The thermistor works by decreasing current resistance in a manner that is inversely proportional to the temperature of the thermistor. The PCB sends a current to the thermistor and can tell whether more or less heat is needed by the resistance.
Wet sensor
Technical specification
TypeWet SensorCompatible WithFerroli Domina 80 E MF01, Ferroli Domina 80 E MF02 and Ferroli Domina 80 E MF03Manufacturer Model No39805620Brand NameFerroli