I'm a complete beginner to data acquisition to PXI data acquisition card and Digitizers/Oscilloscopes.
Forgive me if I asked anything dumb.
My purpose is to measure peak-to-peak voltage with a frequency less than 20khz.
Conversion must be done if DMM/DAQ is used as both of them give a RMS reading.
Digitizers such as PXI-5922 allows you to see the waveform in which Vpp can be measure but I believe the DMM PXI-4071 can also function as a digitizer?
So what are the differences between all three of them? Accuracy?
That 5922 is definately going to give you the best accuracy. But it is another card. You can get a waveform out of the DMM and the DAQ as well. If you already have the 5922, use it. If not, I would try to get the DAQ to return a waveform. With the waveform, you can process it however you want.
What DAQ are you using? Or is it the DMM?
As I already said, configure your DAQ to acquire a waveform and read it in.
Quickly looking at the specs, your accuracy would go in this order (best first) when digitizing a waveform: Digitizer, DAQ, DMM. If you don't already have the digitizer, use the DAQ. Save some money.