Detection of impurities in water by measuring capacitance

Detection of unhygienic impurities in water is one of the major concerns of human society. The detection of impurity in water is not only important for drinking water but also for water in industrial use. The type of impurity to be detected varies with the variation of the use of water. A low cost parallel plate based capacitive sensor is designed and implemented for the experimental setup. The detection circuit proposed is a RC oscillator with a time constant proportional to the capacitance. The resulting time constant is measured by Arduino Uno microcontroller board. Simulations of the oscillator circuit are performed using Proteus. This paper investigates the impurities with different concentrations of Sodium Chloride (NaCl), Sugar(C₆H₁₂O₆), Ferrous Sulphate (FeSO₄) and Copper Sulphate (CuSO₄). Empirical relationships are developed to identify the type of impurity and its concentration.