Comment by holowoodman

Comment by holowoodman 9 hours ago

> Also, the most popular rain gauge manufacturer has shifted to tipping buckets to a tipping spoon design. [...] they no longer sell the tipping bucket design, so I'm guessing there is good reason they did that and there is some advantage (maybe in terms of calibration?)

Yes, tipping buckets are less exact than tipping spoons, especially in low-rain season. The bucket is never perfectly symmetrical and the mounting is never perfectly level, so one side of the bucket will hold more water than the other before tipping, leading to asymmetric tips.

geokon 8 hours ago

Their design doesn't look particularly amenable to tuning though. I'd imagine some design with the weight on a screw that can be screwed in and out to adjust the centerpoint.

The two bucket design doesn't seem overly problematic though. Often you can see this in the record as time-to-tick will follow a sawtooth pattern. I haven't tried it myself, but .. assuming you don't have any skips in your record.. I imagine you could periodically use a long syringe and measure the exact volume that triggers a tick on each side. And then correct the record in software.

A bit of a tangent.. but I've also not found any software or algorithm for correct interpolation of rain volume. Maybe you know of something? ChatGPT suggests a few things :)) but I wonder if there is some standard method people use

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holowoodman 7 hours ago

Yes, for larger volumes of rain, that sawtooth pattern is visible and can be corrected for, or even ignored and averaged out. But for low volumes of rain, there will only be one tick. Usually you don't know which side of the bucket that tick was on, because most sensors just count the tipping of the bucket, not the direction or resting position. So for the one-tick-per-day case, you will very often not know whether to count the "large" or "small" bucket amount.
Calibration will also be drifting off for dirt accumulation and evaporation. Different fill states of each bucket lead to different evaporation in each bucket (smaller will evaporate faster, deviating towards even smaller amounts), and different resting times lead to more dust and algae settling in the bigger bucket, making it even heavier.

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