BSA Flow Software Installation and User's Guide - CSI

Implementation in BSA
Flow Software The above equations are given for documentation. Phase shift calculation
with geometric optics at a point can be accomplished without regard to the
scattered light intensity. BSA Flow Software calculates the phase shift
differences by integrating over the aperture. Integration provides a better
size-phase relationship then point calculation alone. The two methods
produce differences, though they are small.
Slope of the diameter- As appears from the expressions for β i above, the geometrical factor and,
hence,
phase relationship the sensitivity and range of the PDA can be altered by changing any of the
angles ϑ, ϕ i or ψ i .
This is further discussed in 7.3 Setting up a PDA system.
In practice, the three angles cannot be chosen freely. Typically, the selection
of scattering angle, ϕ, is quite restricted, either to ensure a particular mode of
scattering or a sufficient signal-to-noise ratio, or from practical considerations
of the measurement situation. The required working distance also
affects the possible range of ϑ and ψ i .
Figure 7-21 illustrates the increase in the slope of the diameter–phase
relationship when the angular separation between the photo-detectors is
increased, i.e. increasing ψ 12 (in the middle), and when the fringe separation
is reduced by increasing the angle ϑ between the incident beams.
Changing ψ 12 only affects the slope of the diameter–phase relationship, i.e.
the sensitivity and range of the sizing, and has no effect on the velocityfrequency
relationship. In practice with the Dantec PDA receiving optics it
can be achieved either by changing the focal length of the front lens or
selecting another aperture plate as described later in this chapter.
7-26 BSA Flow Software: Reference guide