How to properly generate a sin wave and take it fourier transform?

[ZainAli02]

I am trying to take a digitized sine wave and then plot the magnitude and the phase of its FFT spectrum separately. However, the phase plot I am getting does not seem to be correct. I have attached my VI for reference. 

[RTSLVU]

Your Vi is one version newer than I have so I can't open it.

Anyway, what results you are expecting doing a frequency (FFT) analysis on a sine wave? 

A sine wave only contains the fundamental frequency. Try a more complex waveform.

[altenbach]

When attaching a VI, make sure that all controls have typical default values. Currently, your frequency, sampling rate, and # of samples are all zero. Please tell us what input values you are suing and what you expect as result.

You are using an FFT function that expects a waveform, but you give it a naked 1D array, i.e. no timing information at all. The FFT thus assumes a dx of 1. (did you notice the red coercion dot?)

Also make sure to place a small wait inside your loop (e.g. 100ms) because it seems pointless to repeat the same calculation millions of times per second, burning 100% of a CPU core.

[ZainAli02]

Thank you for the suggestions. I am using the following values: 
No. of Samples: 100
Signal Frequency: 100
Sampling Rate: 1000

[ZainAli02]

What I dont understand is the phase plot. Isnt it suppose to be at pi/2? Here is my block diagram: 

[raphschru]

Wild guess: try increasing the resolution of your input signal.

Here the sine does not seem very smooth:

Regards,

Raphaël.

[altenbach]

There are two main issues:

• Your FFT by default applies a windowing function, so eliminate that. It is designed for real signals!
• You should make sure that your signal has an integer number of cycles to avoid spectral leakage

See if this can give you some ideas:

[ZainAli02]

I have been asked to used the sin function and not the sine waveform generation sub vi

[altenbach]

You can built your array into a waveform by just defining dt, right?

[ZainAli02]

yes, that should result in an array