On 26/06/13 17:21, newshound wrote:
On 26/06/2013 15:29, thescullster wrote:
Hi all

I have come by an old barometer - something like the item shown here
http://www.hemswell-antiques.com/ant...ter-33028.html


(although not quite of the quality).
Now I know that these devices measure atmospheric pressure, but I am not
clear on how much this will be affected by the instrument location.

Does a heat source like a radiator change atmospheric pressure?
Can I mount this on a wall above a radiator and expect it to work?

From my memory of the barometer, the needle doesn't appear to move much
in operation. Is this because it was previously in a centrally heated
house, or is there likely to be something wrong here?

Thanks

Phil

The heat source doesn't change atmospheric pressure, but the pressure
reading will cycle a little as the instrument temperature changes,
something like 3% for a 10 degree C variation. If the needle isn't
moving much it's likely that the bellows has a leak, or there is a
problem in the (relatively fragile) linkage between the bellows and
the needle.
The latter.
It will almost certainly be what mine is. a teensy sprocket chain round
a drum, very prone to rusting if left in a loft or a shed. I've never
had the aneroid capsule itself go ..on several I have owned over the years.

the final shaft bearing may be seized too. gentle working of the
mechanism and light oil gets it all back.

If a smart tap on the face doesn't cause the needle to jump, its seized
in some way. If it jumps, but doesn't move with the weather, the capsule
has gone.

--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers.