EARTH unit is a Soil Moisture Sensor for measuring the moisture in soil and similar materials.
The soil moisture sensor is pretty straight forward to use. 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 ADC.Inside this Unit we put an extra potentiometers tochange the measurement range.