CISPR 11: “Industrial, scientific and medical equipment – Radio-frequency disturbance characteristics – Limits and methods of measurement”
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.