Why the measured output voltage of frequency converter is inaccurate?

It is generally difficult for multimeter to detect burr signal in AC signal, as what multimeter detects is the value at a certain time point. When the multimeter converts digital to analogue, the sampling point may not be the burr peak, so the test result can not reflect whether there is burr in the waveform signal. For detection by oscilloscope, what detects is continuous waveform generally, and the MAX/MIN value can be captured through oversampling, thus the burr signal will be displayed.