On 2014-01-25 15:37:46 +0000, Vidcapper said:

On 25/01/2014 11:06, Norman wrote:
Vidcapper wrote:

Would the mounting poll being slightly off-vertical (presumably knocked that
way by the recent strong winds) adversely affect recorded totals?

Presumably the buckets would each tip with different amounts of water, but
wouldn't they offset each other?


I don't know how much difference it might make. In general, though, the Davis
VP raingauges seem to under-read compared to a standard 5-inch manual gauge.
Mine under-reads by 15-20%. It's the most disappointing feature of the Davis
VP. Undoubtedly, one of the reasons is that it is usually located some distance
above the ground whereas the standard 5-inch gauge is usually at ground level.


IRO rain gauge heights, I've found this interesting, if old, article :

http://www.hydrologynz.org.nz/downlo...v9_2_Green.pdf


I have the same problem with my VP, and after several 'experiments'
last summer, I concluded that the reed switch was not always activating
as the buckets tipped from one to the other, or if it was it was not
generating enough instant voltage to increment the counter at the base
station. This seemed to be more prevalent on one side of the bucket set
up to the other, but it was difficult to be certain.

If I counted the tips and then compared that with the display, I
always counted a higher figure; but even the display varied from one
experiment to the next. If I poured in enough water for 10 tips, quite
often the display total would be 8, but there were a number of times
when it was as low as 6.

I had intended to replace the reed switch, to see if that might help;
but I did not trust my quasi-accurate soldering ability, so at the
moment I have left it as it is.