EC‑5 uses capacitance to measure the dielectric permittivity of the surrounding medium. The volume of water in the total volume of soil influences the dielectric permittivity of the soil most heavily. This is because the dielectric permittivity of water is much greater than that of the other constituents of the soil. When the amount of water changes in the soil, the EC‑5 probe measures the change in capacitance (from the change in dielectric permittivity) that can be directly correlated with a change in water content. Circuitry inside the EC‑5 probe changes the capacitance measurement into a proportional millivolt output.
The two-prong design and high 70 MHz measurement frequency allow the sensor to measure volumetric water content (VWC) from 0 to 100 % (VWC of saturated soils is generally 40 to 60 %, depending on the soil type), making this sensor accurate in almost any soil or soilless media, over a wide range of salinities.
EC‑5 is easy to install, and its robust design makes it easy to push it directly into undisturbed soil to ensure good accuracy. The sensor's analog output signal is proportional to the excitation voltage, and the sensor is easily integrated with Vaisala systems.
The standard configuration provides only a hardware interface for EC‑5. The software configuration always requires project-specific tailoring. For more information about EC‑5 and for installation and maintenance instructions, see Decagon Devices EC‑5 Soil Moisture Sensor User's Manual.