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Practical Engineering: Pre-compliance for Product Safety

EMC Pre-compliance Testing

Many articles, entire books, and chapters of books promote the benefits of performing pre-compliance electromagnetic compatibility (EMC) testing and show how easy it is to carry out bench-top EMC measurements using relatively inexpensive and homemade test apparatus.

EMC pre-compliance testing is highly beneficial. I strongly encourage doing it if you are interested in discovering EMC-related weaknesses in your design as early in the product development cycle as possible. Discovering EMC design weakness early means more and less costly solutions are available before the final design is locked down. So, the question is this: If pre-compliance activities are good for discovering EMC design weaknesses early in product development, why not apply the same thought process to product safety?

Product Safety Pre-compliance Testing

The tests required for product safety are less complex than those for EMC. Typical product safety tests are dielectric strength (high-potential or hipot), impulse, insulation resistance, ground bond continuity, breakdown of components, etc. You need a tester for each to perform hipot, impulse, insulation resistance, and ground bond continuity. Breakdown of components is a methodology – you need to know which components to short out to cause a fault in the system to see that it responds safely. The only test equipment required is an insulated wire used for shorting out components.

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A Dash of Maxwell’s: A Maxwell’s Equations Primer – Part Two

Maxwell’s Equations are eloquently simple yet excruciatingly complex. Their first statement by James Clerk Maxwell in 1864 heralded the beginning of the age of radio and, one could argue, the age of modern electronics.

Product Safety Test Equipment

Unfortunately, there are no practical ways to build the test equipment required for product safety as there is for EMC pre-compliance testing. However, if your organization is developing safe products, having this equipment on hand is necessary. The positive side is that product safety test equipment is not as expensive as required for EMC testing, and the same product safety test equipment used for pre-compliance testing is often used for full-compliance testing.

If you are involved in developing safe products, have this equipment on hand and start doing pre-compliance product safety testing like you are likely doing for EMC. You will be glad you did.

Product Safety Pre-compliance Design Reviews

Something else you can do early in the product development cycle regarding product safety compliance besides just pre-compliance testing is to have a thorough review of the design conducted by a product safety expert.

Where do you find product safety experts? Experts are found in-house (a staff member from your company’s product compliance department or someone on your team skilled in the art), or out-of-house (a product safety consultant or someone from the NRTL you are using for end-product certification).

Essential Design Review Activities

Once you find a product safety expert, involve them early in the product development cycle and have them start reviewing your design for product safety issues. Specifically, have the expert:

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  • Review spacings (creepage and clearance distances) to ensure the numbers you are using are adequate and meet the requirements of the product safety standard applicable to the end-product.
  • Review printed circuit board layout files to confirm spacings are met.
  • Comb through your list of safety-critical components to ensure they have the necessary ratings and approvals.
  • Review your instruction/installation manuals to ensure they contain the necessary safety precautions.
  • Review the rating label to ensure it contains the required information in the correct format.

It is not 100% guaranteed that if you follow all the above, your product will make it through third-party safety certification of your product on the first attempt. Still, you will be closer to achieving success than had you not engaged in these product safety pre-compliance activities.

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