Waveform Comparison

[sandeep]

Hello All,

I need to compare two waveforms resulting after the surge test of coils....the first waveform I am acquiring and the other one I am reading from file ..... I need to compare their frequency of the waveform but I am just intersted in the width which is marked by arrow in attached picture....how can I do this in LabVIEW.

And Could anybody suggest me how to compare the two waveforms with respect to their frequency their Y values and RMS ......I tried it using their Y value comaprison by making an array of the Y values of waveforms and comapring them in 5% Error range but not got correct results also I am not able to write the waveform file which I am acquiring by using Write Waveform VI...Please suggest some hints.

Regards

Sandeep

Download File:post-3565-1152607864.vi

[crelf]

the first waveform I am acquiring and the other one I am reading from file...

Can you pls upload a copy of the data file?

[mross]

Hello All,

I need to compare two waveforms resulting after the surge test of coils....the first waveform I am acquiring and the other one I am reading from file ..... I need to compare their frequency of the waveform but I am just intersted in the width which is marked by arrow in attached picture....how can I do this in LabVIEW.

And Could anybody suggest me how to compare the two waveforms with respect to their frequency their Y values and RMS ......I tried it using their Y value comaprison by making an array of the Y values of waveforms and comapring them in 5% Error range but not got correct results also I am not able to write the waveform file which I am acquiring by using Write Waveform VI...Please suggest some hints.

Regards

Sandeep

Your vi won't open for me so I have to talk generally about the task.

You have to ask yourself, "How would I evaluate two traces and compare them, if I did it without the help of a computer?" You will have to get LV to do roughly the same things. You will have to identify the maxima and minima - by what criteria will you decide a maxima or minima has occured? (How would you decide what is noise or a real signal? How much noise that could cause faulty analysis can really occur?) Then you know what data to compare from the two waveforms - The first rise of one signal gets compared to the first rise of the other signal, and so on. The time measure measurements are taken at some amplitude. What is the amplitude criteria? Is it some absolute value or a percentage of the total rise or fall of the wave that must be calculated?

I have never used Write Waveform. Typically, I will acquire a triggered acquisition into a circular buffer. The example vis of this sort are usually titled "Acquire N Scans ..." The result is an array of the voltage readings that can be analyzed in whatever way you wish. If you want a record saved as a file the you can use Write to Spreadsheet File to produce a comma or tab delimited file.

You can find examples (included with the LV software or found at ni.con, OpenG, or LAVA) of how to locate the maxima and minima (and get the array index of that data). Once you know the index of the maxima and minima then you can parse out the data between them and see where the threshold of your choice occured. You would do this to the various segments of the signal and make your comparisons.

Mike

[jhoskins]

Your vi won't open for me so I have to talk generally about the task.

You have to ask yourself, "How would I evaluate two traces and compare them, if I did it without the help of a computer?" You will have to get LV to do roughly the same things. You will have to identify the maxima and minima - by what criteria will you decide a maxima or minima has occured? (How would you decide what is noise or a real signal? How much noise that could cause faulty analysis can really occur?) Then you know what data to compare from the two waveforms - The first rise of one signal gets compared to the first rise of the other signal, and so on. The time measure measurements are taken at some amplitude. What is the amplitude criteria? Is it some absolute value or a percentage of the total rise or fall of the wave that must be calculated?

I have never used Write Waveform. Typically, I will acquire a triggered acquisition into a circular buffer. The example vis of this sort are usually titled "Acquire N Scans ..." The result is an array of the voltage readings that can be analyzed in whatever way you wish. If you want a record saved as a file the you can use Write to Spreadsheet File to produce a comma or tab delimited file.

You can find examples (included with the LV software or found at ni.con, OpenG, or LAVA) of how to locate the maxima and minima (and get the array index of that data). Once you know the index of the maxima and minima then you can parse out the data between them and see where the threshold of your choice occured. You would do this to the various segments of the signal and make your comparisons.

Mike

You could also use the waveform monitoring VI's in the waveform pallette. try one called mask and limit. It may help.