LASER IN SITU SCATTERING AND TRANSMISSION

Sequoia offers a comprehensive range of turbidity meters, operating on the unique and patented principle of 'forward laser diffraction' . This method guarantees excellent precision without the need for any calibration - like required in function of the particles to be measured, like with backscatter measurements.

Click here to download the FAQ page (pdf document - 320 kB)

Click here to download a study by US University to compare measurements carried out by ADP, OBS-3 and LISST sensors (pdf document - 130 kB)

LISST-100X LISST-25X

LISST-100X

LISST-25X

Measures in situ: particle size spectra:
volumetric concentration in 64 log spaced classes 1.25-250µ or 2.5-500µ
Volume Scattering Function (VSF)
Optical transmission: Measures in situ:
Total volume of particles in µl/l
Total surface of the particles in the water
The Sauter Mean Diameter = Volume/Surface
The mean particle size D50.

Technical information:
LISST-100X
LISST-25X

LISST-ST

Measures the settling time of particles in situ - classifies into 8 subdivisions.

LISST-PORTABLE

Measures next to the parameters recorded by the LISST-100 the fall-back speed of various particles. Lab version of the LISST-100.

Built-in mixing chamber and mixer. Completely autonomous.

LISST-INFINITE
 

The LISST-INFINITE is an automated dilution system designed to extend the high end of sediment concentration measured with the LISST series instruments. The LISST- INFINITE integrates with either the LISST-100X or LISST-25X to produce a shore-based, pumped high concentration system. The submersible instruments can be easily removed for standard field deployments.

The system receives commands from the LISST-100X or LISST-25X when dilution is required and executes a dilution and measurement sequence. By employing 2-steps of dilution, extremely high concentration of sediments up to 500,000 mg/l can be measured. .

THE RINGDETECTOR: 
OPERATION PRINCIPLE

The ring-detector consists of  64 segments.
Each ring segment measures the  laser light which is diffracted under a certain small angle.
Specially developed software then processes the measurements.

Laser light with a wave length of 670 nm, which is visible red light, is sent through the sampling volume. Particles in suspension of different diameter are diffracting the laser light under known angles. A special lens then projects this diffracted laser light onto the  ring detector with  64 segments.

• The quantity of particles per volume  is precisely measured  in situ.
• The one-time calibration of the equipment is carried out by the manufacturer - an individual calibration curve is delivered with each equipment.
• The measurements are completely independent of varying particle sizes, a major advantage over other turbidity meters.  
• Measures next to particle distribution also optical transmission and volume scattering (VSF)
• Temperature- and pressure sensors standard.
• Connection and interfacing to other instruments possible via  2 I/O ports.
• In situ and in the lab measurements of turbidity, particle distribution, VSF, optical transmission.
• Measures the d50 of sand in situ. (version till  500µ)
• Particle distribution in silt and sand fractions.
• Settling speed of all fine materials in suspension (LISST-ST).
• Measurements in the field or in the lab with same instrument. (mixing chamber delivered as standard)