"xmetman" wrote in message
...

All the data logger is collecting for wind speed I imagine is the number of
revolutions that the anemometer cups make in 2.5 secs, and it would be a
good idea if these values were accessible ....

As Freddie rightly says, these 2.5sec values are available in the real-time
or LOOP data from the logger (see the Serial Tech Ref for further details).
But you must poll and process them on some external device as they become
available otherwise they are indeed lost as discrete packets. The shortest
interval records that can be stored in the logger for later retrieval are
indeed 1-minute - maybe this is what you're thinking of? (Actually, IIRC
wind speeds are actually measured over a 2.25 sec gating period at the ISS
and then the latest available value transmitted at 2.5625 sec intervals on a
VP2 set to channel #1 (it's a progressively different interval on other
channels)).

I realise that my Vantage Pro is coming up for 12 years old this April

OK, so that is likely to be an original VP (VP1). So the transmission
interval (channel #1) is indeed 2.5 secs on these older stations.

but I would like to think that with technology such as the Raspberry Pi,
that either Davis or someone else would be able to put together a cheaper
weather station

The problem with the RPi is its power demand (say 2W continuous). Most users
want a wireless sensor transmitter that is not tied to an external power
supply so that there's much more flexibility on where the sensors can be
located in order to achieve optimum sensor exposure (and of course no need
to worry about running a vulnerable cable out to the sensors). This is just
not compatible with anything as power-hungry as an RPi, at least not without
a solar panel PSU potentially costing as much as the weather station. It's
why microcontrollers rather than microprocessors are usually used in the
sensor transmitter - these allow a continuous power budget of maybe 20-30mW,
which is compatible with a small/affordable solar panel PSU running 24/7/365
even at higher latitudes.

Personally I've always thought that the anemometer has always under read..

That's going to be related at least in part to height and exposure, although
if you still have the original anemometer then the bearings will also be
seriously worn by now. Examples of the 7911 and 6410 VP1/VP2 anemometers are
calibrated in different orientations in wind tunnels to 150mph. This is
necessary to generate the lookup tables that are used to correct the
measured wind speed for the smallish errors in raw speed caused by the wind
flow from different directions interacting with the anemometer arm.

John Dann
www.weatherstations.co.uk