SoilgSenS 30.2: an Affordable ASIC-based Portable Soil Moisture Sensor Module

A portable integrated circuit-based soil moisture sensor and system with a modular design is presented in this paper. The sensing circuit comprises a custom Application Specific Integrated Circuit (ASIC) fabricated in 180 nm CMOS technology. The proposed system operates at a frequency of 100 MHz, clocked through a stable MEMS oscillator. The frequency of operation is highest among commercial capacitive moisture sensors. The high-frequency operation helps reduce inaccuracies due to the Maxwell-Wagner effect. Measurement results show that the system measures soil moisture with an accuracy +/- 2 % Volumetric Water Content (VWC) while the sensor board consumes a power of 9.82 mW. The proposed system is affordable due to its indigenous ASIC, which can be mass-produced. The sensor module measures 37 mm x 73 mm and weighs 7 gm. The additional modularity, with a power, control, and communication module, provides flexibility in interfacing with different applications.