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Strange data appearing from VP/VirtualVP

Discussion specific to Davis weather stations
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broadstairs
Posts: 745
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Weather Station: Ecowitt GW1003/GW1103/GW2000
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Strange data appearing from VP/VirtualVP

Post by broadstairs »

I had a problem yesterday where Weather Display shows a wind gust of 280.5mph for some 16 minutes, the strange data in Cumulus was not the wind, that flatlined, the strange thing in Cumulus was a negative rain rate of -0.3. Now I know none of this was the fault of Cumulus (or Weather Display for that matter). What I am intrigued to try to find out is what on earth data could have been sent to Cumulus which would have caused a negative rain rate to be recorded? Note that there had been no rain up to that point on that day so totals were zero.

Stuart
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steve
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Re: Strange data appearing from VP/VirtualVP

Post by steve »

broadstairs wrote: What I am intrigued to try to find out is what on earth data could have been sent to Cumulus which would have caused a negative rain rate to be recorded?
It would have been sent a negative value for rain rate. So that's what it recorded.

I suppose I could start putting in checks for silly data like I've done for the Fine Offset stations, but I was hoping I wouldn't have to do that for Davis stations.

Steve
broadstairs
Posts: 745
Joined: Thu 14 Aug 2008 7:17 am
Weather Station: Ecowitt GW1003/GW1103/GW2000
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Re: Strange data appearing from VP/VirtualVP

Post by broadstairs »

Well in my experience it is rare for this kind of thing to happen with a Davis station, however its not impossible. Either you get a transmission problem with or from the ISS, sometimes if the battery in the ISS is low things like this can happen. I have also seen problems where the ISS itself develops a fault. So the bottom line is yes it can happen.

Stuart
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steve
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Re: Strange data appearing from VP/VirtualVP

Post by steve »

To communicate with the VP, I use the DLL from the Davis SDK. The DLL has 'error' values which it supplies when something odd happens (e.g. sensor disconnected). You would have thought that they would have checked for negative rain rate and supplied an error value instead - the DLL is supposed to make programming much easier. I have found this not to be the case in some situations, and often regret my decision to use it. This is one reason why you might sometimes see different behaviour from Cumulus and other software connected to the same station via VirtualVP.

Steve
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Paul C
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Weather Station: Davis VP2 with solar
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Re: Strange data appearing from VP/VirtualVP

Post by Paul C »

I had a problem with wind speed and direction overnight. Stopped transmitting at 0315hrs. Yet temp, rainfall continued to work ok. I have been up and checked the box and spun the wind direction manually a few times around a few times and its now working again. I have had my VP2 for nearly 2 years now and as yet havent changed the battery, the solar panel even points North East, somehow its kept going. Perhaps this is a sign to change the battery now

I was thinking of starting a new thread for Weather Station problems, seperate from Cumulus etc ?
Paul C
Brampton, Cumbria, UK
117m ASL
http://www.bramptonweather.co.uk
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steve
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Re: Strange data appearing from VP/VirtualVP

Post by steve »

I changed the battery in my ISS a while back because it was misbehaving. Not sure if it needed it.

I'm happy for hardware discussion to be in the Cumulus forums, under the appropriate station. Which reminds me, I should probably move this thread...

Steve
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