Whirling hygrometers, also known as sling psychrometers, employ the wet and dry bulb principle to determine percentage relative humidity. They are designed to be rotated, by hand, to provide adequate and consistent ventilation of the bulbs. The compact psychrometer incorporates a slide rule type calculator to determine the % RH. The body of the instrument slides away into the handle providing complete protection when not in use. Fitted with environmentally friendly spirit filled glass tubes. Refill tubes available.
