Hi Tore,
Think I just answered you on email? Just incase it wasn't you, here's the reply:
The WS2080 does not output a rain rate to the computer so WeatherCat has to calculate it.
It does this by measuring the time between rain bucket tips - for example if at 11:00 there's a tip, and then another at 11:01 it knows it received 0.3mm in 1 minute, so the rain rate per hour is 0.3*60 = 20mm/h.
If the time between bucket tips is too long then there won't be a rain rate.
Hope this helps,
Stu