Generating High/Low Limit Waveforms

[wd8ivl]

Hello list...

I'm kind of new to Labview, and don't want to reinvent the wheel here (or re-write something that's already been written)

In my applications, I acquire waveforms from a Tek 3014B scope & transfer them into Labview.

I want to compare the measured waveforms with a previously acquired, known-good waveforms that I saved in the form of a csv files using the scope's FDD.

Because I've got to do this in numerous, ongowing applications, I don't want to spend the time drawing the limits in the "Mask & Limit Testing.vi" each time I develop a new app.

I'm looking for a vi that can take my previously saved, known-good waveform file and programmatically generate the upper and lower limits given simply the amount the amp
litude and time it is allowed to vary. I would then use these as the limit mask inputs to the "Mask and Limit Testing.vi" to compare the acquired waveform to.

Thanks to all,
Mike

[srm@viewpointusa.com]

Do you simply want to offset the magnatude of the waveform or allow for time shifting of the waveform as well? One method I have used is to offset the waveform and rotate it forward and reverse taking the maximum value of all three waveforms for the new upper limit. similar for lower limit. If you have multiple "known good" waveforms, take the maximum values of each waveform as your starting point.

[wd8ivl]

Thanks for the reply.

I need to allow for time shifting also. Part of the waveform has a pretty fast risetime & falltime, so just allowing for an increase or decrease in magnatude won't give me the same width of a pass "window" around the good waveform. Also, I won't always have the luxury of having several slightly different known-good waveforms, and if I did, they may not represent the actual maximum deviation of what would be considered good. I guess what I'm looking for is a vi that I can feed the know good waveform into and set a (+) & (-) % time shift and a (+) or (-) % of amplitude and it would programmatically generate the high or low limit waveform that I could feed into the "Mask and Limit Testing.vi" for comparison. I guess if you look at th
e "Mask and Limit Testing.vi" and open the "Define" panel - what I'm looking for is a vi that will programmatically generate that defined set of points.

Mike

[srm@viewpointusa.com]

I tried to attach a Zip file. It was a demo I put together a while ago. It also included sample data files, an envelope builder and limit evaluator. It is a large zip. I could not get it to upload. If you want the zip, send me your e-mail. This is the heart of the problem tho. It shifts the array one point at a time keeping min and max as it goes along.