Whirling Hygrometer (A)

Whirling hygrometers offer the maximum level of accuracy because of the nature of the measurement. It is used to monitor relative humidity that utilises the wet and dry principle. Housed in a robust yellow plastic frame and black folding handle, the instrument has a water cistern linked to the “wet” bulb by means of a cotton sleeve. The hygrometer works by rapidly whirling for thirty seconds, after which time the reading of two thermometers is taken, normally the wet bulb thermometer reads first. This is repeated until two consecutive reading are obtained which are comparable. Then the relative humidity can be determined by correlating the readings with those on the hygrometric table supplied with each instrument. The hygrometer also comes with a carrying case.