Ask Lewis Bass: A Question About F47 Testing Semiconductor Equipment

Ask Lewis Bass: A Question About F47 Testing Semiconductor Equipment

Welcome to another blog in our ongoing series, Ask Lewis Bass!

This series features actual submitted questions from companies in the industries we provide engineering safety consulting services to.

Topics covered include those associated with our work in 3rd party field labeling, SEMI S2/S8/EMC/F47 testing and design, CE Marking evaluations, and general engineering safety consulting questions.


Hi Lewis Bass, I have an interesting situation concerning the need for completing F47 testing on a machine that is now delivered to the client, but that we no longer have access to, due to covid-19 restrictions.

Here is the situation we are encountering below and our ideas on how to proceed with the F47 testing by proxy:

  • A company purchased a model of our system with Line Conditioner “1”.
  • We will have in our factory the same model with Line Conditioner “2” and access to Line Conditioner “1”.
  • Our client will definitely want us to inspect the model and configuration as close to their model and configuration as possible, however we will not have that exact model in our factory.
  • One idea we have been tossing around is, to minimize differences, to test the the current machine model in our factory with both line conditioners (1 and 2).  Model 2 is used going forward and will be applicable to future new systems.  Model 1 would be for our client.
  • Another possibility/question for you is about potentially applying the certification to a family of systems by using similarity.  Is that possible? If so, what would it require?


Asked by Emily in Milpitas, CA


Lewis Bass:

Thanks for the thought provoking question, Emily.

The answer is actually fairly straightforward even with taking into account the vagaries and complexity of your current situation. With regards to line conditioners “1” or “2” – I’m not sure if this means a line filter or a UPS for the same tool’s power supply, but regardless, when performing F47 testing, the testing is linked into the tool no matter which “line conditioner” is being used. In this case, either configuration will be valid.

Also, as long as the main AC power supply and accessories (like filters or UPS) are being used in all tools that are electrically the same, then only one F47 test should be good enough for both.

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