Convert a signal into a time signal of labview

[Abuzar]

hello,

Working on some signal available as a text file, I was succeeded in plotting it on waveform chart.

While having its frequency response, I have to convert it into time signal to apply FFT Spectrum.

Kindly tell me how could I go through this step.

Regards

[GerdW]

Hi Abuzar,

do you talk about "waveforms"? There's a full palette of functions dedicated to waveforms, just look at it!

[Abuzar]

Hello GerdW, thanks for replying

Actually the issue is of difference of data type, the output of my data file is floating point while the input of FFT Spectrum is Time Signal

So how can i make my signal compatible of it.

Thanks

[GerdW]

Hi Abuzar,

yes, I understand your question. Did you follow my advice of message #2?

There's no "time signal" in LabVIEW (atleast I didn't come across such labels). Open the context help and use the wording used in the help...

[Pianne]

Hi Abuzar,

As GerdW said, the datatype you need to connect to 'Time signal' connector of the FFT function is 'WaveForm'.

You can easily convert an array of floating point to waveform, using the 'Build Waveform' function on the Waveform pallette.

Like this for example:

[Abuzar]

Thanks v.much to Gred W and Pianne, i solved my problem,

One thing to ask more that we have to supply the sampling frequency to get the waveform, what about if we dont have any information of the sampling frequency than what would be the technique of converting such signals into waveforms.

Thanks alot

[Pianne]

Abuzar,

Glad we could help.

If you don't know the sampling frequency, I would just enter '1' as dt, emulating a sampling frequency of 1 Hz.

[wacker]

Hi, do you have any idea how should I analyse the data, if the time steps of data collecting are not the same? I tried to use average time step but it changed the data a lot 😕

[johnsold]

If the time steps differ, you need to be very careful with any analyses. Most of the analysis VIs (filters, FFT, and so on) assume uniformly sampled data (meaning that every dt is the same). There are VIs which can "resample" non-uniformly sampled data and I think there may be a few VIs which can handle non-uniformly sampled data.  The resample VIs essentially interpolate between the actual data points and estimate the values at the fixed dt sample points.

Lynn