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Particle Sizing by Dynamic Light Scattering NanoPlus Operator’s Manual
E-4 Mar 2014
Here, A
i
is the relative intensity of light scattered by a particle with decay constant

i
and is related
to relative amount of such particles.
Figure 2. Intensity Autocorrelation Function
Correlator
Two correlators are included in the instrument. One correlator is based on a log-scale decay time
and the other on a linear-scale time. The log-scale correlator covers the range of six orders of
decay time, thus can be adapted for most particles. The linear-scale correlator has high resolution
within the limited range of decay time, and is suitable for very small particles of narrow
distribution.
The Correlation Method
During a sample run, the scattered light intensity is collected as a data train of photon pulses per
sampling time,

, or sampling times (number of clock pulses) between two photon pulses. The
former method is called the Time Domain (TD) method and the latter is called the Time Interval
(TI) method. The length of the data train is specified by the parameter. The correlation function is
then calculated for a specified number (channel number) of multiples of sampling times. The
process is repeated for a number of times (accumulation times) and the correlation function is
summed to reduce contributions due to noise.