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| Low flow of the Rietholzbach |
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| Gauging station with gauge in m absl where bubbles came out |
Theory
Air bubbler An air bubbler system uses a tube with an opening below the surface of the liquid level. A fixed flow of air is passed through the tube. Pressure in the tube is proportional to the depth (and density) of the liquid over the outlet of the tube. Air bubbler systems contain no moving parts, making them suitable for measuring the level of sewage, drainage water, sewage sludge, night soil, or water with large quantities of suspended solids. The only part of the sensor that contacts the liquid is a bubble tube which is chemically compatible with the material whose level is to be measured. Since the point of measurement has no electrical components, the technique is a good choice for classified “Hazardous Areas”. The control portion of the system can be located safely away, with the pneumatic plumbing isolating the hazardous from the safe area. Air bubbler systems are a good choice for open tanks at atmospheric pressure and can be built so that high-pressure air is routed through a bypass valve to dislodge solids that may clog the bubble tube. The technique is inherently “self-cleaning”. It is highly recommended for liquid level measurement applications where ultrasonic, float or microwave techniques have proved undependable. (source: wikipedia)
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