The 225-564 Fan Psychrometer is used for determination of dew point and relative humidity. It consists of 9.5" dry and wet bulb thermometers mounted on a common back, a water bottle, fan, motor, and 6-volt battery. It is easier to read and provides more consistent results than a conventional sling psychrometer.
The components are mounted on a wooden base. The bulb of the lower thermometer is covered with a close fitting tubular muslin wick. When the fan is turned on for a period of 2-3 minutes, water is evaporated from the wick-covered thermometer. The wet bulb and dry bulb temperatures are recorded and the humidity is determined using the chart provided or a psychrometric slide rule. Thermometer range is -20° to +120°F or -30° to +50°C. The unit comes complete with battery, humidity chart, and instructions. Replacement wicks are available.