M00000504
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ISO 20998-2 1st Edition, August 15, 2013 Measurement and characterization of particles by acoustic methods - Part 2: Guidelines for linear theory
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Availability date: 07/13/2021
Description / Abstract:
This part of ISO 20998 describes ultrasonic attenuation
spectroscopy methods for determining the size distributions of a
particulate phase dispersed in a liquid at dilute concentrations,
where the ultrasonic attenuation spectrum is a linear function of
the particle volume fraction. In this regime, particle– particle
interactions are negligible. Colloids, dilute dispersions, and
emulsions are within the scope of this part of ISO 20998. The
typical particle size for such analysis ranges from 10 nm to 3 mm,
although particles outside this range have also been successfully
measured. For solid particles in suspension, size measurements can
be made at concentrations typically ranging from 0,1 % volume
fraction up to 5 % volume fraction, depending on the density
contrast between the solid and liquid phases, the particle size,
and the frequency range.
NOTE See References [9][10].
For emulsions, measurements may be made at much higher
concentrations. These ultrasonic methods can be used to monitor
dynamic changes in the size distribution.
While it is possible to determine the particle size distribution
from either the attenuation spectrum or the phase velocity
spectrum, the use of attenuation data alone is recommended. The
relative variation in phase velocity due to changing particle size
is small compared to the mean velocity, so it is often difficult to
determine the phase velocity with a high degree of accuracy,
particularly at ambient temperature. Likewise, the combined use of
attenuation and velocity spectra to determine the particle size is
not recommended. The presence of measurement errors (i.e. "noise")
in the magnitude and phase spectra can increase the ill-posed
nature of the problem and reduce the stability of the
inversion.