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Marine Instruments » Multiparameter Sondes, CTDs & SVs » Turbidity Sensors » Product Details

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OBS-3+ and OBS300 Turbidity Sensors

The OBS-3+ and OBS300 use OBS® technology to measure suspended solids and turbidity to 4000 NTUs. They are submersible sensors. With the stainless steel body, these turbidity sensors can be submerged in fresh water to a depth of 500 metres.


With the titanium body, the sensors can be submerged in both fresh and salt water to a maximum depth of 1500 metres.


The OBS-3+ and the OBS300 use the innovative OBS method for monitoring suspended sediment and turbidity. With this method, the probe uses its optics to emit a near-infrared light into the water. It then measures the light that bounces back from the water’s suspended particles.


The OBS-3+ has optics on the side of its body, which allows you to avoid obstructions above or below the probe (see picture). The OBS300 has optics on the end of its body, which allows you to avoid obstructions around the sides of the probe.



Rivers and stream gauging
Dredging and mining operations
Controlling water quality in settling ponds and tanks
Sediment transport research
Providing laboratory measurements



Provides a compact, low-power probe that is field proven
Supports fresh water and salt water applications (salt water submersion requires titanium body)

Compatible with all contemporary dataloggers as well as many retired dataloggers
Contains an integral voltage clamp and optional 4–20 mA current loop
Fitted with MCBH-5-FS, wet-pluggable connector - multiple mating cable length options available
Offers an optional 5-point sedimentation calibration


Technical Specifications


Maximum Depth
Stainless-Steel Body: 500 m (1640.5 ft )
Titanium Body: 1500 m (4921.5 ft )
Drift: <2% per year
Maximum Data Rate: 10 Hz
Input Voltage
For Voltage Output: 5 to 15 Vdc
For Current Output: 9 to 15 Vdc
Typical Current Drain
For Voltage Output: 15 mA
For Current Output: 45 mA
Operating Wavelength: 850 nm ±5 nm
Daylight Rejection: –28 dB (re:48 mW cm–2)
Optical Power: 2000 μW
Turbidity: -T1 Measures the lower range of 0 to 250 NTUs or higher range of 0 to 1000 NTUs.
-T2 Measures the lower range of 0 to 500 NTUs or higher range of 0 to 2000 NTUs.
-T3 Measures the lower range of 0 to 1000 NTUs or higher range of 0 to 4000 NTUs.
-T4 Measures the lower range of 0 to 2000 NTUs or higher range of 0 to 4000 NTUs.
-T5 Measures the range of 0 to 4000 NTUs on both channels. When the low channel has a 4-20 mA output
(i.e., OBS-3+-20 or OBS300-20), the turbidity sensor.Maximum Concentration*
Mud: 5,000 mg/l to 10,000 mg/l
Sand: 50,000 mg/l to 100,000 mg/l
Turbidity: 2% of reading or 0.5 NTU (whichever is larger)
Mud: 2% of reading or 1 mg/l (whichever is larger)
Sand: 4% of reading or 10 mg/l (whichever is larger)
Housing Material: 316 stainless steel or titanium
Connector: MCBH-5-FS, wet-pluggable
Weight: 181.4 g (0.4 lbs)
Diameter: 2.5 cm (0.98”)
OBS-3+: 14.1 cm (5.56”)
OBS300: 13.1 cm (5.15”)


*Range depends on sediment size, particle shape and refl ectivity.

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