EARTH unit is a Soil Moisture Sensor for measuring the moisture in soil and similar materials. The soil moisture sensor usage is pretty straight forward, the two large exposed pads function as probes for the sensor, together acting as a variable resistor. The higher moisture that is in the soil means the better the conductivity between the two so that the sensor will result in a lower resistance, and a higher SIG out. You can read the moisture in soil by using the ADC. Inside this Unit we've added an extra potentiometers to change the measurement range. Product Features Adjustable threshold, including 10K adjustable resistor Analog & Digital output GROVE interface, support UIFlow and Arduino Two Lego-compatible holes Color: White Material: plastic Package Contents: 1x EARTH unit 1x GROVE Cable Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.