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Weather Station Hardware => Hydreon RG-11 Optical Rain Gauge/Sensor => Topic started by: SLOweather on November 14, 2011, 04:52:25 PM
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Friday we got some rain. I was out in it, wiring up an RG-11 in drop counting mode to get a feel for how it works. It was pretty cool to see the OUTPUT LED flash every time it detected a drop.
The storm wasn't very varied in rainfall intensity, so I didn't get to make a lot of observations. I timed 10 drops on the counter at 1 minute, looked out the window and called it a light rain, and then checked the rain rate on my VP2 at about 0.25" per hour.
So there's a baseline to start playing with integrating drops into an analog voltage intensity value.
The RG-11 was set in 100 ms/drop counting mode since I didn't have a way to differentiate between larger drops/longer pulses in the other mode.
This experiment begins to reveal how the unit functions inside. I don't have the actual numbers at hand right now, but roughly 6,000 counted drops equaled 0.65" of rain.
When I was timing the drops, it took a longer that I expected to count up some consecutive drops. Empirically, for an hour while it was raining, I studied the rainfall pattern in a 7 foot square collector, as well as in a collector about the same diameter as the RG-11. It was interesting to see the size of the drops affect the size of the splash, as well as how few drops actually made it into the small collector for the intensity I perceived.
(Translation: I sat in the hot tub while it rained and drank a glass of wine. :) )
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It's raining pretty well this afternoon (up to 1" per hour), and I have an answer to one of my open questions about how this works in single drop sensing mode. I hooked up a lighted relay to it, and it's chattering away like a Morse Code sounder. When the RG-11 senses a new raindrop before the 100 ms is up for the previous one, it just holds the relay closed longer.
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When the RG-11 senses a new raindrop before the 100 ms is up for the previous one, it just holds the relay closed longer.
It's a shame that the documentation isn't more detailed on this mode. Sounds like you're in 1ppd (pulse per drop) mode rather than multi-ppd (DIP #3 on) mode. Are the pulses really 100msec - documentation seems to suggest 200msec in the 1ppd mode? Just fine detail of course, but interesting to try to pin down the operating characteristics more exactly.
One other question: are you in micro-power mode? I guess possibly not? It does seem to me that the only way to run the RG-11 at many remote sites will be in micro-power mode - the current drain would be too great to run long-term in standard mode with eg just D cells, unless you have access to a mains power or a big-panel solar PSU. And then there's a question of just how much rain is needed to wake the RG-11 from the sleep state in micro-power mode - hopefully not too much (maybe eg just 0.1mm or some such), but it would be useful to get a fix on.
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If you write them at info@hydreon.com I'm sure they would be able to answer all of your questions. I'm not using micro-power mode on any of the 3 units I have running.
Yesterday in some pretty heavy rain (>1.5" per hour) I was watching the "sounder relay" installed on the single-drop unit. The longest I saw it stay on was about 7 seconds.
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I have my RG-11 working......
System is an Argent Data WS-1 with the RG-11 in place of the tipping bucket. I process the output of the WS-1 on an embedded Linux system. So far, not enough rain here to judge the accuracy.
Has anyone got enough data to determine if the RG-11 is as good as that graph they show on their webpage?
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Has anyone got enough data to determine if the RG-11 is as good as that graph they show on their webpage?
Not as yet, but as soon as the revised-firmware sensors arrive here I'll be setting up a trial at a location where professional quality rainfall readings are taken on a daily basis. Probably won't be enough data to get a good sense of RG111 accuracy until Jan/Feb at least but I'll make the results available.
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Thanks for the detailed account. I think this is a fascinating device (if it works).
I studied the rainfall pattern in a 7 foot square collector, as well as in a collector about the same diameter as the RG-11. It was interesting to see the size of the drops affect the size of the splash, as well as how few drops actually made it into the small collector for the intensity I perceived.
(Translation: I sat in the hot tub while it rained and drank a glass of wine. )
I was really wondering what type of fancy-schmancy professional rainfall-pattern observation system you were using. Perhaps you shouldn't have given away your secret. It looks like a valid tax write-off for your "research equipment" to me.