This book is the first to present flow measurement as an independent branch of the measurement techniques, according to a new global and unitary approach for the measurement of fluid flow field, starting from finding its unitary fundamental bases. Furthermore, it elaborates the method of unitary analysis/synthesis and classification of compound gauging structures (CGS): the UASC – CGS method. These methods ensure, in a systematic and predictable way, both the analysis of the types of flow meters made until present (i.e. CGS) and the synthesis of new types of flowmeters. The book outlines new contributions in this field, including separately, for flow meters, and CGS: structural schemes and their unitary, unitary classification, unitary logical matrix, method of unitary analysis/synthesis and classification.