Mechanism and Experiment of Planar Electrode Sensors in Water Pollutant Measurement

This paper investigates the detecting mechanism of planar electrode sensor in water pollutant detection. A system composed of electrodes, bulk media, and electrode-solution interface is built up, and the corresponding equivalent circuit containing bulk and interfacial impedances is established. The influence of each part is discussed while the impedance at interface is especially focused on. The impedance spectroscopy of the circuit is divided into three parts by the cutoff frequencies caused by interfacial and bulk impedances, and each of the frequency range can be used for the measurement of different physical quantities in water. The effect of electrode, especially the combination of interdigital and coils, is analyzed, and nine different sensors were designed and fabricated. Experiments validate the accuracy and validity of the model, and the sensor with best sensitivity is found. The stability of the planar sensor is proven in the experiment too.