VEGAPULS WL 61 - 4 … 20 mA/HART - two-wire

4 MountingFoam generationFlow measurement withrectangular flumeThrough the action of filling, stirring and other processes in the vessel,compact foams that considerably damp the emitted signals may formon the product surface.If foams are causing measurement errors, the biggest possible radarantennas, the electronics with increased sensitivity or low frequencyradar sensors (C band) should be used.As an alternative, sensors with guided microwave can be used. Theseare unaffected by foam generation and are best suited for such applications.The short examples give you introductory information on the flowmeasurement. Detailed planning information is available from flumemanufacturers and in special literature.3 ... 4 h max≥ 50 mm90°1h maxd min90°2 3≥ 2 mm x h max4Fig. 21: Flow measurement with rectangular flume: d min.= min. distance of thesensor (see chapter "Technical data"); h max.= max. filling of the rectangularflume1 Overflow orifice (side view)2 Headwater3 Tail water4 Overfall orifice (view from bottom water)In general, the following points must be observed:Install the sensor on the headwater side• Installation in the centre of the flume and vertical to the liquidsurfaceDistance to the overfall orificeDistance of orifice opening above groundMin. distance of the orifice opening to bottom water• Min. distance of the sensor to max. storage level38061-EN-121011VEGAPULS WL 61 • 4 … 20 mA/HART - two-wire21