic flow meter, the difference between the transmitted and received frequencies become __________ as the velocity of the fluid increases.

A

greater

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

Which of the following types of energy are radiated from a perfect blackbody?

a)

emitted

b)

reflected

c)

transmitted

d)

all of the above

A

a)

emitted

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

Assume two ingredients are added together, processed & then stored.

This would be an example of a (n):

a)

Discrete product - producing process

b)

Batch process

c)

Continuous process

d)

Individual product-producing process

A

b)

Batch process

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

When testing an RTD, it is not necessary to disconnect it from the circuit

A

False

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

The automatic control of process operations are performed by ____.

a)

open-loop systems

b)

closed-loop systems

c)

both a and b

A

C both a and b

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

Signal conditioning involves:

A

c)

converting input & output signals to a usable form

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

Which of the following terms identify the unit of measurement for flow?

A

a)

volumetric flow rate

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

A new steady-state condition occurs ____ time constant(s) after a controlled variable is exposed to an energy change.

A

b)

5

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Illustrated here is a solenoid valve.

They are available to control:

a)

oil flow

b)

air flow

c)

water flow

d)

all of the above

A

D all of the above

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

The altitude at or above sea level must be considered when measuring hydrostatic pressure of a liquid in an open container.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

A component of a device or system

A

Element

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

A decrease in signal magnitude.

A

Attenuation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

The ratio of the change in output for a given change in input.

A

Gain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

The upper limit and lower limit in a quantity to be measured.

A

Range

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

A device which responds to a measured variable and converts it to a standardized signal.

A

Transmitter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

The difference between the upper and lower values in a measured quantity.

A

Span

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

The device which directly responds to the measured variable.

A

Sensor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Data represented by a set of separate and distinct numbers.

A

Discrete signal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Data represented by a set of binary numbers.

A

Digital signal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

The smallest interval between sequential values.

A

Resolution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What is a tuning parameter?

A

A parameter that determines the accuracy of a controller

43
Q

A(n) ________ is an electrical meter consisting of several thermocouples connected in series to provide a higher voltage output

A

thermopile

44
Q

A boiler operator is typically responsible for control systems that measure temperature, pressure, flow, and other variables.

A

True

45
Q

A thermocouple produces a voltage that is proportional to the __________.

A

difference in temperature between the hot and cold junction

46
Q

The ____ is sent to the final control element.

A

control signal

47
Q

A “Variable Gain Error” in a measuring device is also known as a _____________ error.

A

Linearity

48
Q

Hydrostatic pressure is determined by the __________ of the material in the vessel

a)

density

b)

height

c)

both A and B

d)

None of the above

A

c)

both A and B

49
Q

__________ readings of a thermocouple are taken to determine temperature measurements

A

b)

Voltage

50
Q

What is a deadband?

A

A range of values in which the process variable can fluctuate without triggering an adjustment

51
Q

How an indicated value conforms to an accepted standard value
or true value. Normally “reference accuracy” is used which defines
the limit that errors will not exceed when the device is used under
reference operating conditions. Reference accuracy is normally
expressed in a number of forms typically preceded by a+ and a -
sign. e.g. ±0.1 °C, ± 2% of scale length. (Do not confuse with
precision)

A

ACCURACY

52
Q

signal representing a variable which may be
continuously observed and continuously represented.
i.e. The signal has an infinite number of points between
any two values.

A

ANALOGUE SIGNAL

53
Q

A transducer converts:

A

One form of energy to another

54
Q

decrease in signal magnitude. Also, the reciprocal of gain.

A

ATTENUATION.

55
Q

When a valve is selected that is sized too large, the controller of the closed-loop system will cause it to operate at or near the ____ position.

A

closed

56
Q

When the core of an LVDT is located above the center position, the AC waveform at the secondary is ___________ phase shift with the primary

A

0°

57
Q

A domestic “Automatic” washing machine is an example of a closed loop control system

A

False

58
Q

Which of the following input field devices would most likely be used with an analogue interface input module?

A

Photocell

59
Q

What is a process variable?

A

A variable that changes during a process

60
Q

The voltage _______________ at the secondary indicates if the core of an LVDT is located above or below the center position

A

phase

61
Q

Simple “ON-OFF type” control is used in which of the following heating systems?
a)

Electric baseboard heaters controlled by a line-voltage thermostat

b)

A domestic central natural gas forced air furnace controlled by a low voltage mercury switch type thermostat
Correct Answer
c)

Both above choices are correct

d)

None of the above are correct

A

C) both a and b are correct

62
Q

The emissivity value of a non-blackbody is ______________.

A

Less than 1

63
Q
  1. Determine the angular distance the encoder shaft moves for the four pulses.
           ( 4 pulses / # of pulses per revolution) x 360 degrees
  2. Because of the difference in the pulley diameters, the angle traced out by four pulses in the larger pulley will be less than the angle in step 1 above.
         Encoder shaft angle in Step 1 x (# encoder teeth / # drum teeth) = angle on shaft drum.
  3. Find drum circumference = π x 14 cm = 43.96 cm for one revolution.

4.Final answer: (angle on shaft drum in Step 2 / 360 degrees) x 43.96 cm =

A

This drawing shows the rear drum of a conveyor belt.

This drum is 14 cm. in diameter.
The timing gear on this drum shaft has 28 teeth.
The timing gear on the encoder shaft has 18 teeth.

This encoder is rated to put out 350 pulses per revolution.
How far will the object travel on the belt during 4 pulses of encoder output?

64
Q

From the list below, select the example of an output transducer
a)

Infrared LED

b)

Strain Gauge
Incorrect Response
c)

Thermistor

d)

RTD

A

a)

Infrared LED

65
Q

______________ pressure can have a negative measurement reading

A

gauge

66
Q

A __________ is capable of accurately measuring temperatures from a distance.

A

pyrometer

67
Q

Which of the following Transducers are considered to be “active” Transducers?
1)

Limit Switch
Incorrect Response
2)

Inductive Proximity Switch

3)

Capacitive Proximity Switch
Correct Answer
4)

Piezo Crystal

5)

All of the above

A

4)

Piezo Crystal

68
Q

A load demand change will alter the value of a controlled variable.

A

False

69
Q

The _____________ of the secondary voltage of an LVDT indicates how far the core has moved.

A

amplitude

70
Q

a calibrated input range of -80 to 100 degrees F,
with an output range of 4 to 20 mA.
Using the calibration table below, what is the applied input temperature for this transmitter? (Assume perfect calibration)

Applied Input Temperature (°F) % of Span Output Signal (mA)
? ?? 50%
_____________________°F

(Place just your number in the space provided, using one decimal place)

Answer:
10.0

Hide question 6 feedback
Feedback
Find the input span total, from the negative low to positive high.
Apply the % given to this total span.
Subtract the negative amount to find temperature

A

answer

71
Q

A conductive probe makes __________ measurements.

A

point

72
Q

An ____ diaphragm valve allows flow to pass when the activating signal is not applied.

A

air-to-close

73
Q

What is the purpose of process control?

A

To maintain a consistent quality of a product or process

74
Q

The most common combination of control modes found in the typical process plant is:

A

Proportional-plus-integral

75
Q

The four main measurements in process control are :

A

pressure, flow, temperature, & level.

76
Q

As the fluid flow through an orifice plate reduces by 3 times, the differential pressure across it ______ times

A

reduces by 9

77
Q

What is an active transducer

A

Active transducers generate energy output by changing the input! No external power source is required.

78
Q

With a capacitive probe, the level of a solution in a tank determines the capacitance by effecting the __________.

A

dielectric

79
Q

A solenoid actuator has a(n) __________ in its symbol.

A

S

80
Q

What is a derivative controller?

A

A controller that adjusts the process based on the time rate of change of the error

81
Q

What is feedforward control?

A

A control system that anticipates changes in the process and adjusts accordingly.

82
Q

An instrument index lists the manufacturer of the devices in a process. T/F

A

Trrue

83
Q

Which type of encoder is normally used if angular position is required ?

A

Absolute

84
Q

What is a control valve

A

A valve that controls the flow of fluids or gases in a process

85
Q

Which type of control is used to adjust the speed of a motor?

A

Servo control

86
Q

A controller with what kind of control mode eliminates offset automatically? ________

A

Integral

87
Q

The function of the optical encoder’s Schmitt trigger is to convert ______________.

A

pulses into square waves

88
Q

The power source of static pressure is __________.

A

gravity

89
Q

Variable resisitance sensors that have a positive temperature coefficient include:

A

R.T.D.’s

90
Q

The term __________ is used to describe how consistently a sensor responds to the same input value

A

Reliability

91
Q

infrared radiation is that part of the electromagnetic spectrum with ______________ wavelengths than visible light

A

longer

92
Q

What type of control system is used to control the temperature of a furnace?

A

Proportional control

93
Q

The hydrostatic pressure created by a liquid in a closed container __________ when its temperature increases.

A

increases

94
Q

The differential pressure method takes measurements in a(n) __________ container.

A

pressurized

95
Q

You can use a capacitance sensor to measure

A

position

96
Q

What is the difference between a set point and a process variable?

A

The set point is the target value, while the process variable is the measured value.

97
Q

Which electrical component does not have analog characteristics?

A

Temperature Switch

98
Q

What is a proportional-integral-derivative (PID) controller?

A

A controller that adjusts the process based on a combination of proportional, integral, and derivative control actions

99
Q

What type of capacitance sensor can detect the presence of an object without actually touching it?

A

Proximity detector

100
Q

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

the instrument in a control loop

b)

the inertia of the controlled variable
Incorrect Response
c)

dead time
Correct Answer
d)

all of the above

A

all of the above

101
Q

An RTD increases its resistance when it is exposed to _________________.

A

heat

102
Q

What type of control system uses a combination of feedback and feedforward control?

A

Hybrid control

103
Q

Which electrical component does not have discrete characteristics.

A

Thermistor

104
Q

Which transducer is a packaged silicon P/N junction that can detect IR light when reverse biased?

A

photodiode

105
Q

____ control valves are not used for high pressure application.

A

Single-seated

106
Q

Which component of a control system generates the output signal?

A

Controller

107
Q

__________________ is the degree to which an observed value matches the actual value of a measurement over a specified range

A

Accuracy

108
Q

What is a proportional-integral-derivative (PID) controller?

A

A controller that adjusts the process based on a combination of proportional, integral, and derivative control actions

109
Q
A

automatic controls test study (3 decks)

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