Knowledge Base 3 Flashcards
T F
Pilot duty devices are normally used to switch horsepower rated loads
d
Which of the following is a primary control device
Flow Switch
Thermostat
Motor Start
Pressure Switch
motor starter
T F
A push button would normally be considered to be a pilot control devvice
TRUE
A manually operated switch is one that is controlled by ___
HAND
What do the SPDT and DPDT switches look like
look at the pictures
T F
The DC current rating of a switch would have a value of lower magnitude than the AC rating
TRUE
Identity your symbols from page 1
d
The NC push button ___ the circuit when it is pressed and returns to the ____ position when the button is released
OPENS
CLOSED
Electrical ____ are designed to protect their contents from operating environmental conditions
Enclosures
A push button may consist of one or more ____ blocks, a(n) ____ device, and a(n) _____plate
Contact Blocks
operator
legend
_____head push button operators are used for emergency stop push buttons
Mushroom
T F
A pushbutton assembly can only have one contact block
FASLE
Once actuated, ______type pushbutton operators are required to be actuated a second time to return the contacts to their normal off state.
Maintained
Emergency stop push buttons must be of the maintained contact type.
(True/False) _________
TRUE
Draw the NEMA and IEC symbols used to represent a red pilot light:
f
Push-to-test pilot lights can be energized from two separate signals of different voltage values. (True/False
TRUE
All selector switches operate with spring return to provide momentary contact operation. (True/False)
FASLE
Drum switches are only used for starting and reversing three-phase squirrel-cage motors. (True/False
FASLE
A mechanically operated switch is one that is specifically controlled by hand. (True/False
False
Limit switches are designed to be operated:
a. By the machine operator
b. When a predetermined pressure is reached
c. When a predetermined temperature is reached
d. By contact with an object
D
Identify each of the switch symbols shown in Figure 4-3:
f
The type of limit switch shown in Figure 4-4 would be classified as a
LEVER TYPE A
- Micro limit switches require a large amount of pressure to be applied to the operating lever in order to actuate the contacts.(True/False)
FALSE
The type of temperature switch shown in Figure 4-5 is
Capillary tube temperature switch
All temperature switches use only N.O. (normally open) contacts.
(True/False)
FALSE
The three categories of pressure switches are _____________________
pressure, _________________ pressure, and _____________________ pressure.
Positive pressure
Vacuum (negative pressure)
Differential pressure
Pressure switches open or close when a preset pressure is reached.
(True/False)
TRUE
The type of switch shown in Figure 4-6 would be classified as a
Float Switch
Sensors are devices that are used to ____________________ and ______________the presence of something
detect
measure
A proximity sensor can detect the presence an object without physical
contact. (True/False)
TRue
An inductive proximity sensor can be actuated by both conductive and
nonconductive materials. (True/False)
TRUE
Identify each component block of the inductive proximity sensor shown in Figure 4-7.
- Coil
- Oscillator
- Detector
- Output
Draw acceptable NEMA and IEC symbols used to represent an N.O. proximity switch.
f
The proximity sensor shown in Figure 4-8 would be classified as a:
3 wire connection
A proximity sensor should never normally be used to directly operate a
motor. (True/False)
TRUE