In order to detect moisture content of granular grain rapidly and accurately

a probe of the same cylindrical surface capacitive sensor is designed. The probe uses edge effect of capacitor to sense dielectric constant of the surrounding object.The mathematical expressions of the permittivity of the sensor and the relative permittivity of the particles are derived by using correlation theory of electromagnetic field. And the sensor probes of specific size are designed

and the expressions of the relative permittivity of grain and electric capacity are calculated.At a certain temperature

the probe conducts a preliminary test on rice and it is found that the capacitance of the device has a linear relationship with moisture content of grain. The results show that the mathematical model for the same cylinder surface capacitive sensor is correct.