Water content reflectometer user-calibration

While the Topp equation works well in a wide range of mineral soils, there are soils for which a user-derived calibration optimizes accuracy of the volumetric water content measurement. The Topp equation underestimates the water content of some organic, volcanic, and fine textured soils. Additionally, porous media with porosity greater than 0.5 or bulk density greater than 1.55 g cm^–3 may require a media-specific calibration equation.

In these cases, the user may develop a calibration equation to convert CS650 permittivity to volumetric water content over the range of water contents the sensor is expected to measure.