Established in 1995, Sequoia Scientific, of Bellevue, WA, US, is the manufacturer of the LISST series of submersible laser diffraction sensors for measuring the size distribution and concentration of suspended particles in the aquatic environment. The workhorse of this brand, the submersible LISST-100X, is routinely used for measuring the size and concentration of suspended sediment, plankton, and oil droplets in situ.
Sequoia is the only company in the world to manufacture laser particle sizers meant for submersible and field use.
Submersible laser sensor for measuring and monitoring oil droplets
Sequoia’s LISST-100X is a fully autonomous, programmable, submersible laser sensor for measuring the size and concentration of suspended particles (sediment, plankton, oil droplets) to a depth of 300m. The size range covers particles from 0.0025mm to 0.5mm in 32 size classes.
The LISST-100X is normally deployed in its autonomous mode, but if desired it is also possible to have the instrument transmit data to a topside PC using a serial cable. In this mode the instrument will display the concentration in each of the 32 size classes every second so that changes in particle size and concentration can be immediately observed.
The LISST-100X has been used intensively by the oil spill research community to estimate the effectiveness of dispersants under changing conditions such as variations in water temperature, breaking waves, etc.
During the monitoring work carried out in connection with the Deepwater Horizon accident in 2010, numerous LISST-100X instruments were used by a range of monitoring groups to monitor the oil droplet size distribution in the Gulf of Mexico and estimate the effectiveness of the dispersants.
Lightweight laser sensor for measuring and monitoring oil droplets
The LISST-100X is housed in a black-anodized aluminium pressure housing, and is equipped with a pressure and temperature sensor for easy profiling applications. Weighing just 25lb in air (8lb in water), the instrument is easy to handle. For flow-through applications, a range of flow-through cells are available.
Portable laser particle sizer for mud
Sequoia’s LISST-Portable is the world’s first and only portable laser particle sizer. The LISST-Portable weighs in at 10lb, and has a rechargeable battery and a touch-panel display for easy programming, data analysis and viewing of data. The size range covers mud from 0.0025mm to 0.5mm in a concentration range from 10mg/l to 2,500mg/l.
Mud measurement and monitoring laser particle sizer
In order to measure the size and concentration of a sample of mud, the sample is introduced in the mixing chamber of the LISST-Portable, suspended in an appropriate dispersant. Using the touch-panel display the user is then guided through the measuring process, which takes less than 2min.
The size distribution and concentration of the mud sample is displayed on the touch-panel display for immediate viewing. Data are stored on-board in ASCII file format and can be offloaded for viewing in Excel or other spreadsheets.
Rugged mud measurement and monitoring laser particle sizer
Compact, lightweight and housed in a moisture-tight, shock-resistant case, the LISST-Portable is built for the rigors of field use.