- To reach an accurate measurement result take care on the following points:
- The Venturi can not be used in channels where a flow stop or back flow is expected.
- The flume have to be installed horizontal. (maximum allowed difference is 1,5 o/oo)
- The Venturi must be installed exactly in line to channel.
- On no flow condition, there should be no water staying on the Venturi floor.
- Downstream the flume there shall be nothing installed that obstruct the flow.
- The side walls of the channel, where the two flume parts are installed, have to be vertical
- Upstream the flume (15 up to 20 x the channel width) the flow of the water has not to be obstructed. There shall be no hydraulic disturbance e.g. curves, installations, jumps, changes in the channel width etc.
When measuring flow by using a Venturi flume and an ultrasonic measurement device, please note:
- The best position of the ultrasonic transducer is approx. 2 x the height of the flume side parts upstream the flume.
- The transducer has to be installed 90° to the surface of the water.
- Use ultrasonic units with temperature compensation. Avoid direct sun light on the t-comp of the transducer, or use separate t-comp. It can be installed under a shadow roof.
- For accuracy reasons, the distance between maximum level and transducer should be as small as possible. The minimum distance between transducer face and maximum level must be 30cm (11.9in)!
 vndba4.pdf (329 KB)
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