How to acquire 1 data point per trigger ?

[hbin]

Dear all, anyone can help me in acquiring 1 data point per trigger? just as a Sample/hold circuit?

I changed the example from Labview "Acquire 1 point digital trig", however, it doesn't work, it says data acquiring is inconsistent with buffer. The program is attached.

and I try to use "AI Sample channels.vi", but there is not trigger input and sampling rate input.

Thank you very much for your help.

[Milqman]

Which version of LV are you using?

(1 of the 2 questions that always get asked, fortunately, you got the other one)

~milq

[hbin]

7.1

Thanks.

[hbin]

Anyone can help me? thank you very much!

[Milqman]

Does LV 7.1 utilize DAQmx?  If it does, you should be using those blocks.  I think you will find the example finder really helpful, there is probably an example you can use without even editing.

~milq

p.s. if I had LV installed on this computer I would tell you the name of it.

[hbin]

Yes, there is DAQmx, but it doesn't work .  The example "Acq one sample" can not run, and  there is no  hardware trigger in this example too.

[Coal_Man]

There is a good example that can do almost exactly what you want to do.  It is called Acq&Graph Voltage - Int Clk - HW Trig Restarts.vi.  There are only three things you need to change.  Change the triggering VI to trigger off of a digital signal, then change the read VI to read a single channel and single sample and finally, change the Samples per Channel to 2.  I have included screenshots of the VI.

The VI works by setting up a digital start trigger that is retriggerable, so that you can have this trigger start the acquisition over and over.  Once the trigger happens, a sample is acquired, read, and then the hardware waits for another trigger.

Have a great day,

Brian

Message Edited by Brian C on 03-28-2007 01:48 PM

[hbin]

Thank you Brian!

But I can not find the example you mention, is it available in Labview 7.1? Could you attached this example?
 I attached a graph of the available examples in my disk.

I tried several examples, most of the examples are "start" trigger, after start the acqusition, it can run without the tigger.  what I want is every acquisiton waits for the trigger.


 

[hbin]

Sorry, the examples in my disk is attached

[Milqman]

hbin

You might be able to just use your "trigger" as an external sample clock.  That way you get one data point per "trigger"

I think you will find the Cont Acq&Graph Voltage-Ext Clk.vi useful for that purpose.  This will start acquiring when you run the application, acquire 1 sample for each "trigger" and graph it.  Depending on what you want to do with the data, you might want to slow down the loop too.

Best of luck,
~milq