When you use the default settings of the humidity sensor (absolute humidity), you may see there will be significant increase to 100% after you irrigate the soil. Then, after a short period of time, the reading drop sharply from 100% to about 30%. Please be assured, all of our soil probes have been calibrated in the factory. Calibration including data points is conducted by placing the probe in the air to reach the minimum of 0% and pure water to reach the maximum 100%. For very wet soil, the reading is expected to be around 30% depends on the soil type. Please note that when the soil is waterlogged, the reading may jump from the values of 30%-35% to 100% as it is very close to the situation of soaking the probe in the pure water.
Therefore, you don’t need to calibrate the probe when the above phenomenon happens.