Synchronization of AI channels on PCIe6351 card?

[jcannon]

Hi everyone,

I have a quick question; hopefully an easy one to answer...

I am acquiring multiple AI signals from the card above... When sampling these AI signals, is it necessary to include a "trigger" in the DAQmx code necessary for data synchronisation, or is setting the sample clock source to the "PCIe6351/ai/sample clock" sufficient?

Thanks,

Jack

[Dennis_Knutson]

A trigger is not necessary unless you want to start acquisition with a specific event. The default clock is 'Onboard Clock' so if you want to change that, then use the DAQmx Timing function and specify whatever you want. You'll be using the timing function to set sample rate and number of samples.

[jcannon]

Hi Dennis,

Thanks for the reply... So I can e assured that all AI signals acquired in the code below are synched?

Also, for clarification, what is the "On Board Clock"? Does it refer to the clock on the PC or the DAQ card... How does tjhis differ form the ai sample clock?

Thanks,

Jack

[Dennis_Knutson · Accepted solution]

The onboard clock is on the DAQ board. The onboard clock is the master clock.

The LabVIEW help has a lot of details (as does DAQmx help) on the various clocks. For LabVIEW, go to Contents>Taking Measurements>NI-DAQmx Key Concepts>Timing and Triggering.

[jcannon]

Thanks Dennis for clearing this up...

Regards,

Jack