The object of this Supplement is to define and describe the proper measurement of any flow required or recommended by any of the Performance Test Codes. Flow measurements performed as specified herein satisfy the requirements of all relevant ISO flow measurement standards in effect at the time of publication.

This Supplement describes the techniques and methods of all flow measurements required or recommended by the Performance Test Codes. Newer flow measurement techniques of comparably high accuracy are included to provide alternative flow measurements for special situations in which deviations from the requirements of a code are agreed to be necessary. This is a supplementary document that does not supersede the mandatory requirements of any code unless such an agreement has been expressed in writing prior to testing.