Abstract: The present invention relates to a method of manufacture of an electric moisture-content sensor comprising a porous layer of alumuniumoxihydroxide, the so-called boehmite, obtained by hydration of an aluminium substrate in boiling redistilled water and subsequent passivating tempering.This method, due to its simplicity, results in a larger yield in manufacture, reduced variations of parameters of individual sensors and a higher stability of their calibration curves.Due to the extraordinary prolonged stability of sensors manufactured according to this method, they can be for example applied for measuring of the moisture content of stored goods, for air-conditioning systems, for drying plants, in meteorology and also for microelectronics and in medicine.

Abstract: Electric humidity detecting sensing element on the basis of a layer of porous aluminum oxide, treated by sealing in boiling water, passivation and tempering at 70.degree. to 110.degree. C., achieving thereby a substantial reduction of subsequent variations of calibrating curves. The time of tempering may range from 2 to 24 hours. A preferred average time of tempering is 8 hours, with a practical upper limit of 12 hours.