Glossary – Definitions
Calibration and periodical verification of gas flowmeters

Volumetric flow; actual flow rate

Flow rate in m³/h measured under actual conditions of pressure, temperature and gas composition.

Débit normal (or standard); standard flow rate

Flow rate in m³(n)/h measured under normal (or standard) pressure and temperature conditions. In France: T₀ = 273.15 K and P₀ = 1.013 x 10⁵ Pa.

Compressibility Z; compressibility

Correction factor to take account of the variability of the volume of a real gas as a function of its pressure, temperature and composition.

Volume, débit de référence; reference volume; flow rate

Flow measured by reference meter (nozzles or secondary reference).