New Contactless Conductivity Detection (CCD) Sensor for Fluid Conductivity Measurement

A new contactless conductivity detection (CCD) sensor, which is on the basis of the capacitive reactance elimination principle, is developed in this work. The CCD sensor has two AC paths, the detection path and the compensation path. The unfavorable capacitive reactance produced by the coupling capacitances in the detection path is cancelled out by the capacitive reactance produced by an introduced capacitance in the compensation path. The resolution of the CCD sensor is hence improved. Three prototypes of the new CCD sensor (the inner diameters are 0.50 mm, 1.00 mm and 1.65 mm respectively) were developed, and fluid conductivity measurement experiments were carried out to investigate the measurement performance of the CCD sensor. The experimental results show that the development of the CCD sensor is successful and the conductivity measurement accuracy is satisfactory. The research results verify that the capacitive reactance elimination principle is an effective way to overcome the unfavorable influence of the coupling capacitances on the conductivity measurement, and therefore the new CCD sensor has a very good development potential.