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Calculation of potential and current power spectral densities

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At the next iteration, a segment of identical size is extracted from the time record, the calculation repeated,  and the results assigned to the time value corresponding to the first point of the second extracted segment.  The spacing between segment can be adjusted by modifying the overlap parameter in the preference window.  For example, if a step size of 1024 is selected and an overlap of 50 % is selected, the first points of two consecutive segments is spaced of 512 points. The spacing between one segment and the following is displayed on the Parameters screen and is rounded to the higher closest integer. Any value between 1% and 99% overlap can be selected in the preferences menu.




Figure 3.0. The Time position is represented graphically by a moving point  ( a diamond shape ) in the Time record.



Figure 4.0 ECN Analysis 1.0 calculates the linear trend for the potential and current segments

The segment iteratively extracted from the complete potential and current noises time records are displayed on the Processing screen.  The length of the extracted segment can be adjusted between 128 and 4096 points in the preference menu by changing the Length of FFT parameter.   On the same screen, the linear trend line is displayed overlapped the extracted segment. Such trend line is subtracted, to obtain the linear trend removed potential and current segment, required for FFTs.


Fig 5.0 Linear Trend Removal

Prior to performing fast fourier transform (FFT), a window is applied to the linear trend removed segments . The window type can be selected from the preference menu under “window type”. Once the segment are de-trended and windowed, the power spectral density is calculated by using  FFT (single side), and displayed both in screen Processing and screen PSD.



Figure 6.0  Current Power Spectral Density and Potential Power spectral Density.