Regan, I think the EMC community can agree that just because a device label indicates it is compliant doesn't mean it really is. We see that in the lab very often.
ANSI C63.4 does offer quite a bit of detail regarding EUT setup & operation, connection of EUT ports and peripheral and accessory devices, simulators, interconnected cabling, etc. Too much detail in fact for anyone to try to explain in an email. If I may put in a little plug for the ASC-C63(r) standards committee, there is a monumental effort put forth by these brave and knowlegable volunteers who write and continually update the ANSI C63 standards. I think you will find all your answers there in the standard. If you still have questions interpreting a section of the standard, you might find the answer on the "interpretations" web page provided by ASC-C63(r): http://www.c63.org/documents/misc/posting/new_interpretations.htm. In general, it is understood that you can't test every combination of connected devices, so you test a typical setup that you can justify as presenting "worst-case" for emissions. As for daisy-chained equipment under test, you really have to look at how it is use in actual applications. If multiple pieces of equipment can be daisy chained together and used in a small local area, i.e. rack or table for example, they should be tested together. If it can be shown that at some point adding additional daisy-chained devices does not add to the emissions profile, then you can stop adding at that point. In the end the system under test should represent worst-case of what actually might be seen in an actual application, while keeping the test setup within the realm of reasonable possibility. Just be sure to detail it all in your test report. Best of fortune to you. If you use a good accredited test lab, they deal with this daily and should be able to guide you through the whole process. Bill Stumpf - Lab / Technical Manager D.L.S. Electronic Systems, Inc. EMC Testing, Certification & Consulting 166 South Carter Street Genoa City WI 53128 Ph: 262-279-0210 From: Regan Arndt [mailto:re...@empowermicro.com] Sent: Thursday, March 09, 2017 11:50 AM To: Bill Stumpf <bstu...@dlsemc.com<mailto:bstu...@dlsemc.com>>; EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: RE: EMC co-location distance question Hi Bill. Thanks for this great info! Much appreciated. The second part of my original email was merely philosophical discussion points. Let me clarify. I would love to hear what people think: 1. How many different types of ancillary equipment shall you test with your main EUT? i.e. PCs or laptops with HDMI & USB ports......the sky's the limit as to the myriad of devices that now can be connected. Where does one 'stop'? a. Also, not all devices (that claim to be Class B) are noise free. I've personally experienced extremely noisy devices using a reputable brand name (yes, FCC logo on the device), but had to exchange it for their competitor to ensure no unintentional emissions, so my main EUT passes. (Moral of the story....don't believe everything you read on the label - lol) 2. Another related question: what about identical devices that can be daisy chained? i.e. some devices allow a daisy chain of up to 12 or more. (i.e. telecom trunk card). Does one use the chamber table as the determination for the quantity of daisy chained samples to test? Or does one compile all the max # of daisy chained devices on the table despite the congestion of I/O & power cables (not recommended)? Or is there a rule of thumb that one shall prove that there will not be an increase in emissions past a certain number of devices? (The latter is my preference). Thoughts? From: Bill Stumpf [mailto:bstu...@dlsemc.com] Sent: Thursday, March 09, 2017 6:54 AM To: Regan Arndt <re...@empowermicro.com<mailto:re...@empowermicro.com>>; EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: RE: EMC co-location distance question Regan, I'm not sure I understand your question correctly, but I will try to provide an answer. ANSI C63.4 is used when testing for FCC part 15 subpart B compliance for unintentional radiators. When testing a table-top system, the collocated equipment should be spaced at 10cm, unless this is not typical of normal operation. If so, then the EUT and its accessories/peripheral devices should be placed as they would be in typical applications. It is important to read the text of the ANSI standard, as it goes into great detail on how to set up and select accessories for testing. The drawings are for general reference only and the text always takes precedence. As for EN/CISPR standards, they mostly accept similar setup conditions to ANSI C63.4, but you will have to verify the specific requirements in each standard. The <20cm you refer to was at one time unofficially (FCC) considered the distance for collocation of transmitter antennas, but this is no longer the case. The FCC considers that two transmitters/antennas are collocated if they are in the same product / enclosure. I hope this helps. Bill From: Regan Arndt [mailto:re...@empowermicro.com] Sent: Wednesday, March 08, 2017 1:50 PM To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: [PSES] EMC co-location distance question Greetings members, Can anyone shed any light on what ANSI defines as the max distance/limit of a 'co-located' piece of ancillary equipment or other support equipment (on the table) to the main EUT being tested for FCC Part 15 class B for 'unintentional radiators'. I seem to recall 20 cm but I think this was referring to 'intentional' radiators. Is there a similar requirement in the EMC directive and/or EN/CISPR standards? Or is this really dictated on your recommended set-up? Shall that device be removed from the test bed if typical installation indicates that it will be greater than 20cm from the main EUT? I believe that the set-up in ANSI only showed the PC, printer, mouse, keyboard & monitor but that's it. There are so many other/different electronic devices that connect to a laptop/PC/other, etc. (i.e. smart phone) these days, it is not viable for anyone to test all devices/configurations. I understand that one must use good judgment and exercise due diligence but there must be a limit. Agree? Some of these electronic devices state compliance to Class B, it may still have interference with another closely co-located device because they did not test it fully to the myriad of other electronic devices out there that it could be connected to. There is no guarantee per se. Can anyone comment? Thanks in advance. Regan - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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