Wind Chill line and Dew point drop

[iandrews]

So, my Davis Pro 2 has been running a few weeks, and all seems ok with it. However looking at my graphs I notice that the wind chill is a up / down spiky line. I can’t 100% remember but thought with the Fine Offset the line used to be “straight” as such, not sure if’s it’s because I have set Cumulus to not calculate it itself (i.e read it from the station) as it used too with the File Offset or if because my wind speed is currently quite low.

Also, noticed quite a drop in Dew point about 8pm last night, seems to be linked to quite a drop in humidity around the same time. I did think that it was maybe a “fault”, but I still have the Fine Offset running (in roughly the same location), and that also showed the same drop. Not quite sure why it would drop quite so much, but does seem to fit in with the wind direction switching from east (which would be blowing onto the temp / hum sensor) to west (which would mean due to my set up the sensor would be sheltered by a wall). Also the lounge window (which is about 5 feet from the sensors) was open at the time, so wondering if it was expelling hot dry air which the wind was dispersing, and then when it switched direction meant that it went out of the window and straight to the sensors.

I have attached graphs.

[steve]

The wind chill line is like that because your wind speeds were hovering around the threshold for the calculation - Davis has a cutoff of 5 mph, below which wind chill is the same as the ambient temperature. Cumulus uses a lower cutoff of 3 mph when it does the calculation, Davis are trying to allow for that the fact that wind speed should be measured at 10 metres, but a human is at 2 metres or so.

[iandrews]

Ok, thanks for that info Steve.

[iandrews]

P.S. Been meaning to do it for ages, but have now just donated. Keep up the good work, and I look forward to Cumulus MX, any eta on a release date.

[steve]

P.S. Been meaning to do it for ages, but have now just donated.

Thanks.

Keep up the good work, and I look forward to Cumulus MX, any eta on a release date.

It will be quite some time before it's out of beta, there's a lot of work to be done yet, and still a few niggles to sort out; despite that, quite a few people, including myself, are now using it for their 'live' system.