Continuous acqusition of data through mutliple triggering

[kentang]

Hi Sean,

You are right, it eventually worked out by using 90k data points.
It seems that this card has limitation as well.
Thank you very much for the suggestion.

By the way,
Is there any way to save the time axis information?
I used the 'Write labview Measurement File vi', but the time axis saved just index numbering (from 0 to N data points).
I want to save it by the time of first point saved until the last point.
Any idea for this?


thanks
andy

[aya1503]

Hi, I have the PXI 5922 and I would like to average data that I capture after a certain pulse sequence which is repeatedly generated by an external pulse programmer.
By using the multirecord acquisition function, I understand that the first trigger source is the source set by the niScope Configure Trigger Source vi, and that subsequent start triggers are from the Advance Trigger Source. By default, this is set to Immediate, so multiple acquisitions are acquired continuously.
My question is, how do I set the Advance Trigger source so that it triggers off the same channel as the initial trigger?? I have looked at the niScope property node, but I don't see how you can set, say channel 1 as the Advance Trigger Source.
Otherwise, will I have to set the number of records to 1 and average like with any other PXI without the multirecord acquisition function??

Thanks a lot in advance

aya1503

[Sean_C.]

Hello aya1503,

When you configure your reference trigger for a multi-record acquisition using the niScope Configure Trigger Source.vi, you are configuring the reference trigger for all records.  Is this what you would like?

If you set the Advance Trigger source to the same source as your reference trigger, then you will only acquire data on every other trigger.  The first trigger will be the reference trigger.  When this is received you will begin to acquire data.  The second trigger will be your Advance trigger (provided the previous record has been completely acquired).  When you receive this trigger, you will transition into the pre-reference trigger sampling state.  You will then wait for your next trigger to acquire a new record.  If this is really what you want then you would set the Advance Trigger source with the Advance Trigger Source Property.  This is a digital trigger, and therefore, you can only set this to a digital source (PFI or RTSI lines).

I hope this helps.  Please let me know if you have any further questions.

Regards,
Sean Close
Product Support Engineer: High Speed Digitizers

[aya1503]

Dear Sean,
Thanks for the quick reply - I would like the PXI scope to capture a waveform every time it is triggered by a pulse (square pulse, on the negative slope) delivered via a BNC connector from a pulse programmer, like a traditional oscilloscope would (such as a Tektronix TDS series, for example). Then, wait for another pulse to start acquiring the next waveform and so on. So I think I would be better off using a single record acquisition in a FOR loop so that the reference trigger source can be set to channel 1 and data taken in on channel 0. Does that sound reasonable?

aya1503

[Sean_C.]

This is exactly what multirecord acquisitions are used for.  You can set up a multirecord acquisition to acquire data from Ch0 for every trigger you receive on Ch1 (or Ext Trig, or PFI, etc...).

Please take a look at the MultiRecord shipping example located at:

C:\Program Files\National Instruments\LabVIEW X.X\examples\instr\niScope\niScope EX Multi Record.vi

Let me know if you have any further questions.

[aya1503]

I see, so I do not need to change the Advance Trigger Source - I just configure ch1, say, for the reference trigger source and data will be captured every time there is a pulse on ch1?

aya1503

[Sean_C.]

Exactly.  You would only need to touch the Advance Trigger Source Property for advanced hand-shaking applications.

[aya1503]

Thank you!!!!!!!!!