Micromeritics SediGraph III 5120 User Manual

Beamsplit Determination SediGraph III 5120
3-2 Mar 2010
Beamsplit Determination
At the beginning of any automatic run, the
SediGraph III 5120 determines the exact
position of the top of the cell relative to the
X-ray beam to establish a known starting
point for the cell movement. The SediGraph
establishes a known position of the cell by
moving it to the point where the top edge of
the cell splits the X-ray beam in half. This
beamsplit data is stored in the SediGraph
software for use in the analysis. A beamsplit
is performed by the SediGraph for each
analysis.
Immediately before an analysis, the operator disperses the sample in the sedimentation fluid.
This dispersed sample and fluid mixture is added to the SediGraph mixing chamber where it is
stirred to maintain dispersion and heated to the analysis temperature. At the appropriate time,
the fluid is pumped into the analysis cell. The SediGraph maintains circulation through the cell
to prevent sedimentation as a second scan determines the maximum (or full scale) concentra-
tion of the sample to fluid mixture.
Full Scale Determination
Shown at the left is a sample cell full of
sedimentation liquid and particles. The
particles absorb some of the X-ray
energy as it travels from the X-ray tube
through the windows (and sample slurry)
to the transparent window of the Photo-
Multiplier tube. The actual change in
absorbance with time is what the Sedi-
Graph uses in determining the particle
size. To speed up the time required for a
test, the SediGraph will move the cell
assembly down looking at finer and finer
particles.
At the 220 data collection points, the X-
ray intensity is recorded and a full-scale
value is calculated. The full-scale value is used for 100% sample concentration because the
cell contains suspended particles, representing the highest particle concentration for the analy-
sis. These particles are not allowed to settle because the cell pump is running during the
operation. For the top 2 mm of the cell, full scale values are extrapolated from the lower por-
tion of the cell. This practice prevents any small variation in concentration of large particles at
the top of the cell from affecting the accuracy of the analysis.

Micromeritics SediGraph III 5120 Specifications

General

Brand	Micromeritics
Model	SediGraph III 5120
Category	Measuring Instruments
Language	English