Abstract: A method of maintaining measurement accuracy of specific constituents in prompt gamma neutron activation analyzers in a flow of bulk material having a known range of flow rates. The method comprises the steps of providing a plurality of samples of the bulk material for insertion into the analyzer in geometries and quantities referred to as loading profiles. Each of the loading profiles is inserted into the analyzer and measured long enough to yield a measurement uncertainty that is small compared to the observed differences in analysis results from one loading to another. The results are recorded and differences computed as measured errors for subsequent mathematical generation of the expected error at any loading value.