DAD Self Test failed due to failed Spectral Flatness


When self test on DAD G7117C with 10mm MaxLight Flowcell is performed, it fails because of the spectral flatness (measured 3.3587 AU and limit is 0.002 AU).

Whats exactly calculated in spectral flatness?
What could be a reason that this test fails?

PM on system was performed a few days ag, lamp is about 1033h on-time.. it was on for 0.68h before test was started..

Kind regards,


  • The spectral flatness test determines the maximum noise (in mAU) on the spectrum. On G1315X/G7115A the test is run with the flow cell removed to eliminate effects due to absorbing solvent or a dirty flow cell. On G4212X/G7117X a test cell should be used. First, a detector balance is done. Next, a spectrum is taken. Theoretically, the spectrum should be flat, however, in practice, noise is superimposed on the spectrum. The amplitude of the noise is a measure of the optical and electronic performance.

    Before replacing hardware, I would try running the test again one or two times, but with longer equilibration time.

  • Update: I just ran the Self Test on my G4212A detector, using a test cell. Spectral Flatness passed with super-low results. If yours are, after re-running the test with longer equlibration time, still that high, I would suspect something with the lamp, the main board or the optical unit.

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