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IEC 61000: “Electromagnetic Compatibility--”
IEC 61000 is a major umbrella standard that encompasses a wide range of documents within it, covering limits and test methods for a variety of scenarios.
The IEC (International Electrotechnical Commission) produces, roughly speaking, a gajillionity different standards. Within that extensive list, IEC 61000 is the one that tackles all of EMC. Within IEC 61000, there are only maybe a few jillion subsections. The IEC website has all the sections available for purchase; you can start with 61000-1-1 here. It is good that you can purchase only the sections you need; however the tradeoff is that if you’re a lab that deals in a wide range of test methods you may need to make a significant investment to purchase all the different official copies you’ll need.
I should note that within the IEC, Technical Committee 77 (TC77) has the primary responsibility for IEC 61000. CISPR is another set of committees within the IEC umbrella.
The basic structure of the numbering is IEC 61000 dash part # dash section #. The parts are broken down thusly:
Part 1: General
Basic concepts (fundamental principles, definitions, terminology) - interference model
Functional safety (what a safety function does and measures of it being performed satisfactorily)
Measurement uncertainty
Part 2: Environment
Description of the environment
Classification of the environment
Compatibility levels
Part 3: Limits
Emission limits
Immunity limits (insofar as they do not fall under the responsibility of product committees)
Part 4: Testing and measurement techniques
Measurement techniques
Testing techniques
Part 5: Installation and mitigation guidelines
Installation guidelines
Mitigation methods and devices
Part 6: Generic standards
Generic emission and immunity requirements in various environments
[Parts 7 and 8 are not currently used]
Part 9: Miscellaneous
This may be overstating the case, but most EMC engineers will probably spend more time with the sections of Part 4 than any others. For instance, IEC 61000-4-2 has the standard test method on ESD. It’s used by the automotive industry and has recently been adopted into the MIL-STD arena by way of MIL-STD-461 Rev G, CS118.
As with MIL-STD-461, there are so many important sub-sections of IEC 61000 that I plan on tackling them in individual articles. I may never get to them all, but over time I’ll do my best.
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MIL-STD-461 with CS118 is freely available here, and has almost identical content to 61000-4-2. They’re also both the same as ISO 10605.
LISN Explainer
LISNs are used in multiple different test methods, with different names and characteristics. What the heck are they, anyway?
I’m indebted to Ken Javor’s 2023 article “Line Impedance Stabilization is in its Seventieth Year and Still Going Strong”.
When we test equipment/boxes/modules for EMC, we are testing them in very different conditions than their installations. For instance, usually there’s only one module being powered by only one power supply. In a real installation, there would be power distribution points that feed many different modules (e.g., in a car, your average 12V module gets power from the body control module (BCM) instead of directly from the alternator or 12V battery, and the BCM may be sending power to dozens of modules). There’s a lot that will vary from installation to installation, depending on the platform, end use, construction, etc.
Enter the Line Impedance Stabilization Network (LISN), also sometimes known as an Artificial Network (AN). The clearest picture I’ve yet found to represent its purpose is the one below from GSFC-STD-7000B. The LISN is meant to represent Zs from the picture below.
If you assume that power is distributed via a single wire running 5 cm above structure, and structure is used for current return, then you can reasonably estimate 1 uH/m inductance from all that wiring. On a very large platform like a naval vessel, 50 m of wiring isn’t unheard of--and now you know the origin of the 50 uH LISN. The very first LISN design, from 1953, is the 5 uH LISN (aircraft in particular were smaller back then), and the 5 uH LISN is still used when appropriate today.
There are plenty of variations. For instance, the typical Goddard Space Flight Center project (JWST notwithstanding) is a small science satellite, a cube not much more than 2 m on a side, with a 28 Vdc battery recharged by solar arrays and never using structure for current return. That’s a very low inductance arrangement, and thus they use a stabilization network with a pair of 10 uF feedthrough caps and a 10,000 uF line-to-line cap.
LISNs also help in providing repeatability of measurements across tests and across different labs. Thus if you’re doing FCC testing, you’ll be using the LISN specified in ANSI C63.4 no matter what your final installation is.
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Take a moment to consider what flavor of LISN is most appropriate for the end installation your product will be used in. MIL-STD-461 Rev G Section A4.3.6 has tailoring guidance on this topic.
MIL-STD-461: “Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment”
MIL-STD-461 is one of the core EMC standards, having evolved with military applications since WWII. It is widely used in the aerospace and defense sectors.
MIL-STD-461 is a landmark document in the world of EMC standards, and there are a lot of other standards that derive from this one. The easiest place to find a copy of MIL-STD-461 (free, as most government standards are) is here, or the official site is here. The current edition is Rev G, and the working group for the standard is currently drafting Rev H.
MIL-STD-461 is more of a document that specifies test methods than a strict requirements document, and while it has suggested limits for many of the tests, in most cases those limits should be tailored. For general aerospace and defense projects MIL-STD-464 is the actual requirements document, and the tests in MIL-STD-461 are how you document compliance to the EMC requirements.
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Tailor, tailor, tailor! Beware of any project that simply tells you to “meet 461”--even accepting 461 as the overarching requirement, tailoring 461 is key for saving testing time and budget and not wasting resources designing to inappropriate or inapplicable requirements. I’ll discuss this more in articles dedicated to each test method.
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Read the appendices! More than most standards, the committee behind MIL-STD-461 documents background information for every section of the main document. This includes context, lessons learned, and why different changes have been made over time. There’s a wealth of information in there.
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MIL-STD-461 does not have a requirement to perform testing in a certified lab. While many of the labs that have the equipment needed to perform 461 testing are certified (to ISO, by ANLAB or A2LA, etc), that is not required. Testing in an uncertified lab or your own facility is allowed as long as you can meet the test equipment and test reporting requirements.