ANSI C63.12

Description / Abstract: This recommended practice presents a rationale for developing emission limits and immunity test levels and recommends that these facets are representative of current practice and user needs. Emission limits generally are written by national and international standards bodies. Emission limits for the most part are specified by regulators, which is the case in the U.S. and Canada. Such regulatory limits take precedence, even if the limits are different from those considered in this document. In the U.S. and Canada, product immunity is not regulated except for some safety equipment. In this way, adequate immunity is more a quality aspect of the product as if it does not operate in its intended RF environment, the user would deem it of poor quality. It should be noted that the entire document does not impose normative requirements, but recommends options.

Purpose

The main purpose of this recommended practice is to aid manufacturers who might need to modify the emissions their products generate (as long as regulatory limits are met) to meet for example intra-system needs for their products. There might also be a need to have different (higher) immunity test levels than what is typically required if the product will be used in severe electromagnetic environments. As the use of electronics is constantly changing (e.g., the Smart Grid [B10]1), the test methods, immunity test levels, and emission limits likewise need to be periodically reviewed to assure that EMC is maintained. In fact, these EMC considerations might have to be tailored for specific designs and go beyond regulatory requirements to ensure proper product operation at the user location, which is exposed to a myriad of RF environments and where it is likely that there are other electronic products that might suffer interference from RF generated by the product. The emissions and immunity measurement technique used can have an impact on the accuracy, repeatability, and reproducibility of the test results. Emissions from products should be controlled to protect radio services by not causing interference, and at the same time, products should have sufficient immunity to be able to operate as intended in the RF environments expected in locations where the products are intended to be used.

As part of the development of emission limits and immunity test levels, the following topics are discussed in this recommended practice:

a) The general properties of both man-made and natural environmental electromagnetic noise (disturbances), as this will impact the product immunity test levels and immunity tests that are needed so that a product performs within manufacturer’s specifications in the intended use environments

b) Selection, capabilities, and use of proper emissions measurement instrumentation.

c) The test instrumentation used to simulate the RF environment to which products are expected to be exposed so that the products work properly with minimal customer EMC complaints.

d) A defensible rationale that can be used in selecting a consistent set of limits for emissions and test levels for immunity,2 subject to good engineering practice and cost-effective EMC management, taking into account any regulatory requirements. Topic a) through topic

d) of this subclause are intended to be applicable to individual products as well as systems of various sizes and, if properly applied, provide guidance for obtaining both intrasystem and intersystem electromagnetic compatibility. This recommended practice assists manufacturers in specifying their own emissions limits (but as a minimum meeting regulatory and user requirements) and test levels as appropriate for their product to function properly and to not cause any undesired interference.

NOTE—Emission limits and immunity test levels along with the necessary measurement techniques described herein are proposed for general use to the extent that they are not covered in regulations or in customer requirements.