How do we calculate repeatability?

In laser diffraction particle size analysis, repeatability refers to the measurement difference between multiple measurements of the same sample under the same measurement conditions in a short period of time. The repeatability is characterized by the following conditions:

● The measurements should be carried out following the same measurement procedure under the same measurement conditions and in the same location.

● The measurements should be implemented by the same operator.

● The sample should be the same.

● The particle size analyzer used for the measurements should be the same.

● The measurement should be repeated over a short period of time.

The calculation of the repeatability for each size channel, such as D50, is shown below:

where n is the number of measurements (usually n ≥10), xi is the each individual measurement result, x_i is the mean of the measurement results, δ is the standard deviation.

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