EMI

What is performance criterion A/B/C/D in EMI tests?

When doing EMI immunity tests, you will often encounter specifications that your device should e.g. “meet Performance Criterion B during the ESD test”.

The performance criteria, as defined in the IEC 61000 series of standards, e.g. IEC 61000-4-5:2014 (surge test standard) are:

  • Performance Criterion A: Your device continues to function normally during the test (i.e. no interruption)
  • Performance Criterion B: Your device shows a malfunction but recovers automatically  (without user interaction) and then continues to operate normally.
  • Performance Criterion C: Your devices shows a malfunction, but continues to operate normally only after user interaction (e.g. the user resets the device)
  • Performance Criterion D: Your device has a permanent malfunction (e.g. some part of its hardware has been destroyed, or data being lost) which cannot be recovered from even after user interaction.

Additionally note that your device must not become dangerous under any circumstances, even if destroyed as per Performance Criterion D.

What defines a malfunction is up to the manufacturer of the device, but usually it’s related to whatever function it is advertised to perform. The manufacturer should define

Example: 230V LED bulb

  • Performance Criterion A: LED Bulb continues to operate normally after the test
  • Performance Criterion B: Bulb flickers during the test, but operates normally after the test
  • Performance Criterion B: Bulb is less bright during the test but then operates normally.
  • Performance Criterion B: Bulb blinks 10 times slowly but then operates normally
  • Performance Criterion B: Bulb stays off for 20 seconds after the test but then goes back to normal.
  • Performance Criterion C: Bulb goes out, but works normally after you switch off and on the power
  • Performance Criterion C: Bulb continues to blink, but works normally after you switch off and on the power
  • Performance Criterion D: Bulb goes out and does not turn on after you switch off and on the power
  • Performance Criterion D: Bulb blinks after the test and continues to blink even if you switch off and on the power.

As a manufacturer you could define e.g.

  • that the light intensity should be judged by eye (i.e. it should not be significantly dimmer after the test than a new bulb)
  • that a luxmeter needs to be used to judge the light intensity after tests
  • that the bulb may stay off for at most 15 seconds

and so on. In all but the most demanding applications, manufacturers define the criteria conservatively in order to increase the likelihood of passing the test. Since EMI laboratory tests are expensive, it’s in your best interest as a manufacturer not to over-define the criteria.

Posted by Uli Köhler in Electronics, EMI