The Grove - Capacitive Moisture Sensor (Corrosion Resistant) is a soil moisture sensor based on capacitance changes. Compared with resistive sensors, capacitive sensors do not require direct exposure of the metal electrodes, which can significantly reduce the erosion of the electrodes. Hence, we call it Corrosion Resistant.
It is important to note that this sensor can only qualitatively test the humidity of the soil and cannot measure quantitatively. Which means when the humidity of the soil rises, the value of the output decreases; conversely, when the humidity decreases, the output value becomes higher.