(1) An aspiration psychrometer could destroy a delicate moisture balance.

(2) The ventilator uses for ventilating psychrometer , which bring even air cur rent as driving impeller.

(3) Psychrometer: An instrument for the accurate determination of relative humidity.

(4) The paper analyses precision of psychrometer used in the closed warehouse by tests, the extent of error is determined, and the method of correction in practice is given.

(5) The ventilator can be used after formed a complete set of ventilating psychrometer .

(6) The method of measuring water potential of plants with thermocouple psychrometer and the flow chart of computer programs for automatic measurement are presented in this paper.