Effects of Relative Humidity on the Eledrical Characteristics of Phosphoric Acid-Ｔetrapanax Papyrifer Paper Hygrometer

The author reported previously on the effects of humidity on the electrical resistance of sodium copper-chlorophyllin-Tetrapanax papyrofer paper (TUSO shi) hygrometer. This system was not suitable for measuring relative humidity lower than 40％. It was considered that P_2O_5, which is deliquescent, would he more available to prepare the elements for the measurement of lower relative humidity. Therefore, several pieces of TUSO shi were immersed into the P_2O_5 aqueous solution, which had several different concentrations, and then dried at room temperature in air. These papers were fixed between Ni-mesh electrodes with plastic spring nippers, and thus elements of phosphoric acid-TUSO shi hygrometer were prepared to study the relationships between relative humidity and A.C. current when A.C. voltage was supplied across Ni-mesh electrodes. (H-I curve) At 2 hours after voltage application, A.C. currents were almost saturated at the given relative humidity and temperature. After 20 days aging, H-I curves of these elements were more reproducible, and by phosphoric acid-TUSO shi hygrometers made of aqueous solution with 4-16％ of P_2O_5, the measurement of relative humidity ranging from 17％ to 90％ was done more exactly. It is expected that using this new system the measurement of relative humidity ranging from O％ to 100％ would be possible