What mode is your RG11 in? 0.01" tipping bucket emulator?
Coincidentally, I have been running a little test this evening in our welcome and long needed rain here. I have 2 RG11s going, one in drop counter mode, one in 0.0001" tipping bucket mode, both logged to an industrial controller. More on that in a day or 2.
The RG11 can apparently discern drop sizes somewhat. That's another thing I am studying. Anyway, in this afternoon's/evening's rain, interpolating some very rough data, I estimate that it takes about 250 average sized drops to equal 0.01" of rain. I emphasize, very rough.
So, if you didn't sprinkle enough water, it would not have registered a hundredth. In drop counter and ten-thousandth mode, they are very sensitive.
A couple things I am looking at...
1) using 2 RG11s to estimate drop size and therefore how hard it is raining (mist/drizzle/rain)
2) Using drop counter or 0.0001" mode to get a quicker qualitative rain rate that waiting for 0.01" tipping bucket tips. Some of you may remember my experiments with my acoustic disdrometer.