8. Notes on some flowmeters for closed pipes

The remarks that follow provide some pointers.

• Orifice flowmeters

  For all these flowmeters, the density of the fluid must be known, even if the mass flow rate is not being measured. In the case of gases, if high accuracy is required, it may be necessary to use standard temperature and pressure measurements, or to measure density directly. These are the only flow rates fully defined by a standard (ISO 5167).

• Orifice plate

  Some orifice plate models, such as diaphragms,...