Temperature sensing devices Flashcards
The amount a metal will expand when exposed to heat is determined by
the type of metal used
the amount of heat applied
the density of metal
when used in an industrial sensing application, a heated metal will
Expand
With the heating of a metal bar
a small movement of the bar causes a great movement of an attatched mechanical arm
if the electrical contacts are permitted to open an close slowely
poor contact pressue will result
cntact burnout can occur
Hot wire starting relays are often used in the
Refrigeration industry
a metal that remains in liquid state at room temperature is
mercury
two dissimilar metals bonded together have
different expansion rates
an RTD is made out of
Platinum Wire
a bellows type thermostat works on a change in
pressure principle
the most common heat sensing device used in room thermostats and thermometers is the
bimetal strip
a long bimetal strip
exhibits a greater movement with greater heat
when the resistive wire heats up due to excessive motor current
the run winding contacts open
with spiral shaped bimetal strip, if collabarated scale is placed behind a pointer when attached to centercenter of the spiral, it becomes a
thermometer
with spiral shaped bimetal strip, if collabarated scale is placed behind a pointer when attached torge center of the spiral, it becomes a
thermometer
the heating of two dissimilar metals to produce a voltage at the junction is known as the
seebeck effect
a device that employs the heating of two dissimilar metals to produce voltage is known as a
thermocouple
a thermopile exists when
two or more thermocouples are connected in series
with an rtd probe
copper is used to provide good thermal contact
a device that works on the principle of a change in resistance with a change in heat is known as
reluctance temperature detector
thermosistors exhibits
a rapid change of resistance with a change in temperature
this type of relay is named because it uses a length of resistive wire connected in series with the motor to sense motor current
Hot wire relay
since thermocouples produce such low voltages they are often connected in series, this connection is known reffered to as
thermopile
a very common and reliable method of sensing temperature is by the expansion of metal
true
Ttwhen two dissimillar metals are joined at one end , and the that junction is heated , a voltage is produced
true
