What is aliasing?

What is aliasing?

Aliasing occurs when an oscilloscope does not sample the signal fast enough to construct an accurate waveform record. The signal frequency is misidentified, and the waveforms displayed on an oscilloscope become indistinguishable.

Aliasing is basically a form of undersampling. The undersampled waveform is constructed to look like a slower frequency waveform or a flat line when the sample rate is the same as the frequency of your signal.

You can detect aliasing by running a horizontal test on your oscilloscope. If the shape of the waveform changes drastically, you may have aliasing. You can also perform a peak detect test and if the waveform still changes drastically, aliasing may be an issue.

To fix aliasing, scale in horizontally, increase the record length or use a combination of the two. The quick fix for aliasing is to select auto-set, which automatically sets the vertical, horizontal and trigger controls for a usable and stable waveform display.

This video video gives you a better understanding what aliasing looks like, and how to fix it.