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Simultaneously we have heard that Ultrasonic waves being used for level, flow, detection, but no it can be also used for temperature detection.
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Principle of operation is very simple acoustic waves travels at different speeds at different temperatures.
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Velocity of acoustic wave is high when temperature is low, and vice-verse.
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Acoustic waves are passed through solids, and based on transit time we are able to determine temperature.
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Temperature of various gases can be determined by triggering pulse and determining transit time.
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Rhenium sensors provide better output in hostile environment.
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They can measure temperature up to plasma level(20,000 C).
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The acoustic pulses are generated by piezoelectric crystal, which resonate at frequency range of about 3Mhz.
Temperature and velocity exhibits relationship derived by the formula:
c is velocity of sound.
R is gas constant per mole.
k is Boltzmann constant.
m is mass of single molecule.
T is absolute temperature.
Advantage:
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High accuracy
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No leakage
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Used where medium is at very high temperature.
Disadvantage:
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High cost.
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No ideal gas behaviour.
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The device posses drift in parameters.
Applications:
- Furnace & Nuclear reactors.
Good effort