Impedance hygrometer based on cellulose and CuPc

An investigation has been made on the properties of an impedance hygrometer fabricated using cellulose and copper phthaiocyanine (Ag/cellulose/CuPc/Ag).A 5wt% suspension of cellulose was prepared in water while the CuPc was dissolved in methanol.Cellulose film was deposited on glass substrates with preliminary deposited metallic electrodes followed by deposition of CuPc film.The resistances and capacitances of the samples were evaluated under the effect of humidity.The impedance was calculated from resistance and capacitance measurements.It was also measured during the experiment.It was observed that the capacitance of the sensor increases and resistance and impedance decrease with an increase in the relative humidity level.It was found that the impedance-humidity relationship showed more uniform changes in the interval of 31%-98% RH than the resistance-and capacitance-humidity relationships that showed visible changes in the humidity intervals of 31%-80% RH and 80%-98% RH respectively.The humiditydependent impedance of the sample makes it attractive for use in impedance hygrometers.The impedance hygrometer may be used in instruments for the environmental monitoring of humidity.