EMC compliance question

Yes, I don't understand that either. I have found some standards "online", if I just need to look. If I need it professionally, I need to buy it of course

All of the EMC tests still needs to be done even if you use a wart. But LVD (safety) becomes a lot easier, if it's below 15W consumption (no glow-wire test etc)

Somebody was talking about 48V warts. Some standards only allow 24V (for wet environments), and 32V for certain parts of the world

The standards bodies are parasites on society, as bad as the worst academic publishers. The standards committees are composed of volunteers, often working for universities or companies who pay their salaries, but never paid by the standards body for their free labour. Then the standards are copyrighted and sold at a huge profit, often to the same organisations whose experts contributed all of the value incorporated in the standards. The standards bodies are generally non-profit organisations, and they ensure this non-profit characteristic by increasing the pay of their directors until they run out of profit.

The standards become referenced in laws, and thereby have the force of law, but are copyrighted by a private entity, and not even the politicians writing the laws incorporating these standards can read them without paying.

Do not ever volunteer your time to work on a proprietary standard.

Here is a nice video by Carl Malamud (of

The phones are cool. I can take one to Hawaii and plug it in and it works just like it does here.

I imagine that europe has tens, maybe hundreds of millions of PoE devices with the chinese version of the CE mark molded into the case.

So if european manufacturers realy have to do all the CE certs and testing, they have one more reason that they can't compete with imports.

So as of 2019 it looks like the US rules are similar to the European "can't enforce" rules in that the manufacturer takes responsibility for everything and it's up to the mfgr how and what tests they perform to determine compliance:

This makes it sound like it's not too expensive to do some basic compliance tests on a small-volume product in house:

Need a 1 GHz-ish spectrum analyzer at least as the main tool which aren't exorbitantly expensive nowadays.

I can buy a spectrum analyzer and a surfboard antenna for under $1000, and can take a product out in the country and do an open-field test and crudely ballpark its EMI signature.

CE requires screen room testing and more quantitative measurement.

The reality today is that few products are honestly certified for EMI or safety, and life goes on pretty well. If a product causes massive EMI problems or hurts people, civil and criminal liabilities apply.

It's impressive how few EMI problems there are in real life.

In these certain parts of the world, what do they use for telephones? The standard central office batteries were and still are 48 Vdc. Which is why the electrical codes in the US and EU ignore anything below 50 Volts or so.

Only very recently are cellphones taking over.

Joe Gwinn

At work, we use PoE phones, through the internet. The PoE switches typically supply about 54 volts. (I've recently been testing PoE power pickoff bricks.)

At home, we use cell phones. Our old Bell System phone number was converted to free service over our cable modem, and probably still works, but we unplugged the phones because it was mostly spam calls.

Maybe someday.

Yeah, although I still keep the landline, even though it is now via fiber. I get at least as much spam and malware from iphone and computer.

Joe Gwinn

My experience differs. Every product that I have been involved with has been independently tested by Intertek or a test lab of similar status. > It's impressive how few EMI problems there are in real life.

Maybe that is because many products are actually tested and compliant. I can remember when audio equipment was very susceptible to interference from many sources. Those days are mostly gone. I have come across exceptions of course.

John

In IEC60730 (safety for household products), 2.1.5 SELV is defined as maximum 42V. Note states that for the US and Canada the SELV voltage is max 30VRMS (which equates to 42.4Vpeak). Those numbers are when dry, when wet it reduces to 15V/21.2V peak.

Normally things are dry, so US is 30V. I do not know how it is possible to allow 48V warts.

Searching a little, it seems the 48V systems are approved against telecommunication standards which may not use the SELV nomenclature

NEC has higher voltages, up to 60VDC, but matters little since most product needs to comply to 60730/60950, and now 62368 has replaced 60950.

The touch voltages are defined in yet another standard, IEC61201. I do not have access to that one.

The 48V warts are also strange in that when the product is tested for peak SELV voltage a single fault must be introduced. So if you mess with the feedback of the SMPS, the trip voltage determines the maximum voltage, and that is most likely significantly higher than 48V.

I have the same experience. I have never worked on a product, or heard/experienced other fellow engineers designed products that did not comply to all LVD standards and EMC regulatory required tests

Most audio equipment is digital now.

Certification costs are trivial for mass market products. China has two advantages over Europe - the real one is that it pays it's workers less, and the other is that it notionally has a even bigger internal market - and the rule of thumb is that manufacturing at ten times the volume lets you halve the price. The European internal market is about 500 million people, and because Europeans are better paid than Chinese it would probably be effectively bigger if the Chinese played fair - which they don't.

China does seem to go in for predatory marketing, where they subsidise a product for long enough to bankrupt foreign competition. Selective tariffs are an effective weapon against this tactic, but they do have to be used selectively, which Trump couldn't manage.

Most of most audio equipment is digital nowadays. The inputs aren't, and neither are the outputs. Domestic audio equipment usually gets it's input as a digital data stream - FM radio is an exception - but creating that input depends on analog microphones.

Standards have become an established method of protecting local industry from lower cost imported goods from less socially responsible sources.

It's one way of encouraging social responsibility and raising technical awareness abroad, if you are an important market for the products of secondary industry.

They try to do this with tertiary industries (financial and service), but the weasels generally tap dance faster than the regulators, have more money and less conscience.

Hence CE.

RL

POE voltage is directly on the pins of the ethernet interface. The designer insources the external wart with 48V nominal voltage (which can be more under single fault)

There may be a loop hole

If you ship the adapter/wart with the product you should test as a system, right?

But if you just state it needs 48V in, you can blame the wart manufacturer if it puts out more voltage.

I just took a random POE ethernet switch which uses a 54V external adapter:

I am doing EMC tests tomorrow at a test-house, so will ask them whats the deal ;-)

Just buy and read all the standards.

I tried wet fingers of two hands grabbing leads from a DC power supply. That was unbearable at 90 volts.

I'm designing some boxes that will run from 10 to 60 volts, with a note that europeans should stay below 12 to be safe and legal.

My Pockels Cell driver goes directly from a 48 volt wart to 1400v, MHz pulses in a sort of flyback circuit, with SiC semiconductors.

Peer-reviewed publication depends of the editors of the journal finding reviewers (who don't get paid for the work, but do get early access to a random sample of the literature that might interest them).

Nobody wants to published papers in journals that don't get read, and the journals that have good reputations, so do get read, get the pick of the papers.

Actually, it does.

The US political system is run on the basis that the people who own the country, run the country. More modern political systems do better, although not all that wonderfully well.