Oscilloscopes detect ECU disturbances from EMI: Page 3 of 5

November 16, 2015 //By Loren Dunn , Mike Hertz & Dan Steinken
Oscilloscopes detect ECU disturbances from EMI
Loren Dunn , Mike Hertz and Dan Steinken examine how to use oscilloscopes to detect ECU disturbances from EMI.
within the useable volume of the reverb chamber on a foam bench having a relative permittivity less than 1.4.

Figure 1. Reverb chamber equipped with a mode tuner (right). Transmit and receive antennas not pictured.

Once available outside the chamber, the signals are typically routed to data-acquisition system, which often requires custom software to analyze and compare the signal information to allowable tolerances and decide if the if EUT meets the specified requirements. Unlike many sensors, ECUs (electronic control units) may have several signals to monitor and evaluate measurements to acceptance limits and the software needed can come at a high development cost. Instead, we use an array of oscilloscopes in place of a complex, custom data acquisition system. Because oscilloscopes are already equipped with mask testing and parameter limit test abilities, they can address many, if not all, of the test requirements directly, without any significant amount of software development time needed.

Figure 2 shows the open doorway to the reverberation chamber, which is to the right of the test bench. On the left side, fiber optic cables, receiver and an array of oscilloscopes for performing real-time analysis.


Figure 2. An array of oscilloscopes is used for real-time analysis of the DUT response to radiated electric fields.

We use waveform masks in the oscilloscope to compare the waveform shapes during exposure to a disturbance relative to the shapes with no disturbance present. The dimensions of the mask depend on the acceptance criteria defined in the test plan.

Figures 3, 4, and 5, show the output of a simulated ECU. For confidentiality reasons, simulated data is used which closely approximates what signals may be monitored with a typical ECU. Channels 1 and 2 show simulated PWM signals which control an output driver actuator signal. The simulated actuator signal is captured on Channel 3, and a CAN split voltage is displayed on Channel 4.

Figure 3 shows the acquisition with mask

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