How do I record a waveform, then us as a reference to compare subsequent waves?

[Bob Edge]

Hi,

I am totally new to labview, so please excuse my complete ignorance.

I wish to monitor a short duration weld. The weld lasts for 20mS to 1.5S, and I will be measuring weld current, and arc voltage.

I need to record a weld, use as a reference, and compare subsequent welds to this. If the waves are the same within a certain percentage then the weld is good. Any problems should flag an error. For example a blob of moultern metal could short out the arc for a short time, giving zero arc voltage, & a high spike of current. This may or may not produce a bad weld, so it would be flagged to the operator.

Any help to get me started would be greatly appreciated.

Regards

Bob.

[josborne]

Sounds like an interesting project.  But my first question is:  How far have you gotten, and where exactly do you need help? 

Have you chosen the sensors and data acquisition hardware yet?  Do you just need help with the comparison part?

Your first task is to build your system (hardware and software) and get it to properly record and display the voltage and current for each weld.  That is the tough part.

Once you can do that, comparing each weld to an "ideal" weld is the easy part.  Here's a quick to a previous discussion on comparing waveforms:  http://forums.ni.com/t5/LabVIEW/Comparing-Waveforms/m-p/386346

- John

[Bob Edge]

Thank you for your reply.

I have not done very much yet. The hardware is no problem. I plan to use a labjack U3 DAQ unit, and build a couple if isolating amplifiers to scale the signals, and to stop the inputs blowing, because the signals do not have a common ground.

It is the lab view part that is puzzling me at the moment. The post you linked was very interesting, but still a little over my head. I keep going through the tutorials tho.

Regards

Bob.