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OTT CBS - Compact Bubbler Sensor

Non-contact, bubbler sensor for longterm surface water level monitoring

The OTT CBS is a compact, accurate, and low power bubbler sensor for surface water level monitoring. The OTT CBS meets or exceeds USGS standards for accuracy, and will not drift over time. It features outputs for SDI-12 and 4...20 mA.

  • Surface water, Groundwater
  • Bubbler-in
  • Drift-free water level measurement - no pressure sensor or electronics in the water
  • 0 to 15 m or 0 to 30 m
  • ± 3 mm (high accuracy version); ± 5 mm (standard and 30 meter versions)
  • No
  • SDI-12, RS-485 (using SDI-12), or 4 ...20 mA
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For water level measurement of:

  • Streams, rivers, channels, or canals
  • Groundwater wells
  • Reservoirs, lakes, and wetlands

Ideal for monitoring:

  • Continuous water level networks
  • Lightning prone areas
  • Channels with long, flat embankments
  • Accurate—Meets and exceeds USGS guidelines for water level accuracy, and will not drift over time
  • Complete Solution—Combining the CBS with an EPS-50 bubble chamber reduces the influence of wave action and prevents unnecessary noise in your data
  • Low Maintenance—No desiccant, pump maintenance, or lubrication required
  • Easy-to-Start/Install—All programming can be completed using DIP switches; connect into existing platforms using 3/8' O.D. or 4mm O.D. measuring tube (no adapters required)
  • Compact Size—small and powerful pump motor generates the required volume of air to perform measurement.
  • Low Power—Intelligent pumping strategy compares the previous measurement to the actual pressure at the current measurement, and optimizes the pumping time depending on the difference (i.e., small changes in level are measured with very short pump cycles)
Brochure - OTT Water level measurement
CBS – Firmware - EN
Installation instructions Air drying unit for Bubble Sensor OTT CBS
Leaflet - Compact Bubble Sensor OTT CBS
Mounting instructions Bubble pot EPS 50
Operating instructions Bubble Sensor OTT CBS (current version)
Operating instructions Bubble Sensor OTT CBS (Version: 04-0211)
OTT CBS - CE Konformitätserklärung | Declaration of Conformity | Declaration de Conformité
OTT CBS - DIN EN ISO 4373 Declaration of Conformity | Declaration de Conformité | Konformitätserklärung
OTT CBS CSI Specifications
Technical Note - Sensor Selection Guide Surface Water
Whitepaper: OTT CBS - Compact Bubbler Sensor for water level measurements
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Water level measurement
Measuring range
Version ''Standard'' and ''USGS specification'' 0 ... 15 m (0...50 ft)
Version ''30 m measuring range'' 0 ... 30 m (0...100 ft)
Resolution 1 mm (0.01 ft)
Version ''Standard'' and ''30m measuring range'' ±5 mm
Version ''USGS specification'' 0 ... 15 ft: ±0.01 %
15 ... 50 ft: ±0.065 % of measurement value or 0.02 ft, whichever is less
Units m, ft, bar, PSI
Electrical data
Interfaces 4 ... 20 mA, SDI-12, SDI-12 via RS-485
Power supply 10 ... 30 V DC, typ. 12/24 V DC
Current consumption
Measuring interval 1 min typ. 320 mAh/day
Measuring interval 15min typ. 25 mAh/day
Housing material ABS
Dimensions L x W x H 165 mm x 205 mm x 115 mm
Weight approx. 1,500 g
Protection class IP43
Environmental conditions
Operating temperature -20 ... +60 °C
Storage temperature - 40 ... +85 °C
Relativ air humidity 10 ... 95 %; not condensing
Measuring tube inner diameter typ. 2 mm or 4 mm
EMV - limit values According to IEC61326 and EN61326
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How do I communication with my sensor using the RS-485 interface?

Communication on this interface follows the SDI-12 protocol. This follows a specific timing which is defined by the SDI-12 standard. Please find detailed information in the attached/linked document. The sensor wont react to simple ASCII commands send through this interface as they do not conform to the SDI-12 standard.

Regarding PLS Sensor: The RS-485 interface might not be active by default. In this case it needs to be activated using the SDI-12 interface of the sensor. Our HydroService will assist you in this matter (

Regarding CBS Sensor: The active interface of the sensor is determined by dip switches on the device. Please follow the sensor instruction to active the RS-485 interface.

Learn more about the datalogger implementation via RS-485