I originally made my manual rain gauge from a standard size funnel.
Collected in a per-tared aluminium container, weighed on my wife's quite
accurate cooking scales in gms to give the exact volume, did the maths and
by entering in a spreadsheet got what seemed to be quite accurate results.
This could be a bit tedious in the old days when it used to rain here (;-)
so I bought an electronic tipping gauge.This works well and gives good
results but it presumably only tips with every complete whole mm. (This
model). For example it recorded 3mm last night but this could have been
3.9mm. If it rains again soon it will only take 0.1mm to get 1mm recorded.
I'm not particularly bothered because these are not official figures and it
will even out over time (unless of course what is already in the tray
evaporates before the next event, which will lead to an overall low bias).
Incidentally I am using an electronic gauge purchased from
www.conrad-direct.co.uk which is identical to the Oregon RGR122 (comes from
same factory) but only costs £22-00. It is useful in that it keeps a running
total and the last 9 days individual amounts.

Dave