ELEC 200 > Pilot & Overcurrent Devices > Flashcards

Pilot & Overcurrent Devices Flashcards

(58 cards)

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1
Q

What type of momentary contact switch is used for stopping?

A

Normally closed

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2
Q

What type of momentary contact push button switch is used for starting?

A

Normally open

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3
Q

How must start buttons be connected for multiple stations?

A

Parallel

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4
Q

How must stop buttons be connected for multiple stations?

A

Series

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5
Q

A ________________ signals a change in condition by opening or closing a set of contacts.

A

Pilot device

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6
Q

A ____________________ stays in its changed position after the actuating force is removed.

A

Maintained contact pilot

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7
Q

What are two examples of maintained pilot devices.

A
  1. Standard toggle switches
  2. Selector switches
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8
Q

A standard push-button switch is an example of a ____________________ contact pilot device since its contacts only remain in their changed position while the push button is pressed.

A

Momentary contact pilot device

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9
Q

What are two basic contact behaviour types for pilot control devices?

A
  1. Maintained
  2. Momentary
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10
Q

A start push-button switch used in parallel with holding contacts for a stop/start station is a ____________________ contact switch.

A

Momentary

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11
Q

A standard single-pole switch is a ________________ contact switch.

A

Maintained

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12
Q

What is the function of automatically operated pilot devices?

A

Detect a change and convert this change to the opening or closing of a set of contacts.

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13
Q

What are two simple examples of automatic pilot devices?

A
  1. Pressure switches
  2. Float switches
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14
Q

What are three forms of change that automatic pilot devices detect?

A
  1. Temperature
  2. Pressure
  3. Liquid levels
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15
Q

_________________________ are a common component of control systems such as those for compressors, liquid baths and fans.

A

Temperature switches

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16
Q

Thermocouples, resistive temperature devices and thermistors are examples of _______________________ .

A

Temperature sensors

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17
Q

__________________ are voltage devices that indicate temperature by producing a change in voltage.

A

Thermocouple

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18
Q

Compare the difference in function between thermocouples and resistive temperature devices.

A

Thermocouples indicate temperature based on a change in voltage.

Resistive temperature devices use resistance to indicate temperature.

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19
Q

Resistance temperature detectors and thermistors are both examples of _________________________ .

A

Resistive devices

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20
Q

RTD’s are more _______________ than thermocouples.

A

Linear

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21
Q

RTD’s have a ________________ temperature coefficient.

A

Positive

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22
Q

Considering RTD’s have a positive temperature coefficient, what is the relationship between resistance and temperature?

A

Resistance increases as temperature rises.

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23
Q

A ___________________________ is a semi conductive device with a negative temperature coefficient.

A

Thermistor

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24
Q

Thermistors experience a __________________ decrease in resistance as temperature rises.

25
___________________________ are non-contacting sensors, meaning they do not need to touch the surface being measured.
Infrared sensors
26
What type of sensor measures the temperature of a surface by virtue of its thermal radiation?
Infrared sensor
27
How do infrared sensors function?
They measure components of electromagnetic radiation radiated by all objects above absolute zero.
28
In what context are infrared sensors considered?
Contamination concerns, or where measurement could damage a contact sensor.
29
______________________ take advantage of the expansion of metals when they are heated.
Bimetallic devices
30
What does the movement in bimetallic devices change?
State of the contacts
31
A non-programmable thermostat is an example of a _____________________ .
Bimetallic device
32
What are two advantages of bimetallic devices?
Portability and independence
33
What's the downside of bimetallic devices?
They're not as accurate.
34
_______________________ sensors can be used over a wide range of temperatures.
Silicon diode
35
What type of sensor can function in cryogenic temperatures which is less than -150 degrees Celsius?
Silicon diode sensors
36
A ___________________ is a switch with both normally open and normally closed contacts connected to an actuator.
Pressure switch
37
The __________________ may be a bellows, diaphragm or a piston.
Actuator
38
What are two features of pressure switches?
They can be dual-stage and operate contacts at two predetermined pressures.
39
What are two examples of dual staging in a pressure switch system.
Alarm stage, shutdown stage
40
In an air compressor, pressure switches maintain air pressure by: __________________ at a _______________ pressure to start the motor. __________________ at a _______________ pressure to start the motor.
Closing at a low pressure to start the motor Opening at a high pressure to start the motor
41
What are two use cases for pressure switches?
Signal a broken fan Prove exhaust flow
42
Which two switches are capable of controlling the following: - Measuring the travel of a piece of equipment for positioning - Stopping or changing directions - Measuring the levels of solids in a container or pile
Limit switches and proximity switches
43
_____________________ require the actuator, lever, cam, or rod to contact the object or material being sensed.
Limit switches
44
____________________ can detect the object or material without contacting it.
Proximity switches
45
Magnetic, inductive, capacitive and photoelectric are designs of ____________________ .
Proximity switches
46
________________________ operate by detecting the presence of an external magnetic field.
Magnetic proximity switches
47
How are magnetic proximity switches often used?
Used in security systems to detect when doors or windows have been opened.
48
What type of switch can be used in a Hall effect sensor to detect the position or speed of the rotor of a motor?
Magnetic proximity switch
49
________________________ operate by creating a magnetic field and then sensing when a ferrous metal object enters that field.
Inductive proximity switches
50
Sensors under the road construction materials at traffic lights to detect the presence of vehicles is an example of an ______________________ .
Inductive proximity switch
51
_____________________ operate by creating an electrostatic field and then sensing when an object enters that field.
Capacitive proximity switches
52
A switch that operates by sensing light reflected off an object or sensing when an object interrupts a light beam is called a ___________________ .
Photoelectric proximity switch
53
What is a common example of a photoelectric sensor and reflector system?
Garage door set up
54
___________________ are also called liquid-level switches and indicate the liquid level in a vessel or tank.
Float switches
55
What are the effects produced when current flows through conductors?
Heat and magnetism
56
What can happen if too much current flows in a conductor?
Can damage the conductor's insulation
57
If there's a very high amount of current flow, this can lead to the conductor being damaged. This is referred to as __________________ .
Overcurrent conditions
58
ELEC 200
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