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The columns contained in this SI/PI/EMC & EMI Fundamentals section come from members of the Signal Integrity Journal community who are experts in their field and have a commitment to providing training and education in SI/PI/EMI issues for other engineers.

4 Things to Look For When Interpreting Standard Requirements

January 20, 2020

Being on several standards committees, I get a lot of questions about how to interpret the information provided in standards and specifications. Sometimes this is from a colleague who is thoroughly reviewing a specification in preparation for a quality audit. As a result of the thorough standard review and the possibility of being assessed a “deficiency” during the audit, they become overly concerned about all parts of the standard. Other times, the person has already been audited and overlooked a requirement. This resulted in a “deficiency” during the audit.

The standards committees have content rules (what is and is not a requirement and how is that defined in the standard) that must be followed when a standard is being developed or revised. In addition, quality auditors are only supposed to audit against the requirements of a standard. Here is brief summary of what is a requirement within a standard…

1. Main Body of the Standard: In general, information provided in the main body of the standard and prefaced with the word “shall” is a requirement. Dimensions and values are also a requirement. If no tolerances are provided in the standard, then general tolerance rules apply (or the tolerances specified in the base standard of a series of standards would apply). Any information prefaced with a should, could, may, etc. (anything other than a shall) could be considered informational and not a requirement.

2. Notes: Notes in a standard are for information purposes only. You will notice that notes within a standard do not contain the word “shall”. Do not confuse “Notes” with “Footnotes”. Notes will always be prefaced with the word “Note:” Footnotes are used many times in tables and can contain very important information. So pay close attention to footnotes (especially in tables).

3. Annex (Normative or Informative): At the beginning of each Annex (sometimes referred to as Appendix in some standards), the word “Normative” or “Informative” will appear. If the Annex is “Normative”, then the information in the annex is a requirement (again keeping in mind the preface word of “shall”). If the Annex is “Informative”, then the annex is for information purposes and is not a requirement.

4. Interpretations: Although the standards committees try to make the information provided within a standard as clear as possible, something always seems to get into the published standard which may need interpretation or clarification. In these instances, the reader will have to use good engineering judgment. When this happens, it is a good idea to ask others in the industry (especially persons on the standards committee responsible for the standard generation) how they interpret the information provided in the standard. They most likely have had the same question and have addressed the issue.

I realize that this is a “crash course” in standards interpretation, but it should provide someone with the basics for interpreting standards. Knowing the basics and what to look for in a standard (also what can and cannot be audited) can really be helpful during a quality audit.

Do you have any questions about EMC Standard Interpretation, EMC Testing, or other related topics? Please share them in the comments section below.

This article originally appeared in Elite Electronic Engineering Inc.’s experts blog.

For further reading: 
Diepenbrock, Jay. Why Are There So Many Standards? Signal Integrity Journal, July 2019.


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