Consumer-grade automatic stations are also apt to under-read, as only a random selection is sampled for accuracy. From other discussions, it seems they can under-record by at least 10%, so it's worth hanging a decent plastic gauge near to your station, so that you can compare results and calibrate if needed. My Davis VP2 collector typically has a good 0.2mm worth in the cup after it stops raining, not quite enough to tip it over and register the reading. This also makes the next rain session look abnormally heavy for the first few minutes. However, an error of this magnitude is entirely acceptable in the overall scheme of things! Next to siting errors, it's utterly insignificant! J.