Sampling/Triggering externally with DSA cards with even sample spacing in frequency space

[laserdud]

Hi there,

Is it possible for the NI DSA cards to trigger on a signal to record at a desired time, at an un-even spacing in the time domain. For my application I need to have the samples evenly spaced in frequency space.

I would set the first channel for acquisition from the source. Would use the external trigger port, or the second channel for the trigger signal? 

This is for a optical coherence tomography system.

Thanks! 

[tnek]

Hi hoju1301,

I am having a hard time understanding what your question is.When you mention triggering, do you want to know if the DSA board can trigger when the signal reaches a certain level or if the DSA board can be triggered at a specific time?

It seems that you also need evenly spaced samples in the frequency domain from some time domain signal. The easiest way to get unevenly spaced samples from a DSA board is to resample the data based on data from another sensor. I am not very familiar with the fundamentals of OCT so you may have to explain in more detail what you are looking for.

Regards,

Kent

Applications Engineer

[laserdud]

Thanks for the response.

So to clarify,

I would need the sampling evenly spaced in the frequency domain, which would mean that the sampling would have to be un-even in the time domain. 

there is a clock signal that is generated from the system for the syncronization of data sampling, which is even in the time domain. This is the similar clock signal box that we are using. http://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=2913

 The clock signal are conditioned comb signals evenly spaced in frequency domain.  are the NI DSA cards able to trigger off this clock signal on either the trigger port or channel B of the DSA card.

However, i would imagine that resampling based on the nearest neighbor or cubic spline would be computationally intensive.

Do you have an example VI of how to resample data to be evenly spaced in the frequency domain?

Thank you for your assistance!

~Anthony 

[tnek]

Hi Anthony,

You may have to excuse some of what I say since I am still a bit uncertain of what you need to accomplish due to my lack of understand of OCT. If you wanted to start your acquisitino at a given time by using an external trigger, most cards have a trigger input which will allow you to do so. However, using an external clock will be much more difficult. While it will be difficult to use an external clock signal with a DSA device, resampling may be a better option. Here is an article which shows some of the resampling functions which, by my understanding, may accomplish what you need to do. Let me know if this puts us in a better direction.

Regards,

Kent

Applications Engineer