In any analytical method, one of the first considerations in obtaining precise and accurate results is the stability of the instrument. Progressive refinement in design and manufacturing techniques over many years has led to short-term stability of X-ray generation, transmission and detection in XRF spectrometers of a magnitude such that, in favourable cases, the random process of emission (and to some extent, absorption) is the major source of error; superimposed on this, however, are other variations, some of them periodic.

Many processes modify the intensity of X-rays recorded by a spectrometer's sealer and timer: besides those produced by the instrument itself there are potential external perturbations perhaps reverting to electricity generating stations or even further. More important effects may be caused by local features such as ambient temperature and pressure, and in the case of improper setting of machine conditions or of existence of a fault, enhancement may be observed.