Continuous signal from virtual channel - novice problems

[aneley]

Hello, I am a novice in LabVIEW and I am trying to build a simple spectrum analysis VI.

I am trying to avoid express VIs, and started by creating a virtual NI-DAQmx and a task for acquiring analog voltage.

wiring all that to a graph, the signal is not nice and continuously seen (it just sort of flashes, tried changing the rate and samples, didn't seem to change much...), and I can't figure out what i'm missing to configure...

Also, I have a question if I wish to use the Amplitude and level.vi or Pulse measurements.vi an error occurs saying that the requested sample was previously available but has since been overwritten, and to solve this I should limit the samples it reads or increase the buffer size - but when I do, the same thing happens.

I really suppose my problem lies in the beginning of acquiring the signal...just don't know where.

I posted the .vi just for clearance.

Any hint? I would appreciate any help.

Thank you

[ValkoA]

Hi Aneley and welcome to NI Forums!

The main issue with your VI (as I see it) is that you set up the graph's properties in every single cycle. Once I removed the property node from inside the main loop, display was smooth. For simple applications it's better just to use the in-built autoscale, or set limnts only once before acquisition.

The other error usually indicates that you have a buffer overflow, because the loop rate can not keep up with the hardware-timed acquisition. To avoid that, you have several options, please check this paper for further information.

Please get back to me if you need help with anything else.

Best regards:

Andrew Valko