psychrometer vs hygrometer

psychrometer and hygrometer both are nouns.

Word	Noun	Adjective	Verb	Adverb
psychrometer	Yes	No	No	No
hygrometer	Yes	No	No	No

As nouns, hygrometer is a hypernym of psychrometer; that is, hygrometer is a word with a broader meaning than psychrometer:

psychrometer: a hygrometer consisting of a dry-bulb thermometer and a wet-bulb thermometer; their difference indicates the dryness of the surrounding air
hygrometer: measuring instrument for measuring the relative humidity of the atmosphere

psychrometer (noun)	hygrometer (noun)
a hygrometer consisting of a dry-bulb thermometer and a wet-bulb thermometer; their difference indicates the dryness of the surrounding air	measuring instrument for measuring the relative humidity of the atmosphere