Yes, in Europe as well. All part of the (heavy) industrial versus residential, commercial and light industrial divide. Particularly that broadcast receivers would be 10m away from an emitter in a heavy industrial area, but only 3m away elsewhere. But that was 50 or more years ago, in the days of AM and FM, and analogue TV. It's a bit different now and  will get more different.

On 2024-11-09 23:38, Ken Javor wrote:

On the west side of the Pond, the major discrimination (for emissions) was in the application of the class A limit at 10 meters, vs. the class B limit at three meters. The differentiator was the expected zone of control. Meaning an apartment dweller might not have control over an offending interference source more than three meters away, vs. an industrial or commercial enterprise where the zone of control would typically be larger.

The same kind of reasoning would apply to conducted emissions, both from the point of view of a radiating power line, but also what culprits and victims might share the same or a close-by branch circuit.

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Ken Javor

Ph: (256) 650-5261

*From: *"James Pawson (U3C)" <ja...@unit3compliance.co.uk>
*Reply-To: *"James Pawson (U3C)" <ja...@unit3compliance.co.uk>
*Date: *Saturday, November 9, 2024 at 10:19 AM
*To: *<EMC-PSTC@LISTSERV.IEEE.ORG>
*Subject: *[PSES] Emissions Class A vs Class B

Hello all,

I’m writing some guidance on Class A vs Class B and I was thinking about the Why. As in why do we separate emissions into Class A and B?

Reasons I’ve heard (which make some kind of sense even if I’ve not actually looked into the figures) include:

 1. Concentration of electronic equipment – domestic premises are more
    likely to have other interference equipment operating in closer
    proximity to receivers than in a commercial/industrial environment.

 2. Quantity of devices sold – consumer devices used in a domestic
    sphere have a much higher sales volume

 3. Nature of installation – Class A equipment installed by more
    technically competent users, Class B installed by less
    knowledgeable users.

Does anyone have any additional justification, historical perspective, or can point me in the direction of a standard that describes this in more detail?

I’ve looked in IEC TR 61000-2-5 which, although it mostly focuses on immunity, mentions these above reasons. CISPR 16-4-4 seems to deal with statistical methods. IEC TR 61000-1-1 deals in general terms with the concept of a margin between Emissions and Immunity. But no definitions for the derivation of these Classes…

Thanks in advance!

All the best

James

James Pawson

Managing Director & EMC Problem Solver

*Unit 3 Compliance Ltd*

*EMC : Environmental & Vibration : Electrical Safety : CE & UKCA : Consultancy*

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