225-566 Battery Operated Psychrometer

The 225-566 Battery Operated Psychrometer quickly and easily measures wet-bulb and dry-bulb temperatures. These can be converted into relative humidity or dew point temperature using a chart on the instrument face, a psychrometric slide rule (provided), or tables (also provided) for a more accurate determination.

The instrument is self-contained and portable. It is small enough to be held in the hand, but it has an opening on the back of the plastic case for mounting on a wall if needed. Three D-cell batteries power up to 1,000 observations. Designed to meet Federal Specification GG-P-725B Type III Style B, the instrument consists of a matched pair of eight-inch-long thermometers, a permanent magnet fan motor, a two-ounce plastic water bottle, and an illuminating lamp. The small fan creates an airflow of 15 feet per second over the thermometer bulbs, and the lamp illuminates the thermometers from behind. There are two available models: the 225-566F, which has a range of +10 °F to +120 °F, and the 225-566C, which has a range of -15 °C to +45 °C.