Why do barometers have different centre readings? I thought 1000 mbar was average, as that's what barometers always used to have as the central reading ("change"), but Wikipedia says it's 1013. I've seen some newer ones with 1010 as the centre.
Barometers and average pressure
Feb 06, 2020
Last reply: 6 years ago
25 Replies
In space the average is 0 mbar
The same as the pressure between your ears.
On mine it's 29.5 inches
Barometers tend to be used on the ground.
So how come the bar was taken to be slightly different to mean sea level pressure? Was it measured inaccurately when they invented it?
A bar is not defined as 1 atmosphere (average) pressure. Just happens to be close (within 1% of it).
1 bar is equivalent to 100 kPa where 1 Pa (Pascal) is a defined SI unit pressure of 1 Newton per m2.
Phwoar! ;-)
All mine have both measurements. It would appear it should be corrected for altitude, but that would mean a rotatable dial. I've got an app on my phone that does it, it'll be interesting to see if it changes the centre position with altitude, 1010 mbar is about right for here.
So pot luck or something inaccurate in the past? The history of it sounds interesting.
Religious folk would say this was a 1% error made by god :-) So he isn't infallible!
Oh I'm not so sure. It does get a little awkward with QNH and QFE, the latter being field elevation of course. Brian
What exactly do you mean by centre and average pressure. Surely with a barometer all you need to know iis the standard elevation of where it is and its then judged relative to that. Brian
Or an adjustment screw on the back for an aneroid barometer or a moveable linear scale on a mercury one. About 50 mb of adjustment needed here.
Yes it could be easily done. Although.... should it be done? If you're at a higher altitude, you have lower pressure, but you also have more cloud. Clouds tend to hang around mountains.
Which is why you have to compensate for altitude. Current standard pressure is about 1020 (Set Fair). Current real pressure is 970 (Stormy). The weather is dead calm, clear and dry. ie that associated with 1020.
Crap barometer or you've not found tweak yet.
Snap.
SteveW
Show me a photograph of your model of barometer that has this.
Are you one of those Merkins?
y barometer has the name of an old established Edinburgh company on the dial.
F*ck off Hucker.
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