[wxqc] Davis Vantage Pro2 Rain Gauge Calibration

Ken True webmaster at saratoga-weather.org
Tue Jul 3 13:37:28 CDT 2007


I haven't seen the adjustment for the tipping buckets mentioned in later 
ISS documentation, but the earlier separate rain collector II  ( 
http://www.davisnet.com/product_documents/weather/manuals/rain_collector.pdf 
) on page 11 shows a diagram of the adjustment screw.  One turn 
clockwise will lower the reading by 6% while one turn anti-clockwise 
will raise the reading by 6%.  Both screws have to be rotated in the 
same direction and the same amount to properly do the adjustment.  So 
two anti-clockwise turns on both screws should raise the measurement by 
about 12%.

I had compared my VP1 collector to a neighbors older VP1 and a manual 4" 
collector and found I needed to adjust the VP collector up by about 11% 
to match the readings.  Now all three are within 0.01 (one tip) for a 
rain event.

Ken True
CW1792
http://saratoga-weather.org/

Victor Engel wrote:
> I'm just waiting for it to stop raining so I can check mine <G>. BTW,
> until this thread started, I was unaware of an adjustment screw. I'm
> going to have to pull out the manual to see where it's located.
>
> On 7/3/07, Trevor <blznqgr at earthlink.net> wrote:
>   
>> It pays to check....I check another station that I run (Davis Vantage
>> Pro1) and it was right on the money...so go figure.....some come out of
>> the factory A-ok and some don't!!
>>
>> de Bastos, Derek wrote:
>>     
>>> Trevor wrote:
>>>
>>>
>>>       
>>>> The rain gauge has never been adjusted since the factory.
>>>> It required an adjustment of +12% to get from 84 tips of
>>>> the bucket (.01 in.per tip) to the 100 tips require to
>>>> measure 1" of water.
>>>>
>>>>         
>>> FWIW, I checked the calibration of my VP1 after changing its battery
>>> this past weekend.  Like Trevor's, my rain gauge has not been adjusted
>>> since it left the factory.
>>>
>>> Coincidently (or not), I got a nearly identical result-- my gauge was
>>> reading low (81 tips for 1") and it took around two turns on the screws
>>> to fix it.  Before reading this thread, I would have not suspected my
>>> gauge could be this far off.
>>>
>>> Derek
>>> CW2463
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