In principle precipitation can be recorded and measured everywhere using simple means. In reality, there are major problems involved in measuring precipitation, however. The knowledge of the interval during which the precipitation was measured is essential for the use of the data. Four measuring networks that cover the whole of Switzerland provide precipitation values for periods of one year, one day, half a day and 10 minutes. (from The Hydrology of Switzerland, 1999)
In this publication of the Federal Office for Water and Geology methods are described for the measuring of precipitation from page 9 onward.