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OBS-3+ Turbidity Sensor
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Overview

The OBS-3+ is a submersible turbidity probe that has sideways-facing optics. It uses OBS technology to measure suspended solids and turbidity for applications ranging from water quality in freshwater rivers and streams to sediment transport and dredge monitoring. Campbell Scientific data loggers measure the OBS-3+ probe's output and calculate turbidity.


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Benefits and Features

  • Sideways facing optics avoid obstructions above and below the probe
  • Measures suspended solids and turbidity for up to 4000 NTUs
  • Provides a compact, low-power probe that is field proven
  • Compatible with most Campbell Scientific data loggers
  • Accurate and rugged
  • Stainless-steel body allows use down to 500 m in fresh water
  • Titanium body allows use down to 1500 m in fresh or salt water
  • Fitted with MCBH-5-FS, wet-pluggable connector—multiple mating cable length options available
  • Offers an optional five-point sedimentation calibration for better measurements (see Ordering Info on the web page)

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Detailed Description

The OBS-3+ uses its sideways-facing optics to emit a near-infrared light into the water. It then measures the light that bounces back from the water’s suspended particles.

If an obstruction is in the emitted light’s range, the light will scatter back and the turbidity reading will be too high. This probe's sideways-facing optics avoids obstructions above and below the probe. The OBS300 is available for locations that have obstructions around the sides of the probe.

OBS® is a registered trademark of Campbell Scientific.

Specifications

Range
  • 0 to 250 NTU
  • 0 to 500 NTU
  • 0 to 1000 NTU
  • 0 to 3000 NTU
  • 0 to 4000 NTU
Maximum Submersion Depth
  • 500 m (1640.5 ft) for stainless-steel body
  • 1500 m (4921.5 ft ) for titanium body
Concentration Accuracy
  • 2% of reading or 1 mg/l (whichever is larger) for mud
  • 4% of reading or 10 mg/l (whichever is larger) for sand
Maximum Concentration Range
  • Maximum concentration depends on sediment size, particle shape, and reflectivity.
  • 5,000 to 10,000 mg/l (for mud)
  • 50,000 to 100,000 mg/l (for sand)
Operating Temperature Range 0° to 40°C
Drift over Time < 2% per year
Maximum Data Rate 10 Hz
Minimum Warm-up Time 2 s
Infrared Wavelength 850 nm ±5 nm
Daylight Rejection -28 dB (re: 48 mW/cm-2)
Optical Power 2000 µW
Turbidity Accuracy 2% of reading or 0.5 NTU (whichever is larger)
Housing Material 316 stainless steel or titanium
Connector MCBH-5-FS, wet-pluggable
Diameter 2.5 cm (0.98 in.)
Height 14.7 cm (5.79 in.)
Weight 181.4 g (0.4 lb)

-2.5 Output Option

Output Voltage 0 to 2.5 V (over selected NTU range)
Supply Voltage 5 to 15 Vdc
Current Drain 15 mA

-5 Output Option

Output Voltage 0 to 5 V (over selected NTU range)
Supply Voltage 5 to 15 Vdc
Current Drain 15 mA

-20 Output Option

Output Voltage 4 to 20 mA (over selected NTU range)
Supply Voltage 9 to 15 Vdc
Current Drain 45 mA

Compatibility

Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.

Dataloggers

Product Compatible Note
21X (retired)
CR10 (retired)
CR1000 (retired)
CR10X (retired)
CR200X (retired)
CR211X (retired)
CR216X (retired)
CR23X (retired)
CR300
CR3000
CR310
CR500 (retired)
CR5000 (retired)
CR510
CR6
CR800
CR850
CR9000 (retired)
CR9000X

Frequently Asked Questions

Number of FAQs related to OBS-3+: 2

  1. This depends on the turbidity of the water. In very clear water exposed to direct sunlight, up to 18 in. of water may be needed to prevent the sun from affecting the readings. Less sunlight penetrates more turbid water, which means the sensor would not need to be positioned as deeply. If the target water is clear and shallow, it may be necessary to construct a canopy above the water to shadow the monitoring site.

    In addition, the sensor must be positioned in the water so that nothing obstructs its field of view. In very clear water, this may require an 18 in. standoff.


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