In recent years the use of turbine flowmeters in industry has become well established. An NEL publication by Myles and Harrison gives an excellent survey of their construction, use and calibration. It seems from ref. 1 that calibration by the manufacturers is done mainly with liquids, presumably in order to use a weighing technique to obtain the volume flow. A typical calibration report for a gas is that of Redding where the flowmeter in question was calibrated on air against a vena contracta tapped orifice. Eight experimental points are given on this calibration curve over the range of the meter. It was considered of interest to calibrate a turbine flowmeter on air against a pitot tube traverse. This method is generally regarded as being of greater accuracy than an orifice or nozzle method. Also it was considered that if a large number of readings were taken the amount of random scatter, if any, would become apparent.