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Figure 2
The sinusoidal cyclic error in the sawtooth form of the encoder output that indicates a need of the Heydemann compensation. As the motion progresses, the encoder DAQ should give a linear output from 0 to 4096 and then roll over to create a sawtooth pattern. Instead of a perfectly linear form, there is a periodical error that repeats itself for every sawtooth visible in the plot for one encoder head. Each individual encoder head has its own unique pattern. As a consequence, each DAQ value needs a small correction. As the encoder DAQ is a measure of the mirror and grating pitch angles, and hence the photon energy, it is the energy scale that needs stretching and compressing in the form of Heydemann compensation to correct for the errors.

Journal logoJOURNAL OF
SYNCHROTRON
RADIATION
ISSN: 1600-5775
Volume 24| Part 1| January 2017| Pages 344-353
https://doi.org/10.1107/S1600577516019056
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