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Conducted EMC equipment for 60W offline PSU

treez

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Hi
Do you know of any cheap place in UK or Europe where we can take our offline PSU for conducted EMC testing?....it doesnt need to be a properly accredited lab.....we just want to use the kit to do some general modify-and-test type work.
We dont need all that aluminium covered floors and walls stuff.....nor a £440k spectrum analyser...just a cheap one....and a LISN.
 

betwixt

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Suggestion:
get yourself an RF sealed room - this doesn't have to be expensive, a garden shed will do. Line it thoroughly with kitchen 'Al' foil. Connect mains to it through a good RF block filter and make sure the foil and filter grounds are well bonded (think short wires to minimize inductance) and also connected to a good 'Earth' ground. Check it by taking a portable radio and a mobile phone inside. If either work well, you need more screening!
That gives you a 'clean' room for very little cost.

Then for EMC monitoring, get a reasonably good HF/VHF receiver, a second hand one will work as good as a new one. Look for a receiver from Icom, Yaesu or one of the more respected manufacturers that covers say 100KHz to 50MHz, there are many on the market.

The signal strength meters on these receivers is calibrated in 'S' points and 'dB above S9', the manual will tell you what S9 absolute level is or you can work it out with a signal generator and attenuator.

Connect a short co-axial cable and a wire probe to the antenna socket and use it as your 'sniffer' for EMC signals.

This is my 'test corner of the room' :
20190804_094358.jpg
Which can measure from about 1KHz up to 960MHz reasonably accurately. Ironically, the biggest source of interference is the PSU! The room is lined with Celotex/Kingspan/Kooltherm thermal insulation which is metal lined on both sides, it makes a very effective RF shield too.

Remember that if you are picking up a suspicious signal that might be coming from your PSU, you can always switch it off to see if the signal is yours or not.

Brian.
 

volker@muehlhaus

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Last edited:

prairiedog

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I don't know of any company offering such a facility- you're asking for EMC lab benefits without the cost. EMC labs have calibrated equipment and shielded rooms, accreditation, operations staff etc. so they are naturally quite expensive.

Pre-scans are typically done in-house. You could purchase a used or low dollar spectrum analyzer, and buy or make a mains LISN, current transformer etc. Just estimate those costs and how many hours of paid EMC lab time they would save, product flops in EMC etc. to see your payback time. It's always worth it. Look at your typical EMC testing costs and compare to say a $6,000 purchase of equipment. It also allows engineers to see and learn EMC, instead of a rude surprise during formal EMC testing.

There are limits to doing conducted emissions testing in unshielded and unfiltered environments, i.e. an ordinary lab. The noise floor is high due to local AM/FM radio station transmitters and other RF, coming in on mains and the airwaves. This is most of the work in making your own lab, getting it quiet inside.

But to look for obvious emissions spikes, compare CM filters, find a port spewing conducted RF, snubber issues etc. I think you will have to make your own lab.
EMC labs won't offer a discounted rate, they don't like strangers operating their equipment and risking damage or the liability from safety issues in their facility.
 

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