USB-6211 overwriting samples from previous acquistition?

[Keith_Schaub]

Hi John -

With your version of the VI, I can get up to ~70 kHz before it starts to misbehave. That's an improvement, so thank you for your help. I don't suppose there's anything else we can do to get it working in loopback at the full 125 kHz (for 2 channels)?

[John_P1]

Hi Keith,

Is it failing in the same way?  At 70 kHz my VI sets an initial delay of 10 us, so I would expect the AO to at least be close to its final value by the time the first sample is taken.

I wonder if the 2nd sample is being taken too late, and the AO is starting its update before the ADC has finished taking the sample.  Can you try increasing the 100 ns time that I added into my sub VI in 100 ns increments?

       

The end result will be less time for the AO to settle, but you will have more time to complete the sampling of the Analog Input before the following Analog Output is generated.  I'm not sure offhand which one of these two behaviors is causing your issue this time, but if the AI sample is being taken too late then allowing an extra few hundred ns for the convert should give you the best results.  If the AO settling is still the issue then there's not much else you can do.

Best Regards,