Product certifications

Hi All,

In regards to creating a product with a Spark Core/Photon as the brains, can anyone give an overview of the certifications testing process and recommend any testing houses in the US? Also, what is the ballpark cost we are talking about?


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@matt_ri, all Spark products are certified so you don’t have to! :smile:

That’s not strictly true; whilst you can use FCC modular certification in some circumstances (follow the notes in the certification filing), you can’t in others - eg if you have multiple radios in a product. If you are making a product that’s hand-held you may also need to perform SAR testing, which is even more expensive ($5k+) unless you want to turn down the power so the EIRP is <50mW, which gets you into waiver territory.

Also, the certification only covers the intentional emitter portion of the product. You will still need to ensure your product passes the unintentional emitter testing that every electronic device has to adhere to.

Certification labs are generally expensive - often $1000/day - but are generally really good with giving advice of what you need to have sorted before you go there. After the testing is done there’s a documentation fee of generally $2k+. If you’re planning on selling outside the US then you can get CE testing done at the same time and save some money, as there are a lot of common aspects.

Labs I’ve used in the past include db Technology (UK), CKC labs (California) and NW EMC (Oregon). You want to find one that has certified a wifi product in the past, otherwise you’ll end up training the engineer on your dime :wink:


Thanks @hfiennes. That’s helpful.

@peekay123 Yes, I know the sparks are certified as themselves, but my product would be adding some LEDs and buttons to the spark. So, I’d still need to unintentional emitter testing.

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Hi @matt_ri

I am guessing the the RI in your username could be a New England state–if so I have used these folks:

As @hfiennes said, you are much better off having your ferrites and caps already in place on your board before you go for testing. A roll of copper foil tape can be useful too–in my case the plastic enclosure with nickel spray shielding on the inside worked great except at the ends where we need a little redesign.

@bko Yup! I’m in Rhode Island. Thanks for your suggestions.

Things to look out for, and general advice on EMI:

  • for any non-trivial system, or one with a switching power supply, you should be using a 4 layer board. This will give you a contiguous, low inductance ground path which is essential for low EMI
  • ditto for a power plane.
  • even if you don’t stuff them, place footprints for small (0402) caps near any power consuming devices (ICs, wifi module, etc), in addition to your normal bypass caps. Pads cost nothing and to be able to drop down a 22pF cap (or be able to try several values to get one that helps) in the lab during testing and fix a problem with no board change (which would necessitate another lab visit when you have the new board fabbed) is wonderful. At high frequencies these caps will appear to be a short to ground for the RF and hence suppress the emission.
  • bypass caps should be as close to the consumer as possible to minimize loop area. Via down to the planes right at the cap.
  • for any off-board signals, have pads for a cap to ground and a series element right as the signal leaves the board. Stuff 0R in series to start with, but the pads mean you can drop down a ferrite bead and get rid of the lower frequency stuff that radiates from connecting wires (this happens even with switches, speakers, etc)
  • if you’re running USB off board, put a common mode choke in the D+/D- lines. Like a ferrite bead but only filters common mode interference without (much) affecting the differential signaling.
  • ideally, never use oscillator modules. They just make loads of harmonics due to their high drive outputs. Crystals are much quieter, but layout is critical there too.

As @bko says copper tape is used a lot during debug, and shielding spray can work well too (though EMI absorber material has never, ever worked for me), but with a good board layout you usually don’t need these (relatively) expensive band-aids. When you see a phone teardown with visible copper tape, you know they didn’t sort EMI in time but had to ship anyway so used the band-aid :smile:

TL;DR: preparation is everything. Board turns cost time and money so throw pads down for every eventuality and you’ll be glad you did!