"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.