Miscellaneous Debris > Chit-Chat

Insights from a decade of rain gauge deployment

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EdMallon:
I know these janky looking installations will have more than a few weather nerds out there inhaling through their teeth,
but even in the harshest environment critters are the biggest threat to actual ‘boots on the ground’ research (both the four and the two legged kind)
Even so I hope some of this information is useful to people here, or at least provides a bit of amusement. Cheers!

https://thecavepearlproject.org/2023/04/15/insights-from-a-decade-of-tipping-bucket-rain-gauge-deployment/

DaleReid:
The R/C circuit debounce something that I'd heard about but never figured the values needed.  This was new and I'll look to see  about adding it to the tippers connected to dataloggers.

I wonder if things like Heathkit and Texas Weather Instruments, Peet Bros and such have this taken into account in their internal circuitry?

And his pictures of some of the various gauges is great.

thanks for the link.

Dale

miraculon:
Interesting article on multiple levels.

Be cautious with the debounce addition. Too slow of an RC time constant can affect the switching performance of the receiving circuit (ISS, etc.). At the extreme, the signal will not transition before the next tip pulse, since the signal will look like a sawtooth. Personally, I take the "if it ain't broke, don't fix it" approach. If I saw/suspected double counts due to bounce, I might consider it.

Greg H.

EdMallon:
The other thing that's tricky about adding debounce is that several microcontrollers leverage internal circuitry that's not immediately obvious. We build our loggers around the 328p (used on older Arduinos) so you could remove the 5k pullup and use the internal pullup on D3 - but that would change the capacitor rise time from 10msec to 25msec. I've also seen TipRG circuits using the internal comparator that processor has on D6/7 to register tips. So you need to know what's going on inside the chip, before you add an external circuit.
WRT timing, the problem of water momentum usually kicks in long before the speed of the pullup circuit causes issues. Past a certain point the water flow gets fast enough that it presses down on the tipper causing it to flip before it would have if the water was flowing more slowly. I suspect that's why the companies rarely list accuracy specs above 1-2 tip events per second, and that's far beyond the millisecond timing of a typical debounce circuit.

DaleReid:
Ed, interesting and good points us commoners would never have run across.

One wonders why the expensive research stuff like Campbell, Young and Vaisala costs so much, but then I read papers about a couple summers' worth of testing in the field with many setups and watching wind effect and rain rate.  All important and goes well beyond whether or not the dog's water bowl was full after a rain or not. 

I've even read about thinking of how to reduce evaporation in a tube or siphon by adding a drop of oil to float on top to try to get the most 'accurate' reading.

Strange hobby we got here.
Dale

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