| 摘要 |
PURPOSE:To obtain a material having a stable moisture sensing characteristic for a long-period even without the provision of a heater for preventing the deterioration with lapse of time by using a material consisting of the calcined mixture composed of graphite and alkali silicate. CONSTITUTION:Comb-shaped electrodes 2 are formed of Pt-Pd alloy paste by screen printing on an insulatingbase plate 1 consisting of alumina and are cal cined after Pt lead wires 4 are attached thereto. The mixture prepd. by kneading, for example, about 65.3% aq. sodium silicate soln. (water glass), 25.7wt% graphite and 9.0wt% additive: SiO2 with an agitator is coated to about 50mum thickness thereon by a dipping treatment and is calcined for about 40min at about 360 deg.C to obtain a moisture sensitive film 3. The moisture sensor is constituted by using sucy material. The possible reason for the low resistance value of such material lies in that the alkali ion existing in the graphite is exuded out by the water adsorbed on the surface of the moisture sensing part 3 and contributes to surface electrical conduction. |
