Military standard gets a revision
Version F of MIL-STD-461, which covers the control of electromagnetic interference, introduces significant changes.
Martin Rowe, Senior Technical Editor -- Test & Measurement World, 8/1/2009 2:00:00 AM
MIL-STD-461, “Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment,” has long defined military EMC (electromagnetic compliance) tests. With version F, the standard incorporates numerous changes (both significant and minor) and reinstates an old test method. Released in December 2007, MIL-STD-461F is now being implemented on products and systems developed for Department of Defense applications.
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The current version of the standard incorporates a dozen or so significant changes. Some of those changes are easy to understand, but others may lead to confusion. A paper by Steve Ferguson, VP of operations at Washington Laboratories, spells out these changes in detail. In his paper, Ferguson assumes that you’re already familiar with previous versions of MIL-STD-461.
Ferguson points to a new frequency-scanning technique as a possible point of confusion. He notes that the standard lets you run faster scans, but that the faster scans don’t mean you’ll reduce testing time. You still must comply with a minimum measurement time defined in the standard, even though new equipment can scan faster than older equipment.
A requirement for power-line voltage testing, dropped from the standard with revision D in 1993, has been reinstated for some applications. MIL-STD-461F requires a single 400-V, 5-µs pulse calibrated with a noninductive 5-Ω resistor.
If you perform automated tests, then MIL-STD-461F requires that you verify operation of your software, whether you use commercial software or develop your own. You must describe the control and methodology of your software. If you write your own test procedure for use at a commercial EMC lab, you’ll need detailed knowledge of how the software works.
EMC Symposium: MIL-STD-461F demos
08/18/2009Revision G planned for MIL-STD-810
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