Dew Point Sensors
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The dew point, measured by dew-point sensors, is the temperature at which the liquid and vapor phases of a fluid are in equilibrium. The most commonly used sensor contains a mirror cooled by a Peltier-effect semiconductor cooler. The temperature of the mirror is sensed by a resistive thermometer embedded in the mirror. Light from a light emitting diode is directed toward the mirror surface. The reflected light from the surface is picked up by a photosensor. A condensate is formed on the mirror surface when its temperature is decreased. The condensate causes a scattering of light that is detected by the photodetector. The reading of the temperature at this condition gives the dew point.
Dew-point sensor. 1 = mirror, 2 = cooler, 3 = light source, 4 = photosensor, 5 = heat sink, 6 = temperature sensor.
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