Experiment on fast-measurement of soil moisture based on additional resistance method

In order to eliminate the influence of conductance in measuring the capacitance soil moisture content, the high frequency capacitance soil moisture measurement technique based on the additional resistance was proposed. By analyzing the principle of the soil moisture sensor modulated with a high frequency, the mathematical model of soil water content using a high frequency based on the additional resistors was established. The measurement errors from this conductance were eliminated by solving the equations of capacitance factor from the soil moisture. A parallel board capacitive sensor detection circuit with additional resistors was designed, and the experiment of soil moisture measurement was conducted. The experimental result shows that the soil capacitance value from soil moisture is linear with the soil gravimetric moisture content by 1%-22%, and the soil moisture content value based on additional resistance can be measured below 2% error range of gravimetric moisture content.