Abstract:A kind of noncontact sensor based on capacitance method was designed. With the aid of the network vector analyzer, the probe of the sensor was measured in the organic solution with different dielectric constants, and the capacitance variation range of the ring probe of the sensor was determined as 7.08~22.75pF. This paper formed 11 highfrequency ceramic capacitors with different capacitances respectively connected with 102nH winding inductor in parallel into resonance circuit. Using the circuit to carry out experiment, the decision coefficient of test results and simulation results all reached 0.98. The measurement accuracy of the detection circuit met the sensor design requirements. Clay loam in Beijing area was chosen as experimental sample. The output of sensor detection unit and the corresponding measured values were carried out the polynomial fitting and linear fitting with a coefficient of determination of 0.9959. The static and dynamic performance of the system can meet the soil moisture detection requirements. The effect of temperature on the output of the sensor was analyzed. The output of the sensor was fit with the temperature, and the coefficient was 0.9879. The energy index Ka was further proposed. By the experiment, the influence ranges of longitudinal and transverse were identified as 10cm and 5cm. Finally, the comparison experiments showed that the proposed noncontact type moisture sensor was similar to that of the foreign products. It met the requirements of noncontact measurement of soil, at the same time, it had high costperformance and laid the localization foundation for the similar products.