The Design of the Soil Moisture Sensor Based on FDR

This Paper is based on dielectric theory.The volume water contect in soil can be determined thtrough the measurements of dielectric constant,which changes with volume moisture of soil.The soil moisture can be measured by using the Frequency Domain Reflectometry(FDR).This method can detect the change of soil moisture continuously and can better reflect its trends.The designed soil moisture probe sensor has multiple measure points,so it can be measured in deep underground feastures.The sensor has the features of real-time and fast response etc.by using RS485 communication bus.The sensor has the measurement accuracy less than 2% within the range of(1-35)%,so it has higher useful value.