A practical, high quality sling psychrometer. This psychrometer, like others, uses a wet bulb and dry bulb thermometer for determining exact relative humidity and dew point. However, this one is superiorly designed for the protective case into which the thermometer inserts when not in use. Sling psychrometers are essential for calibrating hygrometers (please note that all hygrometers should be checked periodically for accuracy). Highly recommended for the professional cultivator.