All factories of laser particle size analyzer will choose one standard substance as sample to calibrate instrument, generally use national standard sample, depended on the error between standard D50 value and test D50 value.
E.g. Winner2000ZDE laser particle size analyzer,
Standard sample is Polyethylene microspheres, D50 value is 10.9um, If its test error is within 1%-3%, shows machine is normal work condition for testing other samples.