Abstract
A trial gravimetric hygrometer has been designed and manufactured which can determine the mixing ratio of moist air (mass of water/mass of dry air) by absolute measurement. The structure of the apparatus, the operational procedure and the calibration of measuring instru-ments which compose the hygrometer are described. The source of error and the method of correction are discussed and the precision of the hygrometer is estimated to be about 10-3. The principal features of this hygrometer are as follows; (1) A 4-way valve is used for sam-pling. (2) A bypass attached to the U-tubes of the water absorber lets dry air flow directly into the parts following the apparatus before and after measurement. (3) A sonic nozzle controls the flow rate of the sample. (4) The operation can be automatized by a computer.
