Psychrometers

Psychrometer or wet-and-dry-bulb-thermometer, consists of two thermometers, one that is dry and one that is kept moist with distilled water on a sock or wick.

Psychrometer calculates between wet bulb and dry bulb temperatures. Based on a wet cloth that covers the wet bulb. If the air is dry, the water in the fabric will evaporate, causing the wet bulb temperature to decrease. On the other hand, if the air is very humid, the fabric will not evaporate. The wet bulb temperature will be close to the dry bulb