18/07/2026 10:54 am
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Automotive Q&A
Lab-scope sample rate: how do you recognize an aliased automotive signal?
Review the evidence, add a focused answer, and distinguish confirmed measurements from assumptions.
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A wheel-speed capture at a long time base showed a smooth low-frequency wave that disappeared when zoomed in. The technician had used automatic memory and assumed the sensor itself was slow. We need a simple check for displays that are under-sampling a faster signal.
What settings and repeat capture expose aliasing?
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19/07/2026 8:39 am
Estimate the highest expected edge or frequency, then choose a sample rate comfortably above it and enough memory for the desired time window. Capture a short high-resolution segment first to learn the actual waveform, then extend the time base while watching the displayed sample rate. Peak detect or segmented memory can preserve brief events, but understand the mode.
If changing the sample rate changes the apparent frequency or shape, the earlier display was not trustworthy. Record time base, sample rate, bandwidth limit and probe attenuation with the saved waveform.
Topic starter
20/07/2026 10:08 am
We repeated the wheel signal at ten times the sample rate and found narrow dropouts hidden by the long capture. The worksheet now requires a resolution screenshot beside the overview, and the false low-frequency interpretation has not recurred.