vantage pro rainguage off by half

[w9olbill]

This is the Vantage pro.
I live very close to O'Hare Field.
Every rainfall we have never agrees with the rainfal @ O'Hare.
Always lower by approx. half.
I understand this can happen occasionally due to a local burst but this is almost ALWAYS LOWER.
This weekend, a very heavy widespread storm came over Chicagoland. Almost all reporting areas are within fractions of each other.
In fact the school just 1/4 mile away reports twice the rainfall as mine does.
But my rain guage is again reporting almost half the total of O'Hare.
I check and clean the barrel and cups regualarily.
My rain collector is in the clear, on my garage roof, no obstructions.
I have rain collector set to .01. My software only offers .01, .1 & 2mm.
.1 is far to big an adjustment.
Is there a way to factor a 'adjustement' of approx .05?
please and thank you.

[ocala]

Yes there is. There is a adjustment screw right by the tipping mechanism.
Go to this link and open the PDF document and it tells you exactly how to do it. Go to page 11 of the PDF document.
server.gladstonefamily.net/pipermail/wxqc/2007-July/006399.html
On a side note you should purchase a manual rain gauge.
That way you can adjust it as close as possible. What I did was filled the manual rain gauge to the 1 inch mark and then poured it into a styrofoam cup. I poked a small hole in the bottom of the cup and set it in the rain collector, then repeated the process until I adjusted it as close as possible.
You'll never get it 100% accurate because with heavier rains some water is lost during the tipping process. Sometimes my tipping gauge will read just above or below the manual gauge depending on the type of rain.
Here is a link if you want to purchase a manual gauge.
www.weatheryourway.com/cocorahs/index.html
If you do buy the manual gauge sign up for COCORAHS in your state. It's a national rain database that uses only manual gauges.
You can read about them here.
cocorahs.org/

[w9olbill]

thanks. got out the ladder, in the POURING rain and did an adjustment.
Will get a manual to test it when I can