12/3/2023 0 Comments Emi and emc testing![]() Cable shields are only connected to ground at one end. This often means that the initial fix will be less effective than expected not that it won’t work.Ģ. Commonly, many sources of emissions exist and when the most predominant one is minimized, then the second one in line will predominate. Often the paths that RF currents take aren’t always obvious, and distributed parasitic components in a circuit may have been ignored. Also, the coupling mechanism in an EMI problem may not have been completely identified, or a number of coupling mechanisms may have been at issue. So, the major reason EMC is seen as “black magic” is the lack of understanding in the fundamental principles of electromagnetics. For example, shielding against magnetic fields using thin conductive materials with a relative permeability of just 1 seems like magic, but has a simple explanation if one knows the frequency of the magnetic field. It’s understandable, then, that this phrase could be applied to some aspects of EMC.Īfter some EMI mitigation work, the result often is contrary to what we expected and sometimes actually counterintuitive. These phrases are used to describe results that we don’t understand or can’t comprehend or even can’t make sense of. We often use the terms “black magic” or “black art” when describing an unexpected or unusual result. This is probably the most well-known and most common description about EMI/EMC that I’ve heard from engineers and designers in my 40-odd years working in this field. The intent of this article is to explore some of these myths and provide explanations and clarifications to the reader. Many of these myths were generated simply to make them easy to remember. Myths provide a way to obtain quick answers that are not necessarily accurate, but give us rough estimates. Most of these myths came about based on attempts to balance reality (accuracy) versus the time and cost spent on successfully solving EMI/EMC issues. Many myths circulate through the field of electromagnetic interference and electromagnetic compatibility (EMI/EMC), some of which are untrue, or only partially true, or based on misunderstanding. What is a myth? A myth is defined as a popular belief or tradition that has grown up around something an invented story, idea, or concept an imaginary or fictitious thing an unproved or false collective belief. This file type includes high-resolution graphics and schematics when applicable. These magnetic fields are then compared against European ICNIRP health and safety guidelines or other specifications.This article is part of the TechXchange: Delving into EMI, EMC and Noise Exposure to magnetic fields is assessed by measuring the static and AC magnetic fields generated within the vehicle and on the infrastructure in accordance with EN 50500.The magnetic fields generated by the onboard equipment are mesured by magnetic loop antennas and evaluated against specific axle counter limits. Axle counter compatibility tests are designed to assess the compatibility between the rolling stock and the axle counter detectors.Measurement of psophometric current helps evaluate the effective interference introduced by power equipment in an analogue telephone line as per EN 50121.The recorded current signals are evaluated against the limits defined for the particular track circuits used within the project. ![]() Track circuit compatibility test are designed to evaluate the total harmonic content generated by the vehicle and introduced into the rail network in accordance with EN50121 and TS 50238.The magnetic and electric fields recorded are evaluated against the limits established in EN 5 for the vehicle and in EN 50121-5 for the infrastructure. Field radiated EMI tests focus on characterising the levels of radiated electromagnetic fields emitted from the vehicle to the exterior and on the infrastructure.
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