To operate psychrometer, withdraw thermometer halfway out of case, then moisten wick. Holding the case as a handle, swing the psychrometer for two minutes. Read wet and dry bulb temperatures, then reinsert thermometer slide into case. The slide and case form a slide rule for calculating RH.
Choose °>F or °>C models. The °>F models are available with either mercury- or spirit-filled thermometers,—use spirit filled model in mercury-free environments. Instructions are included.