Including an Update on the Seventh Edition of the Standard

Editor’s Note—This article was originally published in 2010 and 2016 in In Compliance Magazine and has been updated to include recent progress on the development of Edition 7.0 of CISPR 11.

CISPR is the International Special Committee on Radio Interference which was founded in 1934. The International Standard for electromagnetic emissions (disturbances) from industrial, scientific, and medical (ISM) equipment is CISPR 11. The official title of the standard is “Industrial, Scientific, and Medical Equipment – Radio-Frequency (RF) Disturbance Characteristics – Limits and Methods of Measurement.”

The premiere edition of the standard was released in 1975, and the current edition (seventh edition) was released in 2024. The standard includes both limits and methods of measurement for conducted emissions and radiated phenomena. This article details the most recent Edition and retroactively traces the history and development of the content of the standard over the last 50 years.

Seventh Edition – 2024

The Seventh Edition cancels and replaces the sixth edition published in 2015, Amendment 1: 2016, and Amendment 2: 2019. It constitutes a technical revision. The most significant technical changes with respect to the sixth edition are:

1. Introduction of limits for radiated disturbances in the frequency range above 1 GHz for group 1 equipment in line with the requirements given in the generic emission standards;
2. Introduction of limits for conducted disturbances on the wired network port in line with the requirements given in the generic emission standards;
3. Introduction of requirements for equipment which incorporates radio transmit/receive functions;
4. Introduction of definitions for various types of robots; and
5. Consideration of some particular conditions when measuring robots, such as measurement setups and operating modes of robots.

Technical Details of the Seventh Edition

The first significant technical change adds limits on radiated emissions (disturbances) above 1 GHz for group 1 equipment. Table 11 in the standard summarizes the limits (see Table 1).

The second significant technical change added new limits for conducted emissions (disturbances) on the wired network port. Table 7 in the new standard details the new limits (see Table 2).

The third significant technical change deals with equipment incorporating radio transmit/receive functions, which have not been covered in earlier versions of CISPR 11. They are addressed in the Scope, Paragraph 7.1, and Annex F.

The Scope says:

“Industrial, Scientific, and Medical (ISM) equipment which incorporates radio transmit/receive functions (host equipment with radio functionality) is included in the scope of this document, see Annex F. However, the emission requirements in this document are not intended to be applicable to the intentional transmissions from a radio transmitter as defined by the International Telecommunications Union (ITU) including their spurious emissions.”

Paragraph 7 (Measurement Requirements) and 7.1 (General) say: “For equipment with radio functionality, the additional requirements of Annex F shall apply.”

Annex F is Normative (Required) and is titled: “Additional requirements for equipment with radio functionality.” It addresses: 1) configuration of the equipment under test (EUT) during emissions tests; 2) radiated emissions; 3) conducted emissions; and 4) Table F.1 – Disturbance voltage and current limits for group 1 and group 2 equipment measured on a test site (antenna port).

The fourth significant change introduces definitions for various types of robots. They include:

1. 3.1.30 – robot – programmed actuated mechanism with a degree of autonomy to perform locomotion manipulation or positioning;
2. 3.1.20 – industrial robot – automatically controlled, reprogrammable multipurpose manipulator, programmable in three or more axes, which can be either fixed in place or fixed to a mobile platform for use in automation applications in an industrial environment; and
3. 3.1.22 – medical robot – robot intended to be used as medical electrical equipment or medical electrical system.

The fifth significant technical change is consideration of measurement setups and operating modes of robots. This is covered in two paragraphs, four figures, and two tables.

Paragraph 7.5.4 is titled “Measurements of Robots,” and it addresses radiated emissions, EUT arrangements, fixed robots, and mobile robots. Example setups for floor-standing robots are shown in Figures 6 and 7 in the Seventh Edition of CISPR 11 (conducted and radiated emission measurements, respectively). Figures 8 and 9 in the standard show an example of a combination EUT (floor‑standing and tabletop/wall-mount units).

Paragraph 7.6.11 (Robots) initially states “Robots shall be tested in operating modes and under load conditions which are representative of normal use in the intended application according to the instruction manual.”

Other Details in the Seventh Edition

Product Family EMC Standard

The new Edition has the status of a Product Family EMC Standard in accordance with IEC Guide 10-7, Electromagnetic Compatibility – Guide to the drafting of electromagnetic publications (2014).

CISPR Recommendation No. 39/2

The main content of the Seventh Edition is based on CISPR Recommendation No. 39/2 – Limits and Methods of Measurement of Electromagnetic Disturbance Characteristics of Industrial. Scientific, and Medical (ISM) Radio-Frequency (RF) Equipment, which states:

“The CISPR, considering:

1. 1. 1. That ISM RF equipment is an important source of disturbance;
      2. That methods of measuring such disturbances have been prescribed by the CISPR; and
      3. That certain frequencies are designated by the International Telecommunication Union (ITU) for unrestricted radiation from ISM equipment,

Recommends that the latest edition of CISPR 11 be used for the application of limits and methods of measurement of ISM equipment.”

CISPR 11, Edition 6.0

Amendment 2 to CISPR 11, Edition 6.0, 2019-01

Amendment 2 combines two principal changes to Edition 6.0. One addresses semiconductor power converters (SPC) and the other “improvement of repeatability for measurements in the frequency range 1 – 18 GHz.”

Type test requirements were added for two SPC systems: 1) power conversion equipment intended for assembly line photovoltaic power generating systems, such as grid connected power converters (GCPCs) and direct current to direct current converters; and 2) GCPCs intended for assembly into energy storage systems.

The improvement of measurements in the 1 to 18 GHz range involves group 2 equipment operating at frequencies above 400 MHz. The measurements can be made with two different weighting functions: the traditional “LogAV detector” with a video bandwidth of 10 Hz and the new amplitude probability distribution (APD) method.

Amendment 1 to CISPR 11, Edition 6.0, 2016-06

This Amendment introduced the fully-anechoic room (FAR) for measurements of the disturbance field strength in the range 30 MHz to 1 GHz on equipment in the scope of CISPR 11. It contains the complete set of requirements for measurement of radiated disturbances from equipment fitting into the validated test volume of a given FAR. It specified a separation distance of 3 meters and restricts use of the FAR to measurements on table‑top equipment.

CISPR 11, Sixth Edition, 2015-06

The sixth edition cancelled and replaced the fifth edition published in 2009 and its Amendment 1 published in 2010. It constituted a technical revision. It introduced type testing of components of power electronic equipment, systems, and installations. Its emission limits were newly applied to low voltage (LV) alternating current and direct current power ports, irrespective of the direction of power transmission.

Several limits were adapted to the practical test conditions found at test sites. They are also applicable to power electronic ISM RF equipment used for wireless power transfer (WPT), for instant power supply and charging purposes.

The limits in the range 1 to 18 GHz were applied to continuous wave (CW)-type disturbances and to fluctuating disturbances in a similar, uniform, and technology-neutral way. The measurements may be made with traditional Log-AV or the newer (APD) method.

For measurements at (LV) direct current power ports of power electronic equipment, a modern implementation of the 150-ohm delta-network specified in CISPR 16‑1-2 has been made available.

The Sixth Edition also included general maintenance items to address other technical issues in the fifth edition of the standard.

Fifth Edition—2009

Released in 2009, the Fifth Edition of CISPR 11 continued the long-standing practice of Group 1 and Group 2, Class A and Class B equipment classifications. The limits stated in the Fifth Edition were similar to the limits found in the Fourth Edition.

Table 5 presents a side-by-side comparison of the table of contents for the first edition and the fifth edition of CISPR 11, which clearly shows the growth in the length and complexity of the standard over a period of 35 years.

Clause 6 in the Fifth Edition represented a major overhaul from that in the Fourth Edition. Its main clause and sub-clause headings are as follows:

• Clause 6 – Limits of Electromagnetic Disturbance
  • 6.1 – General
  • 6.2 – Group 1 Measured on a Test Site
  • 6.3 – Group 2 Measured on a Test Site
  • 6.4 – Group 1 and Group 2 Class A Measured in situ
• Clause 7 added a new Sub-clause 7.1 (“General”) and a new Sub-clause 7.7 (“Recording of Test Site Measurement Results”).
• Clause 12 (“Assessment of Conformity of Equipment”) added a new Sub-clause 12.1 (“General”) and then the next three Sub-clauses were the same as Sub-clauses 11.1–11.3 in the fourth edition.
• Clause 13, titled “Figures and Flowcharts,” was new to this edition, as was Annex E.

The entire Fifth Edition was written to provide a more transparent structure. Table 17 in the standard was added with a title of “Electromagnetic Radiation Disturbance Limits for Class A (Group 1) Equipment Measured in situ.” It specifically addressed equipment with input power greater than 20 KVA.

Amendment 1 to the fifth edition was released in 2010. It created a new subset of equipment, “Small Equipment.” Small Equipment is defined as “equipment, either positioned on a tabletop or standing on the floor which, including its cables, fits in a cylindrical test volume of 1.2 meters in diameter and 1.5 meters above the ground plane.”

Using this definition, Tables 4, 5, 9, 10, and 11 in the standard were modified to allow testing of Class A and B products meeting the small equipment definition to be tested at a three-meter test distance. The limit at three meters would be extrapolated from the typical test distance of 10 meters using an inverse-distance fall-off assumption (free-field).

Fourth Edition—2003

The Fourth Edition of CISPR 11 was published in March 2003. The fourth edition superseded the third edition (1997), along with its first amendment (1999) and its second amendment (2002).

There were a limited number of changes in the Fourth Edition from the Third Edition. The first two sentences in Clause 4 were changed to read:

“…the manufacturer and/or supplier of ISM equipment shall ensure that the user is informed about the class and group of the equipment, either by labeling or by the accompanying documentation. In both cases, the manufacturer/supplier shall explain the meaning of both the class and the group in the documentation accompanying the equipment.”

Clauses 7.1 and 7.2 were interchanged from the Third Edition.

Clause 6.2.5 (“Artificial Hand”) was added to the Fourth Edition, as well as Figure 6 (“Artificial Hand, RC Element”). The concept of an artificial hand was introduced to simulate the effects of the user’s hand during the conducted emission measurements

The definitions of Group 1 ISM equipment, Group 2 ISM equipment, Class A equipment, and Class B equipment remained basically the same as that in the Third Edition.

With respect to limits of electromagnetic disturbance, Class A equipment could once again be measured either in a testing laboratory or in situ (as preferred by the manufacturer). However, the Fourth Edition continued to require Class B equipment to be measured in a testing laboratory.

The limits of terminal disturbance voltage (conducted emissions) gave the manufacturer two choices: 1) meet the average limit with an average detector and the quasi-peak limit with a QP detector; or 2) meet the average limit when using a QP detector. This was the same as stated in the Third Edition.

For radiated disturbances from 150 kHz to 1000 MHz, the limits stayed basically the same as those found in the Third Edition. Measurements were allowed at closer distances than the specified distances under certain considerations. In case of dispute, however, Class B (Group 1 and Group 2) and Class A (Group 1) were to be measured at a distance of 10 meters, while Class A (Group 2) were to be measured at a distance of 30 meters.

Receivers used for the measurements were expected to meet the criteria of CISPR 16-1. Requirements for the artificial mains network (LISN) remained the same as those in the third edition, that is, a 50 ohm/50 microhenry V-Network as specified in CISPR 16-1. The antennas used for measuring CISPR 11 products were also expected to meet CISPR 16-1 requirements. In a testing laboratory, the antenna must be raised and lowered from one to four meters in the frequency range 30 MHz to 1000 MHz. For measuring products in situ, the antenna’s center must be fixed at two meters above the ground.

Amendment 1 to the fourth edition was released in 2004. Primarily, Amendment 1 replaced Table 6 in the Fourth Edition with a new table that addressed Group 2 (Class A and Class B) ISM equipment producing CW type disturbances and operating at frequencies above 400 MHz.

Amendment 2 added CISPR 16-4-2:2003 to the Normative References. It also added a new Table 2c for mains terminal disturbance voltage for induction cooking appliances. It also modified Clauses 6.5.4 (microwave cooking appliances) and 6.5.6 (single and multiple-zone induction cooking appliances) to more closely match the IEC Product Standard. Amendment 2 also added Clauses 6.6 (“Recording of test-site measurement results”), 6.6.1 (“Conducted Emissions”), and 6.6.2 (“Radiated Emissions”).

Also, Clause 11.4 (“Measurement Uncertainty”) was added, stating that “determining compliance with the limits in this standard shall be based on the results of the compliance measurement, not taking into account measurement instrumentation uncertainty.” However, results of measurements of emissions from ISM equipment were supposed to reference the measurement uncertainty considerations contained in CISPR 16-4-2.

Third Edition—1997

The Third Edition of CISPR 11 was also developed by CISPR Subcommittee B and was released in 1997. It replaced the second edition and its two amendments.

The third edition of the standard reorganized the first Clause, changing it from “Scope and Object” to “General,” and comprised of two Sub-clauses, “Scope and Object,” and “Normative References.”

Clause 6 of the second edition was renumbered as Clause 11 in the third edition, and Sub-clause 6.1, “Equipment in series production,” was replaced with Sub-clause 11.2, “Equipment in small scale production.”

A new Sub-clause 5.4, “Provisions for Protection of Specific Sensitive Radio Services,” was added in Clause 5, “Limits of Electromagnetic Disturbance.”

Clause 7 in the second edition became Clause 6 in the third edition; Clause 8 became Clause 7, Clause 9 became Clause 8, Clause 10 became Clause 9, and Clause 11 became Clause 10.

Annexes A – D remained the same in the third edition as in the second. Two new annexes were added, Annex E, “Safety-Related Service Bands,” and Annex F, “Sensitive Service Bands.”

The classification of equipment remained the same from the second to the third edition, that is, Group 1 and Group 2, and Class A and Class B.

With respect to the limits of electromagnetic disturbance, Class A equipment could still be tested either at a testing laboratory or in situ, while Class B equipment had to be measured in a testing laboratory.

The limits for conducted emissions on the power leads were measured from 150 kHz to 30 MHz using a 50-ohm/50-uH network. The limits remained the same for Class A and Class B equipment from the second edition of the standard, except that another category was added for Class A-Group 2 equipment for mains supply currents in excess of 100 amps per phase when using the CISPR voltage probe. The limits for this special case are shown in Table 6.

However, new limits were added in Table 2c in the standard (“Mains terminal disturbance voltage for inductive cooking appliances”) for Group 2-Class B equipment for both domestic and commercial cooking appliances.

Table 3 in the standard (“Electromagnetic radiation disturbance limits for group 1 equipment”) had a major change, as the measurement distance for Group 1-Class A equipment was changed from 30 meters to 10 meters with a corresponding increase in limits of 10 dB (assuming an inverse distance fall‑off of the radiated electromagnetic field).

Clause 5.2.2 of the third edition also introduced the concept of measuring products at shorter distances than the specified measurement distances for radiated disturbances. For example, it allowed Group 2-Class A equipment to be measured at a distance of between 10 and 30 meters instead of 30 meters. Also, it allowed Group 1 and 2-Class B, equipment to be measured at antenna distances between three and 10 meters. However, it stated that “in case of dispute, Class A-Group 2 equipment shall be measured at a distance of 30 meters; Class B-Group 1, Class B-Group 2, and Class A-Group 1 equipment shall be measured at a distance of 10 meters.”

Tables 3a and 3b were added in the third edition to cover Group 2 induction cooking appliances for Class B and Class A, respectively. Table 3a (“Limits of the magnetic field induced current in a 2-m loop antenna around the device under test”) was intended to use the Van Veen Loop Method measurement method as per CISPR 16-2. Table 3b (“Limits of the magnetic field strength”) is measured at a three-meter antenna distance with a 0.6 meter loop antenna as described in CISPR 16‑1.

Table 4 in the standard (“Electromagnetic radiation disturbance limits for Group 2-Class B equipment measured on a test site”) added a new column of requirements, that the quasi-peak magnetic field (measured at three meters) will not exceed 39 dBuAmp/meter decreasing linearly with the logarithm of the frequency to 3 dBuAmp/meter from 150 kHz to 30 MHz.

Table 5 in the standard changed the measurement distance from 30 meters to 10 meters and increased the limits by 10 dB from the limits found in the second edition.

Table 6 was added to the third edition of CISPR 11. It was entitled “Electromagnetic radiation disturbance peak limits for Group 2-Class B ISM equipment producing CW-type disturbances and operating at frequencies above 400 MHz.” Table 7 (“Electromagnetic radiation disturbance peak limits for Group 2-Class B ISM equipment producing fluctuating disturbances other than CW and operating at frequencies above 400 MHz”) and Table 8 (“Electromagnetic radiation disturbance weighted limits for Group 2-Class B ISM equipment operating at frequencies above 400 MHz”) were also added.

Clause 5.4 (“Provisions for protection of specific sensitive radio services”) was added to the third edition. It referenced a new Annex F which gave examples of bands to be protected.

The same general measurement conditions existed as in the previous edition which is that Class A equipment could be measured at a test lab or in situ. Class B equipment had to be measured on a test site (in a test lab).

For equipment on a turntable, the distance to the antenna was measured from the center of the turntable. For equipment not on a turntable, the distance to the antenna was measured from the edge of the equipment.

Paragraph 6.5.6 (“Single and multiple-zone induction cooking appliances”) was added to the third edition.

Amendment 1 to the Third Edition added requirements for ISM lighting apparatus operating in the frequency bands of 915 MHz, 2.45 GHz, and 5.8 GHz. It also added IEC 60705:1999 (“Household microwave ovens – methods for measuring performance”) to the normative standards. It also added new words in Clause 5.2.2 (discussed earlier) and it added a new Table 5 (“Electromagnetic Radiation disturbance limits for Group 2 – Class A equipment”). All new wording was added to Clause 5.2.3 by Amendment 1. In Clause 6.2.1, it added the requirement that “for measurements at frequencies above 1 GHz, a spectrum analyzer with characteristics as defined in CISPR 16-1 shall be used.” Additionally, in Clause 6.2.4, it added the words “for measurements at frequencies above 1 GHz, the antenna used shall be as specified in CISPR 16-1.” Also, Clause 6.5.4 (“Microwave cooking appliances”) was added by Amendment 1.

An important (and somewhat controversial) Sub‑clause was added by Amendment 1 in Clause 7.1.3 (“Radiation measurements [9 kHz to 1 GHz]”). It added two sentences that impacted the third edition and subsequent editions. The first sentence said “for the test site measurements, an inverse proportionality factor of 20 dB per decade shall be used to normalize the measured data to the specified distance for determining compliance.” Also, it added the parenthetical sentence, “care should be taken in measuring a large test unit at 3 meters at a frequency near 30 MHz due to near‑field effects.” It deleted a key sentence from the second edition that said “at the closer measurement distance the electromagnetic disturbances measured shall not exceed the limit values specified in Clause 5.” In Sub‑clause 8.2 it added the sentence “the distance between the receiving antenna and the EUT shall be 3 meters.” Sub‑clauses 8.3 (“Validation and calibration of test site”) and 8.4 (“Measuring Procedure”) were completely rewritten. Finally, Amendment 1 added Figure 5 (“Decision tree for the measurement of emissions from 1 GHz to 18 GHz of Class B-Group 2 ISM equipment operating at frequencies above 400 MHz”).

Amendment 2 replaced “spark erosion equipment” with “electro-discharge machining (EDM) and arc welding equipment.” It also made additional editing changes to several Sub-clauses.

Second Edition—1990

The Second Edition of CISPR 11 was released in 1990, and it contained numerous changes from the original 1975 Edition, as well as two amendments.

In this Edition, ISM Equipment was divided into two groups and two classes. Group 1 equipment included all ISM equipment that used RF energy only for internal functioning of the equipment, while Group 2 equipment included ISM equipment used for external treatment of material and similar processes. Class A equipment is equipment suitable for use in all establishments other than domestic buildings, while Class B equipment is equipment suitable for use in domestic surroundings.

The frequency bands for conducted emissions were stated as covering 150 kHz to 30 MHz. The second edition included new separate limits for Class A and Class B equipment. The Class A-equipment limits in dBuV are shown in Table 7.

The Class B-equipment Limits in dBuV are shown in Table 8.

Electromagnetic radiation disturbance limits in dBuV/m for Group 1 equipment in Edition 2 are shown in Table 9.

There were additional limits for radiated emissions for Group 2 equipment. In the frequency range 1 GHz to 18 GHz, the limit for radiation disturbance power was 57 dB above a picowatt (effective radiated power), referred to a half-wave dipole in the narrow frequency range 11.7 GHz to 12.7 GHz.

The standard used statistics for compliance conclusions. Clause 6.1 stated “it cannot be shown that equipment in series production fails to meet the requirements of this publication without a statistical assessment of compliance being carried out.”

In the General Measurements Requirements clause, the standard provided for the measurement of Class A equipment either on a test site or in situ as determined by the manufacturer. However, the standard mandated that Class B equipment be tested and measured in a testing laboratory only.

Measuring equipment used by a testing lab had to comply with CISPR 16. Receivers needed both average and quasi-peak capability. An artificial mains network (LISN) was needed for conducted emissions, and it was a 50 ohm-50 microhenry network. Antennas used included a loop antenna below 30 MHz and a balanced-dipole antenna from 30 MHz to 1000 MHz. Measurements were made in both horizontal and vertical polarizations. Class A equipment was measured with the center of the antenna three meters above ground while, for Class B equipment, the center of the antenna had to be adjusted to between one and four meters.

The testing laboratory had to meet special provisions for measuring radiated emissions, including a minimum-sized ground plane, and an area free of reflecting structures and also large enough to allow for the appropriate separation of the equipment under test and the receiving antenna.

Amendment 1 to the second edition was released in March of 1996. It changed some conducted emission limits, especially for Class A equipment. Amendment 2 was also released in March of 1996 and it contained limits for induction cooking appliances for both conducted limits and radiated magnetic field limits. Amendment 2 also modified radiation limits for Group 2 equipment.

First Edition—1975

The title of the Premiere Edition was “Limits and Methods of Measurement of Radio Interference Characteristics of Industrial, Scientific, and Medical (ISM) Radio-Frequency (RF) Equipment (Excluding Surgical Diathermy Equipment).” It summarized the technical content of a significant number of CISPR publications, recommendations, and reports over a period of eight years, from 1967 to 1975.

The frequency range covered by the first edition of the standard was 150 kHz to 18 GHz. The terminal voltage limits were quoted in millivolts and covered the frequency range 150 kHz to 30 MHz. Terminal voltage limits from the first edition are reproduced in Table 1 of the standard (see Table 10).

The radiated limits were quoted in microvolts per meter for the frequency range 0.150 MHz to 1000 MHz. They were quoted at antenna-measurement distances of 30, 100, and 300 meters from the equipment or 30 meters or 100 meters from the boundary of the users’ premises. Limits of radiation in microvolts/meter and decibels (uV/m)] from the first edition was recreated in Table 2 in the standard.

There was a special limit for radiation from microwave equipment used for heating and medical purposes in the frequency range from 1-18 GHz; it was 57 dB above a picowatt effective radiated power (ERP), referred to a half-wave dipole.

Methods of measurement quoted CISPR Publications 1, 2, and 4 for quasi-peak measuring sets. Measurement of the radio-frequency voltage on supply mains (AC voltage lines) was conducted with a V-network with an intrinsic impedance of 150 ohms.

Magnetic field measurements are made with a balanced loop antenna below 30 MHz. For signals greater than 30 MHz, an “electric aerial” would be used as per CISPR Publications 2 and 4. The center of the “aerial” would be 3 meters above the ground.

Above 1 GHz, the “receiving aerial” was to be made with a directive aerial of small aperture capable of making separate measurements of the vertical and horizontal components of the radiated field. The height of the aerial had to be the same as the height of the approximate radiation center of the equipment under test.

Conclusion

The CISPR 11 standard for measuring disturbances (emissions) from ISM equipment has been in existence for 50 years. It has grown from a simple document to a complex document involving several types of products. It has grown from measuring products at a larger distance (100 meters and 30 meters) for Class A equipment to measuring them at three meters. Class B equipment measurement distances have shrunk to three meters, the distance used in the U.S. since the release in 1979 of FCC’s rules on personal computer emissions.