LISST-25 marks a generational advancement in the measurement of suspended
sediments. Unlike all prior sediment sensors, optical or acoustic, the LISST-25X
maintains its calibration over a 200:1 range of particle sizes. This is the
only sensor capable of holding calibration for sediment concentration regardless
of particle color or size within this broad a range.
The idea behind the
LISST-25X is to use shaped focal plane detectors. These detectors (see figure)
derive their shape from the physics of light scattering. The shape is found such
that for any size of particle in the 2.5 to 500 micron range, the instrument
reports the correct volume concentration. A different shape is found to yield
area concentration. The ratio of volume to area is called the Sauter Mean
Diameter. The instrument employs 2 paris of shaped detectors. One pair measures
particles in the 2.5 to 63 micron range, the other in the 63-500 micron range.
An anti-fouling accessory BioBlock is
also available for this instrument.
The instrument is self-contained,
with memory and batteries. It is fully programmable to set sample rate. Data can
be internally stored or captured in real time. A depth sensor is included as
standard.
Software for data offload and display is
provided.
The LISST-25A is
discontinued since July 2005.
This instrument was the original
version. It has been superseded by the more powerful LISST-25X described
above.
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