water sensor or rain sensor?

Question

WORKING PRINCIPLE OF WATER SENSOR WITH LINK

Answer 1

Rain sensors for irrigation systems are available in both wireless and hard-wired versions, most employing hygroscopic disks that swell in the presence of rain and shrink back down again as they dry out - an electrical switch is in turn depressed or released by the hygroscopic disk stack. However, some electrical type sensors are also marketed that use tipping bucket or conductance type probes to measure rainfall. Wireless and wired versions both use similar mechanisms to temporarily suspend watering by the irrigation controller - specifically they are connected to the irrigation controller's sensor terminals, or are installed in series with the solenoid valve common circuit such that they prevent the opening of any valves when rain has been sensed.

Answer 2

The most common water sensor is two wires close together connected to an amplifier chip that detects the small current when water bridges the two wire, either because the basement has flooded or a rain drop has fallen on the wires. Modern drop sensors use a printed circuit to put more lines of conductors in the path of rain drops. As stated, a funnel can be used to collect enough water to have weight to sense pressure or use a photocell to detect the drops.