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CISPR 11: “Industrial, scientific and medical equipment – Radio-frequency disturbance characteristics – Limits and methods of measurement”
This is an important standard limiting radiated and conducted emissions from non-consumer electronics, which have different concerns in terms of operating environments than tests such as FCC/ANI C63.4.
Like most CISPR standards, CISPR 11 aims to control the unintentional emission of RF energy from equipment, in this case industrial, scientific and medical (ISM) equipment. These are units designed to operate in more restricted areas than general consumer electronics. They divide ISM equipment into two classes, Class A and Class B, where Class B equipment may be used in a residential setting. However its main concern is higher power equipment, such as arc welders, that are not found in casual use. It also distinguishes between Groups 1 and 2, where Group 2 equipment includes intentional generation of RF signals. A newly revised version of CISPR 11 was published in 2024 and can be purchased here. It informs IEC 60601-1-2 on medical equipment.
CISPR 11 looks at both conducted and radiated emissions, although as Henry Ott pointed out years ago, in these cases conducted emissions tests are really radiated emissions controls in disguise. Section 6 lays out the emissions limits for different equipment in different situations, and Sections 7 and 8 concern measurements methods. Limits start at 150 kHz and, depending on application, go up to 18 GHz. They are generally expressed as both Average and Quasi Peak levels. It refers back to CISPR 16 for most measurement equipment specifications.
The test methods of CISPR 11 acknowledge that the equipment that falls under this standard may be considerably more complex than the kinds of modules you might test under MIL-STD-461 or CISPR 25. Hence it allows Class A equipment to be tested in situ (on site) if needed. As such, it has a different approach to, for instance, characterizing ambient noise levels. It also describes different kinds of LISN/Artificial Network configurations. It spends quite a bit of time concerning cable arrangements, which can be critical for accurate, repeatable measurements.
Some useful information in the appendices (Always Read the Appendices!) includes protection and concerns when using spectrum analyzers around ISM and other potentially higher power equipment; ways to handle existing RF transmissions in the environment when you can’t use a shield room; and worldwide frequency allocations and particular safety-related bands that should be protected.
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Some limits changed in the 2024 revision, mostly to cover newer equipment configurations. It also now addresses industrial robots specifically.
ANSI C63.16: “Guide for Electrostatic Discharge Test Methodologies and Acceptance Criteria for Electronic Equipment”
This is a guidance document for ESD testing that helps the users of IEC 61000-4-2 (as well as ISO 10605 and MIL-STD-461 CS118)
ANSI C63.16 is a useful document meant to provide guidance for engineers and technicians conducting ESD testing to IEC 61000-4-2. Which means it is also useful for people testing to ISO 10605 and MIL-STD-461 CS118 by extension, since those documents are close to identical with the IEC standard. The 2016 version of C63.16 can be purchased here, but you might want to wait. A new version is expected to be published in late 2024/early 2025, which will have several technically substantial updates. I’m on the working group for this revision, so it’s near and dear to my heart.
Some of the topics addressed in C63.16:
Climate conditions during testing
The use of air vs. contact discharges
Test setups
Considerations for the ESD gun return cable
Considerations for the bleed resistors (in the revision, issues of degradation over time are raised)
Test procedures
Selecting test points
Handling large EUTs or those with complex peripheral arrangements
Approach speed for air discharges
In situ testing
Pin discharges
A lot of the guidance found in this document is based on decades worth of lessons learned. It points out things that are easy to miss until they go wrong.
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There have been a large number of cases where customers report issues in the field that hadn’t been caught and can’t be replicated in the lab. C63.16 aims to add to the minimum number of tests and test conditions called for in IEC 61000-4-2 in order to reduce these situations.
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The new revision contains an extensive discussion of relative humidity. Humidity can vary dramatically between indoors and outdoors, as well as different locations within a building, so knowing what the conditions are specifically where testing is occuring helps with repeatability. ESD events, in particular air discharges, are known to be sensitive to humidity conditions. On many occasions, the fact that equipment is used in environments far outside the 30 - 60% relative humidity called for by IEC 61000-4-2 is the cause for disconnects between field issues and lab testing as noted above.
NASA-HDBK-4001: “Electrical Grounding Architecture for Unmanned Spacecraft”
This NASA guidance document has conceptual and practical information and recommendations for people designing grounding for complex systems.
I have long complained that the word “grounding” means too many things in electrical engineering. It can mean (1) A connection to Earth/dirt; (2) A current return path; or (3) A voltage/potential reference. At least in this publicly available NASA document (free to download here) we don’t have to worry about meaning #1–there’s no way we’re connecting a spacecraft to the dirt back on Earth. This guidance document from 1998 has useful information for anyone looking at implementing “grounding” (both in terms of (2) and (3)) on a mobile platform with largely conductive structure.
Although fairly concise at 29 pages, 4001 covers a lot of ground (pardon the pun). It acknowledges up front that there’s no single “correct” grounding approach, and it covers which design considerations are most important in designing a grounding architecture. It approaches grounding design from the systems perspective, largely looking at the connections between modules. I find the conceptual diagrams to be particularly helpful, such as the ones highlighting power distribution and signals below.
Topics addressed in NASA-HDBK-4001:
Ground isolation and ground loops
Different requirements for different frequencies of interest
Single point ground (SPG or “star” grounding) vs. multiple point ground
Bleed resistors
Bonding
Different requirements depending on platform size
Grounding for sensors, RF systems, pyro devices, etc.
Ground fault isolation
It also shows a fascinating example in the appendix drawn from the Cassini mission of what this kind of grounding architecture looks like on a large and complex spacecraft
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NASA-HDBK-4001 calls out MIL-B-5087B for bonding guidance, but today the recommendation would be to refer to NASA-HDBK-4003. The latter document had not yet been written in 1998 when 4001 was first published.
Designing in appropriate grounding for complex systems is such a large topic that it’s not captured in many other standards. While its main applicability is to a very specific set of hardware, NASA-HDBK-4001 is a good starting point for people outside of NASA and outside of aerospace who are having to make grounding-related design decisions.
IEEE 299 and 299.1 on Measuring the Shielding Effectiveness of Enclosures
These two IEEE standards look at shielding effectiveness measurements for enclosures both large and small.
IEEE 299 is titled “Standard Method for Measuring the Effectiveness of Electromagnetic Shielding Enclosures” and is by far the most widely used IEEE standard sponsored by the EMC Society. IEEE 299.1 is the “Standard Method for Measuring the Shielding Effectiveness of Enclosures and Boxes Having All Dimensions between 0.1 m and 2 m”. It is also widely accessed. While both of these standards are considered currently “inactive”, you can purchase 299 (here) and 299.1 (here) from the IEEE.
IEEE 299 is a relatively straightforward standard, with 39 pages of technical content of which 13 are found in five informative annexes. IEEE 299.1 is rather more complex, since it deals with situations where enclosure dimensions are small compared to the wavelengths of the RF fields and frequencies of interest. The copy I have has 44 pages in the main document, plus another 38 pages in 12 informative annexes.
Dealing with enclosures where the smallest dimension is 2 m or greater, IEEE 299 defines test methods from 9 kHz - 18 GHz, extendable down to 50 Hz and up to 100 GHz. The table below shows the recommended antennas for different frequency ranges.
Depending on the frequency range, the measurand might be voltage, H field, E field, or power. After that, shielding effectiveness can be calculated in a straightforward way, comparing the value without the enclosure (Value1) to the value with the enclosure (Value2):
[linear values] SE = 20 log10 (Value1/Value2) (or 10 * log10 when comparing power)
Or
[dB values] SE = Value1 - Value2
The measurements involved aren’t trivial, but with enough space to place equipment the procedures are relatively simple.
IEEE 299.1 has a harder job, since the smaller dimensions seriously constrain test equipment and configurations. It officially covers the same frequency range as 299. The standard divides itself into two sections, one covering 0.75 - 2 m and the other 0.1 - 0.75 m. At this point, testing within a reverb chamber becomes a much more attractive option than in IEEE 299, and the standard spends a lot of time on those methods (see also IEC 61000-4-21). Data collected this way takes a little more math to interpret correctly, due to the statistical nature of reverb chamber measurements. The standard as currently written feels somewhat incomplete and refers to continuing research in the area of measurements of physically and electrically small enclosures.
Both of these standards have been approved to move forward with renewal by the EMC Society and will be moving to IEEE Standards Association approval in the Fall of 2024. After that approval comes through a working group will be formed under the leadership of Dr. Davy Pissoort of KU Leuven. The expectation is that IEEE 299 will be renewed with only minor updates to the technical content, where 299.1 will require more extensive revisions. If you are interested in being involved in this effort, please contact me at standards@emcunited.com and I can put you in touch with Dr. Pissoort.
NASA-STD-4003: “Electrical Bonding for NASA Launch Vehicles, Spacecraft, Payloads, and Flight Equipment”
NASA-STD-4003 is the rare EMC standard that covers electrical bonding in a comprehensive way.
NASA-STD-4003 is unusual for its focus on bonding–which is more of a concern for aerospace projects than for most others. If you look in Henry Ott’s classic EMC Engineering or Michel Mardiguian’s useful Controlling Radiated Emissions by Design, you won’t see bonding mentioned much. But for aerospace, given its severe electromagnetic environments (lightning, plasma charging, EMP, etc.), bonding is critical. Following the guidance of NASA-STD-4003 gets you a long way to meeting the requirements of MIL-STD-464. 4003 can be freely downloaded here.The most recent revision is Rev A with changes, dated January 2016.
4003 separates bonds into different categories depending on their purpose. There are five categories, as seen in the main summary table below.
This table illustrates how broadly applicable this document is: although NASA spacecraft rarely use chassis for power return, the Class C bond category covers exactly that case–useful for aircraft and other vehicles types, beyond just space missions.
One challenge with NASA-STD-4003 is that some of the numbers it has in the summary table have been imposed as hard-and-fast requirements without an understanding of where those numbers come from and how they can be tailored to particular programs.
One example is “2.5 mOhms” for RF and lightning. Lightning and RF currents both have high frequency components. We’re trying to establish a low impedance path for these currents, but 2.5 mOhms is a DC resistance value. The reason for this is simply that it is MUCH easier to measure the DC resistance of an installed bond with a milliohm meter than it is to measure the high frequency impedance of a joint. IN GENERAL, if you can establish a 2.5 mOhm bond upon installation, you have likely also created a low impedance joint, since you have to have excellent metal-to-metal contact to get 2.5 mOhm at DC. But that doesn’t mean that if you have an 8 mOhm joint that your hardware will fail; it means you need to put more thought into the specific mission parameters are driving the need for bonding at that joint.
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Bonding measurements per NASA-STD-4003 are taken per joint, not on a point-to-point basis. Example: I have a cable harness going from one metal box to another with an overbraid shield installed, connected to MIL-STD-38999 connector backshells on both ends. Let’s say the bonding requirement for this particular shield is deemed to be the 2.5 mOhm Class R category. In this case, we do not need the measurement from box to box to be less than or equal to 2.5 mOhm. Here are the measurement requirements in that case:
Box A to connector backshell A < 2.5 mOhm
Connector backshell A to shield < 2.5 mOhm
Shield to connector backshell B < 2.5 mOhm
Connector backshell B to Box B < 2.5 mOhm
OR: Box A to Box B < 10 mOhm
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The origin of the 2.5 mOhm requirement goes back at least 70 years, and derives from the need to keep the voltage developed across any single joint under 500 V in the event of a 200 kA lightning strike. Nothing in its origin relates to controlling the impedance of structure for RF systems. Even the 500 V number is somewhat arbitrary and likely stems from the need to prevent sparking between structural elements surrounding fuel tanks. The 2.5 mOhm number has been adopted because it is a conservative value that is easy to measure and, if met, generally ensures proper system functioning. However, for new systems, and particularly any systems using novel materials such as composite airframes, new analysis should be done to determine what value of Class R bonding is needed for that particular project. This is a case where detailed simulations can give good answers early in the program and help drive reasonable requirements development.
One excellent way I’ve seen to capture bonding information is in a diagram such as the example below. In it you see places where different metallic elements join together. At each joint there’s a circle specifying the purpose of that particular joint. So from one box to structure a joint is necessary to carry fault current. Between two different kinds of structural panels, Class L bonds are needed, and to ensure proper functioning of an RF system Class R bonds are needed. In one area where a joint is needed both for lightning protection and for RF performance, a hybrid joint is specified. (In this case, the lowest bond value requirement is imposed.) This kind of diagram gives an at-a-glance image for the people setting structural bonding requirements, as well as a quick reference for people monitoring installations. It also helps ensure that if bonding requirements change later in the program, a relaxation of the Class L bond requirement (for example), won’t be blindly applied to a joint that has both a Class L and Class R function.
RTCA DO-160: “Environmental Conditions and Test Procedures for Airborne Equipment”
RTCA DO-160 is critical for qualifying electronics modules for use on aircraft.
RTCA DO-160 is key for getting electronics modules tested in order to ensure proper operation and support certification of aircraft. The current Rev is G and can be purchased here. Its history traces back to 1958, about the same time the precursors to MIL-STD-461 were coming into existence. It follows the same general principles as many MIL-STD-461-derived standards: test individual units very thoroughly, and when you integrate them into a larger system you have a good chance that will operate together successfully. In DO-160, EMC-related topics are a subset of a larger realm of environmental testing, including thermal, humidity, shock & vibe, sand & dust, salt spray, etc. Sections 16 - 23, plus 25, are the ones with the most EMC/E3 impact.
Section 16 specifies “Power Input” and can be thought of as a power quality spec. It controls things like normal operating voltages, both AC and DC, normal transients, ripple voltages, phase imbalance for AC power, and abnormal conditions as well. It has more in common with MIL-STD-704 than 461 or 464. This section assumes the equipment under test (EUT) is getting power in one of the following forms: 14, 28, or 270 Vdc, or 115 or 230 Vrms AC at 400 Hz.
Section 17 is for “Voltage Spike” testing. This is most similar to MIL-STD-461 CS06/CS106 testing, which was removed from the latest 461 Rev G. It can be found in the older versions of 461, as well as in GSFC-STD-7000.
Section 18, “Audio Frequency Conducted Susceptibility”. This is closely related to MIL-STD-461 CS101, which can be a tricky test to execute.
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Figure 18-1 of DO-160G shows an optional current monitor as part of the test setup. Always use this if you have the equipment–it gives you a lot of additional information for not a lot of extra effort. In particular it gives you the ability to calculate how the input impedance of the EUT is changing over frequency.
Section 19 covers “Induced Signal Susceptibility”. This doesn’t have a direct MIL-STD-461 analogue, but in general it is looking for susceptibility to low frequency stimulus induced in signal lines, as opposed to Section 18 focusing on power lines.
Section 20, “RF Susceptibility (Radiated and Conducted)” covers similar test methods to MIL-STD-461 CS114 and RS103. The radiated test includes both semi-anechoic and reverb methods.
Section 21, “Emission of RF Energy”, covers similar test methods to MIL-STD-461 CE102 and RE102. As in Section 20, the radiated test includes both ALSE and reverb methods.
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Use reverb testing whenever possible to save time. DO-160G Section 20 has excellent information about the mathematical and statistical techniques needed to ensure a chamber is set up correctly. The math is scarier, but there’s a significant savings in terms of testing time-in-chamber.
Sections 22 and 23 cover lightning testing (“Lightning Induced Transient Susceptibility” and “Lightning Direct Effects”). These share a lot of heritage with MIL-STD-464 as electromagnetic environmental effects tests. Section 25 covers ESD, and like most ESD specs basically follows IEC 61000-4-2.
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One of the things that separates DO-160 from other standards is the use of alphanumeric codes to describe the EUT and the applicable tests. Whenever you pin down a letter/number designation that applies to your EUT, write it down somewhere. Otherwise you’ll spend a lot of time flipping back and forth across many pages trying to find the right code again.
SpaceX Payload User’s Guides
SpaceX User’s Guides are particularly useful in summarizing EM environments for launch and ground handling.
SpaceX provides “User’s Guides” (Payload User’s Guides, or PUGs) for payloads going on Falcon 9, Falcon Heavy, or taking advantage of its Rideshare program. They’re all free to download from SpaceX. These are fairly comprehensive documents, including mission planning timelines and different environments: thermal, shock/vibe, pressure, etc., along with necessary mechanical and electrical interface specs. For our purposes, the section within “Environments” on “Electromagnetic” can be useful beyond only specific payload missions.
The purpose of this section is to let the user know what electromagnetic environments it might be exposed to, and also how it must limit its emissions in order to protect the RF and avionics systems of the launch vehicle. The limits are, on the whole, more lenient than the default limits found in MIL-STD-461, both for emissions and susceptibility, and can be very useful for tailoring EMC requirements and testing.
What I find particularly helpful is the set of limits in the image below. This is an envelope of the worst-case EM radiation environment between both the Eastern and Western launch ranges where SpaceX operates. (Presumably when Starship gets its own User’s Guide, the environment for the Texas base will be included as well.) This is incredibly helpful for planning what levels a piece of equipment should be robust enough to handle during all phases of operations leading up to launch: shipping, ground handling and checkouts, stacked and awaiting launch, as well as launch itself. This helps inform EMC radiated susceptibility test levels with a lot more granularity than the 20 V/m level set by MIL-STD-461, and is information that used to be hard to find.
CISPR 16: “Specification for radio disturbance and immunity measuring apparatus and methods”
CISPR 16 is one of the key standards governing the measurement instrumentation used in EMC testing.
CISPR 16 is a core standard governing the measurement instruments used in many forms of EMC testing, both for other CISPR standards such as CISPR 12, but ISO and others as well. It is generally harmonized with ANSI C63.2, which is the instrumentation standards called out by ANSI C63.4, which is the test method required for FCC testing. (The tangled knots we weave in standards!) The most recent official version is from 2019, and it can be purchased here. It generally covers the frequency range 9 kHz - 18 GHz, although it can be extended higher.
This standard gets deep into the weeds for the details of how measurements are taken, both for immunity/susceptibility and for emissions. For instance, this is one of the few places where the mathematical definitions of how quasi-peak measurements are weighted are written down.
As with other IEC/CISPR documents, there are a lot of sub-parts of CISPR 16:
Having official copies of these documents is critical if you are an instrument manufacturer or certified test lab.
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CISPR 16 explains the differences between spectrum analyzers and EMI receivers and treats them separately. This is a subtle difference since they both give the same apparent output to the casual observer (voltage amplitude vs. frequency). If you are using this equipment it is important to know the strengths and weaknesses of both and understand which one you’re working with.
ICNIRP: “ICNIRP GUIDELINES FOR LIMITING EXPOSURE TO ELECTROMAGNETIC FIELDS (100 KHZ TO 300 GHZ)”
ICNIRP 2020 Guidelines help determine limits on electromagnetic fields for human protection.
ICNIRP (often pronounced “ick-nerp”) is the International Commission on Non-Ionizing Radiation Protection. They are a global research group that has been studying the safety implications of electromagnetic radiation (as opposed to nuclear ionizing radiation, e.g. Chernobyl), from DC to 300 GHz, since 1992. (The commission was chartered in 1992, but includes research and researchers going back to 1973.) They publish a wide variety of freely available guidelines, statements, and papers on their website. The most recent major guideline document for RF energy (100 kHz - 300 GHz) was published in 2020 and can be downloaded here.
ICNIRP has published major guidelines on safe levels of electromagnetic energy for both the general public and specialist workers in 1998 and 2020. It has had a significant influence on related standards such as ANSI C95.1. The two main categories of potential EM field/human body interactions with RF fields are nerve stimulation (more prevalent at lower frequencies) and tissue heating. Probably the table that product designers will reference the most is Table 2 on basic restrictions (2020), as seen below.
SAR = specific absorption rate, which is the key metric when looking at exposure from devices such as cell phones.
After this table there is a lot more information on refining these levels for different scenarios. And as always, there is extremely useful information contained in the appendices.
There is a 2010 document that covers 1 Hz - 100 kHz for low-frequency effects and exposure to magnetic fields. There’s also a 2014 document with guidance on fields that vary at less than 1 Hz.
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In general, the exposure guidelines have relaxed over time, as additional research allows the commission to refine its knowledge of human effects and move away from worst-case assumptions. However, since many medical devices are still in circulation that were built assuming the stricter guidelines from 1998, if you need to set default limits, you should use the 1998 document as your guidance.
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ICNIRP has gotten drawn into numerous controversies and public panic about high voltage power lines, cell phones, 5G specifically, and other topics. If you have concerns about any of these topics, I highly recommend you go through their meticulously researched and documented (and freely available) publications on your specific concerns. I have learned a lot about EM interactions with human bodies through reading their research.
AIAA-S-121: “Electromagnetic Compatibility Requirements for Space Equipment and Systems”
AIAA-S-121 adapts MIL-STDs 464 and 461 specifically for space missions, including ground handling and launch vehicles.
AIAA-S-121 is an interesting beast. It is a tailoring of the combination of both MIL-STD-464 (system level) and -461 (equipment/module level) with an eye to making them specifically applicable to space systems. It can be purchased from the AIAA. It was reaffirmed in 2023, and there’s an effort underway to make it a joint standard with the IEEE. It’s something that the EMC Society standards committee and also Technical Committee 8 (Aerospace EMC) have been involved in, so if that’s of interest to you, please get in touch (standards@emcunited.com).
AIAA-S-121 draws from MIL-STD-1541 and SMC-S-008 (both freely available), and has similarities with GSFC-STD-7000. However it is very much its own document and should be read independently. Generally speaking, Section 6 follows MIL-STD-464, Section 7 follows MIL-STD-461 Section 4, and Section 8 follows MIL-STD-461 Section 5. Section 7 starts with a helpful table that explains many of its deviations from MIL-STD-461. Like MIL-STDs 464 and 461, it has appendices with excellent additional information that reward the thorough reader.
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Just because a unit is compliant to MIL-STD-464 and -461 does not guarantee that it will be successful in meeting AIAA-S-121. At a minimum, the radiated susceptibility levels are different. MIL-STD-461 RS103 for space systems specifies a threat level of 20 V/m, where AIAA-S-121 requires levels up to 50 or 100 V/m depending on frequency range and mission phase.
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For those concerned about Multipaction in space RF systems, MIL-STD-464 requires verification by test but does not specify or even recommend or reference a specific test method. AIAA-S-121 helps us out by pointing to “ECSS-E-20-01A, Space Engineering – Multipaction and Test, European Space Agency (ESA) for the European Cooperation for Space Standardization (ECSS), 5 May 2003.”
TIP: EverySpec.com
EverySpec.com is a site that just about every EMC engineer should have bookmarked.
Everyone knows about EverySpec.com, right? While it doesn’t have every spec, it sure has a lot of them. You won’t find illegal copies of the must-purchase ISO, CISPR, ANSI, etc. standards here. But you will find many of the publicly available ones. For me, being able to quickly and easily find MIL-STD and NASA standards has made this a go-to resource. Not only that, but the page for each standard has a nicely organized table where you can see not only the current revision of a document, but links to download each previous revision. That can be a real life-saver when you’re dealing with legacy systems and heritage hardware.
MIL-STD-464: “Electromagnetic Environmental Effects Requirements for Systems”
MIL-STD-464 is the main aerospace/defense document that applies E3 requirements to full systems and platforms.
MIL-STD-464 is an interesting beast, less well known than its counterpart MIL-STD-461. MIL-STD-464 is currently on Rev D and can be officially downloaded for free.
This document is concerned with making sure full systems (aircraft, tanks, etc.) are able to operate safely in regards to all the potential threats from the electromagnetic environment. Testing to MIL-STD-461 is part of making sure that a given component will integrate safely with the larger platform, ensuring electromagnetic compatibility. However, the broader MIL-STD-464 standard has many additional concerns: making sure aircraft are safe when hit by lightning; making sure space RF systems don’t suffer from multipaction; controlling intermodulation products from RF systems installed on naval vessels; making sure that personnel and ordnance isn’t affected by the excess charge picked up by aircraft in flight, and much more. It includes sections on lightning, EMP, RADHAZ, TEMPEST, ESD and several others. So while it is one of the primary sources of EMC requirements on defense and aerospace projects, it encompasses a much broader universe of E3 (electromagnetic environmental effects).
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As with MIL-STD-461, anyone who takes the extra time to read the appendices will be amply rewarded with context, lessons learned, and additional technical details.
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It was frustrating to me for a long time that MIL-STD-464 requires testing as verification for Multipaction (relevant to space RF systems), but did not give any hints or pointers to a test standard. AIAA-S-121 does include such a reference, to ECSS-E-20-01A, Space Engineering – Multipaction and Test, European Space Agency (ESA) for the European Cooperation for Space Standardization (ECSS), 5 May 2003.”
ISO 7637: “Road vehicles — Electrical disturbances from conduction and coupling”
ISO 7637 is the automotive standard that sets out test methods for evaluating conducted immunity at the module level.
ISO 7637 defines test methods for determining how modules react to transient disturbances (conducted immunity).. ISO 7637-1 sets out general principles and can be purchased and downloaded from the ISO. It has four separate parts, with parts 2, 3, and 4 outlining specific test methods. A summary of what is in each part is included below.
For a given electronics module that draws typical 12V power, testing to both ISO 7637-2 and -3 will likely be needed. For units that interface with shielded high voltage power lines in an electric vehicle, ISO 7637-4 will apply. There are a lot of transients associated with operating a car/bus/truck–power surges on startup, transients from large inductive loads (motors) switching on and off, transient interruptions as connections are jostled loose by the bouncing of the car over roads for multiple years, etc. Testing for conducted immunity can be a significant portion of your overall EMC testing schedule.
ISO 7637 shares with ISO 11451 the structure of evaluating unit performance based on a functional performance status classification system, which is useful even outside the automotive industry.
ECE Reg 10: “Uniform provisions concerning the approval of vehicles with regard to electromagnetic compatibility”
ECE Reg 10.06 is a key automotive standard for manufacturers planning to sell vehicles in Europe.
UN/ECE Regulation No. 10 is a key automotive standard for manufacturers planning to sell vehicles in Europe. It is officially on its 6th revision (which can be freely downloaded here) and has been amended twice, most recently in 2022. Revision 7 is currently in work. It is an official publication of the United Nations Economic Commission for Europe. Ultimately a vehicle manufacturer will apply for “type certification” for a given vehicle line to be sold in Europe. In addition to the paperwork, a representative vehicle will need to be tested to ECE Reg 10 in the presence of an official EU witness.
It covers immunity, emissions, and the specific hazards concerning plugin electric vehicles with concern to the power grid. The limits for different tests are found in Appendices 2 - 7. The test method details are found in Annexes 4 - 22. In general, ECE Reg 10 adopts the following international standards:
CISPR 12 for off-board radiated emissions
ISO 11451-2 for off-board radiated immunity
CISPR 25 for radiated emissions from modules
ISO 11452-2, 3, 4 or 5 for radiation immunity of modules
ISO 7637-2 for module-level immunity to transient disturbances
The following apply to plug in electric vehicles in their charging mode only, either at the component or vehicle level:
IEC 61000-3-2 and -12 for measuring the harmonic conducted emissions on the AC power lines
IEC 61000-3-3 and -11 for measuring voltage flicker on AC power lines
CISPR 16-2-1 to measure RF conducted emissions
CISPR 22 to measure RF conducted emissions on wire network port
IEC 61000-4-4 for conducted immunity to fast transient/burst disturbances
IEC 61000-4-5 for conducted immunity to power surges
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Because ECE Reg 10 has detailed test setups for adapting various international EMC standards to its exact automotive concerns, you can learn a lot about EMC standards and testing by reading through this freely available document.
ISO 11451: “Road vehicles — Vehicle test methods for electrical disturbances from narrowband radiated electromagnetic energy”
ISO 11451 is a collection of test methods addressing vehicle level immunity to electric fields.
ISO 11451 is a collection of documents that describe automotive test methods for testing at the vehicle level to show immunity to various levels of electromagnetic environment. You can purchase 11451-1 here, and the same site has the other parts available as well. The parts are all revised on their own schedules, with Part 1 (current version published in 2015) expected to have a new revision published in 2024.
ISO 11451 is applicable to any kind of passenger car or commercial vehicle, whether traditional internal combustion engine or electric. Its test methods cover the frequency range 10 kHz - 18 GHz, but it is more often applied within a narrower range, such as 1 MHz - 2 GHz. Table 1 lists the different test methods available.
*LUF = lowest usable frequency of a particular reverb chamber.
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Remember that the plane wave illumination at each frequency in ISO 11451 testing isn’t a constant continuous wave. Different modulations are applied to different frequency ranges to better capture real world threats.
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ISO 11451 defines a set of functional performance status classifications (seen below). Widely used in the automotive industry, these categories can be helpful in defining the success criteria for immunity/susceptibility testing for many complex systems, either at the platform or module level. When a device under test has many functions, some of them may be more critical than others. For instance, if the infotainment system gets knocked offline, that’s inconvenient for the user, and the manufacturer may want to address the issue if it happens at too low of a field strength, such that it might happen often. On the other hand, if the headlights can get turned off by any of the test exposures, that would be a major safety concern that would have to be addressed. Combining the criticality of different functions with the performance status classifications from ISO 11451 in a test plan can be a good way to predetermine which “failures” or “anomalies” are acceptable and which must be labeled failures and fixed. It’s a more detailed framework than the “must function normally” criteria found within some immunity/susceptibility test plans.
CISPR 36: “Electric and hybrid electric road vehicles - Radio disturbance characteristics - Limits and methods of measurement for the protection of off-board receivers below 30 MHz”
CISPR 36 is specific to electric vehicles and covers low frequency magnetic fields, 150 kHz - 30 MHz.
CISPR 36 is a relatively new standard, with its first official release in 2020. You can purchase a copy here. While it is strongly influenced by an earlier Chinese standard, GB/T 18387, CISPR 36 has a narrower frequency range, starting at 150 kHz instead of 9 kHz. It stops at 30 MHz, which is where CISPR 12 picks up.
CISPR 36 is unusual in focusing on low frequency magnetic fields, although its purpose is still to protect the radio reception of receivers outside the vehicle. On board receivers are protected by CISPR 25, same as any other vehicle. CISPR 36 only applies to ground vehicles with electric motors that draw power from a traction battery with voltage between 100 and 1000 V.
CISPR 36 uses magnetic field (loop) antennas positioned 3 m away from the vehicle. Measurements are taken with the vehicle at speed (on a dynamometer) at four positions (in front, behind, and to either side of the vehicle) and two orientations, for a total of eight sweeps. The sweeps are from 150 kHz - 30 MHz with a resolution bandwidth of 9 kHz. The limits are the magnetic field strength in dBuA/m, taken as a quasi peak (QP) measurement. In general most test operators will sweep in peak detection mode first, and only return to take QP measurements at specific frequencies where the peak value is above the QP limit. (See our explainer on quasi peak measurements.) Measurements can be taken in a semianechoic chamber or properly characterized open air test site, not in a reverb chamber.
Right now CISPR 36 does not address the charging mode, either via plug in or wireless power transfer (WPT). Other committees are looking into those modes, and ANSI C63.30 was published in 2021 describing test methods for WPT specifically.
CISPR 25: “Vehicles, boats and internal combustion engines - Radio disturbance characteristics - Limits and methods of measurement for the protection of on-board receivers”
CISPR 25 is an automotive standard that covers the main emissions testing methods needed to ensure self-compatibility between a vehicle and its own on-board receivers..
CISPR 25 governs emissions related to automotive components, both for ground vehicles and boats. It includes both component level and vehicle level tests. The current version is the 5th edition published in 2021, and you can purchase it here. Some of the component level test methods in CISPR 25 are very similar to comparable methods in MIL-STD-461, but they are not at all similar to emissions testing done for the FCC via ANSI C63.4. (You can check out one of my presentations that dives pretty deep into that comparison.) And obviously MIL-STD-461 does not have an equivalent of the full vehicle testing found in CISPR 25.
More than anything, CISPR 25 is aimed at self compatibility. Historically this meant limiting emissions that would interfere with onboard radios (AM/FM/DAB) so as to avoid customer complaints. Today with vastly more complex vehicle electronics and the HV components of EVs, there are a lot more “victims” that can be affected by emissions than just AM/FM radio. [Aside: I once worked on troubleshooting an EV where a CISPR 25-noncompliant inverter interfered with the vehicle’s twisted/shielded CAN lines to the extent that whenever the driver stepped on the “gas” pedal, the battery control module shut down, requiring a full restart. In that case the solution was improving the shield terminations on the CAN lines.]
In general, vehicle level tests are done in four possible modes: key on, engine off; internal combustion engine (ICE) in driving mode (spinning wheels on a dyno); EV in charging mode, and EV in driving mode. (A plugin hybrid electric vehicle would need to test in all four modes.) For testing on the full vehicle, you need to disconnect each antenna from its receiving radio module, and feed the antenna coax into the measurement receiver, often through an impedance matching unit.
At the component level, CISPR 25 includes both conducted and radiated emissions tests. Conducted emissions can be measured via voltage measured from an artificial network (AN, equivalent to a LISN in the aerospace/defense world), or via a current probe measured at a minimum of two locations along the cabling. For radiated emissions the main test method is conducted in a semi-anechoic chamber, with an informative Annex F describing a stripline method. It currently does not provide for a reverb chamber method.
TIP:
Pay close attention to the flowchart in Figure 1 of CISPR 25. Because of the different limit lines for different detectors(peak, quasi peak, and average) and how they apply to narrowband vs. broadband noise sources, there are a lot more steps before saying something definitively “passes” or “fails” than in a method like MIL-STD-461 RE102.
TIP:
CISPR 25 is a critical standard for the HV components of electric vehicles as well as the traditional 12 Vdc systems. Take this as one consultant’s experience, but every EV on which I’ve done troubleshooting had problems with an HV component that failed CISPR 25 testing (particularly inverters and DC/DC converters). I have not yet had to troubleshoot on an EV where every component passed CISPR 25. It is a major challenge to design an HV inverter that passes CISPR 25 limits, but it can be done–and it’s likely worth investing the extra time to design a compliant system, or the extra money to buy one. You can also see my presentation on Noise Sources in EVs for more.
TIP:
Getting to the audio head unit (radio) to disconnect the AM/FM radio for vehicle level testing can be painful, and the sweeps can take a long time, especially if there are a lot of frequencies where quasi peak measurements are needed. CISPR 25 is not a regulatory test, so judgment of compliance is up to the manufacturer. It may make more sense to run the vehicle and tune through stations looking for audible problem areas, then only run the CISPR 25 sweeps on frequency ranges where there are issues. Making sure the audible test is legitimate has its own set of challenges, but once set up, it can run considerably faster than full CISPR 25 sweeps.
IEEE 1560: “IEEE Standard for Methods of Measurement of Radio-Frequency Power-Line Interference Filter in the Range of 100 Hz to 10 GHz”
IEEE 1560 contains test methods for testing power line filters.
IEEE 1560 was first published in 2005, then reaffirmed in 2012. It has been inactive since 2023. It’s available for purchase here. Inactive doesn’t mean that there’s anything wrong with it, it mostly means that people got behind on the paperwork. We were able to approve a renewal effort to move forward at the EMC Symposium in the summer of 2024, and it will be up for IEEE SA approval in the Fall. Once that comes through, a working group will be organized under the leadership of Dasha Nemashkalo of the University of Twente. If you would like to be involved in that effort, please contact me at standards@emcunited.com.
Once upon a time, a customer asked for help evaluating the effectiveness of certain power line filters they had procured. They were building a secure shield room and wanted in situ measurements to determine if the filters were performing as advertised. I looked up the filters and the marketing copy said: “Our shielded room filters are designed to meet or exceed the requirements of MIL-STD-220 with 100 dB attenuation from 14 KHz to 10 GHz.”
So I looked up MIL-STD-220 (download here) and found a test method that looks like this:
Which assumes 50 Ohm coaxial connections throughout. This makes perfect sense for the kind of RF filters that MIL-STD-220 was written for (“Method of Insertion Loss Measurement”, freely available here). It does not make sense for systems that look like this, with not a coax connector in sight:
It turns out that prior to the first publication of IEEE 1560 in 2005, there was no widely accepted standard document governing the testing of power line filters, so the industry picked up the closest related standard, MIL-STD-220 for RF filters. Now, I have to admit, the proof is in the pudding: manufacturers have been testing to this method for decades and obviously haven’t had any massive customer revolts over inadequate performance. So something is working right-most probably some excellent design practices by the suppliers in question. But in any sane universe, we would have switched to the more tailored and rigorous IEEE 1560 document by now. (I went on a bit of a rant about this during a talk I gave to the SE Michigan EMC chapter on how different standards stack up to each other.)
The following test methods are included in IEEE 1560:
Quality assurance--No load (10 kHz to 1 GHz)
Quality assurance--Loaded (10 kHz to 20 MHz)
RF characteristic mismatched impedance--No load (100 kHz to 30 MHz)
Variable source impedance attenuation measurement (100 Hz to 100 kHz)
Attenuation measurement (100 kHz to 30 MHz)
Aperture leak test by electric fields (1 GHz to 10 GHz)
Voltage drop and waveform quality test (linear/non-linear loading)
S-parameter measurement (100 Hz to 30 MHz)
Eagle-eyed readers will notice that the only test covering 30 MHz - 1 GHz is “Quality assurance--no load”, which is described as a workmanship test more than a performance characterization measurement. As we move forward with the 1560 renewal effort, this is the kind of thing we’ll need to decide how to address.
GSFC-STD-7000B: “General Environmental Verification Standard (GEVS) for GSFC Flight Programs and Projects”
GSFC-STD-7000B contains something like a version of MIL-STD-461 specifically tailored for small, metal chassis, science satellites
GSFC-STD-7000, affectionately known as GEVS, is a huge document covering a wide variety of environmental testing, including shock, vibe, thermal, etc. For our purposes we’re only concerned with Section 2.5 on EMC. Written by John McCloskey and Ken Javor, it is worth making sure to get Rev B. While both revisions have the same approach--tailoring MIL-STD-461 for the kind of missions most common at Goddard Space Flight Center--Rev B has a greatly expanded Section 2.5.3, which serves the same function as the appendices of MIL-STD-461. It is a wealth of additional information and context on each test method and how it came to be specifically tailored in this document. This is hands-down one of my favorite standards documents, and I refer to it even when I’m not working on Goddard or NASA programs. The document is freely and officially available here.
The tailoring in GEVS is based on certain assumptions that hold true for the most common GSFC programs:
Uncrewed satellites
Generally cubes, generally smaller than 2 meters on a side
They have metal chassis
They never use structure for current return
28 Vdc power bus, sourced from batteries and recharged from solar panels
The table below shows a summary of the requirements they arrived at, and a top-level comparison with MIL-STD-461.
TIP:
One thing that I appreciate is that it includes a test not found in MIL-STD-461, which is a common mode conducted emissions test. It’s found in Section 2.5.2.1.2. While MIL-STD-461 CE101 and CE102 have differential measurements taken from a LISN, this test uses a current probe to measure the common mode currents flowing on the cables--which is one of the prime indications of potential crosstalk or radiated emissions problems. It also has a method for extending the test range from 30 MHz up to 200 MHz using an absorbing clamp as described in CISPR 16-1-4. GEVS section 2.5.3.3.2.1 contains an extremely thorough and well-thought-out discussion of why absorbing clamps are appropriate at the higher frequencies, and it left me thoroughly convinced. For people in the automotive industry, the 30 - 200 MHz is particularly critical for EVs seeking to pass CISPR 12 testing, and the common mode, absorber clamp method may be a useful pre-compliance test for that purpose.
TIP:
Instead of the more commonly found 50 uH or 5 uH LISNs used in much MIL-STD-461 and automotive component testing, GEVS uses a 10,000 uF cap network. It’s worth reading the rationale in Section 2.5.3.2.2 (with related discussion in MIL-STD-461 Rev G Section A.4.3.6) to broaden your thinking about LISN/Artificial Network choice. For more on LISNs, see this post.
ISO 11452: “Road vehicles — Component test methods for electrical disturbances from narrowband radiated electromagnetic energy”
ISO 11452 is a standard with multiple parts and test methods that covers testing components that will go on vehicles (cars, trucks, etc.) for immunity.
ISO 11452 covers automotive components for immunity testing--with, as we see with several other standards, a whole lot of parts that can be bought separately. You can see which parts cover which test methods in the tables below. You can start by looking at ISO 11452-1 (“General principles and terminology”) which is available for purchase here. The current version is from 2015 and a new revision is expected in the next year or so.
ISO 11452 uses CISPR 16 to govern the measurements equipment used. Annex A of ISO 11452-1 has a very useful normative guide on how to classify the performance of different functions during testing (you would not call a test a failure if an infotainment system spontaneously reset during moderate level testing; the brake system doing the same thing would be considered a critical failure).
You might notice similarities between ISO 11452 and its various parts and those of SAE J1113. That’s not a coincidence--J1113 was essentially the North American version of the same document until they came into agreement.
TIP:
If you have the facility available, testing in a reverb chamber (ISO 11452-11) is often the fastest way to test and also the one most likely to find problems. That sounds like a bad thing, but it’s much better to find problems when it’s one component in a chamber instead of troubleshooting an entire vehicle.