Working of Wet and dry type hygrometer.

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In this method there are two mercury-in-glass thermometers. one thermometer is always covered with Muslin or wick. And one end of this thermometer is kept in a water containing vessel as shown in the figure.This thermometer is called wet bulb thermometer.

other dry bulb thermometer  is kept near the  wet bulb thermometer as shown in the.

Continuous evaporation of the water from the surface of wet bulb keep its temperature lower than that of dry bulb. 

By using psychrometric table we can know the relative humidity of the atmosphere or any place where our device is placed.

Temperature difference indicated by the two thermometer is the related to relative humidity of the ambient atmosphere.


Note:

The variant of this hygrometer is called sling psychrometer. It has a sling attached to it so that unit can be whirled manually before reading is taken.

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