Design and Development of a Low-Cost Hydrogen Sulfide Sensor System for Biogas Monitoring

Biogas systems in low-resource settings often lack affordable tools for monitoring hydrogen sulfide (H2S), a toxic, corrosive gas produced during anaerobic digestion, since commercial instruments are costly and poorly suited to the required range. This thesis presents the design and development of a low-cost H2S sensor system for biogas monitoring, built around a three-electrode electrochemical sensor covering 0-2000 ppm. A custom PCB handles signal conditioning, analog-to-digital conversion, timekeeping, and battery power with USB-C charging; a diaphragm pump draws sampled gas through a 3D-printed flow chamber, with readings shown on an onboard display and firmware written in C++. All major subsystems integrated successfully, baseline noise over one hour stayed within 3.65 ppm, and the CHF 193.80 component cost was about 95% lower than a commercial reference instrument.