The Auto Power Spectrum vi is only calculated on one set of data. However the waveform vis "FFT Power Spectrum.vi" and "FFT Power Spectral Density.vi" will do what you need. The Welch procedure is a combination of spectrum averaging and windowing. These functions allow both. The keep a history of data with a cluster input for the averaging parameters. There is also an input for a window type.
Auto Power Spectrum vi is defined in help as FFT*(signal)*FFT(signal/N^2. This is the same as the FFT Power Spectrum vi (ie it should be normalised the same way)
