The equipment should have passed the emissions scan. It should not be susceptible to this noise. The filter analysis said this was not a problem. The case should be an excellent shield. Why doesn’t this pass?
There are two statements I have heard about electromagnetic interference which are both related and true: EMC is the science and engineering of things that are typically not on the schematic , and EMI is often caused by issues of geometry . The first statement speaks to the issues of parasitics, or cross coupling of energy due to magnetic induction or capacitance. The second says that the parasitics can be controlled or reduced if the proper routings and separations are maintained, and that once a degree of understanding about these coupling mechanisms is understood the control of them can be obtained.
Today’s electrical and electronic devices are subject to mandatory EMC requirements throughout the world. Many devices operate at high frequencies and are very small. They are placed in nonconductive plastic cases providing no shielding. Essentially, all these devices cannot meet these mandatory requirements or they may cause interference to other devices or receive interference causing susceptibility problems without a proper program of EMI control. This program consists of identifying the “suspect” components and circuits that may cause or be susceptible to EMI. This is completed early on in the program to allow for an efficient design in keeping the cost of dealing with EMI as low as possible. A complete EMC program consists of proper filtering, grounding and shielding. This article will discuss the latter, but the other factors cannot and will not be ignored or given insufficient priority.
When we think of grounding systems, we tend to think only of resistance and how resistance can be reduced. But the things we do to lower resistance may increase inductance, which could actually make matters worse, especially for fast-rising secondary surges.
Sooner or later, anyone involved with EMI will be involved in troubleshooting an EMI problem, wherever it may surface. Most commonly, the problems will be uncovered during EMI testing, generally very late in the product design cycle, resulting in costly patches and schedule delays. It is best if preliminary EMI testing is done early in the design stage - EMI problems can be uncovered early enough that corrective action can be done in a timely fashion, ideally at the circuit board level. On the back end, EMI problems are often encountered in the field - perhaps because the environment is harsher than that expected by the regulatory agencies or because of an installation problem.
The immunity to ESD of present-day electronic components and devices has further decreased due to the high sensitivity of ICs.
Electronic devices can be exposed to electrostatic discharge (ESD). The discharge process generates rapid electric and magnetic processes that can impair the function of the electronic devices. Devices are tested for their immunity to ESD using special ESD generators and test setups (EN 61004-2).
Ethernet’s success in the marketplace is undeniable, and market-driven standardization has been instrumental in its success. It’s a cycle of synergistic innovation and market growth that has been spinning for decades. Ethernet has become entwined with almost every pattern and process of every-day life around the world. Whether a personal computer (PC) has a direct connection to a router or an indirect connection through a “Wi-Fi®” access point, it is highly likely that Ethernet is providing the connection to the Internet.
The job of the product safety engineer is to reduce the risks associated with a product to an acceptably low level. The product safety engineer is interested in protecting the life and health of the customer wh... Read More...
To many people, Electrostatic Discharge (ESD) is only experienced as a shock when touching a metal doorknob after walking across a carpeted floor or after sliding across a car seat. However, static electricity and ESD has been a serious industrial problem for centuries. As early as the 1400s, European and Caribbean military forts were using static control procedures and devices trying to prevent inadvertent electrostatic discharge ignition of gunpowder stores.
Associate Professor Neils Jonassen authored a bi-monthly static column that appeared in Compliance Engineering Magazine. The series explored charging, ionization, explosions, and other ESD related topics. The E... Read More...