analysette 22 „ECONOMY“ Page 3
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A centrifugal pump is flange mounted below the bath and
allows for suspension throughout the entire measuring cy-
cle. Due to the high flow speed of the suspension, even
large particles of high density can be correctly measured.
The centrifugation also allows for the gentle treatment of
the samples. The inflow and outflow of the suspension and
the automatic rinsing and filling procedures are controlled
by means of electromechanical control valves.
Do not use for flammable liquids such as alcohols, ke-
tones, petroleum spirits, etc.
Ensure that no liquids can penetrate the machine.
Principle of operation
Laser diffraction instruments use the physical principle of
diffraction of electromagnetic waves to determine the parti-
cle size distribution in suspensions or emulsions. The light
of a parallel laser beam is deflected by the particles. The
angle of deflection is determined by the diameter and the
optical properties of the particles. The conventional design
includes a convex lens focusing the scattered light to form
a ring on the focal plane, where a detector measures the
Fourier spectrum (light energy distribution). The particle
size distribution is then calculated with advanced mathe-
matical methods on the basis of the Fraunhofer or Mie the-
ory.
FRITSCH is uses its own patented optical system referred
to as "reverse Fourier optics". The sample is brought into a
converging laser beam, whereby the distance between the
measuring cell to the detector corresponds to the focal
length of the convex lens used in conventional systems.
To change the measuring range, the measuring cell can
simply be moved along the optical axis. The lens system
must thus not be exchanged and recalibration of the device
is not necessary. With this patented design, it is possible to
cover the entire measuring range. There is no need to ad-
just the equivalent diameter to suit the different systems
(e.g. additional detectors, complex lens systems, additional
optical devices, etc.). By increasing the distance between
the measuring cell and the detector, large particles can be
measured. To measure small particles down to submicron
size the distance between the cell and the detector is sim-
ply decreased without any need for cumbersome exchange
of lenses.
1.3.2 Description of the device
The ECONOMY model consists of a combined device pro-
viding highest user-friendliness.
It includes various state-of-the art features of modern proc-
essor and computer-controlled technology.
The dispersing unit for the measuring of suspensions is
equipped with a separate process control system for all
functions from sample preparation to introduction.
