The Whirling Hygrometer or sling pyschrometer is a established and well-known method for determining the relative humidity and if there is any moisture on steel prior to painting. The Whirling Hygrometer is one of the most economic methods of monitoring relative humidity and dew point. Two models are available: BS Whirling Hygrometer with mercury bulbs fitted and a Budget Whirling Hygrometer with red spirit bulbs fitted. Easy to use, rotate the Whirling Hygrometer rapidly in order to achieve the required air movement around the thermometer bulbs. One thermometer bulb is exposed to the ambient air temperature, providing the dry bulb reading. The other thermometer bulb, which is kept wet with the aid of a fabric sleeve and built in water reservoir, provides the wet bulb temperature. The relative humidity and dew point can now be calculated using the tables provided. Used in conjunction with the Dewpoint Calculator, it will allow easier calculations of the relative humidity and dew point. Complies with International Standards: BS 2842 and ASTM E 337-B. Supplied in a Protective Pouch. | 
