An Internet-of-Things Enabled Smart Sensing System for Nitrate Monitoring

Monitoring the nitrate concentration in the field is an excellent ability for a water-monitoring study. We report an interdigital FR4-based capacitive sensor, which is characterized for nitrate concentration. The concentration range of nitrate is 0-40 ppm (mg/L). Different unknown samples were measured and validated with standard UV-Spectrometry. A smart sensing node has been developed which can collect water from a lake, stream, or river, measure the instantaneous nitrate concentration, and transfer the data through the gateway to a user-defined cloud server. The system is completely autonomous and solar powered, robust, and trialed in the field successfully. A simple moving-average algorithm is used to smooth the collected data in the cloud side. The LoRa protocol and WiFi protocol are compared in terms of power consumption. The proposed system is trialed in the field continuously and the result validated with standard UV-Spectrometry. The developed smart system can be easily deployable and friendly to use, and offers new possibilities for both spatial and temporal analysis for nitrate concentration.