relation between sampling rate ad the signal freq

[ASHLY19]

Hello:

I have a problem when generating a sine wave that when increasing thee frequency (>100hz) the shape of the signal changes ,there is an attachment for the problem,any one can help me to explain this phenomenon; 

[GerdW]

Hi Ashly,

apparently you don't use LabVIEW as marked for your thread, but LabVIEW NXG.

explain this phenomenon; 

Several scientiest explained that phenomenom decades before: Shannon, Nyquist…

See Wikipedia for them!

[ASHLY19]

Hello;

I have some confusion on the relation between sampling rate ad the signal freq that when generating sine wave with sampling rate (1000) and freq(10) there is no problem but when increasing the freq to (100)Hz the sine wave shape changes (some information lost) , although it achieve the  Nyquist Theorem ,there is an attachment for this problem

[GerdW · Accepted solution]

Hi Ashly,

when increasing the freq to (100)Hz the sine wave shape changes (some information lost) , although it achieve the  Nyquist Theorem ,there is an attachment for this problem

Which problem?

You still can recognize your sine wave and you can still determine its frequency!

Remember: at sample rate = 1kHz and sine frequency= 100Hz you get only 10 samples per sine period - as can be seen/estimated in your plot…

[crossrulz]

Nyquist only states that you can get the frequency content when your sample frequency is >2x the signal frequency.  In the time domain, you lose resolution as you have less samples per cycle of the signal.  What you are seeing is expected.

[ASHLY19]

hi GerdW;

the shape of the sine wave changes as the frequency increasing ?

[GerdW]

Hi Ashly,

the shape of the sine wave changes as the frequency increasing ?

Wouldn't it be most easy to test this with your VI on your own?

Hint: set the plot style to show also points to see each sample more easily…