hpa, MB...or what??

[Kafinater]

I've been wanting to get one of these weather station set ups so have bought a Maplins special...WH1081. I think I've pretty much sussed out most things, maybe a few small details will be brought to the Forum now and again, however, in the setting up, I'd like to know how to best to display the pressure.

On my LCD weather station I have displayed for example 1010.1hpa set at rel. I noticed on the stats for a local station on Weather Underground that the figure was much lower, ie 998hpa. Also in Cumulus I changed the prefs from MB to hpa and then read the note that unless its done at set up its all meaningless...So, before I get too many hours into my weather recording can someone advise me what my weather station should be set at, ie, abs, rel, hpa, mmhg...and what I should select on the prefs in Cumulus, ie, MB or hpa

Just one more thing, after selecting abs on the weather station my hpa reading was 989 whereas the local stations hpa was 998, is this difference normal bearing in mind the other weather staion is only a mile away as the proverbial crow flies...or is that another topic...whatever, I'm new to this and advice is required

[steve]

You're OK switching between mb and hPa because numerically they are the same. hPa is the SI unit, and strictly speaking you should use that in the UK, but many people use mb.

You should ignore the 'abs' reading and set the station so that your 'rel' reading is close to a reliable reference (i.e. a Met Office station, airport etc) from not too far away from you.

[Kafinater]

Ok, thanks for that. So my station has a reading of, currently, 1009.6, but a local station to me, about 12 miles south of me is at 993.4, why is there such a difference and can I calibrate it to match other readings? Strictly speaking this isnt a question about the software, more the station, but I guess someone will be able to help!

[steve]

Assuming the other station's reading is actually correct, the difference is because until you actually set the station's barometer, the reading from it is meaningless. It measures absolute pressure (the actual pressure at your location), but in order for the reading to be useful, it has to be adjusted to sea-level equivalent, taking into account your altitude etc. The way you do this is adjust the relative (i.e. sea level) pressure until it matches the sea-level pressure of a reliable reference. The station then maintains the difference between absolute and relative pressure, so that in theory it continues to display the same sea-level pressure as the reference value.

Instructions for adjusting the relative pressure should be in the manual, if you got one. If not, there's a copy in the wiki.

[Kafinater]

Forums never cease to amaze me!

Thanks

[Kafinater]

Just had a look at the wiki and saw what looks to be a link to the PDF for a manual http://wiki.sandaysoft.com/a/Fineoffset_manual but it spoke to me in HTML! What did I do wrong

[PaulMy]

I just tried it and following the appropriate links it displays in pdf.

Paul

[Kafinater]

Hmmm... I did a bit of searching for how to set my pressure on my Station, the WH1081. Found out that by going to various weather stations such as wunderground and weather.co.uk to check the pressure locally, I can use Easyweather to set the stations pressure. In the settings of Easyweather you can edit the values, which I did and blow me it went and told the station the new values and bingo we are all now compatible with readings from the locality. Opening up Cumulus the weather station spread the secret and told Cumulus the news. I'm happy and I think as accurate as I'm going to be