3 Introduction
The OTT CBS, working on the air bubble principle, can be used for measuring
ground water or water levels depending on the bubble chamber used.
To meet the various demands of the station, three different versions of the OTT
CBS bubble sensor are available:
Standard version:
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Measuring range 0 … 15 m or 0 … 1500 mbar
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Resolution
1 mm or 0.1 mbar
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Accuracy
±5 mm
USGS specification version:
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Measuring range 0 … 15 m or 0 … 1500 mbar
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Resolution
1 mm or 0.1 mbar
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Accuracy
measuring range 0 … 15 ft: ±0.01 ft
measuring range 15 … 50 ft: ±0.065 % of measured value
or ±0.02 ft, whichever is less
30 m measuring range version:
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Measuring range 0 … 30 m or 0 … 3000 mbar
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Resolution
1 mm or 0.1 mbar
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Accuracy
±5 mm
The compressed air produced by a piston pump flows via a measuring tube and
the bubble chamber into the water to be measured. The pressure created in the
measuring tube is directly proportional to the water column above the bubble
chamber. The OTT CBS determines the barometric air and bubble pressure one
after the other. By taking the difference between the two signals, the OTT CBS
calculates the height of the water level above the bubble chamber.
The power supply can be provided from a mains adapter, battery or solar power.
The OTT CBS contains a purge function. This clears the measuring tube and the
bubble chamber of any minor contamination by pumping a large volume of air
into the measuring tube.
By using an intelligent pump strategy, no air drying unit is necessary for the
measuring range of 0 … 15 m.
Hose co
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ectio
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or
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easuri
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g tube
Air
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ilter
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or
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co
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g air
DIP switch co
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part
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Status LED
Butto
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or activati
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the purge u
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al blocks A a
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d B
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or co
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ecti
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g the datalogger
a
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d power supply
Fig. 1: Overview of OTT CBS.
5