OT Barometer Location

[thescullster]

Hi all

I have come by an old barometer - something like the item shown here
http://www.hemswell-antiques.com/antiques/barometers/oak-cased-aneroid-banjo-barometer-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

[mark]

"thescullster" <thescu...@dropthespam.com> wrote in message
news:TradnfJEiuBJZ1fM...@eclipse.net.uk...

Not sure about the instrumentation but I don't think it would be a good idea
to put antique oak woodwork above a radiator.

mark

[Frank Erskine]

On Wed, 26 Jun 2013 15:35:21 +0100, "mark"

Especially if the barometer has a built-in thermometer :-)

--
Frank Erskine

[Brian Gaff]

No certainly not it tends to crack.
Actually these are just a sealed bellows I think that operate a needle by
clever gearing.
If the unit is leaky though it will never work. I've not got one now but
they dont seem to care where they are unless you have forced air air
conditioning to keep pressure high, most houses are the same as outside.
I see we are all supposed to be using Hecto Pascals now instead of
Millibarrs etc.
Ho hum, pass me that altimeter.
Brian

--
From the Sofa of Brian Gaff Reply address is active
"mark" <ma...@reepham2003.force9.co.uk> wrote in message
news:JsGdnTXVQNSaYVfM...@brightview.co.uk...

[Brian Gaff]

Or indeed a hygrometer as mine had.

Brian

--
From the Sofa of Brian Gaff Reply address is active

"Frank Erskine" <frank....@btinternet.com> wrote in message
news:qb0ms89l7q8k5uitu...@4ax.com...

[Nick]

"thescullster" <thescu...@dropthespam.com> wrote in message
news:TradnfJEiuBJZ1fM...@eclipse.net.uk...

Location will not affect the baro, but it will affect the thermometer and
possibly the wood.
Don't know much of aneroids, prefer mercury.
As regards movement of the needle.
Set baro in desired position. Align the cursor with the hand. Repeat at 10am
every day of course.
Note the movement of the hand over a 24hr period.
If the swing is 30 deg or more- Sun hat if up, raincoat, hat & wellies if
it's down. Do you have a dinghy?
Just keep an eye on it for a few days. I suspect most aneroid baros would
not be repairable. TBH, they're not worth it.
I think the seller of the item you show is utterly and completely off
trolley. Delete the first number, divide the remainder by two and you might
be in the real world.
hth Nick.

[Dave Liquorice]

On Wed, 26 Jun 2013 15:29:40 +0100, thescullster wrote:

> Does a heat source like a radiator change atmospheric pressure?

Not that would be measurable by that instrument in a normal (non-air
tight) house. B-)

> Can I mount this on a wall above a radiator and expect it to work?

I wouldn't, as others have said the oak won't like it and if you are
getting wide temperature variations (rad on v rad off) that could
affect the readings as the works expand/contract. Try an find a place
with a fairly stable temperature to be kind to the wood and the
instrument.

> 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?

Well ATM the UK is under the influence of a high pressure and it's
not changing very much at all.

Normal sort of range would be about 29.25" to 30" of mercury (1000 to
1030 mb) changing from one to the other normally over couple/three
days. Though it can change faster. These type of barometers might
need a gentle tap to make the needle move properly to the current
pressure reading. There also ought to be a small adjustment screw to
compensate for your locations altitude, so the instrument reads "sea
level" pressure. Now is not a bad time to check that as most of the
country is pretty much at 1032 mb (30.5" Hg)

Depending on how windy it is and how exposed/draughty your house is
that can cause a few mb of reduced pressure inside by venturi effects
of chimneys etc. I've noticed on several occasions when a gale
suddenly stops there is a coresponding step up in the air pressure.

--
Cheers
Dave.

[newshound]

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.

[Harry Bloomfield]

thescullster was thinking very hard :

Pressure is the same pressure irrespective, providing it is in the same
geographical area. So mount it in any sensible location, but not over a
radiator as that will affect the wood. You can calibrate it, by
comparing it to your local weather station - note the pressure
indicated by your instrument, at the times the pressures are suggested
to be have measured, then compare your reading with what they suggest
the pressure was at that paticular time. From that, you should be able
to work out what your error was and make an adjustment.

Best to do it when the pressure has been steady for a good while
though, when the isobars are widely spaced / not much wind.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

[harryagain]

"thescullster" <thescu...@dropthespam.com> wrote in message
news:TradnfJEiuBJZ1fM...@eclipse.net.uk...

Re the instrument itself, it measures air pressure.
The only influence you have on it's reading is the altitude of your house.
(Altitude also affects air pressure)
Normal pressure is 1013mB.=760mm of Hg

They often don't work because the stack of capsules inside develop cracks.
It is and aneroid barometer.
http://en.wikipedia.org/wiki/Barometer#Aneroid_barometers
There are specialist repairers of them

[The Natural Philosopher]

On 26/06/13 15:29, thescullster wrote:
> Hi all
>
> I have come by an old barometer - something like the item shown here
> http://www.hemswell-antiques.com/antiques/barometers/oak-cased-aneroid-banjo-barometer-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.
>

Unless in a hermetically sealed room, not at all.

> Does a heat source like a radiator change atmospheric pressure?

Nope,
But it can affect instruments in any case. But normally yoi calibarte
once its oin its final location.

> Can I mount this on a wall above a radiator and expect it to work?
>

yup

> 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?
>

no its because the air pressure only moves slowly over days.

> Thanks
>
> Phil


--
Ineptocracy

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[The Natural Philosopher]

I did repair one I got at auction. REMARKABLY similar to that.

It turned out there was a little teeny bicycle chain inside it that
connected the capsule to the pointer shaft and that was all rusted up.
Some easing oil and brushing with paraffin got it all cleaned up and
free, then it got some very light machine oil.

> I think the seller of the item you show is utterly and completely off
> trolley. Delete the first number, divide the remainder by two and you might
> be in the real world.
> hth Nick.

i think I had to bid against another nutter like me and i paid 85 quid.

I like shit like that.

[The Natural Philosopher]

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.

[Phil L]

It needs to be in a hallway, near an elephant's foot full of walking sticks
and umbrellas, and you need to tap it with your pipe every day before you go
outside.

[Tim+]

Are you quite sure it's aneroid? You do get mercury gauges (with a "clock"
display) and you need to a bit careful handling those.

Tim

[thescullster]

On 26/06/2013 15:29, thescullster wrote:

Many thanks to all respondents - I'll give it a tap with my pipe and see
what the needle does!

Looks good held up above the hall rad, but I understand the concerns
over the wood.

Phil

[Grimly Curmudgeon]

On Wed, 26 Jun 2013 16:21:55 +0100, "Brian Gaff"
<Bri...@blueyonder.co.uk> wrote:

> I see we are all supposed to be using Hecto Pascals now instead of
>Millibarrs etc.

Fuck the Frogs - that's a slap in the face for the Barrs.