The detmon template produces a series of lamp flats with different 
exposure levels. These plots shows the flux in the most illuminated lamp flat, 
the upper boundery of the recorded flux range of the frame sequence.

As the QC paramater for linearity expresses the non-linearity correction
at the reference level of 40000 ADU the flux range should exceed 40000
ADU to obtain reliable (interpolated) QC values.

More information can be found on
the <a href="http://www.eso.org/observing/dfo/quality/FORS2/qc/detmon_qc1.html">plot tutorial page</a>