Data Acquisition

[gPoUL]

Hi everyone!

I’m a real novice in data acquisition and I would really appreciate some help….

Here’s my problem:

I am receiving a signal with a period of 0.6 ms which is consisted of 3 peaks and one valley. Next to it I’m receiving a signal (a trigger or clock I presume) which is consisted of pairs of pulses (amplitude about -4V and width about 2μs) with a time interval between each pair of about 0.12 ms. These pairs correspond exactly with the peaks and valleys I’m interested in.

 I’m not interested in acquiring the whole waveform but just the values of the 3 peaks and the valley in each period.

Now, if I connect the pulse pair signal to the external analog trigger of an appropriate DAQ card, will I get the data I want? (I don’t have one so I can’t just try it)

Or perhaps is there another way I can get this managed?

Thank you in advance…….   

[hoffiz]

Hi,

You are in the correct track but there are some considerations to be aware. Depending on the width of the valleys and peak you might be able to read the data correctly of your trigger is synchronize with these values.

So my suggestion and what I think would be the easiest way; would be to acquire the whole waveform and the trigger signal. Handle the calculation with post-processing in LabVIEW after the acquisition is done. This is because your trigger cannot be use as an external triggers since it is not TTL compliant unless you do some kind of singal conditioning.

So depending on the DAQcard that you use you can read both the signal and the trigger and using some math and coding find the values you are looking for.

Some useful resources that will help you a lot are: Learn 10 Functions in NI-DAQmx and Handle 80 Percent of Your Data Acquisition Applications, Tips and Techniques in Data Acquisition Triggering - NI-DAQmx, Building an Analog Input VI in NI-DAQmx and Answers to Frequently Asked Questions about NI-DAQmx and Traditional NI-DAQ (Legacy).

Let me know if it helps

Message Edited by Jaime F on 03-09-2008 03:59 PM

[gPoUL]

Hi Jaime!

First of all I would like to thank you for your reply.

Yes I had to be more clear...

The peaks and valley have a plateau of about 0.1ms. And the trigger is sychronized with these values. On each plateau I have one pair of trigger pulses. The pairs, as I said, have equal time intervals between them.

I was hoping that I could use the trigger signal (since it's not TTL compliant) with a card that accepts external analog trigger and get my job done.

The reason why I stick to this is that I want a real time representation so I'm afraid that if I do this with post processing in LabVIEW I will have errors since I will rely on software.

But I will follow your advice and resources.

Thanks again!!!!