Changes in product after EMC testing - Page 1
Forum section: electronics / projects

author: michaelym
author_rank: Regular Contributor
timestamp: May 01, 2013, 07:39:00 am
content: I wonder if anyone here has experience in such a thing, from the technical or regulatory point of view.Say I tested my product (medical device) for EMC and then changed a few thing on my circuit, do I need to do the testing all over?My product includes a shielded network cable used for SPI signals etc. (and not Ethernet). If I change the cable to one from a different manufacturer do I need to do the testing all over?

author: AndyC_772
author_rank: Super Contributor
timestamp: May 01, 2013, 08:26:01 am
content: To some extent it's your call.When you CE mark a product - I presume this is the regulatory environment you're involved with - then you are asserting that your product is compliant will all applicable EU directives, of which the EMC Directive is one.The claim is yours alone to make, and you must make it based on your own knowledge of the product, your expertise, and the results of any testing you've had carried out.If you have your product tested at an independent lab, and pay for it, you'll get a report which includes test results, details of the experimental setup, and the results from the lab's calibrated measurement equipment. Nevertheless, it's still you who has to make the final call as to whether you believe your equipment is compliant or not.One of the requirements of the Directive is to maintain a technical file on the product, which includes all the relevant information on how the product is constructed, what the EMC critical parts are, the results of any testing you've had carried out, and any changes which have subsequently been made.You are not prohibited from changing your product after testing has been carried out, but you must decide for yourself whether or not you believe the change is likely to adversely affect the product's EMC signature, and risks pushing it over the limit. If you are sure that your replacement cable won't have any harmful effect, put a note in the technical file to the effect that you have changed it. If you believe the change could or will cause the product's EMC emissions to become non-compliant, you should consider a re-test - at least, for the parts of the test which you think might be affected.In practical terms, what you'd need to be able to do is show, if challenged by the authorities, that you had reasonable grounds for believing your product was compliant. Mistakes happen, and nobody is likely to throw you in jail if you've made an honest and reasonably thorough attempt to show your product is compliant.One of the best places to ask for advice could actually be your compliance lab. I'm not familiar with specific rules which may apply to medical devices, so these may be more stringent than those for normal commercial and industrial electronics. The lab should be able to advise on what you're actually required to do; if they try too hard to steer you down the road of testing which isn't actually required by law, it may be time to change labs.

author: Niklas
author_rank: Frequent Contributor
timestamp: May 01, 2013, 05:53:56 pm
content: For a consumer product I would agree with AndyC, document and assess the impact of any changes.For a medical product I am not so sure. A friend of mine worked for a hearing aid company and even the slightest change had to be reviewed, tested and documented extensively. Even a change of a single resistor value or resistor supplier had to be fully traceable.

author: Ghydda
author_rank: Regular Contributor
timestamp: May 02, 2013, 09:00:06 am
content: Quote from: Niklas on May 01, 2013, 05:53:56 pmSurely that has nothing to do with EMC but rather ensuring product quality by retaining traceability of components within the medical equipment and ensuring personnel/patient safety.No sane person performs a retest on the EMC for a smd-resistor manufactorer swap. That's both mad and ludicrous

author: Niklas
author_rank: Frequent Contributor
timestamp: May 02, 2013, 09:13:45 am
content: Quote from: Ghydda on May 02, 2013, 09:00:06 amIt does not have with EMC to do, but with medical equipment more generally. Would you like to answer for a complete halt of your company's deliveries to the USA just because you changed something "not very important"? FDA makes unannounced inspections at suppliers' manufacturing and they can stop deliveries on the spot. At some occasions the inspectors even bring firearms for their own protection.

author: mswhin63
author_rank: Frequent Contributor
timestamp: May 02, 2013, 03:10:57 pm
content: I too am waiting on a product that my distributor is trying to get approved. 9 months after receiving the item, 1 or 2 components had to be changed and a whole series of documentation had to be re-submitted to go through the second stage of testing.I don't think it has been re-submitted yet but one statement my distributor said was CSIRO had to wait for a cool day to carry out a test. mmmmm I wonder if that was an excuse for delaying. I notice that Dave has not much time for CSIRO, and I was concerned they don't have a temperature controlled booth for testing. Maybe someone could shed some light on this. Do they need a cold day with pollutants in the air mmmm!Quote from: Niklas on May 01, 2013, 05:53:56 pm