I've started to notice an issue with the newer Davis spoon tipper after 6 months of keeping an eye on it..
It doesn't do well in when there's a lot of rainfall in a short space of time.
In the 6 months I have been using it, we've had unusual rain events here where a lot of rain falls in the space of 6 - 10 hours.
I've got 2 manual gauges, the Davis one and another self tipping one. The Davis gauge, a manual gauge and the other self tipper are all at the same height. The self tipper is 12ft away, from the Davis. The manual gauge is 2ft away. The 4th manual gauge is on the ground.
If around 15mm falls in a 12 - 24 hours period - steady rain - they are evenly matched. If we get big downpours of 15mm+ in the space of 1 or 2 hours, or even 25mm+ in 6 hours, the Davis gauge is regularly 3mm or more, higher than the rest of the gauges.
I know someone will post something along the lines of "rainfall can vary within short spaces" but I have had a lot of days with downpours to be able to monitor it. There's a clear sign that it overreads in heavy/very heavy rain. It seems to not be able to cope and tips extra times in downpours.
Back in August, we had a thunderstorm which produced some of the heaviest rainfall I have ever seen, which produced a rain rate of 411 mm/hr. I'm doubting that figure now based on what keeps happening. It's overread rainfall by at least 3mm on 9 occasions in the last 6 months, and it has again today.
I've checked the gauge thoroughly every single week. The spoon is clean, no cobwebs and nothing I can see to cause it to produce these spurious amounts. As I said above, the problems arise during very heavy rain. It's like it can't cope with the influx of water and the spoon tips multiple times before it has a chance to reset.
It's all good in steady dynamic rainfall events. Anything convective / downpours, it goes off on one.
There is a clear signal that it has issues in heavy rain events and it doesn't leave me with any confidence now, as you cannot really adjust it in this situation. If you did, you'd get lower rainfall readings during the steady rain episodes.