A Capacitive Model of Water Salinity Wireless Sensor System Based on WIFI-Microcontroller

Monitoring for water salinity is very important in many industries, especially fishery and farming. Therefore, it is necessary to build a wireless water salinity sensor system capable of tackling obstacles in the field. This research proposes a low-cost wireless water salinity sensor system using parallel capacitive plate model. Capacitance effect that is proportional to salinity value is transformed into digital pulses using a circuit of an a-stable multivibrator. Frequency of these pulses is counted using a WIFI-microcontroller and inverse transform is carried out according to the relationship characteristics of salinity and frequency. Water Salinity data acquired by the WIFI-microcontroller are then transmitted to the Control Station Unit (CSU) via gateway WIFI. Testing results show maximum coverage range of 30 meters to the gateway. Nonetheless, the use gateway WIFI can increase the coverage range of this wireless water salinity sensor. Calibration tests also indicate an error of 2.3% in water salinity measurement by the instrument developed here.