Rain Sensors

Rain sensors for irrigation systems are obtainable in both wireless and hard-wired versions, most employing hygroscopic disks that bulge 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 alike mechanisms to momentarily suspend watering by the irrigation controller - purposely they are connected to the irrigation controller's sensor terminals, or are installed in series with the solenoid valve common circuit such that they stop the opening of any valves when rain has been sensed.Some irrigation rain sensors also contain a freeze sensor to keep the system from operating in freezing temperatures Some US states, such as Florida, New Jersey, Minnesota, and Connecticut mandate the use of a rain sensor in all new lawn sprinkler systems.

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