The systematic uncertainty of laboratory flow calibrations

There are two axioms applicable to this paper: the first is that no flowmeter can be more accurate than the laboratory which calibrated it; the second that no uncalibrated flowmeter can be more accurate than a like one that is calibrated in a recognized standards laboratory. The fundamental systematic uncertainty in flow measurement is that inherited from the flow calibration laboratory. This paper focuses on ascertaining this fundamental systematic uncertainty by deriving from the published instances of interlaboratory comparisons a value in which one may be 95 percent confident. For water flow measurements, this value turns out To be +/-0.28 percent, and for liquid hydrocarbon fuels it is +/-0.77 percent. Cold water calibrations are the most accurate.