Battery-powered psychrometers are used to measure the air and wet bulb temperatures, in order to determine the relative humidity and dew point temperature. The Psychro-Dyne is a portable, self-contained psychrometer containing two bulb thermometers, a cotton wick and a small motorized fan to pull the ambient air across the bulb thermometers. The thermometers are back-lit for easier reading, and are filled with black organic fill or mercury. Complete with small water bottle, humidity curve and three D-cell alkaline batteries. Range of thermometers is 10-120°F. Accuracy of the thermometers is +/- 1% of reading. Instrument conforms to ASTM E 337. Made in the USA.