Air velocity and flow measurement using a Pitot tube

摘要

The accurate measurement of both air velocity and volumetric airflow can be accomplished using aPitot tube, a differential pressure transducer, and a computer system which includes the necessaryhardware and software to convert the raw transducer signals into the proper engineering units. Theincorporation of sensors to measure the air temperature, barometric pressure, and relative humiditycan further increase the accuracy of the velocity and flow measurements. The Pitot tube measures airvelocity directly by means of a pressure transducer which generates an electrical signal which isproportional to the difference between the pressure generated by the total pressure and the still air(static pressure). The volumetric flow is then calculated by measuring the average velocity of an airstream passing through a passage of a known diameter. When measuring volumetric flow, the'passage of a known diameter' must be designed to reduce air turbulence as the air mass flows overthe Pitot tube. Also, the placement of the pitot tube in the passage will influence how accurately themeasured flow tracks the actual flow through the passage. Calibrating the measurement system in awind tunnel can further increase the accuracy of the velocity and the flow measurements. Thisobjective of this paper is to provide the field engineer with single, concise source of information onflow measurement using a Pitot tube.