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

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OBS-3A Multi-Parameter Turbidity System

The OBS-3A combines our OBS probe with pressure, temperature, and conductivity sensors in a battery-powered recording instrument. The monitor is operated
with software running under Windows® 98, 2000, and XP.


Users can program sampling schedules with a PC. When
surveying, data are displayed in real time as they are recorded.
During autonomous operation, the unit records data in FLASH memory which can be post-processed and graphically displayed with EXCEL or LOTUS.


The OBS-3A is a battery-powered measurement system which offers measurement of turbidity and suspended solids plus pressure, temperature, and conductivity. All sensors are housed in a container capable of operating at depths of up 300M (depending on which pressure sensor is selected)

Turbidity and suspended solid concentrations are measured by the renowned OBS optical back scatter sensor which this system is built around. The sensor detects near infrared radiation as it is scattered from particles in the water.


Temperature is measured by a fast response thermistor which is clad in stainless steel, whilst pressure is measured by a semiconductor piezo resistive strain gauge and different working depths must be selected as an option. A four electrode conduction type cell takes care of conductivity measurements.

The monitor is operated with software compatible with Windows 98, 2000, or XP.



Measures sediment concentrations to 5,000 mg/l and turbidity
to 4,000 NTU with fieldproven OBS* technology
Logs depth, wave height, wave period, temperature, and salinity
Records 200,000 lines of data in FLASH memory
No cable required, runs 1,500-8,000 hours on 3 “D” cells
Compact package - 76 mm (3”) by 362 mm (14.3”)
Program setpoints and sampling times
Record turbidity at remote sites



Monitor dredging and mining operations
Wastewater effluent measurements
Sediment transport research
River and stream gauging
Permit compliance



Technical Specifications


Turbidity: 0 to 4,000 NTU
Concentration* - Mud: 0 to 5,000 mg/l;
Sand: 2 to 100,000 mg/l
Depth: 0 to 10, 20, 50, 100 or 200 mtrs
Temperature: 0-35oC
Conductivity: 0-65 mS/cm
*Depends on sediment type
Turbidity: <2%
Concentration - Mud 2% of reading, sand
3.5% of reading
Pressure: ±0.5% of f.s.2
Temperature: ±0.5oC
Conductivity: 1%
2f.s. = 50, 100, or 200 dBar
Other Data
PC interfaces:
RS-232 / 115 kbps
RS/485 / 115 kbps with external interface
Maximum data rate: 25 Hz
Infrared wavelength: 875 nm
Maximum depth: 300 m
Drift: < 2% / year
Connector: MCBH-7-FS, wet-pluggable
Physical Dimensions
Diameter: 76 mm (3.0”)
Length: 362 mm (14.3”)
Weight: 1.5 kg (3.4lb) without batteries

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