IEC 61000-4-21: “Testing and measurement techniques–Reverberation chamber test methods”

IEC 61000-4-21 doesn’t give any pass/fail criteria; it is solely aimed at standardizing radiated test methods conducted in reverb chambers. It was originally published in 2003 and last revised in 2011. You can purchase a copy here.

TIP:

Whenever possible, consider testing in a reverb chamber to save test time. Particularly for automotive testing, you don’t have to move the test object to illuminate three different orientations, since in reverb testing it will be hit from all angles. This is also a better correspondence to real-world conditions; in the automotive industry I ran into a few cases where a unit that passed ALSE testing failed during vehicle testing; the unit was then re-tested in reverb and failed there. It’s always better to troubleshoot at the module level than at the platform level.

This is one of those standards where the meat of the technical content is in the Annexes, so I’m listing them here:

Annex A (informative) Reverberation chamber overview

Annex B (normative) Chamber calibration for mode-tuning

Annex C (normative) Chamber calibration for mode-stirring

Annex D (normative) Radiated immunity tests

Annex E (normative) Radiated emissions measurements

Annex F (informative) Shielding effectiveness measurements of cable assemblies,cables, connectors, waveguides and passive microwave components

Annex G (informative) Shielding effectiveness measurements of gaskets and materials

Annex H (informative) Shielding effectiveness measurements of enclosures

Annex I (informative) Antenna efficiency measurements

Annex J (informative) Direct evaluation of reverberation performance using field anisotropy and field inhomogeneity coefficients

“Informative” annexes have information and context that may be useful for the user, where “normative” annexes contain steps and procedures that must be followed to use the standard correctly. 

The annexes provide a fairly clear and practical overview of reverb chamber testing, including the statistical math needed to properly setup the test environment and interpret measured data. It has details about tuner steps and field uniformity volume, as well as chamber loading and sampling requirements.

TIP:

I’d like to draw attention to Annex F, for measuring shielding effectiveness of cables. This is generally an excellent option for testing cables at high frequencies, and not otherwise covered in IEC 62153. However, the test method compares the power received by a shielded cable to that received by a reference antenna within the uniform field volume of the chamber (see below). This may overestimate the attenuation provided by the shield, since an unshielded cable may not have similar gain as the reference antenna. Although it requires an extra step and extra cable sample, it may be more representative of real-world conditions to test both a shielded and unshielded cable, then compare the power received by each instead of comparing to a tuned antenna.

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IEC 62153: “Metallic communication cables test methods”

I’ve been thinking a lot about shielding lately, both in the run-up to a couple of focused seminars and also as a member of the IEEE P2855 working group (our modest goal is to become the “Recommended Practices for the Electromagnetic Screening Effectiveness Characterization of Cable/Connector Assemblies (CCAs) in Frequency Range of DC to 40 GHz” by 2026). One of the standards that comes up a lot when you’re discussing test methods for evaluating cable shielding is IEC 62153 “Metallic communication cables test methods” and its sub-parts. You can purchase any sub-part individually. I’m including a list of all the sub-parts here, since it’s annoyingly hard to find in one place:

• Part 1-1: Metallic communication cables test methods – Electrical – Measurement of the pulse/step return loss in the frequency domain using the Inverse Discrete Fourier Transformation (IDFT)

• Part 1-2: Metallic communication cables test methods – Electrical – Reflection Measurement

• Part 4-0: Metallic communication cable test methods – Electromagnetic compatibility (EMC) – Relationship between surface transfer impedance and screening attenuation, recommended limits

• Part 4-1: Metallic communication cable test methods – Electromagnetic compatibility (EMC) – Introduction to electromagnetic (EMC) screening measurements

• Part 4-2: Metallic communication cable test methods – Electromagnetic compatibility (EMC) – Screening and coupling attenuation – Injection clamp method

• Part 4-3: Metallic communication cable test methods – Electromagnetic compatibility (EMC) – Surface transfer impedance – Triaxial method

• Part 4-4: Metallic communication cable test methods – Electromagnetic compatibility (EMC) – Shielded screening attenuation, test method for measuring of the screening attenuation as up to and above 3 GHz

• Part 4-5: Metallic communication cables test methods – Electromagnetic compatibility (EMC) – Coupling or screening attenuation – Absorbing clamp method

• Part 4-6: Metallic communication cable test methods – Electromagnetic compatibility (EMC) – Surface transfer impedance – Line injection method

• Part 4-7: Metallic communication cable test methods – Electromagnetic compatibility (EMC) – Test method for measuring the transfer impedance and the screening – or the coupling attenuation – Tube in tube method

• Part 4-8: Metallic communication cable test methods – Electromagnetic compatibility (EMC) – Capacitive coupling admittance

• Part 4-9: Metallic communication cable test methods – Electromagnetic compatibility (EMC) – Coupling attenuation of screened balanced cables, triaxial method

• Part 4-10: Metallic communication cable test methods – Electromagnetic compatibility (EMC) – Shielded screening attenuation test method for measuring the screening effectiveness of feed-throughs and electromagnetic gaskets double coaxial method

• Part 4-11: Metallic communication cable test methods – Electromagnetic compatibility (EMC) – Coupling attenuation or screening attenuation of patch cords, coaxial cable assemblies, pre-connectorized cables – Absorbing clamp method

• Part 4-12: Metallic communication cable test methods – Electromagnetic compatibility (EMC) – Coupling attenuation or screening attenuation of connecting hardware – Absorbing clamp method

• Part 4-13: Metallic communication cable test methods – Electromagnetic compatibility (EMC) – Coupling attenuation of links and channels (laboratory conditions) – Absorbing clamp method

• Part 4-14: Metallic communication cable test methods – Electromagnetic compatibility (EMC) – Coupling attenuation of cable assemblies (Field conditions) absorbing clamp method

• Part 4-15: Metallic cables and other passive components test methods - Electromagnetic compatibility (EMC) - Test method for measuring transfer impedance and screening attenuation - or coupling attenuation with triaxial cell

• Part 4-16: Metallic cables and other passive components test methods - Electromagnetic compatibility (EMC) - Extension of the frequency range to higher frequencies for transfer impedance and to lower frequencies for screening attenuation measurements using the triaxial set-up

• Part 4-17: Metallic cables and other passive components - Electromagnetic compatibility (EMC) - Reduction Factor

Probably the most often cited sub-part is 4-3 on the triaxial method for measuring surface transfer impedance. Although it is less rigorous, my favorite method due to its flexibility and intuitive nature is 4-6, the line injection method. 

TIP:

Keep a close eye on exactly what value is being measured in each test setup. While they are all closely related, transfer impedance, transfer admittance, screening attenuation, coupling attenuation, etc. are different in important ways. Likewise, when comparing shield characterizations between different vendors, understand what values they’re displaying and how those were measured. It may not be straightforward to compare values between vendors if they’re different measurands or derived using different test methods. 

Although it’s less commonly used, give some consideration to the methods using absorbing clamps. My favorite, GSFC-STD-7000B, Section 2.5.3.3.2.1 has arguments in favor of using absorbing clamps for the frequency range 30 - 200 MHz that I found quite convincing. 

IEC 62153 is not the only place to go looking for cable shielding test methods–IEC 61000-4-21 describes a method using reverb chambers, which I hope to write about soon, and eventually we hope IEEE P2855 will become a go-to document. However, if you’re looking to understand the details of some of the most common test methods, 62153 is a very good starting point.

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ESD: IEC 61000-4-2, MIL-STD-461 CS118, ISO 10605, et. al.

The basis for most ESD (electrostatic discharge) tests comes from IEC 61000-4-2, “Testing and measurement techniques–Electrostatic discharge immunity test”. The active 2008 version can be purchased here, with a new version expected in 2025. ISO 10605, “Road vehicles — Test methods for electrical disturbances from electrostatic discharge” (purchase 2023 version here) adopted the test method for the automotive industry. MIL-STD-461 included ESD testing for the first time with Rev G (freely available here) with the CS118 test method–and it looked pretty familiar. See comparisons below. 

TIP:

If you have questions about ISO10605 or IEC 61000-4-2, you can see if there are answers in the freely available MIL-STD-461G CS118 or related appendix (Section A.5.16) before purchasing from IEC or ISO. 

Testing is specified for units that are powered off (representing the danger from discharge when being handled or installed) and when turned on (representing threats present in its operating environment). They also include air and contact discharge, with air discharge generally being more severe. Contact discharge is mating two conductive objects at different potentials together and seeing the surge of charge transfer. Air discharge is when you reach for a metal doorknob on a dry/cold day and feel an actual spark just before you touch the door. Maximum testing voltages should be adjusted based on the expected operating conditions (how often humans interact with the unit, if it is installed in a humidity-controlled environment, etc.).

TIP:

ANSI C63.16, “Guide for Electrostatic Discharge Test Methodologies and Acceptance Criteria for Electronic Equipment”, is an available guidance document for ESD testing (the 2016 version is available for purchase here; a new version has been drafted and is currently going through ANSI approvals). It gives additional context 

Almost all ESD test standards and commercially available ESD test guns/simulators base their waveforms off the human body model (HBM). The CS118 version is below. 

However, there are cases where the main threat does not come from human interaction. Generally speaking the industries have determined that testing based on the HBM is adequate to identify most hardware weaknesses to ESD (although the ANSI C63.16 working group will tell that’s definitely not 100% true). I was once looking into a case where the main threat to a satellite orbiting in Low Earth Orbit was definitely going to be spacecraft charging, and did some research to see if there were other standard models available. 

TIP:

The only one I was able to find was from an outdated military standard, MIL-STD-1541A (1987) (freely available here). You can see an alternate discharge model below, and the document has information about ways to vary different parts of the circuit to address different threat waveforms. 

MIL-STD-331D (download here) includes circuit values for helicopter-based discharges for fuzing systems and ignition protection devices as well, to be inserted into a more traditional IEC 61000-4-2 circuit setup. Appendix A.5.8.3.2 of MIL-STD-464D also has information on helicopter-borne discharges & ordnance.

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IEC 61000: “Electromagnetic Compatibility--”

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.

TIP:

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.

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