I really don't understand why this is so complicated for calibrating a
rain guage. The diameter, radius, nor circumference have nothing what
so ever to do with calibrating the rain guage. It is mearly a funnel to
guide the water (rain) to the tipping bucket. As per the instructions
quoted below:
"To measure rainfall accurately, you will need to calibrate the tipping
bucket by making sure it is level and dripping water through the
collector top. Adjust the calibration screws so that 16 oz at the 1 inch
per hour rate produces 100 counts. This can be measured using the rain
guage display in the weather station software. Use a paper cup with a
pin hole in the bottom to supply the water at the proper rate."
So get 16 oz. of water and a paper cup or whatever prick a pin hole in
it and start pouring water (this will take a long, long time) and
calibrate the tipping bucket screws while monitoring with software.
Once you have it calibrated, then hook it up to the T-238.
Now if you do not want to waste your time refilling a paper cup over and
over. Go to the local pet store (even Wal-Mart) buy some air hose a air
value (plastic regulator), and your favorite 2 ltr. drink on sale.
Drink the soda or pour it out, drill hole in cap for hose, seal it, fill
bottle with 16 oz measuring cup. Put cap w/hose back onto the bottle
and adjust the regulator for the proper flow to produce 100 counts.
Hope this is of any help to anyone. Else you're going to go bald or
gray haired way before your time. I know, I am already there!