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WMR200A problem with Rain Reading in Cumulus 1.9.2

Discussion specific to Oregon Scientific weather stations
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MarystownWeather2012
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WMR200A problem with Rain Reading in Cumulus 1.9.2

Post by MarystownWeather2012 »

I have a Oregon Scientific WMR200A that is linked into Cumulus 1.9.2 software.

Cumulus software is reading rain in whole numbers. Like, 1.0MM , 2.0MM and so forth. Yet my station is report readings 1.5MM , 0.7MM and so forth.

Does anyone know how to fix this in the Cumulus software? I have data logger enabled.
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steve
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Re: WMR200A problem with Rain Reading in Cumulus 1.9.2

Post by steve »

The WMR200A rain gauge has a resolution of 1mm, i.e. one tip of the gauge is 1mm, so it's not possible for Cumulus to record rain totals that aren't whole numbers of mm, and nor can the console. I think you must be looking at some other figure on the console - the rain rate, perhaps?
Steve
g0wfs
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Re: WMR200A problem with Rain Reading in Cumulus 1.9.2

Post by g0wfs »

steve wrote: I think you must be looking at some other figure on the console - the rain rate, perhaps?
FWIW: My WMR200 and additional WMR100 consoles do this too??

E.G the WMR200 console display can show " Past 24hrs 2.1mm".

And the WMR100s will show the same (for accumulative total), as well as being able to view the history for the same time period (by spinning the wheel)e.g..

"-1 hour 1.0mm"
"-2 hours 1.1mm"

Accumulative totals on the consoles are not always rounded to 1mm either. You can often see a total like say 56.1mm or 56.8mm? And not 56mm or 57mm, rounded, if that makes sense?

If you reset the the console(s) and sender unit (all at the same time), everything is 0.0 as expected. But as soon as bucket tipping starts, it isn't long before you start to see .somethings re-appearing again?

You never see a figure of less than 1mm when viewing the history on the consoles, but often see figures above 1mm resolution. E.G when looking over the last few hours you may see 1.2mm for one of them, but you never see a figure like 0.8mm (impossible).

Now, logic says that 1mm bucket tips mean accumulative totals (on the console) would read like, 22.0, 23.0, 24.0 and so on. But this is simply not the case here. E.G I recently reset my rain gauge along with the totals on the consoles. Right now I have 2.1mm of rain showing in the "last 24 hours". Which is also shown as two separate hourly entries of 1.0 and 1.1mm in the hourly history. My accumulative total (shown on both the WMR100 and WMR200 consoles as "Accum") is currently 56.8mm?

Make of that what you will? Because it's been boggling my mind for a while now? :?

And the odd thing is, the over all totals are really quite consistent with both of my FO stations? As well as a good old manual rain gauge stuck in the middle of the lawn.
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steve
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Re: WMR200A problem with Rain Reading in Cumulus 1.9.2

Post by steve »

It appears that the resolution is actually 0.04 inches (the station's 'native' rain unit is inches) which is slightly more than 1mm, so after several tips, the discrepancy is enough to make an extra 0.1mm. I've just been experimenting with mine, and Cumulus does display fractions of mm after a few tips. What it won't do is display exactly the same fractions as the console because of the different ways that the console and Cumulus calculate ran totals. Neither the console nor Cumulus should display those fractions, really, as it implies an accuracy that the station doesn't actually have.
Steve
g0wfs
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Re: WMR200A problem with Rain Reading in Cumulus 1.9.2

Post by g0wfs »

Steve,

Since posting my last, I have been digging around looking for an answer on this and discovered the following on OS tech support..
The rain gauge collects rain into the pivot-point of a two-sided "bucket." When one side fills, it pivots down, causing the "bucket-tip" to be recorded, emptying the bucket and bringing the empty side under the collection point. Each bucket-tip occurs when 0.04 inches (1 mm) of rain has been collected. After at least two bucket tips, software calculates rainfall in inches/hour.
Note the very last sentence?

That perhaps explains quite a lot.

As you say, the native rain unit is inches?

E.G logic says that 5 bucket tips at 1mm each is equal to 5mm? But this may not be the case, because it's actually taking an inch per hour rate from those 5 tips and then converting it back to mm. Which will often not be whole (mm) values. For example, 5 bucket tips would be around 4.9mm when converted back, not 5mm as human logic might tend to think.

That would explain why the console(s) often shows values after the decimal point, because they are NOT counting bucket tips as whole mm numbers, but rather as conversions of the hourly inch rate.

May be wrong of course, but makes perfect sense.
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Re: WMR200A problem with Rain Reading in Cumulus 1.9.2

Post by SUBYDAZZ »

I have only recently purchased a WMR200 and am very disappointed by the way it "calculates" rainfall and the accuracy. At a price nearly 3 times what my old Fine Offset station cost and being advertised as a "Professional" weather station you'd think it'd be a lot better than that. A rain event of 1mm (minimum which it shows it's has rained) is quite a rare event where I live, and it's pretty frustrating to see that more often that not when it has rained here, the sensor reckons it hasn't. Is there any way around the issue with this? I'm thinking of junking this station because of this and the poor resolution of the barometer.
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steve
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Re: WMR200A problem with Rain Reading in Cumulus 1.9.2

Post by steve »

It was one of the things I didn't like about my first weather station, an Oregon Scientific WMR928, which also had a resolution of 1mm. So I fitted a funnel to the rain collector to increase the area, and set a multiplier in Cumulus, so that each tip was 0.2 mm (if I remember correctly).

The poor barometer resolution was the other thing I didn't like about it!
Steve
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