Laser particle size analyzer
LISST-100™ Sequoia Scientific

The LISST-100 instrument is a multi-parameter system for in-situ observations of particle size distribution. It also records the optical transmission, pressure and temperature. The instrument is fully self-contained with battery and data-logger. It can be used with supplied programs, or in specially designed modes, e.g. event triggered based on storms (pressure variance) or fronts (temperature front). Two size-ranges are available: 1.25-250 microns (Type-B) and 2.5-500 microns (Type-C). Standard memory size is 16MB, suitable for storing approximately 156,000 size distributions, with option to expand to 125MB, or 1,260,000 size distributions. Special versions are available for deep-ocean, high-concentration, or low-concentration environments.

At the heart of the instrument is a collimated laser diode and a specially constructed annular ring detector. Scattering at 32 angles is the primary information that is recorded. This primary measurement is mathematically inverted to get the size distribution, and also scaled to obtain the volume scattering function (VSF). The size distribution is presented as concentration (micro-l/l) in each of 32 log-spaced size bins. Optical transmission, water depth and temperature are recorded as supporting measurements.

An auxiliary salinity sensor is available as an option to obtain full CTD capability. Designed for extended field application, the LISST-100 is a self-contained battery-powered instrument that can be deployed on a tripod, used in a profiling mode, towed, or moored. Many custom versions of the instruments have been built, including for deep-sea applications. Custom inquiries are welcome.