XN-8000 Frequently Asked Questions

Why do the power spectral averaging results differ between offline and online analyses?

In online analysis, A/D conversion data is continuously updated even when the system is stopped. When the system starts, data prior to the start time is also processed using FFT and averaged. In online analysis, the FFT calculation is performed on past data plus new data corresponding to the overlap amount.

On the other hand, offline, since there is no historical data, it uses zero data plus file data equivalent to the overlap amount. As a result, the signal suddenly changes from zero, causing differences in the low-frequency components.

Online analysis

Offline analysis

■ How to respond

In "Menu => Analysis => Analysis Conditions => Measurement," turn on (check) the delay time in the start conditions and set the time. The set time should be the length of one frame of the time waveform (sample interval × data length).