Hello Ghery,
Thank you for clarifying the difference between the test methods in IEC 61000-4-6 vs. the spec CISPR 35. My reason for mentioning IEC 61000-4-6 was because of the statement regarding AM modulation and the fact that similar voltage levels appear in this document as the others. I was curious if there was a significance to the choice of 1V, 3V, 10V as reference/guide levels, because I’ve seen these test levels in other places. To be clear, I’m not claiming that the test levels are wrong, just trying to understand the rationale behind them. My questions are essentially: * Why 3V rms? Why not 2V, or 5V? * Was this value chosen based on a specific scenario or measurement(s), or in response to a specific threat? (Such as the AM radio telephone interference that Joe Randolph mentioned.) * Have there been studies to characterize the conducted interference levels that are present in various environments, such as residential? Again, I am not arguing that the levels should be changed, just trying to understand them. On the safety side, we have reports like IEC TR 62368-2 which provide explanatory information that gives some insight into how the safety standard was defined. I was curious if there was anything similar for CISPR 35 or CISPR 24. Thank you again for your reply. Jeff From: [email protected] <[email protected]> Sent: Thursday, March 25, 2021 5:30 PM To: 'Jeff Keyzer' <[email protected]>; [email protected] Subject: RE: [PSES] rationale behind conducted immunity levels in EN 55035 / IEC 61000-4-6 Jeff, I’m not sure what the technical rationale was back when CISPR 24 was originally published (yes, the 3 V limit dates back to then) but as I recall the idea was that above 80 MHz you could generate a uniform field and below 80 MHz this was far more difficult. Why 80 MHz? Because it was convenient (as best as I recall). When we wrote CISPR 35 the thought was that 3 V/m resulted in a lower voltage than was tested to in CISPR 24, so the limit was lowered. The test levels called out in IEC 61000-4-6 have no bearing on the levels actually called out in CISPR 35. The same goes for radiated immunity above 80 MHz. The IEC 61000-4-x documents are called out as test methods, the test levels are called out in the product family standards, in this case CISPR 35. If you (or the client) feel that the test levels are wrong I would suggest that you join the US CISPR I TAG and make your concerns known. Contact me privately and I’ll be happy to provide you with the email address of the US Technical Expert who will (I’m sure) be happy to have you join the TAG. I hope this helps. Ghery S. Pettit Chair, CISPR SC I From: Jeff Keyzer <[email protected] <mailto:[email protected]> > Sent: Thursday, March 25, 2021 10:21 AM To: [email protected] <mailto:[email protected]> Subject: [PSES] rationale behind conducted immunity levels in EN 55035 / IEC 61000-4-6 Hello all, I am looking for background information on the rationale behind the conducted immunity test levels defined in EN 55035 / CISPR 35 and IEC 61000-4-6. Specifically, in 55035:2016 table 2, clause 2.1 calls for a test level of 3V rms from 0.15 to 10MHz. It also defines a slope that reduces the signal level above 10MHz. What is the technical rationale behind 3V rms being the desired immunity level for ITE equipment? Second, why does the voltage level taper above 10MHz in 55035, as opposed to 55024, where the test remains constant from 150kHz - 80MHz? IEC 61000-4-6 also calls for 1V, 3V, 10V rms test levels and calls for 80% AM modulation "to simulate actual threats". Is the rationale behind this documented somewhere? What threats were considered? I suspect this is a rabbit hole, but curiosity (and a concerned client) has gotten the best of me. -- Jeff Keyzer MightyOhm LLC [email protected] <mailto:[email protected]> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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