I’ve been troubleshooting a rain gauge related problem with my relatively new WMR928NX (about 2 months old now) and I’m hoping somebody here might be able to add some ideas to the potential cause. The problem, simply put, is that every now and then the weather station console (and therefore WD) records 2mm of rain when the bucket has only tipped once in my rain collector, but only intermittently.
The problem first became apparent when looking at my rainfall graphs in WD, I noticed on occasions the graph had jumped by 2mm in a single minute. I thought this a little strange, as anybody with a 1mm rain gauge would know, you need quite heavy rain in order to collect 2mm within a single 1 minute period and I knew the rain at the times of these recordings was light to very light. I started to investigate by un-installing my rain gauge (to eliminate environmental factors, wind, etc), bringing it inside and doing some manual testing.
To test, what I did was this:
- Reset the daily total on the console to 0mm of rain.
- Let the rain gauge send 3-4 data packets (about 3-4 minutes) to confirm there was no buffered data waiting to be reported to the console from the rain gauge transmitter.
- Manually tip the bucket once.
- Wait for the total rainfall on the console to increment by 1mm
- Back to step 3 and repeat.
This would work flawlessly up until around the 7mm mark and then the problem becomes apparent. At or around 7mm, a further single tip of the bucket causes the rainfall to increment by 2mm instead of 1mm, even though the bucket has been physically tipped only once. This meant that the console was now displaying 1mm of rain more than the total number of times I had actually tipped the bucket in the collector.
I say around 7mm as sometimes the jump occurs from 7 to 9mm and other times the jump occurs from 8 to 10mm and sometimes 6-8mm, but in each case the console is advancing 2mm when the bucket has only tipped once, and therefore over-reads the rain by 1mm at that time. This of course becomes a cumulative error over time and by the end of the year my totals would be significantly out.
I also tried doing multiple tips within one update cycle of the transmitter. This had no bearing on the symptoms whatsoever. In otherwords, I tried tipping the bucket 7 times within one minute (OK, that’s really heavy rain) and to no surprise, the console read 8mm when the transmitter sent the next packet. I also tried combinations, like doing 5 tips, wait for update, 1 tip, wait for update, etc, etc. It didn’t matter when the tips occurred in relation to the update cycle of the transmitter, the net results were still the same. At some point between 6 to 8mm, the console increments by 2mm when the bucket has tipped only once.
The problem is very easily reproducible in that I can rarely (one in ten times maybe) get the console to get to 10mm without jumping 2mm on a single tip at some point.
To try and resolve this problem I have tried:
- Resetting the console
- Resetting the solar transmitter
- Replacing the rain gauge
- Replacing the solar transmitter (by swapping it with my temp gauge transmitter)
All of these things have had zero impact on the problem, which remains consistently reproducible after around 6-8mm of rain. The only thing I can conclude is that perhaps I have another faulty rain collector unit? Either that, or my console can’t count to 10! I’ve googled and searched high and low but can’t find anybody else experiencing this problem.
Does anybody know of a way to test what the collector is sending to the transmitter (unfortunately I don’t have a CRO, just a multimeter which doesn’t help), or any way to verify that the rain collector is sending the correct tip count? It would be so much easier if I could narrow down where in the chain the double-up is occurring. It also strikes me as odd that it always occurs around the 6 to 8mm mark!
Any thoughts or ideas would be more than welcome as I’m running out of ideas! Thanks everybody!