Logic 8 - Logging large Analog data

Hello everyone,
I recently picked up a Logic 8 for my Acoustic Emission experiments and have been really happy with the results.
However I currently have to move on to larger tests (1 hour or so) and I wish to have minimal downtime during the acquisition.
I have 2 Analog channels sampling at 2.5MS/s so my RAM gets crowded quite fast !
I read in the documentation the following 2 points.

  • ''If you are recording analog, turn off the up-sample option" I could not find it. Is this only in old Logic software versions ?
  • " Analog signal needs to be sampled 10 times faster than bandwidth" Is 2 times faster not enough ?

Also I tested for shorter tests (1GB data) and the time for saving the capture was not negligible compared to the acquisition time. Do you believe I could speed up the process with a custom python extension ?
I’m looking forward to your comments and wish you a great day.
Alexandre

@ableuset Glad to hear you’ve been happy with using Logic 8 so far. Some comments on your questions below:

  • ''If you are recording analog, turn off the up-sample option" I could not find it. Is this only in old Logic software versions ?

This is actually just in the older Logic 1.x software. This option was there simply to improve waveform display and rendering performance. Rendering performance has been improved pretty drastically in Logic 2.x compared to Logic 1.x, so this setting isn’t necessary anymore.

  • " Analog signal needs to be sampled 10 times faster than bandwidth" Is 2 times faster not enough ?

Sampling analog at 2 times the frequency of your signal is not enough if you want a reasonable approximation and reconstruction of the analog signal you are recording. For digital recordings, 2 times the frequency (Nyquist) is borderline for just avoiding aliasing. Though, our general rule of thumb is:

  • Digital recordings be sampled at least 4x the frequency of the signal
  • Analog recordings be sampled at least 10x the frequency of the signal

Also I tested for shorter tests (1GB data) and the time for saving the capture was not negligible compared to the acquisition time. Do you believe I could speed up the process with a custom python extension ?

I assume you are saving captures as per the instructions below?

Unfortunately, it’s not possible to improve this via a python extension. The performance is tied to our back-end. What kind of save times are you experiencing? Can you share a copy of your capture preset file? Also, what are your PC specs? As a first step, I’d like to see if the capture save times you are seeing are within what we expect.