This sensor bases its operation on the variation in resistance between its two contacts in the presence of liquid to commute a switch reed from open to closed, commuting to open again when the liquid disappears (take care when it is used to detect liquids of high viscosity which may remain between the terminals blocking its drainage and preventing it from re-opening).
Sensor specifications
Maximum Switching Voltage: 100 V
Operating temperature: +5 ºC ~ +80 ºC
Detectable liquids: Water