Measuring velocity or volume of air flow in duct
A small flow nozzle with an egg crate air straightener located upstream in a large duct provides an accurate, easily constructed air velocity measurement system. Air velocity distribution at the point of discharge across the outlet of nozzle is uniform, and static pressure is zero (atmospheric). Consequently, in the low flow area upstream from the nozzle, static and total pressure at nozzle outlet. As a result, the air velocity and/or volume of flow is easily calculated. The Series 2000 Magnehelic® differential pressure gage or manometer can be calibrated to read air velocity or volume directly - assuming standard or constant air density (i.e. temperature, humidity, and pressure). A Series A3000 Photohelic® switch/gage can be used if an alarm or control function is required at a given air velocity or volume.