How to Test CAN Bus Signal Quality with Eye Diagrams

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Essential Benchtop Oscilloscope
+ Essential Benchtop Oscilloscope
Essential Benchtop Oscilloscope
+ Essential Benchtop Oscilloscope

Evaluate CAN Physical-Layer Signal Quality

CAN is a differential serial bus used throughout automotive systems to exchange control and status information between electronic control units (ECUs). As messages travel across the network, propagation delay, jitter, edge distortion, and other physical-layer effects can influence overall CAN signal quality. Engineers need a practical way to evaluate whether the electrical characteristics of the bus remain within acceptable limits before these effects begin impacting communication reliability. A CAN eye diagram combines many waveform acquisitions into a single display, providing a comprehensive view of CAN physical-layer performance rather than the behavior of an individual frame. This makes it possible to evaluate the overall quality of the bus and quickly identify waveform characteristics that may indicate degraded signal integrity.

Performing the test requires an oscilloscope connected across the differential CAN bus using a differential active probe. Engineers use automotive oscilloscope software to enable CAN triggering, protocol decoding, CAN eye diagram generation, and automated mask testing while capturing repeated CAN waveforms. The resulting display highlights eye opening, jitter, edge behavior, and mask violations that may indicate reduced CAN signal quality. Instead of reviewing individual waveform captures one at a time, engineers can evaluate the overall condition of the CAN physical layer in a single measurement, making it easier to identify signal integrity issues, compare waveform quality against the mask, and verify that the bus meets expected communication performance requirements.

CAN Eye Diagram Analysis Solution

Testing CAN bus signal quality requires a measurement setup that can combine repeated differential waveform acquisitions into a CAN eye diagram and automatically evaluate the results against a defined mask. An Essential benchtop oscilloscope captures repeated CAN waveforms, while a differential active probe acquires the differential bus signal with minimal circuit loading and preserves signal fidelity during measurement. Automotive analysis software enables CAN triggering, protocol decoding, CAN eye diagram generation, and automated mask testing to evaluate CAN physical-layer performance from the captured waveforms. Together, the oscilloscope, software, and differential probe allow engineers to assess CAN signal quality by examining eye opening, jitter, edge behavior, and mask violations within a single measurement display. This integrated setup provides an efficient way to validate the CAN physical layer and identify signal integrity issues before they affect communication reliability.
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