A study of the repeatability of conducted RF emissions

Automotive testing requires a series of validation measurements, usually spreading over a significant time frame. An initial series of measurements during product development will be repeated months later during product validation. It is essential that the levels measured at these two different times correlate with each other. If they do not, it can be an indication that something in the process, sometime between development and validation, has changed. When a divergence is noted, the product engineer must be convinced that measurement variance is not the issue. This paper describes a series of measurements performed in order to better understand the limits of repeatability of measurements, both on a local time scale and on a global scale. The modules tested included a single processor engine controller and a multiprocessor engine controller.