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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.
TIP:
Some limits changed in the 2024 revision, mostly to cover newer equipment configurations. It also now addresses industrial robots specifically.
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.
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.
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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.
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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.
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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.
CISPR 32: “Electromagnetic compatibility of multimedia equipment - Emission requirements”
CISPR 32 is the international standard most comparable to the FCC standard on consumer electronics.
CISPR 32 governs emission, both conducted and radiated, from “multimedia equipment”, which encompasses most consumer electronics, such as computers, televisions, radios, etc. It is the international standard most similar to the testing of unintentional emitters required by the FCC and found in ANSI C63.4. CISPR 35 is the corresponding immunity requirement document. In the EU, CISPR 32 is incorporated as a regulatory document with the number EN 55032.
The most current version is from 2015 with amendments in 2019 and can be purchased here. It superseded CISPR 13 and 22, which makes sense--CISPR 13 had covered broadcast media equipment and CISPR 22 had covered IT/computer equipment, and they were managed by different committees. That was fine until digital TV, digital broadcasting, and then streaming became ubiquitous--now broadcast equipment was IT equipment and it all got very confusing (no one likes testing their equipment twice). CISPR 32 is the result of a harmonization effort. It uses CISPR 16 to govern the standards of its measurement equipment. Officially the standard covers the frequency range 9 kHz - 400 GHz, although most equipment does not need to be tested to the extremes of that range. Generally equipment will be tested up to 6 GHz, but check the tables carefully--the upper testing limit depends on the frequency usage of the equipment under test. The conducted emissions testing will generally start at 150 kHz.
Like the FCC, CISPR 32 classifies units as “Class B” if they are intended for use in residential environments; those have stricter emissions requirements. Everything else is “Class A”. There are limit lines for both quasi-peak (QP) and average detector methods; see this explainer for information on quasi-peak and how to minimize QP test time. Also like FCC, limits are provided for measurements at both 3 m and 10m distances.
Interference Technology has good articles on the 2012 version of CISPR 32 by Dan Hoolihan and the 2015 version by Ghery Pettit.
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The actual limits that are required to be met are found in Annex A of the document.
CISPR 12: “Vehicles, boats and internal combustion engines – Radio disturbance characteristics – Limits and methods of measurement for the protection of off-board receivers”
CISPR 12 is a key automotive standard that details the test method for ensuring cars and other vehicles don’t emit too much RF energy at a distance, usually 10 m away. It’s often referred to as an “off-board radiated emissions test”.
CISPR 12 is one of the critical standards that apply to full vehicles, whether using traditional internal combustion engines, electric vehicles, or hybrids. The current edition is from 2007, with amendments in 2009, and you can find it for purchase here. The intent of the requirement is to protect radio receivers that are external to the vehicle, such as an FM radio in a nearby house, or the two-way communication system of a passing ambulance. It applies to boats and ground vehicles, with both internal combustion or high voltage EV engines. The test is generally at 10 m distance, although if only a 3 m separation between the vehicle under test and the test antenna can be achieved, the limits can be increased by 10 dB to account for the difference (this linear extrapolation is doable since both 3 m and 10 m measurements are reliably in the far field in the 30 MHz - 1 GHz range--don’t try this with 1 m measurements such as in CISPR 25).
TIP:
CISPR 12 has limits that are expressed in Average and Quasi Peak. Quasi Peak (QP) testing takes forever, so the standard recommends speeding things up by doing a Peak sweep first. If all the Peak values are below the QP limit lines, then it’s accepted that any QP measurements will also pass the requirement. (This is true probably 95% of the time, but not always.) In that case you’re done and you’ve saved yourself a lot of time compared to taking QP measurements. If there are specific frequencies where Peak values are over the QP limits, you can go back and take QP measurements at only those frequencies. Quasi Peak detection is a little strange and can be hard to track down information on, so see this Quasi Peak article for a quick explainer.
TIP:
Another way to speed up testing is to increase the bandwidth of your initial scan, keeping dwell time the same. If you pass the specified limit with the wider bandwidth, you can be assured that you would have passed with the smaller bandwidth. Then if you run into exceedances at a specific frequency range, you can go back and test that range with the smaller spec bandwidths.