Relative Humidity Sensing using PANI/PVA integrated with Feedback Oscillator Circuit

In this work, polyaniline polymer is used for relative humidity level sensing mounted on a planar microwave oscillator. This intrinsically conducting polymer becomes lossy with water ingress. The sensing transducer is based on two concentric split-ring resonator that is designed at high frequency of 5 GHz to exploit the sensitivity. The loss of the resonator is compensated with positive feedback loop and the oscillation is controlled with varactor as the phase modifier. Relative humidity levels of ~ 5 % - 65 % is measured linearly using the proposed sensor with a sensitivity of 833 kHz/degree that agrees with commercial sensor.