Why Does the Sampling Rate Display Disappear During FFT Analysis for the DL1500 Digital Oscilloscope Series?

The FFT is computed based on the ACQ data. In order to perform the FFT over 1 k points, the ACQ data are decimated (reduced) from 10 kW to 1 kW. At this point the sampling rate is equivalent to 100 kSs (1/10 of 1 MS/s). Therefore, the sampling rate display is turned OFF. For example, to perform an FFT over the data sampled at 1 MS/s when the memory length is 10 kW, the data are decimated from 10 kW down to 1 kW. This means that the sampling rate is equivalent to 100 kS/s at this point. Therefore, to avoid misinterpretation, the sampling rate display is turned OFF. In this case, the actual sampling rate is 1 MS/s, which means that the frequency bandwidth of the time axis waveform is 500 kHz. However, because the sampling rate is reduced to 1/10 as explained above, the frequency bandwidth of the FFT is 50 kHz.