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CHAPTER 4 - Coggle Diagram
CHAPTER 4
Bimetallic Thermometer
Use the principle of solid expansion and consists of a ‘bimetal’ strip usually in the form of cantilever beam.
Comprises of two metals which having different coefficient of thermal expansion, joint together
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Advantage: self generating type with low cost with no maintenance. Disadvantage: Inability to measure rapidly changing temperatures.
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Thermocouple
A thermocouple is a temperature-measuring device consisting of two dissimilar conductors that contact each other at one or more spots
It produces a voltage when the temperature of one of the spot differs from the reference temperature at other parts of the circuit
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For increase its sensivity, thermocouples may be attached in series or parallel which known as thermopile
Quartz Thermometer
Piezo-electric crystal (quartz) provides a highly accurate and sensitive method of temperature measurement based on the change in its resonant frequency which is directly proportional to the temperature change
To archive above properties the crystal is cut in the form of shear type LC (Linear coefficient) cut.
The detection of change in frequency of oscillation of 1 Hz gives a resolution of 0.001° C, thus temperature in the range of -40 to 230°C can be measured precisely and accurately