Effect of Position of Electrodes in Polarization Type Flowmeter: Analysis and Experimental Evaluation

Abstract

Measurement of the flow rate of any conductive liquid plays as one of the major roles in any process industry. Generally, electromagnetic flow meters are mostly used to measure the flow rate but electrode polarization impedance-based flow sensors can be a very good replacement of it due to its simple construction and low cost. In this sensing technique, four metal electrodes are inserted in a nonconductive flowline of the conductive liquid. The flow sensor is driven by a small ac voltage supplied through two electrodes and another two electrodes serve as pick-up ones to measure the output voltage. According to the flow rate, the output voltage is changed due to the change in polarization impedance. Simultaneously, there are other factors also, such as electrode size and material, current density, and excitation frequency, which effect the impedance polarization. The effect of the position of electrodes inside the pipe plays as a very crucial effecting factor to the sensor’s performance. In this article, to analyze the effect, an experiment is performed with three different arrangements for placing the electrodes, whereas the third arrangement is a novel one. The third arrangement also increases the sensitivity of the sensing unit and uses a new equivalent model to make analysis theoretically. Equivalent electrical models for three arrangements are analyzed and experimental results are also compared to make a proper evaluation to get a clear idea of the influence of the electrodes’ position.