[D2L Practice] 104A Flashcards
What are the sub-components all types of controllers in a closed-loop control system?
1) sensor
2) a comparator or null detector
3) a transmitter
4) all of the above
All of the above
What type of temperature controller is used in a typical residential household?
Thermostat
What are the main type of sensors used in the HVAC/R industry?
1) temperature
2) pressure
3) humidity
4) all of the above
All of the above
What type of sensor consists or two different strips of dissimilar metal?
bimetal strip
In a bimetal strip the two metals have the same coefficients of linear thermal expansion
T or F
False, different coefficients of thermal expansion
The bending of a bimetal strip is based on pressure
T or F
False
What type of sensor can be formed in a Helix, disk or spiral shape?
bimetal strip
Where would you find an averaging element?
Across the face of a heating coil
What does a bellows react to?
1) pressure
2) temperature
3) resistance
4) A & B
pressure
where is the best place to mount a fast response element with regards to off cycle defrost?
evaporator
What sensor uses a thin flexible membrane that stretches across the mouth of a bell shaped container?
flexible diaphragm
What sensors react to pressure?
1) diaphragm
2) bellows
3) bourdon tube
4) all of the above
All of the above
Where is a flexible diaphragm most commonly used with regards to heating?
combustion air proving switch
Why would use a bellows over a diaphragm?
more accurate
Where is a bourdon tube most commonly used?
Refrigeration gauge
A bourdon tube will straighten out as pressure increases
T or F
True
Which sensor is the most accurate?
1) bourdon tube
2) bimetal strip
3) diaphragm
4) electronic
electronic
What do humidity sensors measure?
wet bulb temperature
What types of humidity sensors are used?
1) hygroscopic sensor
2) electronic sensor
3) all of the above
All of the above
A hygroscopic sensor will absorb moisture when the humidity decreases
T or F
False, absorbs moisture when the humidity increases
Which is an example of a hygroscopic sensor?
1) bimetal strip
2) nylon ribbon
3) copper wire
nylon ribbon
What is a comparator?
compares two electronic signals in order to detect the difference between a reference signal and a feedback signal
What is a transmitter?
transmit signal to the actuator in the controlled device
What is the difference between the actual condition and the desired condition at any moment in time?
1) controller deviation
2) controller set-point
3) controller offset
4) controller span
controller deviation
The Output signal changes in the same direction that the controlled variable changes. An increase in the controlled variable results in an increased output signal.
Direct Acting
What is the maximum and minimum valves to which you can set a controller?
controller range
What is another word for design condition?
controller set-point
What is the single parameter that represents the difference between the highest and lowest values the user can set the controller?
controller span
What are the signals for an on/off control mode?
digital
What is another name for a variable resistor?
analog
