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  Frequency-Domain Sensors (FDS) advert image shown if present

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A method used by a soil moisture meter to measure soil moisture content. It measures the frequency from a sensor within the soil which is connected to an oscilloscope. The higher the soil moisture, the higher the reading (called the dielectric constant).
There are two types of sensor used:
1. Capacitance sensor (Frequency Domain Reflectometry), and
2. Electrical impedance sensor (Coaxial Impedance Dielectric Reflectometry).