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Measurement and Control System

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What is radiation thermometer?
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The radiation thermometer is known by many name, such as infrared thermometer, pyrometer, and optical thermometer or called as I. R. T. and measures surface temperature of a material to be measured without contact with an object. The instrument measures the temperature by converting heat energy emitting from the surface of an object into electrical energy

Basic principle
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All substances, whatever they are, have higher heat than absolute temperature of 0K(-273¡É) and heat energy content is related to temperature of a substance.

This type of energy emits from the surface in the mode of electromagnetic spectrum of different levels

In industrial fields, temperature is measured by using infrared wavelength emitting from the surface of a substance. (Figure 1). Heat energy is concerned with emissivity of a material.

    
How far is it possible to measure the temperature?
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Pyrometer works irrespective of distance. It becomes possible to measure temperature if there is no obstacle between a thermometer and an object which is within the range of measurement.

Temperature measurement
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An infrared thermometer is optically designed so that radiating heat is focused on inside of a special detector. The field of view is determined by optical parts such as lens or optic fiber. Other types of detector, optical instrument and infrared filter, also contribute to focusing radiation energy under different conditions.

For measurement, it use short wavelength (0.7~1.0§­) for high temperature, long wavelength (8~14§­) for low temperature, respectively.

A certain thermometer just uses narrow waveband to measure the temperature. The device named ratio thermometer measures the temperature of an object by using two or more wavelengths under a limited condition.

The figure shows the response of a low temperature thermometer, where the window display is used to indicate correct measurement value even under poor measurement conditions.

Temperature conversion
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  • Absolute temperature
  • £Ë £½ ¡É £« 273
  • Fahrenheit
  • ¢µ £½ ¡É ¡¿ 1.8 £« 32