Fabrication of a High-sensitive Small Signal Processing Circuit to Monitor Groundwater in Slope of Highway Road

Groundwater monitoring in the area of the highway road near the mountain is important to prevent the road from collapsing. Our group has been studying to observe the groundwater using small water content sensor. To measure small water content, a high-sensitive small signal processing circuit using shielding type water content sensor chip was fabricated. Because the shielding electrode was needed to operate same voltage compared to current detecting electrode in the sensor chip, the constant voltage applying circuit was designed in the processing circuit. The proposed circuit connected the shielding type sensor chip was able to reduce the leakage current by 55% compared to previous circuit connected previous sensor chip. The measurements of model soils with volumetric water content in the range of 0.11% to 27.58% were performed. Proposed circuit with sensor chip was able to detect the water content volumes of all model soils. We succeeded in the fabrication of the signal operating circuit which achieved to measure small water content in the soil.