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 Post subject: Re: RG11 Accuracy
PostPosted: Sat Jul 07, 2012 5:19 pm 
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Joined: Wed Jan 07, 2009 10:36 pm
Posts: 236
Location: Oban Scotland
Weather Station: wh1081
Operating System: xp pro/vista/windows7/windows8
hi Alan

just had a bit play with the rg11 set at 0.001 inches and under light rain comes close to the tip bucket rate.

admit it is early days and need more rain to confirm.

inside the rg11 is two ir diodes and two ir detectors so as long as the drips land on either of the 4 areas it will detect the rain drop. if water runs over the area as in dripping down this could cause false readings.

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 Post subject: Re: RG11 Accuracy
PostPosted: Sat Jul 07, 2012 5:48 pm 
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Location: Oban Scotland
Weather Station: wh1081
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Steve

if this was proved to work would it be possable that if you were changing the tip bucket with a rg11 having someway of changing the tip bucket settings.

the results for light rain looks promising same amount showing for both so far

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 Post subject: Re: RG11 Accuracy
PostPosted: Sat Jul 07, 2012 5:55 pm 
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Joined: Mon Jun 02, 2008 6:49 pm
Posts: 17586
Location: Sanday, Orkney
Weather Station: Davis VP2
Operating System: Windows Home Server 2011
bruce45 wrote:
if this was proved to work would it be possable that if you were changing the tip bucket with a rg11 having someway of changing the tip bucket settings.
Sorry, I don't understand what you're asking.

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 Post subject: Re: RG11 Accuracy
PostPosted: Sat Jul 07, 2012 5:59 pm 
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Joined: Sun Apr 26, 2009 7:30 pm
Posts: 417
Location: West Cornwall UK
Weather Station: w8681 BlakeLarsen Sun Recorder
Operating System: Windows 7 SP1
Hi Bruce
Surely the rain is going to run down so the firmware must somehow take account of that and if runs were detected as well as drops the RG would ovr read.
Regards
Alan


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 Post subject: Re: RG11 Accuracy
PostPosted: Sat Jul 07, 2012 6:07 pm 
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Joined: Wed Jan 07, 2009 10:36 pm
Posts: 236
Location: Oban Scotland
Weather Station: wh1081
Operating System: xp pro/vista/windows7/windows8
Steve

what i was meaning is if you are going to replace the tip bucket on a fine offset unit with a rg11 unit could the tip bucket settings be changed to 0.01,0.001,0.0001 inches. the tip bucket is set at 0.3mm per tip.

Alan

without a diagram of the cct it could be only the 4 areas with either diodes or detectors that records rain. rain on other areas might not trigger a response.

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 Post subject: Re: RG11 Accuracy
PostPosted: Sat Jul 07, 2012 6:11 pm 
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Joined: Mon Jun 02, 2008 6:49 pm
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Location: Sanday, Orkney
Weather Station: Davis VP2
Operating System: Windows Home Server 2011
bruce45 wrote:
what i was meaning is if you are going to replace the tip bucket on a fine offset unit with a rg11 unit could the tip bucket settings be changed to 0.01,0.001,0.0001 inches. the tip bucket is set at 0.3mm per tip.
That's what the rainfall multiplier is for in the calibration settings.

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 Post subject: Re: RG11 Accuracy
PostPosted: Sat Jul 07, 2012 6:16 pm 
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Joined: Wed Jan 07, 2009 10:36 pm
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Location: Oban Scotland
Weather Station: wh1081
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arh right so if the rg11 was set at 0.001 set the multiplier to 10 at 0.0001 set to 100.

thanks

bruce

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 Post subject: Re: RG11 Accuracy
PostPosted: Wed Jul 11, 2012 9:28 pm 
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Joined: Wed Jan 07, 2009 10:36 pm
Posts: 236
Location: Oban Scotland
Weather Station: wh1081
Operating System: xp pro/vista/windows7/windows8
Hi

just had a reply from Hydreon about how the rg11 works.it would seem that it does count the number and size of the drops but works this out from the changing levels of light. so i think having the tip bucket set more sensitive should give more accurate rates.interesting statment in the second paragraph "and not physically measuring the amount of rain. "

the full reply is below

Hello Bruce,

The RG-11 bounces beams of light within the lens. When drops hit the outside surface, it allows some of the beams to escape. The RG-11 detects the change in beam intensity, and determines the size of the rain drop that caused the change. The RG-11 Rain Gauge counts the number and size of the drops hitting the sensing surface. The algorithms within the RG-11 interpret this data and produce the same sort of output produced by a tipping bucket style rain gauge.

One condition that may affect the accuracy of the RG-11 is if small droplets get stuck on the lens. The can happen because of wind pushing droplets back up the surface of the rain gauge, or any other condition which would keep droplets on the lens for a longer than normal period of time. That said, the software is calculating a predicted amount of rain based on data and statistical analysis that we have gathered in the past, and not physically measuring the amount of rain. Even in perfect conditions, there may still be some variation between the RG-11 and an accurate tipping bucket. Hopefully this answers most of your questions.

Regards,
Anders Hendrickson


please feel free to comment of there answer im sure you will.


bruce

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