This document considers liquid atmospheric precipitation (rain) and defines the procedures and equipment to perform laboratory tests, in steady-state conditions, for the calibration, check and metrological confirmation of non-catching rainfall measurement instruments. This document is not applicable to field performance.
It provides a classification of non-catching measurement instruments based on their laboratory performance. The classification does not relate to the physical principle used for the measurement, nor does it refer to the technical characteristics of the instrument assembly but is solely based on the instrument calibration.
Attribution of a given class to an instrument is not intended as a high/low ranking of its quality but rather as a quantitative standardized method to declare the achievable measurement accuracy to provide guidance on the suitability for a particular purpose, while meeting the user’s requirements.