I believe the company Oregon Scientific might have what you are looking for, or they have developed methodology you could adapt in your laboratory.

http://store.oregonscientific.com/us/weather-stations/rain-gauges.html?gclid=CJyxy9yJncYCFQkUHwodzQQA5Q

You can follow the link for calibration of  

http://www.wxforum.net/index.php?topic=20317.0

No, but this is an excellent idea, because you can somehow adjust the intensity of rain and thus to know as the response time can change or the collected amounts of precipitation. Much it is said that rain gauges have the problem that when rain is intense, the tipping bucket does not full sending an impulse which is not complete and registering a precipitation amount not corresponding to that which it was calibrated in the lab. So you can have the random error that can be generated in response to different intensities of precipitation.

I tested my rain gauges network with a peristaltic pump wich can provide different intensities from 2mm/h up to 200 mm/h following the method of Humphrey et al (1997). First of all you need to test the resolution of your rain gauges and then you can perform the calibration. If you need more information about the method you can contact me, I made a publication about the method wich currently under press.

Basile Pauthier

I´m very interested in your work on raingauges calibration . Please indicate the journal where you will publish it . Is there already a digital version of this work on line?

Dear Iza Machado Kaiser,

This work have been accepted in the journal named "Climatologie". There is, for the moment no digital version available but I hope there will be one in September. If you need informations I will be happy to help you before the publication of this article.

Basile Pauthier

I can wait the publication in September - as we are now here in final exams - so with no time at all .

Ilza