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Killicks common > Automation controls > Flashcards

Automation controls Flashcards

1
Q

What are the three types of control?

A

Manual
Remote manual (servo)
Automatic

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2
Q

What are the three types of control systems?

A

Regulatory
Positional
Programmable

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3
Q

In what type of control system would a finite error exist when operating normally? (speed, voltage, current, temperature)

A

Regulatory

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4
Q

In what type of control system would the O/P and I/P ideally align under steady state conditions? (steering gear, stabilisers)

A

Positional

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5
Q

In what type of control system is a laid down sequence of events followed until the cycle is completed or the machine cycle is interrupted? (chilled water & diesel generator start routines)

A

Programmable

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6
Q

What are the four types of control medium?

A

Mechanical
Electrical
Pneumatic
Hydraulic

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7
Q

In an open loop system, what is the role of the inlet valve?

A

Controller

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8
Q

In an open loop system, what is the role of a diesel generator?

A

System

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9
Q

In an open loop system, what is the role of the input?

A

Desired value

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10
Q

In an open loop system, what is the role of the output?

A

Measured value

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11
Q

In an open loop system, what changes will effect output speed?

A

Fuel pressure
Load change
Wear (long term)

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12
Q

What is added to an open loop system to create a closed loop system?

A

Feedback
EMD (error measuring device)

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13
Q

Explain feedback?

A

The relaying of output information back to the input

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14
Q

Explain what an EMD is?

A

Any device which compares the input value with the output value and produces an error signal

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15
Q

What three things does an electronic governor consist of?

A

Controller
Electromagnet pickup
Actuator

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16
Q

The error signal is the output of which component of a closed loop system?

A

Controller

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17
Q

What are the two forms of feedback?

A

Positive
Negative

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18
Q

Explain positive feedback?

A

Regenerative
De-stabilising
Used in oscillators

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19
Q

Explain negative feedback?

A

Non-regenerative
Subtract feedback from input at the EMD
Used in control systems

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20
Q

What systems use negative feedback?

A

AVR
Steering gear and stabilisers
Cathodic protection

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21
Q

What is it called when the signal in an open or closed loop system changes from one medium to another and gets bigger or smaller?

A

Gain

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22
Q

What system will always return to its starting point after a disturbance?

A

Stable

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23
Q

What system will result in oscillations that build until failure after a disturbance?

A

Unstable

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24
Q

What is a damper?

A

A device used to reduce sudden changes of motion without affecting the steady state position

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25
Q

What level of damping results in a response which quickly reaches steady state value but oscillates for a significant period of time?

A

Underdamping

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26
Q

What level of damping has a damping ratio less than 1?

A

Underdamping

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27
Q

What level of damping is very slow to reach steady state value but does not have any oscillations?

A

Overdamping

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28
Q

What level of damping has a damping ratio more than 1?

A

Overdamping

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29
Q

What level of damping will reach the steady state value the fastest without being underdamped?

A

Critically damping

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30
Q

What level of damping has a damping ratio equal to 1?

A

Critically damping

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31
Q

What level of damping is fast and has minimum oscillations, resulting in a slightly underdamped system?

A

Optimally damped

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32
Q

How many oscillations will a optimally damped system go through before entering the acceptance zone?

A

One and a half

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33
Q

What are the five types of time varying signals?

A

Sine wave
Impulse
Pulse
Step
Ramp

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34
Q

What are the two types of common lag within a control system?

A

Process/transfer lag
Distance velocity lag

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35
Q

How is the time constant defined?

A

The time taken for the output to reach 63% of its final value when a step input is applied

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36
Q

What voltage will a 1st order system reach after one time constant is 10V is applied as the input?

A

6.3V

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37
Q

How many RC combinations are in a 1st, 2nd and 3rd order system?

A

1st - 1
2nd - 2
3rd - 3

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38
Q

What are the two basic types of interlocking systems?

A

Power
Control

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39
Q

In which type of interlocking system is the power source of the hazard interrupted by the switching of a circuit?

A

Control

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40
Q

In which type of interlocking system is the power source interrupted directly by the opening of the guard?

A

Power

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41
Q

What are the two types of interlocking switches?

A

With guard locking
Without guard locking

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42
Q

What are two types of interlocking switches with guard locking?

A

Unconditional
Conditional

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43
Q

What are two types of interlocking switches without guard locking?

A

Mechanically actuated
Non-contact actuation

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44
Q

What are three types of mechanically actuated switches?

A

Tongue operated actuation
Hinge operated actuation
Cam operated actuation

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45
Q

What form of isolation barrier is required in an interlock when it is possible for two sets of contacts to touch each other back to back in the event of a contact weld?

A

Galvanic isolation

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46
Q

What is a transducer?

A

A device that converts a signal from one kind (normally physical quantity) into another kind (normally electrical)

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46
Q

What are the four properties of a transducer?

A

Accuracy
Repeatability
Sensitivity
Response time

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47
Q

Which property is the relationship between the closeness of the output value to the input parameter?

A

Accuracy

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48
Q

Which property is the variation of the output around an expected value for a constant input?

A

Repeatability

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49
Q

Which property is how much the output changes for a change in input?

A

Sensitivity

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50
Q

Which property is the output considered to be equal to the input when 67% of the original error has been corrected?

A

Response time

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51
Q

What effect does a thermocouple use?

A

Seebeck

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52
Q

What does CJCU stand for?

A

Cold junction compensating unit

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52
Q

What does RTD stand for?

A

Resistance temperature detector

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53
Q

What would the fundamental interval of PT100 RTD be if the resistance at 100 degrees is 138.5 ohms?

A

38.5

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54
Q

In a negative temperature coefficient resistor, what will happen to the resistance as the temperature increases?

A

Non-linear decrease

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55
Q

In a positive temperature coefficient, what will happen to the resistance as the temperature increases?

A

Non-linear increase

56
Q

What is Poisson’s ratio?

A

The lateral contraction divided by the longitudinal extension when a material is stretched

57
Q

What is a strain gauge fitted to on the propeller shafts of ships and submarines?

A

Brushless torsionmeter

58
Q

What directly measures linear or angular displacements?

A

Potentiometer

59
Q

What does LVDT stand for?

A

Linear variable differential transformer

60
Q

What three elements does a LVDT consist of?

A

One primary winding
Two identical secondary windings connected in series opposition
A moveable ferromagnetic armature

61
Q

What is linvar used for?

A

To measure angular displacement
For positional feedback

62
Q

What are the two types of proximity sensor?

A

Capacitance
Ultrasound

63
Q

What are the two types of tachogenerator?

A

AC
DC

64
Q

In a DC tachogenerator, what happens when speed is increased?

A

DC voltage level increases

65
Q

In a DC tachogenerator, how can we reduce ripple?

A

Low pass filter

66
Q

In an AC tachogenerator, a rise in what would be undesirable?

A

Frequency

67
Q

When using differential pressure to determine flow rates, what is used to create the difference in pressure in a pipe?

A

Orifice plate

68
Q

What type of flow transducer gives an output relative to flow dependant on the differential pressure developed across a constriction placed in a tube?

A

Orifice plate flow transducer

69
Q

What would cause a decrease in the number of pulses generated by a phonic wheel transducer?

A

A decrease in shaft rotation speed

70
Q

What are the four types of float operated devices?

A

Float
Spiral
Wire
Reed switching

71
Q

What are the two types of pressure operated devices?

A

Strain gauge
Differential pressure

72
Q

How can ships roll be compensated for when using capacitive tank level transducers to measure tank levels?

A

Use two or more level transducers

73
Q

What are the three basic components of an ultra sonic level detector?

A

Transducer/receiver
Comparator and detector circuit
Solid state output

74
Q

What would happen to the sensing range of an ultra sonic level detector if the frequency is increased?

A

The range would decrease

75
Q

What two devices can be used for high and low level alarms?

A

Strain gauge
Float switch

76
Q

What happens to the resistance of a LDR when the intensity of light is increased?

A

Resistance decreases non-linear

77
Q

What is photoconductivity?

A

An optical phenomenon where a materials conductivity is increased when light is absorbed by the material

78
Q

What are the two types of LDR?

A

Intrinsic (un-doped)
Extrinsic (doped)

79
Q

What is backlash?

A

The loss of angular motion when the direction of rotation of a mechanical drive is reversed

80
Q

What would the maximum angle of the output shaft be if a 10 degree step was applied to the input?

A

20 degrees

81
Q

What three types of friction exist in a servo system?

A

Static
Coulomb
Viscous

82
Q

Explain static friction?

A

The initial drag that must be overcome before motion commences

83
Q

Explain coulomb friction?

A

Drag of constant magnitude

84
Q

Explain viscous friction?

A

Drag directly proportional to velocity

85
Q

What does the phase advance circuit do in a servo system?

A

Modifies the error voltage, causing the driving current to reduce before 0o=0i

86
Q

Which type of servo system stabilisation has the disadvantage of being susceptible to electrical noise?

A

Phase advance

87
Q

What is the maximum torque that can be applied to an energised stationary motor without causing spindle rotation?

A

Holding torque

88
Q

What is a stepper motor?

A

A power device that converts DC voltage pulses into proportional mechanical movement of its spindle

89
Q

What is the anti clockwise unipolar operation of a stepper motor?

A

ACBDA

90
Q

What is the anti clockwise half step operation of a stepper motor?

A

A, AC, C, CB, B, BD, D, DA, A

91
Q

What are the three types of stepper motor?

A

Hybrid
Variable reluctance
Permanent magnet

92
Q

What are the disadvantages of stepper motors?

A

Limited in velocity by the maximum stepping rate
Limited by available torque

93
Q

What is the number of steps per second applied to field windings to cause motor rotation?

A

Stepping rate

94
Q

What is the maximum torque which can be applied to a motor, running at a given stepping rate, without losing synchronism?

A

Pull out torque

95
Q

What is the maximum torque against which a motor will start, at a given pulse rate, and reach synchronism without losing step?

A

Pull in torque

96
Q

What is the maximum switching rate at which a motor will remain in synchronism while the switching rate is gradually increased?

A

Pull out rate

97
Q

What is the maximum switching rate at which a loaded motor can start, stop and reverse without losing steps?

A

Pull in rate

98
Q

What is the range of switching rates between pull in and pull out curves, in which a motor will run in synchronism but cannot start or reverse?

A

Slew range

99
Q

What are the advantages of a stepper motor?

A

Easily controlled by computers since winding currents are switched on or off
Speed of rotation can be controlled by setting the time between successive steps
Direction of rotation is controlled by the winding excitation sequence
Rotor position is controlled and monitored by counting the number of steps so feedback of position is not required
If the motor is left energised once a target position is reached, the rotor will resist movement
No brushes or slip rings on the rotor therefore very reliable

100
Q

What are the two types of rotary encoder?

A

Absolute
Incremental

101
Q

Which type of encoder maintains position information when power is removed from the system, meaning that the position of the encoder is available immediately on applying power?

A

Absolute

102
Q

Which type of encoder accurately records change in position but does not power up with a fixed relationship between encoder state and physical shaft position?

A

Incremental

103
Q

What are the three types of absolute rotary encoders?

A

Mechanical
Optical
Magnetic

104
Q

What is the equation for step angle?

A

360/rotor teeth x stator phases

105
Q

What is the equation for half step angle?

A

Step angle/2

106
Q

What is the equation for distance travelled?

A

Step angle x number of pulses / 360

107
Q

How far do 4-20 mA loops work?

A

3km

108
Q

The ability for 4-20 mA loops to work over long distances is a function of what law?

A

Ohms

109
Q

How many components make up a 4-20 mA loop?

A

5

110
Q

What is the least amount of 4-20 mA tank level sensors required to give continuous level output and high and low level alarms?

A

1

111
Q

What are the five components of a 4-20 mA loop?

A

Sensor
Transmitter
Power source
Loop
Reciever

112
Q

What are the two main errors that occur when converting between analogue and digital?

A

Quantisation
Sampling

113
Q

What error is caused when there is an insufficient number of samples to accurately represent the source signal?

A

Sampling error

114
Q

What error is caused when there is an insufficient number of bits to accurately represent the source signal?

A

Quantisation error

115
Q

Which D-A converter only requires two sized resistors?

A

R2R

116
Q

What are the components of a microcontroller?

A

ADC
CLOCK
RAM
CPU
ROM
I/O
DAC

117
Q

What mode of transmission enables two or more communication channels to share the band width?

A

Broadband

118
Q

What are the advantages of digital control?

A

Greater precision
Better repeatability
Greater reliability
Greater accuracy
Ease of change to system operation by software update

119
Q

What are the three common network configurations?

A

Star
Bus
Ring

120
Q

Which network has a central connection point?

A

Star

121
Q

Which network has common backbone to connect all devices to?

A

Bus

122
Q

Which network can work in a clockwise or anticlockwise direction?

A

Ring

123
Q

What are rules to ensure that data transfer is completed correctly

A

Protocol

124
Q

What is the useable frequency range of a copper cable?

A

Bandwidth

125
Q

What mode of transmission has only one transmitting device and several recievers?

A

Broadcast

126
Q

What mode of transmission devotes the entire capacity of the medium to one communication channel?

A

Baseband

127
Q

What are the advantages of fibre optics?

A

Low losses
Lightweight
Intrinsically safe
Non inductive
Small size
Security of data

128
Q

What are the disadvantages of fibre optics?

A

Cable is fragile
Cannot be spliced like copper wire
More expensive than copper cable
Special training required for operatives

129
Q

Whose theorem states that when converting between analogue and digital, the signal must be sampled at a frequency more than twice the signal frequency?

A

Nyquist/Shannon

130
Q

In a bus network, at which percent of network loading will performance problems be caused by collisions?

A

Above 70%

131
Q

What form of data transmission will require each byte of data to contain a timing signal for the receiver to detect it?

A

Asynchronous

132
Q

What is interfacing?

A

The process of converting one signal type to another

133
Q

In a bandwidth diagram, what does the 3dB point mark?

A

Where signal power falls by 50%

134
Q

What are the two junctions called for a thermocouple?

A

Hot
Cold

135
Q

In an RTD, what is measured during temperature changes?

A

Resistance

136
Q

What is added to a positional servo system to modify it to include velocity feedback?

A

Tacho generator

137
Q

What is the construction of a basic stepper motor?

A

Four equally spaced windings which are star connected (ACBD)
Soft iron rotor that works on the principle of minimum reluctance

138
Q

What type of DA converter requires different values of resistor?

A

Binary weighted ladder

139
Q

What are the 5 components of a digital communication channel?

A

Transmitter
Receiver
Transmission medium
Address system
Protocol

Killicks common (4 decks)

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