The Research Of Capacitive Water Content Measuring System Based On Complex Impedance Separation

Capacitive sensor with the advantages of simple structure, high sensibility, noncontact measurement and the cheapness etct has been used widely in the measuremen of water content. Its working principle is mainly based on that the dielectric constant of water is more bigger than the measured stock's. When the water content of stock is different, the sense capacity will have great change. The change of capacitance will transform into electrical signal by using some measuring circuits. Using measuring meter we can transform the electrical signal into the water content indicated value.However, the physical parameter of the capacitive sensor not only has the capacity parameter, at the same time it also has the resistance parameter. The two parameters are often intertwined together,in the environment of high water content.resistance parameter has great effects on the measurement accuracy, and the traditional measuring method is difficult to separate them, even in lots of environments the meter takes off. Particularly in the ceramics industry, the ceramic mud and ceramic slurry have high water content and onductive additives, so the resistance parameter of the capacitive sensor has great effect on the measurement accuracy. To solve the above problem, this paper proposes a new method—digital complex impedance separation. The capacity parameter and the resistance parameter are separated by the method of digital signal processing. The method extract the capacity parameter and eliminate the affection factors of measurement accuracy that the resistance signal cause. This can enhance the measure accuracy of the capacitive water content meter and enlarge its application scope; especially in ceramic industry, there is significant method for the water content measure of the ceramic mud and ceramic slurry.Virtual instrument relates to the computer software technology, communications technology and measurement technology. It is the development tendency of the instrument. This paper chose the most popular virtual instrument software—LabVIEW and develop the capacitive water content measurement system based on the complex impedance separation.