Cumulus Support

Does anyone know if fitting two magnetic reed switches at 180degs to each other would double the wind speed reading.My weather station reads half of what it actually is most of the time.
Also do the different cup sizes make much difference to wind speed readings.I tend to modify most sensors to make them more accurate.Thanks John

Hi John,

The Fine Offset (WH1081) anemometer (should) already deliver two pulses per revolution (when the magnetic field passes either N-S or S-N through the reed) so it sounds as if yours might be faulty. It's quite easy to open up and you might find that moving the PCB (which carries the reed) will get it working properly. You could buy a new reed (make sure you get a good quality one - it needs to work for literally millions of operations each week) but it's hardly worth bothering when replacement anemometers from Maplin cost £2.50.

The calculations of the "Anemometer Factor" are extremely complex, but basically it's the length of the arms which affects the calibration. Many users suspect that their FO anememomter UNDER-reads, but that's probably because it's not mounted high enough. The only independent comparison I've seen (on the Meteocercal forum) with a "good quality" anemometer (and also the calculation of the Anemometer Factor) suggest that the FO might OVER-read by up to 20%. Note that the FO "cups" are exactly the same size as halved Ping-Pong balls - a Coincidence ?

How do you propose to calibrate yours?

Cheers, Alan.

Hi Alan.I am thinking of scrapping my current station and buying a OS WMR 88 which has a up to date spec.The best weather station I had was a Maplins HP2000 with a fantastic display unit,But the main sensor unit all self contained above was badly made and gave up the ghost in a very heavy storm.
I would like the Davis station but can't afford it.
I am using the HP2000 wind device at the moment but doesn't seem much better
My worst buy is the current machine which I have modded for better results,Taking the touch screen off and fitting 8 white LEDs for better display.The WH1081!!!. John