BSA Flow Software Installation and User's Guide - CSI

The constants A and B must be determined by fitting to the measured data.
The measured mean square burst lengths from all size classes that can be set
(default value is 100 samples) is used for curve fitting above equation using
a least squares approach.
Implementation in BSA Flow Software
The above algorithm is implemented in BSA flow Software and allows
estimating the probe volume size in function of the particle diameter from
the measured data. The validated data are sorted in size classes (size
histograms). For each size class with enough particles (see “min particle
2
number), the mean squared burst length L is calculated with equation
7.45 or 7.46 according to the optical configuration by using the measured
particle velocity and transit time (TT).
Mean burst length L^2
[µm^2]
120000
100000
80000
60000
40000
20000
0
burst length
Particle count
0 50 100 150
particle size bin [µm]
Figure 7-77: An example of particle size (blue) and the corresponding mean
burst length (red)
The above example shows a size distribution and the relation between the
mean burst length and the particle size. One can notice that the mean burst
length is unreliable for large particles. It is due to the low number of
2
particles per size class. For that reason the relation between L and the
particle diameter is calculated by fitting (see equation 7.52) the experimental
data. A least squared approach is used for the curve fitting.
For size classes above the classes used for the curve fitting, the equation 7.52
2
= ∗ ln + B (
is used L A d p
7-52. For all size classes below the classes used for curve fitting, the
measured mean square burst length is used. Experience shows that the square
relation between particles size and signal burst length does not hold for very
small particles. Therefore the measured values are more appropriate.
Min particles number To avoid that size bins with low particles numbers introduce a bias in the
curve fitting, it is possible to set a “min particle number”. Size bins with a
particle number below the entered value are not used in the curve fitting. The
default value is 100.
The min particles per bin is a user-selectable parameter from the Diameter
statistics properties (see Figure 7-78). This number should not be too small
for statistical reasons.
7-116 BSA Flow Software: Reference guide
600
500
400
300
200
100
0
Particle count [#]