A precision micrometer head allows the user to accurately adjust the position of the Pitot tip that traverses across the inside of the pipe. The tip measures the change in pressure across the pipe for a given flow rate. This flow meter quickly and easily fits into place between the adaptors in the base unit of the Flow Meter Calibration unit. The manometers of the calibration unit show the pressure differences at the flow meter and across the overall flow meter assembly. Plots of these pressures show the velocity profile in a pipe and explains the ‘boundary layer’ and surface friction in pipes and flow channels. A second tapping in the pipe wall measures the ‘static’ pressure.