psychrometer

from WordNet (r) 3.0 (2006)

psychrometer
    n 1: a hygrometer consisting of a dry-bulb thermometer and a
         wet-bulb thermometer; their difference indicates the
         dryness of the surrounding air

from The Collaborative International Dictionary of English v.0.48

Psychrometer \Psy*chrom"e*ter\, n. [Gr. psychro`s cold + -meter:
   cf. F. psychrom[`e]tre.]
   An instrument for measuring the tension of the aqueous vapor
   in the atmosphere, being essentially a wet and dry bulb
   hygrometer.
   [1913 Webster]