The LISST-100
is a fully self-contained multi-parameter data logging system for in-situ
measurement of particle size and distribution as well as optical transmission,
pressure and temperature. Two ranges are available: 1.25-250 microns
(Type-B) and 2.5-500 Microns (Type-C). Standard memory size is 512KB,
suitable for storing aproximately 6,000 size distribution, with an option
to expand to 26,000 size distributions. The Size distribution is
presented as concentration (micro-1/l) 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 TCD capability, see application note L003. Designed
for extended field application, it can be used with supplied programs,
or in specially designed modes, e.g. event triggered, such as pressure
or temperature variances. The unit can be either deployed on a tripod,
used in profiling mode, towed or moored.
*Special versions are available for deep-ocean, high-concentration, or low-concentration environments.
LISST-25 marks
a generational advancement in the measurement of suspended sediments. Unlike
all prior sediment sensors, optical or acoustic, the LISST-25 maintains
its calibration over a 200:1 range of particle sizes. A comparison of the
LISST-25 and a transmissometer can be seen in Application Note L10. It
is shown that when evaluated with particles of a broad range of sizes and
of several types - manmade spheres or natural terrigenous, or marine sediments
from several locations - the LISST-25 held calibration to within a factor
of 2 whereas transmissometer calibration changed by 2 orders of magnitude.
The LISST-25 uses a newly patented concept. It employs a collimated
laser beam to illuminate particles, and a specially shaped focal plane
detectors behind the receiving lens. A comet shaped detector senses volume
concentration of particles, holding calibration over a 200:1 size range.
A second detector measures the area concentration. A Sauter Mean Size of
sediments is provided from the ratio of these two outputs also. For details,
please see Application Note L005. The instrument incorporates a transmissometer
function. This output is also made available to compare data with historical
records.
Estimating Sediment
Transport Rates and Particle Settling. The LISST-ST is a submersible
field instrument developed for in-situ observation of the size-dependent
settling velocity distribution of suspended particles. It incorporates
a mechanized Settling Column. In a Settling Experiment, a water sample
is drawn and trapped. The evolution of the size distribution near the base
of the settling column during the settling experiment is interpreted to
estimate settling velocities. Settling velocities are estiamted for 8 log-spaced
size classes covering the range 1.25-250 microns (Type B), or 2.5-500 microns
(Type C). For details, please see Application Note L007. The LISST-ST is
designed to carry out multiple settling experiments while submerged. A
motorized mechanism operates the doors that control exchange of water between
the settling column and the ambient environment. This permits repeated
settling experiments. A separate built-in motorized stirrer is used to
agitate and flush out settled particles after each settling experiment.
In addition to particle size distribution histories with each settling
experiment, water pressure and temperature are also recorded. The
LISST-ST is a fully autonomous, battery operated, self-contained unit.
It is engineered for low power consumption and built to withstand the rigors
of field deployment. Easy to program features permit flexibility in duration
of experiments, and in operating modes.
Battery-Powered,
and Portable for Rigorous Field Use. The LISST-PORTABLE is the world's
first battery powered portable particle analyzer. It can be used in the
field, on a boat, factory floor, or in the laboratory. Using the same small-angle
laser scattering principles as our other LISST products, the LISST-PORTABLE
analyzes samples in a wet-state and obtains particle size distribution,
and particle volume concentration. The LISST-PORTABLE incorporates a mixing
chamber with a stirring capability to keep the largest large particles
suspended. The chamber is also equipped with in/out flow-through valves.
Using these, the instrument can be used in-line. The LISST-PORTABLE includes
a rechargeable battery pack, a computer, an LCD display, and a microprocessor
for control and data storage. The instrument is programmable for unattended
use over extended periods of time. Alternately, it can provide measurements
for immediate view if connected to a PC. At only 7 Kg. and housed in a
moisture-tight, shock-resistant case, the LISST-PORTABLE is built for the
rigors of transport and field use.
