CISPR 11 Summary: ISM Equipment Emissions
Scope of CISPR 11 (EN 55011) for industrial, scientific and medical (ISM) equipment, the Group 1/2 and Class A/B classification, measurement methods and how it differs from CISPR 32.
At a glance
- Scope: electromagnetic emissions from industrial, scientific and medical (ISM) radio-frequency equipment. It covers conducted emissions (150 kHz–30 MHz) and radiated emissions (up to 1 GHz, and 1–18 GHz for some microwave equipment).
- The European equivalent is EN 55011 and the Korean equivalent is KN 11.
- Multimedia and IT equipment falls under CISPR 32, ISM equipment under CISPR 11. Check the product-family standard to see which one applies.
- Typical examples are power supplies and motor drives, LED lighting, medical equipment, industrial RF heaters and microwave ovens.
Group 1 and Group 2
| Group | Definition | Examples |
|---|---|---|
| Group 1 | ISM equipment that uses RF energy only for its own internal functioning | Power supplies, motor drives, measurement and control equipment |
| Group 2 | ISM equipment that intentionally generates RF energy for external use such as material treatment | RF heaters, plasma equipment, microwave ovens, electrosurgical units |
Because Group 2 equipment inherently radiates RF, separate limits are defined at the designated ISM frequency bands. Check the relevant clause of the standard for the designated bands.
Class A and Class B
| Class | Intended environment |
|---|---|
| Class A | All establishments other than domestic buildings |
| Class B | Domestic surroundings |
Class B has the stricter limits. When the intended use is unclear, many teams design to Class B.
Measurement basics
- Conducted emissions at the mains port are measured with a 50 Ω/50 µH artificial mains network (V-network, LISN) using both quasi-peak (QP) and average (AV) detectors. The receiver must meet CISPR 16-1.
- Radiated emissions from 30 MHz to 1000 MHz are measured with the antenna scanned over 1–4 m height in both horizontal and vertical polarization. Below 30 MHz the magnetic field is measured with a loop antenna.
- The measurement distance depends on the equipment. On a test site Group 1 and Class B are normally at 10 m and Group 2 Class A at 30 m, and shorter distances (3–10 m) are allowed under certain conditions.
- Small equipment that fits a test volume of 1.2 m diameter by 1.5 m height may be tested at 3 m, with the limit scaled inversely with distance from the 10 m value (Edition 5 Amendment 1).
- Class A equipment may be tested on a test site or in situ, while Class B equipment is tested in a test laboratory.
Distance scaling note
The distance scaling the standard allows is inversely proportional to distance (20·log₁₀(d₁/d₂) dB). Moving from 10 m to 3 m raises the limit by +10.46 dB, but use the exact value in the standard’s table. You can check the conversion with the "Test Distance Conversion" calculator.
Compared with CISPR 32
| Item | CISPR 32 | CISPR 11 |
|---|---|---|
| Scope | Multimedia and IT equipment | ISM RF equipment |
| Classification | Class A / Class B | Group 1·2 × Class A·B |
| Conducted range | 150 kHz–30 MHz | 150 kHz–30 MHz |
| Radiated range | 30 MHz–6 GHz | 30 MHz–1 GHz (1–18 GHz for some) |
Official sources
- Check the latest edition in the IEC webstore (https://webstore.iec.ch). Limits and distance rules differ between editions because of the long amendment history.
Related calculators
Standards summaries
Results and summaries are for reference. For certification and test reports use the latest official standard text and calibrated instrument data.