Precise measurement of flow and leakage of arbitrary gas species over a wide range

Many applications of vacuum technology require the measurement of gas flow rates and leakage rates. Depending on the application, gas flows are described by various units, whose definitions are uniquely given. Primary methods for measuring gas flow are described, which allow the direct measurement of gas flow according to its definition. Examples illustrate practical usage of the methods of measurement. Furthermore, fundamental flow devices are investigated, namely thin orifice and Venturi tube. The gas flow through these devices is well understood and the relationship between flow and pressures is well predictable. Therefore, these devices allow a measurement of gas flow by a measurement of pressures.