A Fast Fourier Transform (FFT) is a numerical approximation of a Fourier Transform (FT). A Fourier Transform is a way of analyzing a set of time-series data (the input signal) so as to determine the input signal’s component frequencies and the strengths of those frequencies. OSIsoft provides an interface with builtin FFT functions that uses a PI tag as the input signal and outputs the resulting array of information to a PI server as well.
The interface starts caching data when it starts and after enough input data has been collected (depending on the size of the moving window configured) the interface calculates the FFT of the data set. Finally, it sends the results to the target PI server, which may require hundreds of tags for each analysis. Utilizing the PI FFT interface may require a custom architecture for the PI System such as PMUs in general.
The available calculations by the PI FFT interface are:
- Real and imaginary parts (rectangular)
- Magnitude (polar)
- Angle (deg and rad)
- Harmonic number
- Peak areas
- Integral of spectrum
- Damping coefficients
- See manual for a complete list.
++: attached is a sample AF Template with attributes modeled for each calculation provided by the interface. This template is also configured to auto create the tags with the appropriate tag settings to connect and collect data from the interface.
