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Rain measurement: Difference between revisions
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{{Version badge 1}}This page was written when only the legacy software was available. All cross-references are to other legacy pages, this page has not been updated for MX yet. | |||
Rain is measured using a rain gauge (also known as a udometer or a pluviometer [Pluviograph ] which gathers and measures the amount of liquid [http://en.wikipedia.org/wiki/Precipitation_(meteorology) precipitation] over a set period of time. | Rain is measured using a rain gauge (also known as a udometer or a pluviometer [Pluviograph ] which gathers and measures the amount of liquid [http://en.wikipedia.org/wiki/Precipitation_(meteorology) precipitation] over a set period of time. | ||
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== Rain day == | == Rain day == | ||
The threshold value which the daily rainfall has to equal or exceed for the day to be considered a 'rain day' is set in [[Cumulus. | The threshold value which the daily rainfall has to equal or exceed for the day to be considered a 'rain day' is set in [[Cumulus.ini_(Cumulus_1)#Section:_Station | RainDayThreshold]] and has a default value of ''-1'' that means 0.2mm or 0.01in. Alternative thresholds can be used by specifying a number in the units your configuration uses. | ||
== Cumulus View Menu == | == Cumulus View Menu == | ||
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== Optical Rain Gauges == | == Optical Rain Gauges == | ||
#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. | #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, via parameters in [[Cumulus. | #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, via parameters in [[Cumulus.ini_(Cumulus_1)#Hydreon_specific:]] that are set using a RG11 screen within the configuration menu. Use a USB to RS232 (serial) adapter on computers which don't have a COM port. See Cumulus ''help'' for more information. The rain sensor's 'normally open' relay contacts should be connected via a serial port (9 way connector) | ||
#*either to the Data Set Ready (pin 4) and Data Terminal Ready (pin 6), | #*either to the Data Set Ready (pin 4) and Data Terminal Ready (pin 6), | ||
#*or to the Request To Send (pin 7) and Clear To Send (pin 8)]. | #*or to the Request To Send (pin 7) and Clear To Send (pin 8)]. | ||
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= Making comparable with official sites = | = Making comparable with official sites = | ||
[http://www.bom.gov.au/climate/how/observations/rain-measure.shtml| This | |||
It is important to note that Cumulus attributes rainfall to the date when the measuring period starts. [[meteorological day|Some nations attribute rainfall]] to the day when the measuring period ends. | |||
[http://www.bom.gov.au/climate/how/observations/rain-measure.shtml| This Australian web site] used to explain more, but they have since reorganised their web site, can anybody identify the new link and update this page. | |||
[[Category:Terminology]] | [[Category:Terminology]] | ||
