How to know if there is noise affecting my signal

Hi

I have a signal shown in the attached figure and the fft of that signal as well. In addition I have also attached the fft of the static noise signal. You can see that in the original signal there are harmonics present specially on the first half of the curve. I really dont expect them coz in my experimental setup i try to eliminate all secondary noise sources. I am wondering if these harmonics are coming from the static noise in the signal? I have also attached the fft of the noise signal as well. But i am really not sure if the noise will affect that much the original signal coz the magnitude of this noise is really small compared to the magnitude of the original signal. Please advice me what could be the cause of these harmonics?

Thanks

Hi,

I don't think that one of the FFT belong to the top diagram signal.

I can neither see signal amplitudes, nor frequencies, nor overtones.

Klaus

Sorry I didn't understand your reply. Could you please elaborate more?

Hi,

How did you calculate both FFTs from the above diagram?

Klaus

No only the first fft is calculated from the above diagram whereas the last fft signal is generated from the static noise in the sensor

Hi,

The FFT of a signal of the first diagram needs at least two peaks on the left side.
One at DC, then the next at about 200Hz, then I expect a lot of overtones...

How many sample points in x axis of the first diagram do you have?

Klaus

Why I do not see a peak around 200Hz?

why do i have a peak at 200 HZ? Please explain this?
Just one correction in last fft figure that the frequency units are KHz and not Hz
Total number of sample points are 500