Temp/Dewpoint Graph

[DaveNZ]

Hi Steve

Sad to say I have got another issue here
The temperature and dewpoint graph here http://howickweather.orgfree.com/weather/trends.htm
Cumulus is mucking up the DP's reported by my VP2 after about 5pm, the dewpoint line should not have dipped down to 14 at all (the dips in the DP line do not correspond to a temp drop or a humidity drop).
"Calculate dewpoint" is turned off in my cumulus settings, and this problem has occurred as live data is feeding into cumulus.
In weatherlink the correct DP values appear on the graph like this (blue is temp, green is dewpoint):

tempDP.PNG

[steve]

Sad to say I have got another issue here

That's OK, that's what this forum is for.

Cumulus is mucking up the DP's reported by my VP2 after about 5pm,

With 'calculate dew point' not set, Cumulus just reads the dewpoint from the Davis DLL and applies any calibration settings, and that's it. You can't compare the dew point logged by Cumulus with that logged by WL for two reasons: 1. The WL data for the same period isn't 'live'. 2. The dew point isn't present in the raw 'loop' data (i.e. the station itself doesn't supply it), so WL must be calculating it; in the Cumulus case, you don't have Cumulus calculating the dew point, so the Davis DLL must be doing it. It seems reasonable to assume that it's a bug in the Davis DLL.

I know that there is a bug in the wind chill calculation in the Davis DLL when logger data is used, so to get around that, even if you don't have Cumulus calculating wind chill, it still does it itself when using logger data. Perhaps this is another bug, but with dew point and live data.

I suggest you change to get Cumulus to calculate the dew point and see how that goes.

[DaveNZ]

I suggest you change to get Cumulus to calculate the dew point and see how that goes.

Alright will do so.

[DaveNZ]

Just to follow up on this, yesterday when looking at the settings in cumulus, completely forgot why I had ticked "calculate dew point" and unticked it, only to be reminded why it was ticked: random spikes, yet the humidity curve was smooth

DP_spikes.PNG

So will definitely keep that ticked from now on, something strange going on there...but as you say if it's the Davis DLL not much you can do about it!