John Hirst wrote:

just change the reed as it looks like a sealed unit, so am thinking of
upgrading to the Oregon Pro WMR 928. A lot cheaper than the Davis -

As I've said, I'm reasonably happy with my WMR 928, given the price. But
if I'd had the choice of a Davis VP at the price John Dann is currently
offering, it seems to me to be what the chaps over the pond would call a
"no-brainer".

Although it does appear that to connect the VP to your PC you have to
buy an add-on at a cost of £176, whereas that functionality comes as
standard with the Oregon.
--
Steve Loft, Wanlockhead, Dumfriesshire. 1417ft ASL
http://www.wanlockhead.org.uk/weather/
Free weather softwa http://cumulus.nybbles.co.uk/
Experimental webcam: http://www.wanlockhead.org.uk/webcam.php

Keith Thompson wrote:
After lurking on this group for ages, I have decided to come out into
the open and ask for some advice.

I want to buy a weather station which I can link to my PC for data
logging and display. We live in a very exposed spot on the west coast
of the Isle of Arran and need something sturdy!

I have the VP2 wireless with tall the toys and I can recommend it
enough. But If you can I would recommend buying via a contact in the US
or France if you can. The UK pricing on these units is a complete rip off.
E.g.
VP2 wireless delux is $999 at todays rate thats 535 GBP mosy uk
resellers want 900 GBP ex vat.
Unfortunatly Davis like to cosy up to the distros so the wont sell to
you even tho they list the UK model in their online shop !
Even better prices can be found at davis resellers on ebay (again they
wont sell to uk address due to pressure from davis)

a Davis Wireless Vantage Pro 2 Weather Station 6152 Pro2 just went for
$400 (thats just over 200 GBP) Uk price on that is about 450 ex vat !
Even takking into account shipping and vat and duty I reckon on saving
50% if you can get some in the states to order it for you !

A

Alun J wrote:

a Davis Wireless Vantage Pro 2 Weather Station 6152 Pro2 just went for
$400 (thats just over 200 GBP) Uk price on that is about 450 ex vat !
Even takking into account shipping and vat and duty I reckon on saving
50% if you can get some in the states to order it for you !

A

Oh and weatherlink is $160 retail !

On Fri, 21 Jan 2005 12:35:55 -0000, "Alan Gardiner"
wrote:

With the Davis equipment I was led to believe that the stik reed switch was
a particular problem with early vantage Pro stations. From what I have seen
recently it seems to have been a problem with other models. More recent
stations may be better but I don't know if this is the case.


Just as a general comment on the reed switches in Davis anemometers
and stressing that this is my personal take on the issue and in no way
based on direct official information from Davis:

The first point is that of all the outside sensors, the anemometer
(and specifically the wind cups) is the component that in a sense
takes the most battering from the weather. While reed switch life (in
static - eg bench-mounted - devices) is indeed measured in the
millions of operations, if you do the calculation then the wind cups
also revolve and trigger the reed switch many millions of times per
year. (1 rev per second - a very low wind speed - gives 30 million
operations per year by my calculation). Factor in the vibration and
buffeting that many anemometers will experience and it's not difficult
to see why the reed switch may not have an indefinite life and may
typically need replacing after eg 5 years although the exact period is
very variable, depending on location, exposure, mounting vibrations
etc.

That said, I've come across WMII anemometers that are a number of
years old (13y is I think the oldest) and that are still providing
sound wind speed readings. But it is true that there seem to have been
a few batches of anemometers that have been more prone to premature
wind speed failure. My guess (and it is just a guess) as to the cause
is as follows: Reed switches can be quite delicate devices, eg where
the connection wires pass through their glass envelope. The switch
needs to be mounted in such a way that there is no stress on the
immediate connections, otherwise what can happen over time is that
minute cracks can start to appear in the glass envelope, which allows
oxygen and especially moisture into the sealed, dry, inert, interior
of the switch. Then, again over time, the switch contacts become
impaired and ultimately results in intermittent wind speed operation.

Now how much stress is on the switch wires will depend on the skill
and care of the operator on the assembly line. It might conceivably be
that the occasional operator over the years has not been quite as
adept at this aspect of the assembly operation as the design demanded,
(which would account for why the problem seems to have appeared in
batches). When new, the anemometer worked fine and therefore passed
all its factory tests, but ended up having a shorter life in the
field.

In the last couple of years (roughly since mid-2003 but depending on
station model), the switch design has been changed a little. AIUI the
reed switch is now mounted on a tiny circuit board, this operation
being done under carefully controlled conditions with the result that
there should now be little or no stress on the switch wires. The
little circuit board is then mounted into the anemometer in a separate
non-critical operation. While it's fairly early days yet, the
indications thus far are that the incidence of premature switch
failure is now very low.

John Dann
www.weatherstations.co.uk

In the last couple of years (roughly since mid-2003 but depending on
station model), the switch design has been changed a little. AIUI the
reed switch is now mounted on a tiny circuit board, this operation
being done under carefully controlled conditions with the result that
there should now be little or no stress on the switch wires. The
little circuit board is then mounted into the anemometer in a separate
non-critical operation. While it's fairly early days yet, the
indications thus far are that the incidence of premature switch
failure is now very low.

John Dann
www.weatherstations.co.uk

Would replacement switches be of the new design? given your remarks I hope
that this is the case.

Alan

On Fri, 21 Jan 2005 14:22:43 -0000, "Alan Gardiner"
wrote:

Would replacement switches be of the new design? given your remarks I hope
that this is the case.


It's unfortunately not quite that simple. Putting in the new format of
switch apparently requires a compatible and revised type of anemometer
body (or at least the part around the speed switch housing) and was
also accompanied by a change from vertical to horizontal magnet in the
speed cups. So unless a supply of the revised body part was available
and the repair was returned with horizontal-magnet cups then the
answer's probably no.

But in part the point I was trying to make is that even with the
original design, then provided the switch is carefully mounted, the
anemometer would in general be expected to have a long life. The UK
servicing staff are skilled at making this replacement and typically
anemometers that have had the switch replaced have a long subsequent
life.

JGD
www.weatherstations.co.uk

In message , John Dann
writes
On Fri, 21 Jan 2005 12:35:55 -0000, "Alan Gardiner"
wrote:

With the Davis equipment I was led to believe that the stik reed switch was
a particular problem with early vantage Pro stations. From what I have seen
recently it seems to have been a problem with other models. More recent
stations may be better but I don't know if this is the case.


Just as a general comment on the reed switches in Davis anemometers
and stressing that this is my personal take on the issue and in no way
based on direct official information from Davis:

I doubt whether reed switches were ever designed for this kind of
intensive operation. IMHO the manufacturers would have been better
advised to have gone for photo-electronic or hall effect devices - all
solid state and no moving parts - except the turning of the cups etc. I
once constructed an anemometer using the photo-transistor route and it
never failed.

Cheers,

James
--
James Brown

On Fri, 21 Jan 2005 15:25:10 +0000, James Brown
wrote:

I doubt whether reed switches were ever designed for this kind of
intensive operation. IMHO the manufacturers would have been better
advised to have gone for photo-electronic or hall effect devices - all
solid state and no moving parts - except the turning of the cups etc. I
once constructed an anemometer using the photo-transistor route and it
never failed.


I wouldn't necessarily disagree with the sentiment of this, though
reed switches are indeed designed for very large numbers of
operations, though possibly not in a high vibration environment. It's
worth remembering that the basic design of the anemometer was fixed
maybe 15 years or more ago when there were fewer cost-effective
electronic altenatives and, the errant few batches aside, did become a
tried and tested design with the merit of simplicity.

And while both PE and Hall-effect (and other technologies too) offer
alternatives at the business end of the anemometer, processing the
resulting signal is not necessarily as straightforward and error-free.
I've no claim to being an electronics engineer and so I can't really
debate this, but from what I understand Hall-effect has been
considered previously but had some susceptibility to RF interference.
But it does begin to sound like these problems are being overcome and
maybe a revised anemometer based on a different technology from reed
switches will appear at some future date.

JGD
www.weatherstations.co.uk

Thanks for the info on reed switches. I know from experience at BT, when
many, many moons ago they used millions of reeds in some of their analogue
Exchanges. Even in static warm and dry environments they eventually would
stick closed. A gentle tap, or any slight vibration would free them, and
they might stay free for many months after, but eventually they would stick
more and more often - just like my wind vane !
A solid state solution, eg. an optical switch, is far better, imo, with the
added advantage of fast switching and no contact bounce issues. I have
mounted my vane close to a wall on a flexible post, so that when the wind
gets up, it knocks up against the wall and hopefully frees the reed switch.
A cheap, but probably temporary solution !

"John Hirst" wrote in message
...
Thanks for the info on reed switches. I know from experience at BT, when
many, many moons ago they used millions of reeds in some of their analogue
Exchanges. Even in static warm and dry environments they eventually would
stick closed. A gentle tap, or any slight vibration would free them, and
they might stay free for many months after, but eventually they would
stick more and more often - just like my wind vane !
A solid state solution, eg. an optical switch, is far better, imo, with
the added advantage of fast switching and no contact bounce issues. I have
mounted my vane close to a wall on a flexible post, so that when the wind
gets up, it knocks up against the wall and hopefully frees the reed
switch. A cheap, but probably temporary solution !
Won't mounting the vane on a flexible post promote vibration and henc early
failure of the switch?

Alan