Topic: Insights from a decade of rain gauge deployment

[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

[EdMallon]

That oil drop idea reminds me that I've been thinking about trying siphon-drain gauges as the idea of having no moving parts sounds interesting. But they are rare and I've never heard any reports back from people who've tried them 'in the field'. How to they respond to debris that inevitably gets pulled into the funnel? If gunk builds up in the tube does the gauge start under or over reporting?

Also just FYI, folks here might find some useful tips our review of methods for 'Waterproofing Electronics" useful for their own projects:
https://thecavepearlproject.org/2023/03/17/waterproofing-your-electronics-project/

[DaleReid]

Ed,
That link to the water protecting materials was a great review and you giving actual brand names when possible and your experience with conformals was great.

I hope my bookmarks find it again when I need it.  I didn't know about the UV trick to blacklight for coverage.

I always wonder about things with solvents doing damage to boards and stuff when you flood them on.

And one thing I need to do a few of in a few days is RH sensors.  I have little tubes over them now and I have been told that just not getting the conformal on the sensor is all you need to do, with them being insensitive to the vapors as the stuff dries, then remove the cover so it is exposed to the air where the humidity is being sensed.

In your experience, do any of the coating things or sealers or the superglue/baking soda trick in the area of some of these open surfaces contaminate them?

Thanks again.

PS, there is so much stuff in that link I wonder if you would post it on a separate, new, heading for those who've never seen it?
Dale

[DaleReid]

Ed,
do you put a tiny amount of dielectric grease on your plug in connections, like RJ-45s? I know that my Rainwise has some RJ-45 connectors and with some other sensors where that is terminating a CAT-5 and will be in higher humidity areas, or even regular connections out of doors, I have found it (so far) harmless to take a tiny amount of that grease on the terminals when assembling them for the last time.  There has been no dreaded green stuff form where power is provided such as POE or my internet cameras.  It is just so slippery and incredibly hard to get off that I only use a super small amount and only at last assembly once tested out ok.

When I did two way radio antenna mounting eons ago, Antenna Specialists would send a small rip open tube of the stuff to put on the contact surface when the loading coil was screwed onto the mount. I had my doubts but it worked well.

thx.  Dale

[EdMallon]

I've not had any problems with solvents hurting the boards because with the exception of bathing them in 90% iso, I use a fairly light hand. But I've had several cases of solvents ruining subsequent steps in the process like PVC glue turning a potting compound into flakey goo.

WRT RH sensors I've had the best luck with ones inside sintered metal cans - I suspect this is because under condensing conditions the moisture forms on the outside metal first, thereby protecting the sensor inside the can. Also new RH sensors have self-heating modes that, while they use alot of power, they do let you recover the sensor after its been 100% saturated. And yes, wicking of your coating into the sensor is the big problem - mostly because I usually try to get the coating right up to the edge of the sensor, and then my shaky hands make a mistake... I've not tried the superglue baking/soda with RH sensors because it's just too hard to control where the baking soda lands & I dont want to plug up the holes.

I suspect any kind of contact/dielectric grease would be fine for those contacts but I'd use simple silicone grease like I use on my o-rings as then I don't have to worry about strange additives with weird chemistry. But we usually keep our contacts dry inside the threaded rain-bird tubes shown in that post. Our go-to is those 4-pin deans connectors which are much more robust than phone/ethernet style contacts because the pins are 'pinched' between prongs rather than just sprung surface pressure.

We create material like that survey of waterproofing techniques mostly for Dr. Beddows students to save us from explaining it over and over again.  I was cautious about posting it here as the WX.net has been around for quite a while, so there are plenty of old hands here that probably know more about that stuff than I do. I also don't use the forum enough to know exactly where to put the stuff? Wouldn't want to get booted because they thought I was spamming their forum(s). Should it go here in Chat?

[zoomx]

Ed,
have you considered to use Hall sensors instead of reeds?

[EdMallon]

I've played with hall sensors for other applications, but their quiescent current is too high compared to essentially zero current for a reed switch.  Most of the garden variety hall sensors I've looked at are 10x that(?). Usually get at least a decade out of reeds, so I'd be interested to hear how long hall sensors last in this application.

To run for more than a year on a coin cell we need quiescent currents in the single-digit uA range.
[ https://thecavepearlproject.org/2022/03/09/powering-a-promini-logger-for-one-year-on-a-coin-cell/ ]

[Lord Volvo]

I have a Heathkit tipping bucket that's been in the wild since 1981.  It's the first generation of their tippers.  The gauge itself is mostly aluminum and has been reliable but not super accurate when compared to my 11" gauge next to it.  In terms of repair, I've had to replace the reed switch twice, a capacitor, and the tipper's fulcrum.  All easy repairs and it still works today.  The display unit has never broken down.