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Altium Signal Length calculation

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  • Altium Signal Length calculation

    I'm using Altium v19 and I'm using the Interactive Length Tuning for the DRD3 signals.
    Each time I close Altium and I open it again, some Signal Lengths in the PCB Panel are "lost" and I have only n/a instead. I have to "touch" the area where I applied the Lenght Tuning for Altium to re-calculate the length again.
    Does anyone know why and what I can do to fix the problem ?
    I have a similar problem with differential pair calculation: the lengths are not "lost" but uncorrectly calculated. Altium tells me that the "+" signal is 10mm longer than the "-" signal and it can clearly be seen that this is not true. Once again, I delete a part of the tracks, I route them again and the correct measurement is given...
    Please, help !
    Thanks a lot,

  • #2
    I would not spend too much time thinking about that. This is a very well known problem with Altium - they have been changing length calculations for years .... and you can get different behavior and different results between different versions and even patches.

    If you are not sure, measure the length manually (select the track and then Reports -> Measure selected objects). Be aware of length in VIA. Sad? Yes.

    PS: what used to work to refresh the numbers in PCB panel lengths is to run DRC (or compile project?) - maybe you can try that.


    • #3
      Thanks Robert !
      DRC does not refresh the length calculation in Altium v19 :-(
      The "quickest" way to have the measurements seems to be: in PCB panel, once the net class is selected and the list of nets appears with the calculated length (or the n/a information), double click on the net name, the Edit Net window appears, you close the window and the good length "magically" appears again (lol).