Newbie questions

[Pete]

Increasing resolution to 8912 looks like this:

Screenshot (482).png (82.9 KiB) Viewed 4831 times

[VirtinsTech]

There is almost no signal in the Oscilloscope, or maybe the signal level is too low, only 0.02% as indicated by the input peak level indicator in the upper right corner of the screen. Please check the connection and the input gain settings.

[Pete]

Screenshots were taken after FR was taken and generator stopped hence no signal showing in the oscilloscope window , while measuring it was around 850mV

[VirtinsTech]

Thanks for the additional explanation. These screenshots are now understood.

The method of measuring magnitude frequency response using a linear frequency sweep in the signal generator along with peak hold in the spectrum analyzer has significant limitations. To achieve higher frequency resolution at the low-frequency end, the FFT size must be sufficiently large. As a result, more peak-held frames are required to form a smooth frequency response curve. In the most optimistic case—assuming each frame produces a peak in one different FFT bin—the minimum number of peak-held frames equals half the FFT size. However, in practice, some FFT bins may be skipped and not captured by the peak hold, even if the sweep duration is very long. This can cause artificial undulations in the measured frequency response curve.

The recommended approach is the "FRswlog" method, which uses a logarithmic sweep combined with 1/96-octave analysis.