Title: 36 Siemens GDB181-MO.pdf.pdf
3 A measuring device for acquiring the differential pressure – usually a measuring cross, measuring orifice or Venturi tube in the airflow – represents the basis for air volume flow measurement.The air volume flow is measured indirectly with a differential pressure sensor. Since the measured value is the differential pressure Dp, the air flow is derived from this value using the VAV box characteristic. Accordingly, the VAV box OEM has to provide the combination of Dpn and Vnom, out of which the air volume flow in m3/h or l/s can be calculated.The air volume flow value (relative or absolute) can be transmitted over the bus together with the actual value of the damper position (in %) to be used by a supervisory controller or for management purposes. The differential pressure sensor operates long-term stable and without recalibration.In critical cases material compatibility tests should be made while giving consideration to harmful substances and concentrations.