LastRainTip error?

[gerardwood]

Hi,

I think the last rain tip calculation may have an error for my setup. I have a slightly non-standard configuration on my Davis Vantage Pro2 - it's a metric unit, but I record the rainfall in imperial (inches). Cumulus.ini thus has

[Station]
RainUnit=1
VPrainGaugeType=0

Everything works fine as far as recording rainfall is concerned, apart from the last rain tip, which is hardly every updated - it's only changed twice in the past month, and it's rained plenty of times. From my observations, it only appears to be be triggered when it rains *very hard* - I picked up a change on 25 July, when the rainfall rate was briefly over 3 in/hr, and I've picked one up this morning when it was at 2.75 in/hr. It's giving the impression that it's only picking up a change when there is more than one tip within the time period being analysed - so I'm guessing that the threshold for a change in the rain counter may be set too high (for my particular configuration)?

[mcrossley]

For a Davis station using inches for rain, the threshold is set to 0.009 inches - i.e. a bit less than one tip, so every tip should trip an update of LastRainTip.

It could be a problem with the #LastRainTip web tag if that is what you are using, does the #LastRainTipISO tag behave the same?

[gerardwood]

Yes, same with #LastRainTipISO. I think it's been doing it for quite a while (could be years!), I noticed it a long while back but never got around to investigating until now.

These observations all with the latest version of CumulusMX, BTW.

[gerardwood]

Just a thought - the metric rain bucket is 0.2mm, I believe? 0.2/25.4 = 0.00787...

[mcrossley]

Yes, so it will take two tips in a single update to trip the update of that value in your case.

There is a flaw in the logic being applied - looks like it has been there forever!

I'll fix this for the next patch release, not sure when that will be at the moment though.

[gerardwood]

Great, thanks Mark!