2. Checking meters at atmospheric pressure and in dry air

French regulations currently only require verification of meters of certain types: diaphragm meters (or meters with deformable walls), rotary piston meters, turbine meters (or speed meters) and ultrasonic meters, as well as any meter involved in financial transactions.

The regulations stipulate that meters must be tested in air at atmospheric pressure. The frequency of verification is set by the decree of October 21, 2010 (consolidated on November 16, 2016) on fuel gas meters (article 21 and appendix 3).

We will only describe the main methods that can be used in this case.

A distinction must be made between the verification of diaphragm meters and the verification of rotary piston meters, turbine meters or ultrasonic meters, known as "industrial meters".