Calculating RMS of Fundamental Component for Unknown Periodic Input Signal

[Baluncore]

http://en.wikipedia.org/wiki/Aliasing

 

[anorlunda]

If you don't know about the noise, then whatever you calculate may be completely meaningless.

Your simulation seems to assume that the signals are sinusoidal and of fixed frequency, which contradicts what you say about lack of knowledge about the signals.

I see don't see in the code where you are taking the mean (average) of the squares of all the samples in one or more whole cycles. RMS means square root of the MEAN of the squares. Did you understand that part?

You also never answered the question about what the application is. Please don't post again until you answer that.

Your earlier answer as to why fundamental component sounds bogus.

I think that you and perhaps the person giving you the requirements are in over your heads. You should hire an engineer to straighten it out. The purpose of this forum is not to read and debug your code.