The soil moisture sensor can read the amount of moisture present in the soil surrounding. It's ideal for monitoring an urban garden, or your pet plant's water level.
This sensor uses the two probes to pass current through the soil, and then it reads that resistance to get the moisture level. More water makes the soil conduct electricity more easily (less resistance), while dry soil conducts electricity poorly (more resistance). The new soil moisture sensor use Immersion Gold which protects the nickel from oxidation so that it can be used for a long time.