Low-cost sensor array design optimization based on planar electromagnetic sensor design for detecting nitrate and sulphate

In recent years, the tremendous development of agriculture sector has been driven by the growing human population. Therefore, the crop productions need to be increased to fulfill the food demands. In order to do it, the amount of fertilizer used, might have been more than required and unabsorbed fertilizer by plants usually washed into water sources like rivers, ponds, and wells. Hence, the water will be polluted and unsafe to consume. Therefore, it is important to determine the contamination level in natural water resources. This paper discusses the development of a low-cost sensor array based on planar electromagnetic sensors to determine the contamination levels of two common fertilizer components which are nitrate and sulphate in water sources. Three types of sensor array, were suggested: parallel, star, and delta. The modeling and simulation of all type of sensor array were carried out using COMSOL Multiphysics 4.2 software to calculate the sensors' impedance value. The contamination state was simulated by altering the electrical properties values of the environment domain of the model to represent water contamination. The simulations results show that all types of sensor array are sensitive to conductivity, σ and permittivity, ε. Furthermore, a set of experiments was conducted to determine the relationship between the sensor's impedance and the waters' nitrate and sulphate contamination. The performance of the system was observed where the sensors were tested with the additional of distilled water with different concentrations of amount of potassium nitrate and potassium sulphate. The sensitivity of the developed sensors was evaluated where the best sensor was selected. Based on the outcomes of the experiments, the star sensor array placement has the highest sensitivity and can be used to measure the water content in the water.