In most flood alert systems, rain precipitation is an early warning for floods. A rain sensor, also sometimes referred to as a rain switch, is a sensing device activated by the presence of rainfall .Currently in our inventory we have two rain sensors. Each has its own set of uses depending on environmental conditions. They are typically located atop of a pole that is firmly secured to the ground.  Rain sensors will typically have a wire going from the sensor to the RTU.
The sensor depicted below in the event of rain, detects raindrops with the help of electrified metal contacts. It forms a conductive link between both electrodes on the sensor surface and trigger a switching signal. Once the surface has dried off, the relay drops out again after a delay.
The sensor surface is equipped with 2-stage heating. The first stage is permanently activated and prevents the sensor surface from either freezing over or thawing. The second stage is switched on when it begins to rain in order to ensure that the surface is dried quickly.
Its key features include compact size, rain and snow detection, binary signal output, internal heating mechanism (to allow operation in temperatures as low as -30°C) and IP65 Safety-Class certification.

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