An Impedimetric Cu-Polymer Sensor-Based Conductivity Meter for Precision Agriculture and Aquaculture Applications

This paper presents a two-electrode type conductivity sensor, using copper as electrodes, coated with a polyimide layer called DQN-60. This sensor is specially designed to be robust yet inexpensive for applications like precision farming and fishery. A new conductivity sensing principle is proposed which is based on impedimetric measurement (both magnitude and phase) at a frequency of 200 kHz. This sensing principle is developed by analyzing the electrical equivalent model of the proposed sensor and is aimed at eliminating the effect of the interface impedance and the cell capacitance thus making the measurement linear and accurate. A prototype meter is developed with 3.75% maximum full-scale error in the range of 0.5 μS/cm to 20 mS/cm. The temperature compensation, calibration, and detailed experimental results are also discussed.