In this plot:
http://img824.imageshack.us/img824/3451/cumrelpress.png
I show a comparison between my barometer and the one in an AWS which is about 200 m away. Over the few days of record, there was quite a large variation in atmospheric pressure.
The stats of the difference are:
Mean: 0.123 hPa - this is just an offset
Std Dev: 0.322 hPa - this is the important number
Skewness: 0.126 - close to zero
Kurtosis: -0.120 - close to zero
which means that the errors are normally distributed and for 95% of the time, my barometer is within +/- 0.6 hPa of the AWS.
What this shows is that our barometers that cost a few dollars are almost as good as the Vaisala in this AWS which cost more than $1,000.
Not bad, eh?
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Latest Cumulus MX V4 release 4.4.2 (build 4085) - 12 March 2025
Latest Cumulus MX V3 release 3.28.6 (build 3283) - 21 March 2024
Legacy Cumulus 1 release 1.9.4 (build 1099) - 28 November 2014
(a patch is available for 1.9.4 build 1099 that extends the date range of drop-down menus to 2030)
Download the Software (Cumulus MX / Cumulus 1 and other related items) from the Wiki
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Accuracy of Fine Offset barometer
- steve
- Cumulus Author
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Re: Accuracy of Fine Offset barometer
When I last did some comparisons, my Fine Offset barometer tracked my Davis VP2 barometer quite closely, and similarly the outside temperature. For other readings, it wasn't so good. Rainfall, wind and humidity were all considerably different. Wind comparisons are a little unfair as they're not quite mounted at the same height.
Steve
- Repairman77
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- Operating System: XP pro SP3
- Location: Cambridgeshire UK
Re: Accuracy of Fine Offset barometer
Yes the barometer does seem fairly accurate when it's in an aspirated container (fan on top of extended sensor unit) and doesn't suffer from too many temperature and humidity problems.
Tracks my Altimeter quite well now.
Mike.
Tracks my Altimeter quite well now.
Mike.
Retired Radio and Electronics Engineer residing in Cambridgeshire, UK.
-
hills
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Re: Accuracy of Fine Offset barometer
That's good to hear.
My rain gauge is proving to be very consistent with 2 manual rain gauges I have in the garden. My FO gauge is currently reading 101.2mm for the month and one of my manual gauges which is over 5m from any structure is reading about 102mm and the other is reading over 105mm, but that one is too close to the house and I suspect is getting some spray off the roof in very heavy falls.
I can't compare the wind to any other stations though as we're on the southern side of a large hill (Mt Lofty) and tend to get slightly different wind conditions to the rest of Adelaide.
My rain gauge is proving to be very consistent with 2 manual rain gauges I have in the garden. My FO gauge is currently reading 101.2mm for the month and one of my manual gauges which is over 5m from any structure is reading about 102mm and the other is reading over 105mm, but that one is too close to the house and I suspect is getting some spray off the roof in very heavy falls.
I can't compare the wind to any other stations though as we're on the southern side of a large hill (Mt Lofty) and tend to get slightly different wind conditions to the rest of Adelaide.