Research on a measuring method with the function of compensating dielectric constant

Abstract

Measurement of solid volume concentration in gas- solid two-phase flow is based on the prerequisite of invariable solid medium dielectric constant, but in the existing industrial measurement, measuring error is caused as a result of neglecting the variation of solid medium dielectric constant. In order to solve this problem, a measuring method which can compensate solid medium dielectric constant is proposed. In the new measuring method, two capacitance sensors are combined: the compensatory capacitance sensor and the measuring capacitance sensor. The compensatory capacitance sensor has a fixed solid volume concentration, so the output can reflect changes of solid dielectric constant and offer a compensation data. The measuring capacitance sensor is used to measure solid volume concentration after the compensation. A mathematical model is built to illustrate how to compensate dielectric constant with the compensation data. The mathematical model is built on the foundation of output characteristics of capacitance sensors, which is studied at the start of the paper. Experiments are carried out to evaluate the performance of the existing and new measuring methods. Experimental results show that when the solid phase dielectric constant varies, relative error is greater than 40% if the existing method is used while it is about 6% if the new method is used. Using the new measuring method can compensate solid phase dielectric constant online and increase the accuracy of concentration measurement.