Hello,

I have recently purchased a technoline WS-3500 weather statio and I am
having trouble understanding how to set the setting for "relative
pressure". I am told that I set this setting to a reading that I can
get from the BBC website for my area and thats it job done? I am
confused as the reading I enter into this setup option is different
from what is read on the actual pressure display - why are they
different and what is the correct way to set this parameter?

Many thanks in advance

Gary

wrote:

get from the BBC website for my area and thats it job done? I am
confused as the reading I enter into this setup option is different
from what is read on the actual pressure display - why are they
different and what is the correct way to set this parameter?

What they call 'relative pressure' is usually called 'sea level
pressure', that is, the pressure that your barometer would be reading at
your location if you were at sea level. This is same pressure that will
be quoted on web sites such as the BBC or Met Office etc.

You may well be setting it correctly, but have you told it to actually
*display* the 'relative' pressure rather than the 'absolute' pressure? I
believe you need to press the pressure section on the display twice.
--
Steve Loft, Glenlivet. 200m ASL
Weather and webcam:
http://www.livet.org.uk/weather

i don't know if this answers your question but, the difference is Relative
Pressure takes into account your current location (i.e. Altitude), and
Absolute Pressure is pressure at sea-level. As for setting that parameter,
i think it differs from weather station to weather station. My weather
station, i simply had to enter the current relative pressure once, and now
its set.

Hope this helps

Mike

www.dudleyweather.pwp.blueyonder.co.uk

Gazza wrote:
I think I understand now. So if I enter the data from the BBC site into
my relative pressure setting the pressure display shown on the weather
station itself will adjust somehow using the entered value as a
reference and offset it somehow thus giving a different reading?

So how does the weather station know how much offset to add?

Thanks again in advance

Gary

That's why you have to enter the current sea level pressure - so that
it knows what the offset is!

Say the sea level pressure is currently 1025mb. The weather station
pressure sensor is reading 1015mb. The offset is 10mb, and once you
have entered it, this will allow the weather station to display correct
sea level pressure.

IIRC, atmospheric pressure falls by 1mb approx with every 9 metres
gained in altitude (at low levels). So the 10mb difference in my
example would be correct if you are about 90 metres above sea level.

wrote:
Gazza wrote:
I think I understand now. So if I enter the data from the BBC site into
my relative pressure setting the pressure display shown on the weather
station itself will adjust somehow using the entered value as a
reference and offset it somehow thus giving a different reading?

So how does the weather station know how much offset to add?

Thanks again in advance

Gary

That's why you have to enter the current sea level pressure - so that
it knows what the offset is!

Say the sea level pressure is currently 1025mb. The weather station
pressure sensor is reading 1015mb. The offset is 10mb, and once you
have entered it, this will allow the weather station to display correct
sea level pressure.

IIRC, atmospheric pressure falls by 1mb approx with every 9 metres
gained in altitude (at low levels). So the 10mb difference in my
example would be correct if you are about 90 metres above sea level.


Sorry for being real dim here but why I am getting confused is because
I am not sure if once I have entered the value from the BBC website
that the weather station should read the same thing as it doesn't - is
this correct? It does not seem right to me as I am entering a value
reported as the pressure and it reads something else??

Many many thanks for your patience.

Gary

wrote:
Is there an option on the weather station to switch between displaying
sea level pressure and actual pressure?

Isn't that what I said hours ago? Do my posts not propagate very well?
--
Steve Loft, Glenlivet. 200m ASL
Weather and webcam:
http://www.livet.org.uk/weather

Hello all,

thanks for all your responses. The penny finally dropped when I got
home last night and discovered that the display could be changed from
relative pressure to absolute pressure as Steve suggested. It all makes
a lot more sense to me now - still more to learn for me.

Thanks again

Gary