Posted by Tom Roberts on December 16, 2003 at 17:03:16:
I recently had a tech support call regarding a primary and secondary ignition capture. Seems the primary and secondary were increasingly out of sync from one side of the screen to the other.
We know that primary mirrors secondary, so it is impossible that they could really be out of sync.
There are two choices when using both channels in PicoScope under Settings/Channels. One is Alternate and the other is Chop. Since the ADC 212/3 has only one processor, it must take turns when running both channels. These settings tell it how to take turns.
If we choose Alternate, then PicoScope samples one full screen of one channel then samples the other. This means that the channels are not going to displayed in the same time frame. So, signals that should be synchronized won't appear that way on the screen. When doing automotive action-reaction diagnostics, we do NOT want to be using Alternate channel sampling.
Chop mode will take an individual voltage sample of one channel and then sample the other, reconstructing both channels across the screen together. Now signals that should be synchronized will be. Sure, there is a minute time between samples but, for all practical purposes, the channels are simultaneous.