relative initial x

[Mark Mutton]

Will someone explain to me exactly what relative inital x is outputting.  The help says " relativeInitialX is the time in seconds from the trigger to the first sample in the fetched waveform. "  I seem to be getting better accuracy then the specs on the scope.  I am assuming that the software is doing some sort of interpolation on the trigger signal to subtract out some of the jitter, but i would like a better explanation.  For example, I have a 5124 12bit 200MS/s board.  I use the full 200MS/s so i am getting a point every 5ns.  I am measuring the peak of a wavelet taking that time and adding on the relativeInitalX.  I seem to be getting sub nano-second time "accuracy" If i take the relativeInitalX i get 5ns accuracy which i would expect based on the scopes specs.  long story short i just need to know how relativeInitialX is calculated.

[Yardov]

Hello Mark,

This number is expected to be sub sample resolution since there is a different circuitry that is calculating it. Look at the picture taken from this link:

As you can see, this number is actually telling you how much time passed from your trigger to your first sample. This circuitry is called Time to Digital Converter or TDC.
Hope this clarifies any confusion about "relativeInitialX".