Analog output Drift PXI 6366

[Gordyh]

Hi,

Im currently outputting a waveform at 5 Hz (200kS @1MS/s) from the analog output. I require this to be in sync with another 5 hz wave from an external signal generator. I have used Strat-Digital Edge with PFI0 as the source and connected the TTL sync from the external sig gen to PFI0. the waveforms start perfectly in phase but the waveforms eventually drift noticably out of phase after a minute or so.

Any ideas how to keep this from happening would be much appriciated.

Gordon

[Chantastic!]

Hi Gordyh, just so I make sure I understand correctly, your set up is as follows:

PXI 6366 

- Analog Output Waveform

- Start Digital Edge: Source PFI0

- TTL Sync Connected to PFI0

External Signal Generator: 

- Analog Output

In order to have synchronized output, you need to share the output signal generator's clock as well as the trigger. You currently have a shared trigger, so they will start at the same time, but the sample clocks are not synchronized, so I'm not surprised you're seeing drift. I'm not sure if this external signal generator you're using can export or import a sample clock, but I do know that the PXI system can PLL clocks through the backplane and have synchronized reference/sample clocks. 

[Gordyh]

Hi Chantastic,

thanks for the reply. Yes you have right understanding

Unfortunately the Sig-Gen is a simple OEM PCB so which I can't really modify to look for a clk out. After posting I tried running the sample clock in finite sample mode and making the analog out re-triggerable. this does keep it in sync but on a few ocassions the output fails to trigger, leaving gaps in the output. (Correct me if im wrong but It's my understanding that re-triggering is not possible in continuous sample mode)