Moisture sensors are for sensing the soil moisture level with their probe, right in the root zone. When the soil moisture reaches the preset level, the sensor will interrupt the next cycle(s) via the controller.

These sensors give very accurate information about the soil condition hence they are widely used for following moisutre levels in planter zones and green walls.

Their accuracy is not just a benefit but can be disdvantage as well. The information supplied by these sensors are quite local. It means if there are plants with different rooting levels in the garden, or the soil has areas with different ingredients (which is possible even in a small garden), the soil sensor will supply misleading information about the moisture conditions of the whole garden soil.