Want to synchronize two waveforms, maybe using PLL?

[RGunm]

Hello there,

I don't have much experience so I will try and do my best to explain my dilemna.  The main thing that I want to do is synchronize two analog waveforms and then compare them by means of amplitude, phase, and frequency.  One waveform being a pre-recorded reference signal and the other waveform being a measurement.  The purpose is to monitor signals off a power harness on a vehicle and compare signals to a baseline/reference signal.  I was looking into phase locked loop IC's that may do the job, they have two inputs, one input being the reference signal and the other input being fed back from the output.  The problem with that is I need to synchronize two waveforms, the PLL IC has two inputs but I need these two inputs independent.  I was contemplating using two PLL IC's to ge these two inputs that I need to do the job, is there some way of connecting two PLL IC's to do this?  Any suggestions and or help/direction will be much appreciated.  I hope this kind of makes sense.

Thank you!

[David L.]

Hi RGunm,

Welcome to the NI Forums! From what I understand, you essentially want to do a feedback loop, creating and outputting a signal, and then comparing the signal that comes back in with the original – is this correct? I do not quite understand how the IC’s come into play – can you elaborate? I do not know if they are required and are part of your project, or if they were just something you were thinking about using

If my above understanding is correct, I would suggest using one of NI’s DAQ cards. The requirements will be analog output (AO) and analog input (AI), but maybe you can post sample rates required for the 2. I may suggest going to http://www.ni.com/dataacquisition/ to help with the selection, but feel free to post back more requirements that you need and I can try to assist with picking a specific card. The M-series cards (62xx) are typically a good way to go, as they have a little bit of everything (AI/AO/DIO) – maybe look at the 6221 or 6259?

The first idea that comes to my mind for programming your project is to generate a signal in LabVIEW, and then we can simply compare this signal to the one acquired to get the differences that you are looking for (amplitude, phase, and frequency). There are VI’s that are installed with LabVIEW to do all of these, so there will be minimal programming on your part. We can make sure to compare the right portion of the waveforms by starting your analog input with an analog or digital trigger, depending on what works best for your project.

Regards,