PSD magnitudes

Hi,

We are trying to study the PSD of a sine signal. We are finding that the magnitude  of the output of the PSD VI does not correspond to the value given by the math equation "A²/4" at the frequency of the sine (and A being the amplitude of the sine).

Moreover the magnitude of the output seems dependent on the number of points generated by the sine wave VI.

Can someone help us understand where this problem is coming from?

Thanks

Ella