3. The different types of depressants

3.1 Normative and commercial law aspects

As the metrological characteristics of flowmeters with depressurizing devices are usually known by design, without calibration with the fluid to be measured, it was very quickly decided to standardize the best-known types, so that the various users could refer to a common, undisputed basis. The first bodies to do this were probably the AGA (American Gas Association) and the ISA (acronym for International Federation of National Standards Associations), succeeded by the ISO (International Organization for Standardization). The most important document in this field is currently ISO 5167 [2], which has been adopted as a European and French standard by AFNOR (Association Française de Normalisation), a document which is still in progress despite the...