Figure 1.

Diagram of a multiple-sensor capacitive soil moisture probe. The probe contains $N-1$ sensors, d is the total water depth in mm, $d_n$ is the water depth relative to the bottom of the n-th sensor and $n_s$ is the sensor sitting above soil level. Each of the sensors returns volumetric water content (VWC) (%), temperature (°C) and conductivity (dS/m) data.