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Rain measurement: Difference between revisions
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The advantages of this type of gauge over tipping buckets are that it does not underestimate intense rain, and it can measure other forms of precipitation, including rain, hail and snow. These gauges are, however, more expensive and require more maintenance than tipping bucket gauges.
== Optical Rain
One design has a row of collection funnels. In an enclosed space below each funnel is a [http://en.wikipedia.org/wiki/Laser_diode laser diode] and a [http://en.wikipedia.org/wiki/Photodiode phototransistor detector]. When enough water has been collected to form a single drop it drips from the bottom of the funnel, falling into the laser beam's path. The detector is set at right angles to the path of the laser beam so that light scattered by the drop of water breaking the laser beam is detected as a sudden flash of light. The flashes from these photodetectors are then read and transmitted or recorded.
The [http://www.rainsensors.com/| Hydreon Optical Rain Sensor] - Model RG-11 - uses an infrared sensor to detect rainfall with high precision. Some car windscreens have a similar sensor to automatically start wipers. Cumulus supports the RG11, [[Cumulus.ini#Section:_Station| via parameters in cumulus.ini Station section]] that are set using a RG11 screen within the configuration menu. It should be connected via a serial port [the rain sensor's 'normally open' relay contacts should be connected either to the Data Set Ready (pin 6 of 25 way 'RS232 standard' connector) and Data Terminal Ready (pin 20), or to the Request To Send (pin 4) and Clear To Send (pin 5)]. You can connect two RG-11 sensors to the same port, one to DTS/DTR and one to RTS/CTS. Use a USB to RS232 (serial) adapter on computers which don't have a COM port. See Cumulus ''help'' for more information.
=Rain Gauge Location=
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