trigger with 1 Khz and measuring in-between with full sampling

[hepman]

I like to measure with PCI-6259 and DAQmx following scenario:
There is a trigger with 1 kHz (1 ms) and between the triggers, Data(Ai0) have to be measured with maximal sampling rate 1.25 MS/s it should be 1000 Datapoints (1.25 MS/s -> 1000 points = 800µs) 200µs time left for next trigger-start.
Is this possible and if yes how.
Is there an example somewhere, i tried Labview examples but they don´t work.

Best Regards

Hepman

[hepman]

ok,  it don't have to be 1.25 Ms/s, it could also be 100Ks/s, but it shoud not miss the next trigger. It is necessary to remove some noise.
Skipping data-acquisition if next trigger pulse is comming could also help.

Some Ideas?

Best Regards

Hepman

[ralfn]

Hello hepman,

it should be possible if there is a timeslot between the last acquired sample and the next trigger-impulse.


At first, please look at the principle: http://zone.ni.com/devzone/cda/tut/p/id/5382


To do so you have to use a counter (retriggerable) which generates the clock-signal for the analog-input task (blocks of e. g. 1000 pulses with the sample-rate).


The LabVIEW-example Multi-Function-Ctr Retrigg Pulse Train Generation for AI Sample Clock.vi should work with your card.

If you get an buffer overflow, you can increase the buffer-size. Best is to write the values in a queue and do the analysis in another loop.
Please note, that you have to split the samples in blocks by your own (after e. g. 1000 values) because it is a continuous analog-acquisition.


Good luck.

Ralf N.
Applications Engineering


Message Edited by ralfn on 04-10-2008 08:39 AM

[hepman]

Dear Ralf,

thank you for reply,

I modify the example and it  look like it should, but as you see the loop time is over 2 ms.
The samples per channel is to high, so you can see next pulse, because time between pulses is 1 ms.
Frontpanel and vi  Multi-Function-Ctr Retrigg Pulse Train Generation for AI Sample Clock_own.vi is attached
the data are triggered so peak is always on the same position.

I tried the example, but if I increase the rate this will result in  AvailSampPerChan=0 and a stuck in the loop.
and if I increase samples per channel to 10000 and get following frontpanel:
Multi-Function-Ctr Retrigg Pulse Train Generation for AI Sample Clock.vi.jpg
data looks not triggered.
What is wrong or what do I not understand?

Best Regards

Hepman