A New Resonant Air Humidity Sensor: First Experimental Results

In this paper, first experimental results obtained on a new resonant humidity sensor are presented. The resonant sensor is made of a piezoelectric material coated with a hygroscopic material, therefore able to adsorb the water molecules contained in the surrounding air. The adsorbed water increases the sensitive layer mass, thus varying the sensor resonance frequency. The sensor is included in an electronic oscillator that tunes its oscillating frequency with the sensor resonance frequency. The output voltage signal is sampled and processed by a microcontroller in order to measure the resonance frequency. By relating the device resonance frequency to the amount of water adsorbed by the polymeric layer, an accurate air humidity measurement can be obtained.