Different types of depressants
Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full

As the metrological characteristics of orifice flowmeters 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 so 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, which has been adopted as a European and French standard by AFNOR (Association française de normalisation).

ISO 5167 concerns "Flow measurement of fluids by...