Elongating a waveform logically

[r_te]

Hello,

In my application, I am acquiring data which is most of the times 0V which I will be plotting as it is. But there can be a short train of pulses(KHz frequency) for 1 to 10ms amount of time intermittently. Now what I want to do is I want the strip chart to display those short train of pulses as 1 long pulse. I tried number of things, but couldn't do it properly.

I am attaching a sample jpg image. the yellow line is the signal I am interested in. Now referring to the image, I want the peak of both the pulses but be joined to make it look as 1 single pulse. Please help!!

[Henrik_Volkers]

Would have been helpful to know what type of DAQ or digitizer you are using ....

can you use the slope of the rectangular signal as a trigger?

Still not clear what you have tried.. vi?

and what you want to get finally... drawing?

[r_te]

I am attaching the vi is am using. and the screenshot of the data that I acquire.

If you refer the screenshots, there is a burst every few intervals. But its seen more like a trangular form with peaks. Now what I want to do is, I want that burst which is looking like the trangular shaped thing to look like 1 single step.

Please help..

[The_Legend]

Hello Rohan,

I would like to know more on the application you are trying to do. As per my understanding, you are able to plot the actual signal you are getting which is in the form of a traingular wave. But, you want the plot of a square wave instead of this.

In that case, you can use the signal you acquire to trigger square plot that will have the width of the burst of signal.

Also, please let me know more on the signal you are acquiring, the Data Acquisition Card you are using and so on.

Thanks.

[r_te]

I am using NI-PCI 6013 and the vi will run on windows xp platform. Actually the burst signal is a square train of pulses, but LabView is plotting it as trangular, may be the train of pulses is too fast for the labview to represent it correctly. Anyway, it doesnt matter to me if its acquiring that way, all I want is to display a square signal for that duration as in 1 elongated square pulse of that duration. In your reply you referred to triggering, can you help me with that with some details as in what exactly and how I should use to achieve it.

[The_Legend]

Hello Rohan,

The PCI 6013 is a Analog Input card with 200KS/s sampling rate. From the Niquist Theorem, for accurant acquisition and processing of the signal, it has been observed that you will need to sample the signal at more than 10 times its frequency.

I would like to know the frequency of this signal. If we can confirm this, this problem can be solved.

Thanks.

[r_te]

Actually, it doesnt matter even if the hardware or software is missing a few samples. There isnt much information in it. If you refer to the screenshots I attached in my previous post, you can see a burst signal. the frequency of train of pulses in the burst signal typically will be 5-10 khz. Here its ok if the sampling is not accurate, all i need to know is the start and end of this burst(which may vary from 1 ms to 20 ms) and the amplitude to plot/display a single square for that duration.

Or if this cannot be achieved, I want to display a 10ms square step at any instant of the burst. the start and end points may not be accurate, its fine for my application.

[The_Legend]

Hello,

Ok.. The signal frequency you are looking at can vary from 5KHz to 10KHz. So the sampling rate should be atleast 50KHz, preferably more.

The Code you have written is for software timed acquisition, where the maximum samping will be 1KHz, due to the limitation imposed by Windows. The while can scan at a maximum rate of 1KHz. If you are looking at going more than that, you will have to hardware timed acquisition.

I have enclosed a modified version of your VI. Let me know how this one works.

Thanks

[r_te]

Hi,

Could you please upload for 2009 version?

thanks!

[The_Legend]

Hi,

I do not have the 2009 version installed.

I have attached the screenshot of the block diagram. Try replicating it.

Thanks