The RG-11 is a novel, futuristic and relatively inexpensive optical rain sensor. This sensor has particular appeal for hobbyists and experimentalists, including those who need a sensor to trigger some electromechanical action when it starts to rain, as well as for more traditional weather-monitoring applications.
The sensor design consists of a clear hemispherical dome within which a set of 4 light beams are reflected and constantly monitored. The dome also covers a circular circuit board, both attached to a sturdy grey plastic mounting bracket. When rain or some other cause of water droplets start to form on the outside of the dome, the beam reflection pattern changes in a way which can be translated by onboard circuitry and firmware into a carefully-processed output signal. As the water droplets run off or evaporate or are replaced by fresh droplets so the reflection pattern changes and is continuously monitored, with outputs triggered accordingly.
The sensor output is provided by contact closure of a built-in miniature relay with contacts rated at 24v DC and 1A. The output can be connected to a low-voltage circuit such as a counter module for further processing or, alternatively, used to control some external device directly.
Because of its optical basis-- not mechanical, chemical, or conductive, the RG-11 sensor is far more rugged, sensitive and reliable than other technologies. The sensor is extremely sensitive, and virtually immune to false trips. Yet, it is completely unaffected by jostling and motion. There are no exposed conductors to corrode, and no openings for bugs to crawl into. Similarly, there is no place for leaves or other debris to collect. Therefore, once assembled and attached to a suitable mounting point by means of the mounting holes provided in the bracket, the RG-11 sensor is fully weather-proof and can be left outside to continue operation for extended periods, needing absolutely no maintenance or other attention.
The RG-11 is not marketed as a highly accurate rain gauge, but is aimed at three categories of application:
- As a potential substitute for a standard automatic gauge under circumstances where robust, long-term and essentially maintenance-free operation is a higher priority than ultimate accuracy;
- As an adjunct and backup to an existing automatic gauge when the extra sensitivity of the RG-11 can provide more detailed records, for example during minimal rainfall or light/heavy dew events;
- For controlling electrometrical devices during rainfall events or in related circumstances, e.g. when condensation may occur.
Full details about the key features and use of the RG-11 optical rain sensor are provided on the Hydreon RG-11 optical rain sensor page at our Main Site.