EMC software takes center stage
Martin Rowe, Senior Technical Editor -- Test & Measurement World, 8/16/2006 10:00:00 PM
PORTLAND, OR. Technical sessions, EMC demonstrations, and product exhibitions continued today at the 2006 IEEE EMC Symposium (August 14–16, www.emc2006.org). This year, EMC design and test software was in abundance as never before. "EMC simulations are simply tests done with computers," said Bruce Archambault, Distinguished Engineer at IBM, one of several companies exhibiting software today.
More from the 2006 IEEE EMC Symposium:
Agilent, Rohde & Schwarz make EMC Symposium news
In general, EMC software takes files from PCB layout software and applies rules specific to EMI emissions. Users get a color-coded plot of expected EMI hot spots on a board. Software for this purpose appeared from IBM (www.ibm.com), Ansoft (www.ansoft.com), Advanced Electromagnetics (www.aemi-inc.com), ScanCAD (www.scancad.com), Zeland Software (www.zeland.com), EMS-Plus (www.ems-plus.com), NEC (www.emistream.com), SimLab Software (www.simlab-emc.com), and Applied Simulation Technology (www.apssimtech.com). Software from Flomerics (www.flomerics.com) simulates not PCB emissions, but system-level emissions. Comsol (www.comsol.com) also exhibited its general-purpose modeling software that includes an electromagnetics module. In addition, software from Quantum Change (www.quamtunchange.com) automates EMC measurements in the lab and Traxstar Technologies (www.traxstar.com) showed software for managing EMC labs.
Today's technical sessions included presentations on EMC measurements and EMC management. In "An Electric-Field Uniformity Study of an Outdoor Vehicular Test Range," Robert Johnk of NIST explained how NIST worked with General Motors to characterize the company's automotive EMC test facility to provide uniform fields for immunity testing. The same session also featured a paper, "Shielding Measurements of the Space Shuttle," where NIST and NASA performed tests for EMI shields on the Endeavour.
In the "EMC Managements and Product Safety" session, consultant Brian Jones described how Britain is adjusting to the new EMC Directive, which becomes effective next year and receives full enforcement on 2009. Jones explained how Britain is defining some of the ambiguities in the directive and how manufacturers will need to cope with them. Later in that session, Hirayr Kydyan of Lucent Technologies discussed how he performs measurements on a system's power bus to predict the product's EMC performance before the product is completely designed.
More EMC demonstrations took place on the exhibit floor as well. Ken Wyatt of Agilent Technologies (pictured) demonstrated the effects of ESD on electronic circuits. He used calibrated ESD sources and uncalibrated sources such as barbeque lighters to create ESD events. He also showed how today's high-bandwidth oscilloscopes reveal more about ESD waveforms than were known about when test standards were written.
The technical portion of the day concluded with a panel discussion of respected EMC engineers who gathered to answer open-ended questions. The panel consisted of Bruce Archambault, Don Heirmann, Elya Joffe, Robert Olson, Clayton Paul, Tom Van Doren, and Clark Vitek. Questions ranged from interpretation of standards to specific PCB layout issues.
An attendee asked why EMC engineers use a 6-dB margin when testing to emissions standards such as CISPR 16. Hiermann responded that you need a 6-dB margin just to cover the 5 dB to 6 dB uncertainty in EMI measurements. Another question revolved around statistics when an audience member asked, "How many units do you measure to gain confidence in a test." Archambault drew a laugh from the crowd when he replied "42." Vitek noted that CISPR 16 says that if you get no failures from seven units, or one failure from 13 units, then your product passes.
Other questions relating to ground loops were raised, to which Archambault replied, "ground is where you grow carrots, but there's no such thing as ground in electronic circuits." He and Van Doren explained that how you connect signal return paths to their sources affects EMC performance.
