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RG11 Accuracy

Discussion of this sensor and its uses
bruce45
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Re: RG11 Accuracy

Postby bruce45 » Sat Jul 07, 2012 5:19 pm

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.

bruce45
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Re: RG11 Accuracy

Postby bruce45 » Sat Jul 07, 2012 5:48 pm

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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Re: RG11 Accuracy

Postby steve » Sat Jul 07, 2012 5:55 pm

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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Re: RG11 Accuracy

Postby apenwith » Sat Jul 07, 2012 5:59 pm

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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Re: RG11 Accuracy

Postby bruce45 » Sat Jul 07, 2012 6:07 pm

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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Re: RG11 Accuracy

Postby steve » Sat Jul 07, 2012 6:11 pm

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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bruce45
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Re: RG11 Accuracy

Postby bruce45 » Sat Jul 07, 2012 6:16 pm

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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Re: RG11 Accuracy

Postby bruce45 » Wed Jul 11, 2012 9:28 pm

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.


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Re: RG11 Accuracy

Postby duke » Fri Jan 31, 2014 6:56 pm

Does any one have an RG11 with the latest firmware (016) or sent one back for an upgrade. After talking to the guys it should add some accuracy in TBR mode but Hydreon will only post results after a 3 year trial period.
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Re: RG11 Accuracy

Postby dc1500 » Sun Nov 16, 2014 8:15 pm

I may be missing exactly what is trying to be achieved here. But in the wider concept Weather measurements are not absolute, but standardised, so that over long periods they are consistent and can be compared. To a large extent the locations are also standardised as far as is practicable. So for over a hundred years rainfall has been measured in inches (mm) falling over a specific surface area. In the UK the recommendation is for a 5" (127mm) funnel 12" (30cm) above the ground in an exposed location. Clearly deviations from this will cause different readings. The excellent calibration feature in Cumulus allows to calibrate against this - in other words simulating the standard gauge. I do this by regularly comparing readings during different types of rain and applying the most appropriate calibration factor for accuracy. Owing to the small,shallow funnel in my Fine Offset unit discrepancies can still be considerable. For me the best consideration will be to raise and enclose the current receptacle and seal it and insert a 5" funnel. Then calibrate. The problems here may be that in heavy rain the tipper won't keep up and /or the rain won't flow out fast enough due to the increased volume. Has anyone tried this? I appreciate some users may be measuring rainfall for other than meteorological reasons so they will have their own criteria.
Dave
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