Topic: Davis Tipping Spoon Rain Gauge - crazy readings

[Tyfelin]

Hi,

I have an older VP2 - about 12 years - and recently I upgraded the old tipping bucket rain gauge to the new tipping spoon mechanism. It was that, or a third replacement reed switch in the old gauge - a mechanism that struck me as very crude even when new. Worked fine for a few months.

After that honeymoon period, I've now had several occasions when the rain rate has registered 214mm per hour, and stuck there. The actual rain rate has been nowhere near that. It's not always even been raining! My first thought was that the gauge is the cause of the problem.

Then - plot twist. I'd disconnected the gauge, not wanting to spew nonsense rainstorms onto Weather Underground and so on. And on a couple of occasions the ISS has now reported 214 rain rate with no gauge attached!

Does anyone know of any incompatibilities or common faults on the ISS board that could cause this issue?

- Tyfelin.

[bbrowncods]

If it is not plugged up to the tipping spoon, it can't be that.  So it has to be either the console, or ISS circuit board.  Most likely the CB.  Hope this helps!

[WheatonRon]

If you live in the USA, call Davis support—they are very helpful—this is the type of question they get probably many times a week. If you live outside the US, email works but I understand Davis is slow to respond.

[Tyfelin]

After my first post I had a newly replaced battery drain over just a week or so. The supercap had blown (my third, I think) and so I replaced it. Tested the new cap with a meter - seemed fine. Heard it charge when I put the battery in. That's all good - right?

Connecting the two issues - gauge and cap - I plugged the gauge back in. Issue still there. And the battery drained over a handful of days.
Unplugged the gauge again, and replaced battery. That was last night. Overnight, 820mm 'recorded' in dry conditions. No idea yet how the battery is doing.

So it's not the tipping spoon gauge. And (unless it's blown in record time - will check) it's not the supercap. All fingers pointing to an ISS circuit board issue.

@wheatonron I live in Wales (it rains a lot here ) so I'll email Davis support and see what they say. Thanks for the help all.

[johnd]

If you have been working on the SIM board recently then are you sure that the front cover was fully home and sealed when replaced. This does rather sound like damp ingress into the socket where the rain gauge plugs in. A PCB fault could give similar symptoms but is pretty rare.

[Tyfelin]

@johnd
It did occur to me. The cover was properly located ( and as near as I can fashion one there is a drip loop on the cable ). It may still be that it doesn't fit as tightly as it ought to. I'll go see what I can see.

[MM0MVX2]

  I am also having rain tipping bucket problems (Just over a year old  think ),no rain and the numbers still keep logging up. I unplugged the rain sensor/Bucket from the PCB  and all felt and looks dry in the ISS box .Prodata have been very helpful in trying to sort this thy told me to change the channel to 4,I have not done this yet for other reasons but hope to do it on Sunday. The lady there had not heard of this before and was going to contact Davis and get back to me . Prodata have been excellent in helping try and sort this. Thank  you very much.
David

[Mattk]

Connected rain gauges can run up huge amounts of recorded rain and not a cloud in sight, gecko's and other little legged things find tipping buckets great to play on, the smallest of twigs lodged down the hole can cause buckets to centre, oscillate wildly and flutter the reed switch, moisture in the socket and general moisture in the enclosure are also known issues, Davis ISS enclosure is not perfect in this regard     

[petec2]

hi I recently posted on a similar issue where 214mm/h recorded and remained recording even when the phone jack was unplugged! It was caused by ingress of water into ISS wetting the phone sockets at base of iss. i dried the sockets and greased them and the issue seals with silicone grease. pete

[MM0MVX2]

 Hi All
I have had the ISS board off and found no moisture on the PCB at all there was just a little ingress at the antenna grommet but it had not reached the PCB I cleaned up the RJ45 sensor sockets and the plugs but I could see no tarnishing just shiny gold. I removed the sensor from the Tipping Bucket and the was no sign of moisture any where The PCB boards are covered in Varnish to keep out moisture and it has a white colour to it. The only thing I could see that looks odd is the resistors R61,R73 R71 .I can not decide if it is just the varnish or there is some thing wrong.
When I started to look for the rain fault the console reading was 14.8mmwe have had no rain at all and now it is reading 22.1mm the app on the phone also shows 22.1mm

 [ You are not allowed to view attachments ]

[davidmc36]

First glance looks like it could be corrosion. But it's out of focus/too low resolution.

[MM0MVX2]

What  resolution is allowed on the forum the first picture was to big and would not send.
Thanks for the reply
David

[davidmc36]

Take high resolution and crop it. Size matters.

Click the "Attachments and other options button below text box for details.

[Ray Proudfoot]

I’m experiencing rain rate problems since I bought a new ISS back in December 2021.

Take today for example. The temperature rose above freezing for a couple of hours causing snow in the gauge to melt. There were only two “tips” of the spoon mechanism but they were so close together the rain rate was determined to be 84”/hour. 

I’ve had to edit multiple records in Cumulus to correct this erroneous new record. It’s happened on 3 or 4 occasions in 3 years but never happened in over 12 with the old tipping mechanism.

A fellow enthusiast a few miles away with the same kit also had the problem. So it’s not a bad unit. It appears to be a design flaw.

Anyone from Davis care to comment? Or anyone else with the same problem?

[WheatonRon]

I’m experiencing rain rate problems since I bought a new ISS back in December 2021.

Take today for example. The temperature rose above freezing for a couple of hours causing snow in the gauge to melt. There were only two “tips” of the spoon mechanism but they were so close together the rain rate was determined to be 84”/hour. 

I’ve had to edit multiple records in Cumulus to correct this erroneous new record. It’s happened on 3 or 4 occasions in 3 years but never happened in over 12 with the old tipping mechanism.

A fellow enthusiast a few miles away with the same kit also had the problem. So it’s not a bad unit. It appears to be a design flaw.

Anyone from Davis care to comment? Or anyone else with the same problem?

If this only has only occurred 4 times in 3 years, don’t worry about it—measuring precipitation in the winter is problematic in the first place—its the nature of the beast.  If it really bothers you, contact Davis support—they will not respond to posts in this forum.

[Ray Proudfoot]

@WheatonRon, it only happens when dew or melting snow drips into the spoon. Normal rainfall is fine. Never a problem.

But when you change one thing and a previously unknown problem starts it has to be something in the design.

I’m in England and from memory Davis support is virtually non-existent for those of us on this side of the pond.

[WheatonRon]

But when you change one thing and a previously unknown problem starts it has to be something in the design.

What does this mean—what did you change? Thought not at all clear from your posts, I believe you meant you replaced the ISS that had the old tipper in it, with an ISS with the spoon. If so, it could be several different parts affecting this issue, not necessarily the spoon itself.

[Ray Proudfoot]

New ISS.

[johnd]

Given that there is no obvious way that the gauge mechanism can ever reliably distinguish between extremely heavy rainfall (eg in an intense thunderstorm) and rapid snowmelt, what would you suggest as the upper limit beyond which a rainfall rate should be ignored by the VP2 system? But any rate slightly below this limit is still going to be reported whether it's attributable to rainfall or snowmelt. So the 'problem' isn't going to go away, it's surely inherent in any mechanical gauge that's able to report very high rainfall rates.

[Ray Proudfoot]

Given that there is no obvious way that the gauge mechanism can ever reliably distinguish between extremely heavy rainfall (eg in an intense thunderstorm) and rapid snowmelt, what would you suggest as the upper limit beyond which a rainfall rate should be ignored by the VP2 system? But any rate slightly below this limit is still going to be reported whether it's attributable to rainfall or snowmelt. So the 'problem' isn't going to go away, it's surely inherent in any mechanical gauge that's able to report very high rainfall rates.

Hi John. This wasn’t rapid snow melt. The rainfall was 0.00 before three tips due to melting snow raised it to 0.03. Without doing the calculations for a hourly rainfall rate of 84” this is SEVEN times the rate my station recorded when a squall line passed through and the rain was “biblical” for those few minutes.

Mark Crossley, in Wilmslow also experienced the same problem but as he’s running Cumulus v2 was able to erase those spikes. I have to manually edit my records. I suspect the same will happen today when temps rise briefly above 0°C.

Why did this never happen in 12 years with the tipping gauge? That’s why I don’t understand why Davis changed the design.

[johnd]

Hi John. This wasn’t rapid snow melt. The rainfall was 0.00 before three tips due to melting snow raised it to 0.03.

I'm confused! Was it due to snowmelt or not?

Why did this never happen in 12 years with the tipping gauge? That’s why I don’t understand why Davis changed the design.

Well, you'll need to ask Davis for chapter and verse. But AIUI it was done because of persistent criticism that the old design was inaccurate, especially for intense rainfall. Most users do find that accuracy is now improved with the new design. But in being able to measure intense rainfall better then the new design will presumably accept more rapid successive tips.

It may well be that 84"/hour as a rate is beyond the bounds of any credible rainfall rate and could therefore be caught by a filter somewhere in the data chain (though I'm not sure what the record is for rainfall intensity - it will surely be several tens of inches/hr even if not as high as 84). My point was therefore that even if you filtered out rates above say 50"/hr as implausible, you could still record 50"/hr, or whatever you set the limit to be, during snowmelt. I don't see how you can ever distinguish between the two different reasons for rapid tipping.

[Ray Proudfoot]

I'm confused! Was it due to snowmelt or not?

Snow melt as I said in my earlier post.

Well, you'll need to ask Davis for chapter and verse. But AIUI it was done because of persistent criticism that the old design was inaccurate, especially for intense rainfall. Most users do find that accuracy is now improved with the new design. But in being able to measure intense rainfall better then the new design will presumably accept more rapid successive tips.

It may well be that 84"/hour as a rate is beyond the bounds of any credible rainfall rate and could therefore be caught by a filter somewhere in the data chain (though I'm not sure what the record is for rainfall intensity - it will surely be several tens of inches/hr even if not as high as 84). My point was therefore that even if you filtered out rates above say 50"/hr as implausible, you could still record 50"/hr, or whatever you set the limit to be, during snowmelt. I don't see how you can ever distinguish between the two different reasons for rapid tipping.

I suppose no system is perfect. I’d be interested to know what the Met Office use. 84”/hr calculates as a tip every 0.023 seconds. Mechanically impossible I would suggest. Ho hum. Just something I’ll have to live with I suppose. Strange t only ever happens with frozen dew melt or melting snow.

[johnd]

I suppose no system is perfect. I’d be interested to know what the Met Office use. 84”/hr calculates as a tip every 0.023 seconds. Mechanically impossible I would suggest. Ho hum. Just something I’ll have to live with I suppose. Strange t only ever happens with frozen dew melt or melting snow.

I think you're saying that you have a 0.01" gauge and not 0.2mm? So 84"/hr = 8400 tips/hr = 8400 tips/3600 secs = 2.3 tips/sec (and not every 0.023 secs). Still fast certainly, but credible I think.

[Ray Proudfoot]

@johnd, thanks for the correct arithmetic.b😁 Yes, I have the 0.01” version. it’s just risen above freezing now so I’m watching the console like a hawk. Given a rainfall rate cannot be determined until tip number 2 it still seems crazy.

[Ray Proudfoot]

It’s now 1.2°C and no rain tips. I suspect the snow has melted and turned to ice.