the voltage.
0 to 1.1V VWC= 10V-1
1.1V to 1.3V VWC= 25V- 17.5
1.3V to 1.82V VWC= 48.08V- 47.5
1.82V to 2.2V VWC= 26.32V- 7.89
2.2V to 3.0V VWC= 26.32*V- 7.89
if you are planning to purchase a new unit, it will also calculate the moisture( real VWC), temp and EC.