Finds the measurement uncertainty of gas orifice and venturi flow systems.The gas uncertainty calculation finds uncertainty in a system where differential pressure transmitters are used to measure the pressure drop across an orifice plate or a venturi flow meter.

References
International Standard ISO5167-1 2003, Measurement of fluid flow by means of pressure differential devices – Part 1. Orifice plates, nozzles and Venturi tubes inserted in cross-section conduits running full.
British Standard BS1042 Section 1.1:1992, Measurement of fluid flow in closed conduits Part 1. Pressure differential devices – Section 1.1 Specification for square-edged orifice plates, nozzles and Venturi tubes inserted in circular cross-section conduits running full.