Practical aspects of EMC testing
 

EU legislation offers two routes to compliance for the vast majority of products:

1. TCF (technical construction file) requires typically some partial testing together with a rigourous engineering assessment of the ‘product’ to justify the declaration of compliance. This route is generally applied to products or systems that cannot be tested by conventional means, or are complex, or form part of a family of similar products when the compliance of one is used to justify the compliance of the family. All TCFs must be audited by a ‘competant body’ who will make an appropriate charge.
2. Self Certification is the issue of a Declaration of Compliance by the manufacturer or supplier who has ‘sound technical grounds’ to justify the declaration. The nature of the ‘sound technical grounds’ are at the discretion of the issuer. They may be results obtained from a test lab, results obtained by more or less limited self testing, a technical appraisal or a mixture of two or more of the above. In general, the requirements of the legislation will be deemed to have been satisfied provided that ‘due diligence’ is observed and any decisions/assumptions/interpretations are ‘reasonable’.

In general it is a good idea to consult with the local Trading Standards Office. Past experience has shown that they are helpful and will, if possible, offer good advise. In either of the above ‘routes’, a vital initial step is the selection of the appropriate standard. This will define the applicable tests, product configuration and other relevant details. To help chose the right standard, see Standard Selector page.

One 'non RF' requirement is the testing of the level of mains harmonic distortion and voltage flicker that a product imposes on the mains supply. (IEC61000-3-2 and IEC61000-3-3) These are manditory requirements as from Jan 1 ^{st 2001. The Laplace range now includes a full compliance harmonics and flicker analyser at an exceptionally low cost.}

When considering radiated emissions testing, the most common test technique specified by the standards (both EU and FCC) is the open area test site (OATS) technique. To ensure accuracy and repeatability, this technique relies on the lack of all reflections in the vicinity of the EUT and antenna apart from the ground plane reflection. In reality, due to limited space and limited resources, the vast majority of tests (both pre-compliance and self test/self certification) outside the test labs are done on very non-compliant sites.
These sites introduce two factors which must be taken into account if results are to have any integrity. Laplace test kits are unique in their ability to address both of these factors.

Before deciding on any test equipment...check the facts!!

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	For most radiated emissions testing the dominant source of measurement error is the test site. This includes OATS (Open Area Test Site), Anechoic chambers, screened rooms and test cells. Laplace emissions test systems (emissions test kits) are unique in having the ability (as standard) to calibrate the test site (ERS) and to automatically apply correction factors to the results.
	The second most important source of error is background interference. This is always a factor on OATS and intermitant background signals are a particular difficulty. The Laplace emissions test software (SA1000 software) includes powerful routines to cope with background interference, even intermittant signals and unstable conditions.
	RFI susceptibility, although a common problem in the modern world, is the most difficult test to perform as it requires considerable resources in terms of test chambers and RF generators. The LaplaCell300(LaplaCell) and associated modules provides a fully compliant IEC61000-4-3 (61000-4-3) immunity test system, easy to use and at a very affordable price. The LaplaCell300 test cell also provides an ideal solution to the problems of OATS as listed above. So the one cell provides a complete solution (clients) for all test site difficulties.

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All you need to create your own test laboratory.

Check the selector chart to choose the kit appropriate for your products.

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Revised: 11 January, 2000
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