Calculation method of repeatability and error

The deviation between the results of multiple consecutive measurements of the same sample under the same measurement conditions is called repeatability.

Repeatability conditions include the following aspects: the same measurement process, the same operator, the same sample, at the same location, using the same instrument, multiple measurements in a short period of time. Repeatability is the main index to measure the stability of particle size instrument and particle size test method. Repeatability is calculated as follows:

Repeatability or reproducibility is:

Among them, xi is the result of each test;

X is the mean value of each measurement; standard deviation;

N is the actual number of measurements (generally n);

ISO13320 stipulates the allowable deviation of repeatability of laser particle size analyzer: D105%, D90, D50, if their values are less than 10um, the error can be doubled.