Measuring Sine wave deformation

[MarkGreally]

Hi Folks.

I am trying to measure the signal deformation coming from a scope. Its a typical sine wave that distorts as the input increases (shown in the attachments). I was initially just going to subtract a known signal from the recieved signal to give the difference. The point by point error is to big for this. I am also trying to determine the slope over time and the rapid change of slope would indicate the point. However point by point calculation of the slope gives too much error to. Is it possible to generate accurate slopes or is there a function that determines if a signal is non-sinusoidal??

Thanks,

Mark.

[Henrik_Volkers · Accepted solution]

For a quick visual check you can use the tone detection vi and export the residual signal, maybe the rms value of the residual is a nice value (THDN)

Measures of deformation of a periodic signal are (usually) often done in the frequency domain and called harmonic distortion. There are also vis that already can do that for you.  (SINAD) . The THD level is usually used.   Look under signal procesing - wfrm measure

Your traces look like a 1g steel ball accelerometer calibration to me. 🙂 

[MarkGreally]

Thanks Henrik.