A Single Chip Integrated Sol-Gel Thin Film LC Sensor for Measuring Moisture in ppm Level

A simple single chip integrated moisture sensor capable of wireless operation through inductive coupling has been proposed. The structure consists of planar inductor and parallel plate capacitor fabricated by sol-gel thin film of γ-Al 2 O 3 (5 μm thick). The sensor chip is capable of measuring ppm level moisture in gaseous environment. The resonance frequency shift of the sensor in the presence of moisture excited by a high frequency ac signal is measured by impedance analyzer (4294A Agilent). The frequency sensitivity of the structure for a moisture range from 100 to 5000 ppm is nearly 119 Hz/ppm. The response and recovery times are 7 and 24 s, respectively. The experimental results show that the output is linear (4.2%), reproducible and stable. Device can be applied for wireless moisture measurement in ppm level.