psychrometer

An instrument that uses the difference in readings between two thermometers, one having a wet bulb and the other having a dry bulb, to measure the moisture content or relative humidity of air.

An instrument for determining the tension of the aqueous vapor in the air or the relative humidity.

An instrument for measuring the tension of the aqueous vapor in the atmosphere, being essentially a wet and dry bulb hygrometer.

Any of several instruments used to measure the relative humidity of the atmosphere; especially a wet-and-dry-bulb hygrometer.

a hygrometer consisting of a dry-bulb thermometer and a wet-bulb thermometer; their difference indicates the dryness of the surrounding air