Did you read the replies in your other thread? http://forums.ni.com/t5/LabVIEW/FFT-Amplitude-is-not-constant-for-Different-Sine-Signals/m-p/3042227...
@johnsold wrote:
Henrik is exactly right. You are experiencing spectral leakage. If you expand the spectral graph to show just one peak, you will see that there are several non-zero values on both sides of the peak. Some of the energy is in those bins resulting in a decrease of the amplitude of the largest peak.
If you run Extract Single Tone Information.vi on each of your frequencies, you will find that it reports the amplitudes of all of the signals as equal. Internally this VI uses FFT but also compensates for spectral leakage and includes the energy in the adjacent bins. The very slight discrepancy in the 20 Hz values are due to the fact that there are not enough points below 20 Hz to completely resolve the leakage there.
Zwired1,
There is no need to convert to 2D arrays to matrix and back to 1D array to array of waveforms. The Ramp pattern VI and one for loop cna generate the same signals.
Lynn
So, read what johnsold offered. There are several non-zero values on both sides of the peak. Let's see if that is a plausible explanation. We look at the graph you just provided and we can see the peaks are not straight lights. In fact, they have several non-zero values on both sides of the peak. If we look at each of the peaks you've provided, the shortest peaks have the largest amount of leakage near them.
