Test Method and Operation
Hygrometers use a manual technique to measure Relative Humidity (RH) and dewpoint.
These instruments consist of two thermometers, the bulb of one being covered by a wick. The wick is saturated by filling the plastic container with water. Hold the Hygrometer by the handle and whirl through 360º facing the wind or any airflow for about 90 seconds.
This is repeated until the wet bulb thermometer cools down to a constant frame temperature and two consecutive pairs of readings agree.
The RH and dewpoint are then calculated from the wet and dry bulb temperature readings using the Dew Point Table or the Elcometer 114 Dewpoint Calculator. Ensure the wet bulb wick dips into the small water container attached to the Hygrometer frame. Check the water level each time before using.
116A Whirling Hygrometer
