Read the article on the following site:

http://ezinearticles.com/?Rain-Gauges&am...

Well I have an in ground sprinkler system and the rain guage can be set between 1/4 and 3/4 inches of rain so it will not come on if there is enough water in the ground.That is an advantage. Now for the disadvantage. They sell rain guages in all sizes so you can tell how much rain is fallen but yours could say 1 inch fell and mine would say 3 inches fell. Because they are not uniform that are useless.