Turbidity Sensors / OBS-3-L
This product is no longer available and has been replaced by: OBS-3+,OBS300. Some accessories, replacement parts, or services may still be available.
OBS-3-L D&A Instrument Company Turbidity Monitor


The OBS-3 measured both turbidity and suspended solids. Its turbidity range was 0 to 4000 NTU. A nearly linear response to particle concentrations of turbidity spanned more than three orders of magnitude. (OBS® is a registered trademark of Campbell Scientific.)

The "-L" on a product model indicates that the cable length is specified at the time of order.



Non-Linearity of Turbidity 2% (formazin, 0 to 2000 FTU)
Drift < 5% (per year)
Settling Time < 1 s
Input Voltage 9 to 16 Vdc
Infrared Wavelength 875 nm
Maximum Depth 500 m (1640.5 ft)
Diameter 3 cm (1.2 in.)
Length 18 cm (7.1 in.)
Weight 181.4 g (0.4 lb)


Datalogger Considerations

Compatible Contemporary Dataloggers

CR200(X) Series CR800/CR850 CR1000 CR3000 CR9000X

Compatible Retired Dataloggers

CR500 CR510 CR10 CR10X 21X CR23X CR9000 CR5000 CR7X


Case Studies

New Zealand: Water Quality Monitoring
High-grade coal has been mined on the West Coast of New Zealand since the 1870s.......read more
OBS Turbidity Sensors
D & A Instruments (now part of Campbell Scientific) assisted the USDA National Sedimentation Laboratory......read more