Nonlinearity Analysis and Compensation of Measuring the Moisture Content of Green Sand Based on Capacitance Method

Abstract

The capacitance method is one of the commonly-used methods for measuring the moisture content of green sand. However, due to the influence of the plate structure, the contact resistance and the parasitic capacitance and so on, there is a big non-linear problem. On the basis of briefly introducing the principle of measuring the moisture content by capacitance method, the nonlinearity of capacitance moisture sensor is analyzed theoretically, and the higher-order harmonics are taken as main reasons. Then, the influencing factors causing the nonlinearity are discussed. Finally, In order to reduce the nonlinear influence, a method for the nonlinear compensation based on the least square is provided and the experiments are performed. The experimental results show that it has good linearity between the input and output of the sensor, and the error is less than 2.0% after nonlinear compensation.