1 Scope
This part of CISPR 16 deals with statistical considerations in the determination of EMC compliance of mass-produced
products.
The reasons for such statistical considerations are:
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a) that the abatement of interference aims that the majority of the appliances to be
approved shall not cause interference;
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b) that the CISPR limits should be suitable for the purpose of type approval of mass-produced
appliances as well as approval of single-produced appliances;
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c) that to ensure compliance of mass-produced appliances with the CISPR limits, statistical
techniques have to be applied;
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d) that it is important for international trade that the limits shall be interpreted
in the same way in every country;
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e) that the National Committees of the IEC which collaborate in the work of the CISPR
should seek to secure the agreement of the competent authorities in their countries.
Therefore, this part of CISPR 16 specifies requirements and provides guidance based
on statistical techniques. EMC compliance of mass-produced appliances should be based
on the application of statistical techniques that must reassure the consumer, with
an 80 % degree of confidence, that 80 % of the appliances of a type being investigated
comply with the emission or immunity requirements. Clause 4 gives some general requirements for this so-called 80 %/80 % rule. Clause 5 gives more specific requirements for the application of the 80 %/80 % rule to emission
tests. Clause 6 gives guidance on the application of the CISPR 80 %/80 % rule to immunity tests.
The 80 %/80 % rule protects the consumer from non-compliant appliances, but it says
hardly anything about the probability that a batch of appliances from which the sample
has been taken will be accepted. This acceptance probability is very important to
the manufacturer. In Annex A, more information is given on acceptance probability (manufacturer’s risk).