OBS-5+

The OBS-5+ monitors high sediment concentrations using an infrared laser and a proprietary dual photo-detection system (U.S. Patent No. 5,796,481). The probe transmits sediment concentration and depth to a PC via an RS-232 or RS-485 link. Data are also stored internally.

The OBS-5+ is ideal for monitoring dredging and site-remediation operations, determining dredge efficiency, providing data for sediment transport research, and supporting undersea mining and trenching.

(OBS^® is a registered trademark of Campbell Scientific.)

The OBS-5+ has a Windows GUI that enables the user to generate and store sediment calibration tables, log data, program logging/sampling schemes, and graphically display data. Using the Windows GUI, an operator can calibrate the OBS-5+ with sediments, change electronics gain to optimize resolution, create as many as 15 unique sediment lookup tables, and store those tables in FLASH memory for future use. Users can complete the entire calibration process without spreadsheet calculations and curve fitting.

Advantage of Multiple Detectors

Unlike single-detector systems such as the OBS-3+, which cannot measure suspended solids concentration (SSC) levels greater than about 10 g l^-1 (mud) and 100 g l^-1 (sand), the OBS-5+ uses multiple detectors. With these detectors and an embedded controller, the OBS-5+ extends the measurement range of the sensor by a factor of about ten. 

The OBS-5+ projects a beam of near infrared (NIR) laser light into a water sample next to two photodetectors. Suspended particles scatter light from the beam onto the detectors and a microcontroller determines SSC from their photocurrents. Because the detectors are unequally spaced from the laser, the particle concentrations corresponding to the peak response are also unequal and after being calibrated with sediment, an OBS-5+ can measure and uniquely resolve sediment SSC values greater than the peaks in response.

The OBS-5+ has been used extensively to monitor dredging and mining operations in the US, EU, China, Vietnam, and Indonesia.

Reference

John Downing. 1998. Suspended Particle Concentration Monitor. U.S. Patent Number 5,796,481.

(OBS^® is a registered trademark of Campbell Scientific.)