On Sunday, August 26, 2012 1:05:52 PM UTC+1, johnd wrote:
A couple of comments:



A VP2 gauge should obviously not stop recording simply because rainfall is

very heavy. There must be some other explanation here. As with most less

expensive RBR's, the gauge will under-record to a limited extent during very

high rainfall rates simply because the tipping mechanism will miss rainfall

for example while it is tipping. The display may also give the impression of

missing rainfall at the time because (i) the console rain reading does not

update instantaneously but is subject to a potential delay of 1-2 minutes;

and (ii) during very heavy rain the signal on a wireless model can drop out

if the signal is relatively weak to start with (but the missing readings

should 'catch up' soon after good reception is restored - provided the down

time is not too long).



A VP2 gauge will typically under-record rainfall by a few % relative to a

reference gauge because eg of the difficulties at very high rainfall rates

mentioned above. But the larger discrepancies sometimes reported are often

not genuine like for like comparisons. Typically the VP2 gauge will be at

least a few feet in the air where it will inevitably under-record by 5-10%

relative to a ground-based gauge because of well-known wind effects. Also

the two gauges are often not exactly side-by-side and so location effects

can also come into play. (If a 0.2mm gauge has been mistakenly configured as

a 0.01" at the console or in software then this can also obviously cause an

apparent under-recording of 20-25%.)



John Dann

www.weatherstations.co.uk

Spot on! I once did a trial of two identical 127mm gauges, installed 15 feet apart which showed a difference of 6%.