Strange Rainfall Readings

[Gina]

I seem to have another problem with my weather station - sudden virtual rain lasting several hours then stopping as suddenly as it started. This has happened a few times in the last few days but the worst was from yesterday afternoon (when I was out) to the early hours this morning. I shall be investigating. I'm thinking RFI which has occurred in the past but I don't know yet.

24hrs-Rain.png

[scottjge]

I have had the same exact problem. Today it says, 387 inches of rain ! Not bad for having the sun shine all day. It doesn't show up on the console as rain fall today just in Cumulus. Isn't that odd ?

[Gina]

I didn't check my console at the time the erroneous rainfall occurred, I was otherwise busy and only noticed the rainfall next day, after it had stopped. I'll try to check next time it happens.

Yes, it is strange!

[steve]

It doesn't show up on the console as rain fall today just in Cumulus. Isn't that odd ?

Cumulus uses the 'total rainfall' counter which the station supplies; it's the only rainfall data available - it just goes up by one every time the rain bucket tips. Sometimes interference can cause that counter to jump up, which Cumulus interprets as rain. Sometimes this jump can actually be temporary - some sort of transmission error, presumably - and later versions of Cumulus have simple checks to try to ignore this. If the counter really has jumped up, though, it's hard to do anything but act on it and leave the user to work out what really happened.

I have no idea how the console works and how it manages to ignore these jumps in the counter, if they're permanent. Gina has her own software, and as you can see, these problems affect her in the same way.

[EvilV]

On the RF interference question, I have recently started up my old Ham Radio hobby again, and the end of the HF antenna is about five feet from my weather station transmitter unit and rainfall gauge. For about two weeks I have been blasting this with 100 watts of RF from five feet away, and touch wood, I have seen no anomalous data. The barrage of RF the station receives might amount to two or three hours on some days and can consist of on off keying of 100 watts at 7Mhz, 10MHz, 14MHz, and 28MHz and at other times phase shifted modulated signals at the same kind of frequencies. I also transmit 50watts of FM and SSB on 145Mhz. The Fine Offset seems not to notice this at all, as far as I am aware (not that I have done a meticulous analysis.

I would stress that the field strength is pretty high at that distance and vastly more than any interference you might pick up from a more distant source of even very powerful radio waves. RF field strength decays very rapidly as you move away from an antenna (inverse square law).

All but one of my anomalous rain events have been associated with shaking the rain gauge and causing ridiculous bucket counts. The unaccounted one just happened and I have no idea why.

PS if anyone ever checked my data on Wunderground and noticed a surprising amount of calm weather re wind, this is because I took down the wind gear temporarily to use the pole for something else.... I'm sure you can guess what for......

[Gina]

It's all very strange! After weeks of seeing no little spikes on my temperature plot, I had a couple of quite big ones about a week or so ago and nothing since. The rain I showed in my OP corresponds to an average of a bucket tip every 12 seconds or so. There was only a light breeze at most and the rain gauge is on a reasonably steady support (though I intend making it better). We did NOT experience a prolonged earthquake at that time!! I cannot see the cause being mechanical.

EDIT... After posting the above I noticed 13mm of rain today. On checking my rain plot, I see that was between 12:00 and 13:00 and I missed it. We haven't had any real rain. 13mm on my system corresponds to 130 bucket tips.

[scottjge]

Hmmmm, interesting. I had another glitch in the rainfall again this morning also. It was not as big as it was yesterday but still it was an error because it has not rained. Cumulus says that it lost connection with a sensor this time when it happened. So it has to be some sort of interference. I know the batteries are goo because I just replaced them last week.

I too, am a Ham and have transmitted with my radio's and have not seen any problems with readings while transmitting.

My rain gauge is sitting on a concrete slab that is 4 foot square and 6 foot deep so I know it is not vibrations, and I did not feel a earthquake this morning. LOL The only thing that I did today was open the garage door with a keyless remote which is somewhere around 139 Mhz. I don't know if some of the fundamental frequencies are close enough to the 433Mhz of the weather station to cause problems or not. I have to look into that theory yet.

[Gina]

We had heavy rain overnight - I heard it - but not the DELUGE my station reported!! The amount shown was more than the rain that caused devastating floods in southern France recently!

24hrs-Rain2.png

[Charlie]

This is probably a silly question, Gina - but have you tried cleaning the contacts? It likely won't make a difference, but you never know...

[Gina]

This is probably a silly question, Gina - but have you tried cleaning the contacts? It likely won't make a difference, but you never know...

Not recently, I'll admit. I'll take a look and clean plug and socket. Thanks for the suggestion

[Gina]

More imaginary rain in the last couple of hours though just two bucket tips. This could not have been mechanical - negligible wind and the animals are well fenced off. I think I'll try a capacitor across the reed switch to short out any interference pulses - probably best at the transmitter end of the cable.

24hrs-Rain3.png

[Charlie]

If it's contact bounce, a cap near the switch sounds right - if it's electrical interference, then it probably would be best at the sensor unit end. If you do both ends you should get it for sure!

I'm getting more convinced these occasional problems are in fact corruption of a data packets during transmission, as it's not unusual to see more than just a rain error when I notice a problem.

It will be great if we can at least find the root cause, even if we can't cure it, so your experiment will certainly help in tracking it down! I've been meaning to try the same thing, but things keep getting in the way.

By the way, we had a 5.6 earthquake with an epicenter about 70 km away this week, and the weather station did not record any additional rain. Go figure.

[Gina]

I've added a 100nF capacitor across the read switch in the rain gauge and a 470nF across the rain connector on the transmitter unit. I also checked the RJ11 connectors for corrosion (none found) and gave them a quick squirt of WD40 to make sure. Now editing the data to remove the errors.

[Steve_AI4ZL]

I have been getting some random readings on my new WS-1080 of 99.99 inch rainfalls on dry days, as well as 123mph winds on calm days. I have read many of your post Gina, and it is discouraging.

http://www.wunderground.com/weatherstat ... &year=2010

[steve]

Yes, you clearly had some sort of interference/corruption problem at about 22:37, and then again something odd happened at about 23:20.