The extraordinary sensitivity of the detector and amplifier of the EDS system produces a marked susceptibility to interference from mechanical and acoustic vibration and stray electromagnetic radiation (figures 1 and 2).


Figure 1: EDS spectrum of a Cr alloy excited by a 15 keV
electrons. For Al and Si, the K alpha - K beta pair is unresolved.


Figure 2: EDS spectrum obtained under identical condition to
Figure 1, except with a source of acustic interference operating
(nearby telephone) Note the noise spectrum exciting to about
2 keV and the degradation in resolution as compared to Figure 1.