Introduction to CISPR 11 EMC Testing

Vessels on open water, whether on a small lake or the open sea, are equipped with electronics designed to keep them safe: communications gear, navigation tools, emergency beacons, and more. These devices need to meet regulatory requirements. The foundation electromagnetic compatibility (EMC) standards are CISPR 11 and CISPR 32. This month, we will provide an overview of CISPR 11 which has importance to marine electronic applications.


What is CISPR?

The International Special Committee on Radio Interference (CISPR: Comité International Spécial des Perturbations Radioélectriques) dates to 1933 when a conference of international groups met in Paris to find a way to deal with radio interference. They agreed that uniform measurement methods were needed to measure radiofrequency (RF) emissions. Doing that would make international trade easier and improve radio operation.

In 1950, CISPR was formally made into a special committee of the International Electrotechnical Commission (IEC). In the years that followed, a series of working groups (WGs) were formed to address specific types of emissions and measurement techniques. 

A family of standards emerged from that work, among them CISPR 11 and CISPR 32. Much of current technology falls under these standards. Next month’s blog will show the application of CISPR 11 and CISPR 32 to marine equipment. This blog’s focus is the set of emission requirements in CISPR 11.

CISPR 11 EMC Compliance

CISPR 11, Industrial, Scientific, and Medical Equipment – Radio-Frequency Disturbance Characteristics – Limits and Methods of Measurement, first published in 1975, is the basic emission standard incorporated into EN 55011, the European Norm used in the European Union (EU). Limits apply to both radiated and conducted emissions. Subsequent editions have been published incorporating updates on limits and measurement techniques.

The title applies to a broad swath of electronic equipment and covers devices that operate in the equally broad frequency range of 9 kHz to 400 GHz. Industrial, Scientific, and Medical (ISM) RF applications are defined in the ITU Radio Regulations as those “designed to generate and use locally radio frequency energy for industrial, scientific, medical, domestic or similar purposes, excluding applications in the field of telecommunications.” The standard covers emission requirements in the frequency range of 9 kHz to 18 GHz.

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CISPR 11 divides equipment into two broad groups:

  • Group 1 equipment contains all equipment that is not classified as Group 2 equipment. Examples are medical electrical equipment, machine tools, and scientific equipment
  • Group 2 equipment contains all ISM RF equipment in which RF energy in the frequency range 9 kHz to 400 GHz is intentionally generated and used or only used locally, in the form of EM radiation, inductive and/or capacitive coupling, for the treatment of material, for inspection/analysis purposes, or for transfer of EM energy. Examples are microwave ovens, inductive charging equipment, and electric welding equipment.

Within those groups, CISPR 11 identifies two equipment classes:

  • Class A is defined as “equipment suitable for use in all locations other than those allocated in residential environments and those directly connected to a low voltage power supply network which supplies buildings used for domestic purposes.” In other words, industrial and heavy commercial equipment.
  • Class B equipment is “suitable for use in locations in residential environments and in establishments directly connected to a low voltage power supply network which supplies buildings used for domestic purposes.” These are the devices typically used in a home or in light commercial applications.
  • Different emission limits apply to the two classes, with Class B being more restrictive than Class A. 
  • Conducted emission limits are specified for the two equipment groups for AC mains power ports and DC power ports. As an example, the AC-port conducted limits for Group 1 equipment are shown for both Class A and Class B. Note the significantly lower emission limit under Class B.

Conducted emission limits for Group 1, Class A equipment measured on a test site

(a.c. mains power port)

Frequency Range (MHz)

Rated Power of ≤20 kVA

Rated Power of ˃20 kVA and ≤75 kVA

High Power Electronic Systems and Equipment, Rated power of ˃75 kVA

Quasi-peak dB(µV)

Average dB(µV)

Quasi-peak dB(µV)

Average dB(µV)

Quasi-peak dB(µV)

Average dB(µV)

0.15 – 0.50

79

66

100

90

130

120

0.50 - 5

73

60

86

76

125

115

5-30

73

60

90

73

80

60

115

105

Conducted emission limits for Group 1, Class B equipment measured on a test site

(a.c. mains power port)

Frequency Range (MHz)

Quasi-peak dB(µV)

Average dB(µV)

0.15 – 0.50

66

56

56

46

0.50 - 5

56

46

5 - 30

60

50

Similarly, radiated emission limits are specified as well, with different limits depending on the measurement distance and the type of test chamber used.

Electromagnetic radiation disturbance limits for Class A Group 1 equipment measured on a test site


 

Frequency Range (MHz)

OATS or SAC

FAR

10 m measuring distance rated power of

3 m measuring distance rated power of

3 m measuring distance rated power of

≤20 kVA

˃20 kVA

≤20 kVA

˃20 kVA

≤20 kVA

˃20 kVA

Quasi-peak dB(µV/m)

Quasi-peak dB(µV/m)

Quasi-peak dB(µV/m)

Quasi-peak dB(µV/m)

Quasi-peak dB(µV/m)

Quasi-peak dB(µV/m)

30 -230

40

50

50

60

52

45

62

55

230 - 1000

47

50

57

60

52

55

OATS = Open Area Test Site        SAC = Semi-Anechoic Chamber        FAR = Fully Anechoic Room

 

Electromagnetic radiation disturbance limits for Class B Group 1 equipment measured on a test site

Frequency Range (MHz)

OATS or SAC

FAR

10 m measuring distance

3 m measuring distance

3 m measuring distance

Quasi-peak dB(µV/m)

Quasi-peak dB(µV/m)

Quasi-peak dB(µV/m)

30 - 230

30

40

42

230 - 1000

37

47

42

 

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CISPR 11 provides specifications for the test equipment to be used for measurement:

  • ambient noise levels; 
  • measurement instruments (receiver and/or spectrum analyzer);
  • artificial mains network to provide a fixed terminal impedance for mains AC power-port conducted-emission measurements;
  • artificial DC network for fixed-impedance termination at DC power ports;
  • voltage probes, antennas, and test chamber specifications.

The equipment under test (EUT) configuration is also defined, with diagrams showing typical setups for different form factors: tabletop, floor-standing, multiple interconnecting boxes, etc. The test plan needs to clearly describe the setup. Clause 6 covers the EUT configuration and Clause 7 addresses the EUT’s interconnecting cables.

CISPR 11 at Sea

CISPR 11 plays a significant role in Marine EMC regulations, but there are others: 

  • EN 60945
  • IEC 60533
  • ABYC-S31
  • Various marine classification societies’ standards that include emission requirements

The ABYC-S31 standard includes reference to the CISPR 11 Class B limits for marine installations for other than at the helm.

 

In next month’s blogs we’ll discuss CISPR 32 and how CISPR 11 compares and relates to other marine requirements. Marine vessels fall under multiple jurisdictions. The type of vessel, its application, and its intended use all have bearing on applicable regulations.

Elite has been performing CISPR 11 tests since the standard’s introduction and can answer questions regarding what you need to know for your product. Contact the experts at Elite and find out how to test your product quickly and accurately.