I posted this back last May. Since then, it seems to under-read fairly
consistently by 10-20%; February 88.3 mm by standard gauge, 80 mm by
wireless 1 mm:

--

I've had two 0.2 mm TBRs logged to my AWS for several years now, and
they typically under-record between 1 and 3% compared to my adjacent
Met O standard 5 inch gauge. This is probably about the best one can
expect as these are professional class instruments (both belong to
the
Environment Agency) and are regularly calibrated. The slight error
most
probably results from some loss due to differences in wetting of the
funnels, and in evaporation of the part-filled bucket contents.

As a matter of interest, three months back I purchased one of the
wireless 1 mm capacity tipping bucket gauges referenced in the first
post on this thread. I hasten to add I use this only for
distant-reading purposes, not climatology! After careful calibration,
I
found the 1 mm tip was surprisingly accurate for an inexpensive
instrument (within 4%, which was as accurate as I could measure the
volume of water poured in while I counted the tips). Daily totals
show
good agreement with the checkgauge when more than 2-3 mm falls, but
where it loses out are small falls ( 0.5 mm or so), especially a day
or two apart, where they simply evaporate and are lost to the record.


Monthly totals from both gauges compared with my standard gauge have
been (making slight adjustments to bring them all to 09-09h UTC
terminal hours):


March - checkgauge 50.9 mm (=100%), TBR 1 49.7 mm (97.6%), wireless
gauge
40 mm (79%)
April - checkgauge 34.3 mm (=100%), TBR 1 34.3 mm (100%), wireless
gauge
30 mm (87%)


I would recommend one of these little instruments, even if you have
an
AWS. They are great for watching thunderstorm rainfall tick up whilst
enjoying the lightning in the comfort of the conservatory, or for a
quick glance on getting up in the morning how much (if any) rain has
fallen overnight. But _not_ recommended for climatological purposes!


Stephen