The volumetric flow is then calculated by measuring the average velocity of an air stream passing through a passage of a known diameter. This objective of this paper is to provide the field engineer with single, concise source of information on flow measurement using a Pitot tube. The Pitot tube measures air velocity directly by means of a pressure transducer which generates an electrical signal which is proportional to the difference between the pressure generated by the total pressure and the still air (static pressure). The density of air at 85oF and 16 psia can be calculated using the ideal gas. Calibrating the measurement system in a wind tunnel can further increase the accuracy of the velocity and the flow measurements. Consider a pitot tube being used to measure air velocity in a heating duct. Also, the placement of the pitot tube in the passage will influence how accurately the measured flow tracks the actual flow through the passage. When measuring volumetric flow, the ‘passage of a known diameter’ must be designed to reduce air turbulence as the air mass flows over the Pitot tube. The velocity pressure is converted to velocity in FPM. The difference between the two is the velocity pressure. It is a double wall tube, the inner tube senses total pressure and the outer tube senses static pressure.
The fluid velocity is directly proportional to the velocity pressure and can be calculated using the formula V 1096. Pitot Tube The pitot tube senses the total pressure and static pressure in the duct or plenum. The Pitot tube measures air velocity directly by means of a pressure transducer which generates an electrical signal which is proportional to the difference between the pressure generated by the total pressure and the still air (static pressure). Magnehelic® Differential Pressure Gage and Pitot Tube Measuring Air Velocity. The incorporation of sensors to measure the air temperature, barometric pressure, and relative humidity can further increase the accuracy of the velocity and flow measurements.
USING A PITOT TUBE TO MEASURE AIR VELOCITY SOFTWARE
The accurate measurement of both air velocity and volumetric airflow can be accomplished using a Pitot tube, a differential pressure transducer, and a computer system which includes the necessary hardware and software to convert the raw transducer signals into the proper engineering units.
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