The Grove moisture sensor module uses the conductance of the soil due to moisture to measure how dry it is. Insert the two prongs of the probe into the soil, plug it into an analog channel of the Grove system, and make your measurements.

Specifications

• 3.3-5VDC
• 0-35mA current draw
• 20 x 60mm (0.78 x 2.36″)
• Reading values
  • 0-300 = dry soil
  • 300-700 = moist soil
  • 700-950 = immersion in water

Links

• Moisture Sensor Wiki
• GitHub – Grove_Moisture_Sensor