"Gianna Stefani" wrote in message
...
"Martin Rowley" wrote in
message
...
I adjusted it on taking it from its packaging (April) and set it as
suggested by the Met Office information (web site) ... I recall it
took two
or three attempts to get it 'just so'. I compared my results daily
with
local reports and was not more than 1 mb different (in either
direction) at
any time during the first month or so. As these differences were
higher or
lower, not always high or always low,

.... try monitoring on a daily basis what you read and what the nearest
observation is at the same time - plot these out on a graph such that
you get a scatter diagram and see if you can draw a line of best fit
(might not be a straight line - might be a curve ... if as you say the
differences are greater at the 'edges' of the range).

If there is no obvious clustering around a particular line, I would
suspect that the errors are random and there would be little you could
do to relate your instrument to the mslp pattern. However - see below.

Also make sure that there are no sources of heat (either radiators, or
direct sunshine) in the vicinity - the unit should be in a thermally
stable environment as far as possible.

I have another (old) barometer in the house which is of a less
accurate
nature, but that is reading over 1040 today (1043 on the Diplex).

.... don't assume the 'old' barometer is no good! In my experience, some
of these (and we have one that is at least 70 years old) are more
accurate than the stuff you can buy today.


As you have raised the issue of accuracy, perhaps you can help me
here -
there has been no noted inaccuracy in my observations of pressure
which has
generally been between 990 and 1030 (rounded figures) during the time
I have
been recording ...... is there a possibility / probability that any
inaccuracy in my barometer will be more pronounced when the pressure
is
higher than that ?

.... yes indeed; if you follow the procedure above, and over a reasonable
length of time (at least 3 months with at least one observation daily),
then you will see if the pattern is systematic or random ... if the
latter then there is little you can do; if the former then you will be
able to work out corrections for different readings of your instrument.

Unless you are on a North Sea oil rig as I send this (07/1100Z or midday
local), then your pressure should not be above about 1040mbar.

Good luck!

Martin.

"Martin Rowley" wrote in message
...


... try monitoring on a daily basis what you read and what the nearest
observation is at the same time - plot these out on a graph such that
you get a scatter diagram and see if you can draw a line of best fit
(might not be a straight line - might be a curve ... if as you say the
differences are greater at the 'edges' of the range).


I will do that and compare it with the station reports on the BBC site as
that is the neares I know of.

If there is no obvious clustering around a particular line, I would
suspect that the errors are random and there would be little you could
do to relate your instrument to the mslp pattern. However - see below.

Also make sure that there are no sources of heat (either radiators, or
direct sunshine) in the vicinity - the unit should be in a thermally
stable environment as far as possible.


It is situated in the screen with the thermometers and hygrometer - it
cannot get direct sun / wind etc.

I have another (old) barometer in the house which is of a less
accurate
nature, but that is reading over 1040 today (1043 on the Diplex).

... don't assume the 'old' barometer is no good! In my experience, some
of these (and we have one that is at least 70 years old) are more
accurate than the stuff you can buy today.


My fault - I meant an "old cheapie" barometer - it is too small and too
inaccurate to use for recording, but was a reasonably useful indicator.
I agree with your point re the 'good old' barometers and remember large
brass-cased examples from my childhood.


Unless you are on a North Sea oil rig as I send this (07/1100Z or midday
local), then your pressure should not be above about 1040mbar.


I was not at home at the time mentioned .... I have 1041 mb at 1430 local.

Good luck!


Thanks for your help - I shall persevere.

Gianna

"Gianna Stefani" wrote in message
...
"Martin Rowley" wrote in
message
...


Thanks for your help - I shall persevere.


.... it's probably worth saying as well, don't get too 'hung up' on the
absolute value! Obviously today is an interesting situation, but for
most purposes, your unit sounds as if it is giving a reasonable idea of
the 'ups and downs' in the pressure field, and it is these, particularly
the rate of change over 3, 6, 12 and 24hr that are important, rather
than the value itself.

Martin.

--
FAQ & Glossary for uk.sci.weather at:-
http://homepage.ntlworld.com/booty.weather/uswfaqfr.htm

"Martin Rowley" wrote in message
...

... it's probably worth saying as well, don't get too 'hung up' on the
absolute value! Obviously today is an interesting situation, but for
most purposes, your unit sounds as if it is giving a reasonable idea of
the 'ups and downs' in the pressure field, and it is these, particularly
the rate of change over 3, 6, 12 and 24hr that are important, rather
than the value itself.

Thank you for your help on this, and yes, I agree with your point on the
absolute value - I did not mind that it was +/- 1 when I began recording -
the nearest official station is far enough away for my reading to have as
good a chance of being correct as incorrect - and as you say, it is the
pattern in the data which matters most.

I was quite uncomfortable today with recording a 'record' reading
(regardless of if it was right or wrong) as on uncertified equipment it
would not be a 'record' anyway.

I shall repeat the comparisons which I made when I got the unit, but for the
longer period as you suggested - it will be interesting - and gives me more
statistics to analyse - every cloud .......

Gianna

"Martin Rowley" wrote in
message ...

"Philip Eden" philipATweatherHYPHENukDOTcom wrote in message
...
If the models are remotely right for the beginning of next
week, we are in for a new record sea-level pressure for
September in the UK. The models suggest anything up to
1043mbar whereas the record stands at 1041, and that
occurred late in the month when one would expect to get
higher values. A quick search indicates nothing above
1038 mbar in the first half of the month.

... worth keeping an eye on the pressure levels across NE Scotland
today (Tuesday). At the moment 08Z, general values appear to be
above 1039mbar, with a spot 1040mbar on the 00Z Exeter analysis.

Looks as though the highest sea-level pressure was
1040.8 mbar at Inverbervie (03088) at 22z on the 7th.
This is on a par with September record which unfortunately
I only have as c.1041mbar at Shawbury on 19th Sept '86.

It's undoubtedly a new record for the first half of Sept.

Philip Eden

"Gianna Stefani" wrote in message
...

I shall repeat the comparisons which I made when I got the unit, but for
the
longer period as you suggested - it will be interesting - and gives me
more
statistics to analyse - every cloud .......


If anyone with similar equipment is following this thread, it may be worth
noting that the unit appeared to be reluctant to fall back from its
around-1042 position this morning (the pressure was 1038 at the time) - I
hesitate to use the word 'stuck' .........

Consequently, I removed it from its location, reset it, and re-installed it.
It has followed the lowering pressure during the day and is reading
accurately thus far.

I shall keep an eye on it (watch it like a hawk).

I am interested in hearing from anyone who also uses that brand (Diplex).

Gianna