Theoretical overview
Débitmètres à pression différentielle

A fluid is considered incompressible if its density does not vary significantly under the effect of the negative pressure used to measure its flow velocity. Since this article is primarily concerned with the engineering and practice of flow measurement using depressurizers, we will limit the theoretical developments to those which can be consulted in the basic literature. A brief summary can, however, be given based on the energy conservation equation established in 1738 by Daniel Bernouilli for an incompressible fluid: