Do I need to adapt this Class A device for home use? - Page 1
Forum section: electronics / rf-microwave

author: paul8f
author_rank: Regular Contributor
timestamp: August 26, 2019, 07:32:31 pm
content: Hi,just bought a 2nd hand back-up unit. It was designed for use in an industrial environment, but I want to use it at home. Do I need to add EMI filters or some sort of suppression?Here is the notice in the User Manual:FCC Warning:This equipment has been tested and found to comply with the limits for aClass A digital device, pursuant topart 15of the FCC Rules. These limits are designed to provide reasonable protection againstharmful interferencewhen theequipment is operated in a commercial environment. This equipment generates, uses, and can radiate radiofrequency energy and, if not installed and used in accordance with the instruction manual, may cause harmfulinterference to radio communications. Operation of this equipment in aresidential areais likely to cause harmfulinterference in which case the user will be required to correct the interference at his own expense.From what I understand..... Class A devices have less strict rules as they are normally used in a factory or in an industrial environment where there are larger distances between devices, so any radiated emissions will have less effect on other equipment. Class B devices on the other hand have much more stringent rules as they are for domestic/home use.Any info welcome

author: sokoloff
author_rank: Super Contributor
timestamp: August 26, 2019, 07:40:11 pm
content: My 2 Euro cents:Use it at home freely.If it causes a problem with your or neighbors' equipment, only then try to figure something out.In many cases, that warning means "this equipmentwas not testedand certified to the stricter standards" rather than "this equipment was tested andcould not possibly be certifiedto the stricter standards".

author: Nusa
author_rank: Super Contributor
timestamp: August 26, 2019, 08:02:55 pm
content: FCC rules wouldn't apply to Ireland in any case, nor are standards and frequencies in other countries necessarily the same as those the FCC certifies in the United States.I don't know what rules do apply to Ireland. I would guess some sort of EU regulation, but there may be local ones as well.

author: paul8f
author_rank: Regular Contributor
timestamp: August 26, 2019, 08:05:14 pm
content: Quote from: sokoloff on August 26, 2019, 07:40:11 pmThanks for advice sokoloff.I have not noticed any effects on my mobile phone or FM radio at home etc, so I agree with what you say. It's highly likely that this device would pass as a Class B device if tested. It's all about the paying for the expensive certification process by the sound of it.If I do notice some sort of interference in the future, besides upgrading toscreened/shielded cables, and making sure thechassis is grounded correctly, what else is recommended as remedial action?

author: paul8f
author_rank: Regular Contributor
timestamp: August 26, 2019, 08:08:55 pm
content: Quote from: Nusa on August 26, 2019, 08:02:55 pmVery true!I think we do have very similarily worded regulations though... (a) device must not emit any harmful interference and (b) must be accept any emissions from other devices without an impact on operations... Something like that....!If anyone knows the EU equivalent of FCC let me know

author: paul8f
author_rank: Regular Contributor
timestamp: August 28, 2019, 07:25:06 pm
content: Quote from: paul8f on August 26, 2019, 08:08:55 pmLooks like there isn't a direct equivalent, but Part 15 is covered under theCE(Conformity, European) of which EMC (ElectroMagnetic Compatibility) is a part.Also found out that EMI/RFI fabric-over-foam (FoF) gaskets can be added to small hardware gaps in the outer metal chassis to help attenuate radiated waves (but obviously never up to the point of obstructing any cooling or ventilation holes...)

author: Andreas
author_rank: Super Contributor
timestamp: August 28, 2019, 08:13:33 pm
content: Quote from: sokoloff on August 26, 2019, 07:40:11 pmDefinitely No!The test for conducted emissions (0.15-30 MHz) is the same.Only the limit is 10 dB higher for Class A than for Class B.So the meaning is: we did not want to spend several $$ for extra components to reach Class B.Physics are the same in US (FCC) and EU (IEC/EN 61000).(And also the limits are comparable; eventually depending on different frequency usage).Usually the conducted disturbances are in AM or long wave frequency range.A suitable line filter would be a measure against conducted emissions.Radiated emissions (> 30 MHz) are measured different (30 m antenna distance (class A) instead of 10 m (class B)).But usually only a 10 m (or even 3m) distance measurement is done and the results are calculated back to the other distances.Radiated emissions can go directly (shielding) or via a "antenna" (mains line, signal lines) (filtering, shielding or ferrites).with best regardsAndreas

author: Towger
author_rank: Super Contributor
timestamp: August 28, 2019, 08:30:06 pm
content: If you it tested for CE compliance in/near Dublin I can give you a name, but I am sure his expertise is not cheap :-)