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MSO-X4154A amplitude measurement

Question asked by RednBlack on Apr 29, 2020
Latest reply on Apr 30, 2020 by RednBlack



I have an odd problem with this scope's amplitude measurement function.  The signal is a sinusoid with significant crossover distortion and the measurement occasionally picks this as the top of the waveform:

Amplitude measurement normal


Amplitude measurement error


The behaviour is not consistent; the lower trace will occur maybe 1 in 20 captures (in single shot mode).  I first noticed this when I had the measurement statistics running with x1000 averaging, and the results deviated from expected values by a few percent.  If the affected measurement doesn't have cursors visible this could easily be missed.


I assume the algorithm is looking for a region of the waveform close to the peak with relatively low dV/dt, this is what is implied in the manual.  How it misses the true top of the waveform that is about double the detected value, I'm not sure.  It does seem to be worse when the peak is near the top of the screen.


I tried updating the firmware to the latest version 7.31.2020012900, this made no difference.  Any suggestions?