What values are returned by "niScope_Fetch" if NI5122 is used to capture data across 2 channels?

[PJ_SJM]

NI5122( or NI1045) is used to simultaneously capture data across two channels. Ch0 is set as the trigger source (edge trigger, positive slope). The "niScope_Fetch" function returns an array of structures containing the timing information about the waveforms. I'm interested in the parameter "absoluteInitialX". If Ch0 was set as the trigger source, the "absoluteInitialX" will return data corresponding to Ch0 only, correct? Does "absoluteInitialX" record any data associated with the waveform on ch1?

[Chris_W.]

Hi PJ_SJM,

The 5122 uses one timing engine to acquire data on both of the lines at the same time. This means that even thought they have separate ADCs when you set up your acquisition for a certain frequency the samples on both channels will be taken on the same sample clock edge. This means that whichever channel you are using as your trigger source does not affect those absolute and relative initial X timestamps. The only things that make a difference is when the trigger is received relative to the sample clock. For more information about the timestamping of your board take a look in the NI High-Speed Digitizers Help. If you go to the index tab and search for the page title timestamps in one word there is a good explaination of how the time stamping works.

Chris W