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.