The sensors are based on capacitive metrology which is reasonably-priced, maintenance-free and highly accurate. Capacitive humidity sensor elements form the basis of these sensors. An electrode system, a moisture-sensitive polymer layer and gold layer that is permeable to vapour are situated on a small thin glass or ceramic substrate. Since the hygrospic polymer layer can absorb water molecules that after its dielectric constant, this layered system acts as a moisture-dependant capacitor, whose capacitance is a measure of the surrounding relative humidity.
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