This compact whirling hygrometer (sling psychrometer) is a reliable instrument for the measurement of relative humidity utilising wet and dry bulb mercury-filled thermometers. The handy self-contained case folds into a compact pocket-sized hygrometer.

The whirling hygrometer measures the wet and dry temperature over the range of 0 to +45°C enabling the relative humidity to be calculated (1 to 97% RH).

The whirling hygrometer incorporates an integral slide rule for ease of reading and convenience. The folded dimensions of the whirling hygrometer are 16 x 35 x 209mm.