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The OBS501 combines a backscatter sensor (better at measuring high turbidity) with a second sidescatter sensor (better at measuring lower turbidity). This SDI-12 probe uses digital processing.

The OBS501 incorporates the ClearSensor® Antifouling Method to ensure the accuracy of its measurements. The ClearSensor® method uses a shutter/wiper mechanism to protect and clean the optics. This antifouling method also includes a chamber filled with a biocide that continuously leaches out over the optics while the probe is in the closed position.

The OBS501 includes a disposable plastic sleeve that can make clean up a snap, as well as an optional copper sleeve that can provide additional protection, especially in sea water.



  • Dual backscatter and sidescatter sensors used to measure turbidity
  • ClearSensor® Antifouling Method for better measurements in biologically-active water
  • Shutter/wiper mechanism keeps lenses clean
  • Refillable biocide chamber prevents fouling
  • Disposable plastic sleeve facilitates clean up
  • Optional copper sleeve for additional protection, or disposable plastic sleeve facilitates easy cleanup
  • SDI-12 and 5V outputs

Technical Specifications

  • Dual Probe: 90° side scatter and backscatter
  • Range: 0 to 4000 NTU
  • Active & Passive Antifouling: shutter, wiper, biocide, copper, optional removable sleeve
  • Accuracy: ±2% of reading or 0.5 NTU (which ever is greater)
  • Temperature Range: 0° to 40°C
  • Temperature Accuracy: ±0.3°C
  • Emitter Wavelength: 850 nm
  • Power Requirements: 9.6 to 18 Vdc
  • Power Consumption
  • Quiescent: <200 µA
  • Measurement: <40 mA
  • Communication : <40 mA
  • Maximum Peak Current: 200 mA for 50 ms when shutter motor starts
  • Active Shutter Motor: <120 mA
  • Measurement Time: <10 s Outputs: SDI-12 (version 1.3) 1200 bps;RS-232 9600 bps; Analog 0 to 5 Vdc Max.
  • Submersion Depth: 100 m (330 ft)
  • Dimensions Diameter: 4.8 cm (1.88 in.)
  • Length: 27 cm (10.63 in.)
  • Weight: 0.59 kg (1.30 lb)
  • Maximum Cable Length: > 500 m (1640 ft)

Data Sheet

  • OBS 501

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