Unit 13 Quiz Flashcards
Bimetal used to sense temperature changes in some applications.
Snap disc
Two unlike metals joined together at one end, when heated on the fastened end, will produce an electrical current flow. What is it?
Thermocouple
Thin flexible metal disc with a large area that will flex up and down due to pressure changes.
Diaphragm
Device used to control/maintain space or product temperature.
Thermostat
Multiple thermocouples wired in series.
Thermopiles
Bimetal device used to sense water heater temperatures.
Rod and tube
Varies its resistance to current flow based on its temperature.
Thermistor
Modulating controls are used to.
Vary the speed of a motor
A thermal system overload may occur if a specific electrical or mechanical component is not cooled properly, resulting in.
Overheating
An example of a Bimetal device is a.
Snap disc
A thermocouple is a device that.
Converts heat into electrical energy.
Adding length to a Bimetal element is done by shaping the element into a coil, helix hairpin or
Worm shape
True or False: The major advantage of a remote bulb control is that the control body can be located outside the controlled area for better access.
True
True or false: A PTC thermistor’s resistance decreases as temperature increases.
False
True or false: Fluid expansion is a way to sense temperature change.
True
True or false: Bellows are normally used with vapor instead of a liquid inside it.
True
True or false: A properly operating thermocouple connected to a solenoid in a gas valve should put out 20 to 30 millivolts.
True
True or false: A thermistor is a device that produces voltage across the hot and cold junctions when heated.
False
True or false: The system overload control may be electrical, thermal or a combination of both.
True
True or false: Vapor is more sensitive to temperature change.
False
True or false: Safety devices are typically normally closed as long as the system is operating properly.
True
True or false: The metal tube in the rod-and-tube control expands and contracts faster than the steel rod.
True
True or false: An increase in pressure under the diaphragm causes it to expand inward.
False
Controls can be classified as _____,_______,_________,__________,__________,and_______________.
Electrical
Mechanical
Electromechanical
Electronic
Digital
Pneumatic
Name two kinds of fluid expansion controls.
Diaphragm
Bellows
Name two types of snap-action mechanisms.
Magnet
Over puddle of mercury
Over center device
The output from a pressure transducer is typically a value of.
Resistance
Capacitance
Inductance
If a thermistor’s resistance decreases as the temperature increases, it has a ______ temperature coefficient.
Negative
Bimetal controls are limited in application by what?
The amount of warp that can be accomplished with a temperature change.
This device can be wired in parallel with a motor start capacitor to cut out the start capacitor once the motor has started.
PTC Thermistor
