This analog capacitive soil moisture sensor measures soil moisture levels using capacitive sensing, rather than resistive sensing like other moisture sensor types.
It is made of corrosion resistant material giving it a long life Insert it into the soil and impress your friends with real-time soil moisture data
This module includes an on-board voltage regulator that gives you a range of 3.3 ~ 5.5V operating voltage 
Applications : Garden Plants Moisture Sensing Smart Farming Specifications: Operating voltage: DC 3.3-5.