Testing a Powered Flow Hood on a Variety of Registers

The paper 'The Zero Pressure Paradox' (Bink et al, 2015), explains the theoretical limitations and some practical issues of the zero pressure compensation method as used by a powered flow hood. It was shown that the needed pressure compensation for supply and exhaust are fundamentally different. Furthermore, based on published results from others and on our own unpublished results, we claimed that the measuring accuracy depends on the type of air terminal device and how and where the pressure to be compensated is measured in the instrument. To minimize these effects we developed the 'extended' zero pressure method. To follow up on this and for further clarification, this paper presents the evaluation of a large number measurements with a powered flow hood. Both measurements of supply and exhaust at a large number of grids are presented together with an uncertainty analysis of measuring ventilation.