Thermal compensation

1. A method of characterizing particles suspended in a fluid dispersant by light diffraction, comprising:

obtaining measurement data from a detector element arranged to measure the intensity of scattered light;

identifying a measurement contribution arising from light scattered by inhomogeneities in the dispersant;

processing the measurement data to remove or separate the measurement contribution arising from light scattered by inhomogeneities in the dispersant;

calculating a particle size distribution from the processed measurement;

wherein:

the detector element is one of a plurality of detector elements from which the measurement data is obtained;

the detector elements are arranged to measure the intensity of scattered light at a plurality of scattering angles, the plurality of scattering angles distributed over a plurality of angles about an illumination axis; and

identifying a measurement contribution arising from light scattered by inhomogeneities in the dispersant comprises identifying measured scattered light that is asymmetric about the illumination axis.

2. The method of claim 1 , wherein at least some of the plurality of scattering angles are alternately arranged between a first and second radial location about the illumination axis with increasing scattering angle.

3. The method of claim 2 , wherein the first and second radial location about the scattering axis are separated by at least 90 degrees about the illumination axis.

4. The method of claim 1 , further comprising performing a diffraction experiment to obtain the measurement data.

5. The method of claim 1 , wherein at least some of the detector elements are arranged with their centroids in a logarithmic series of scattering angles.

6. The method of claim 1 , wherein obtaining a measurement comprises obtaining a time history of the intensity of scattered light from the detector element or the detector elements.

7. The method of claim 6 , wherein identifying a measurement contribution arising from light scattered by inhomogeneities in the dispersant comprises identifying peaks in the measurements for each of the plurality of scattering angles.

8. The method of claim 7 , wherein identifying peaks comprises comparing measurement data with smoothed data obtained from the same measurement data.

9. The method of claim 7 , comprising classifying the peaks as a particle peak, resulting from scattering from a particle, or a spurious peak, resulting from scattering from dispersant inhomogeneities.

10. The method of claim 8 , wherein the smoothed data comprises a moving average obtained from a plurality of moving averages with different temporal width.

11. The method of claim 9 , comprising classifying a peak as a particle peak when corresponding peaks are present within a period t w over continuous range of n detectors with adjacent scattering angles, at least some of the n detectors having angular separation about the illumination axis.

12. A processor or instrument configured to perform the method of claim 1 .

13. A machine readable, non-transient storage medium, comprising instructions for configuring a processor or instrument to perform the method of claim 1 .