I'm trying to understand the meaning of

8 x 20-µs and 10 x 1000-µs

standardized transient impulses (or sometimes it's called a waveform). But what does it actually mean. Why is there a multiplier in front of the time unit?

The quoted line above is constantly mentioned in surge testing document. But no where in the document does it mention what is the meaning of it.

Most Google search results point to Datasheet values. Maybe I'm searching for the wrong search term.


"8 x 20us" means a transient that rises in 8us and decays to a 50% value in 20us: -

enter image description here

There are many specs for transient testing and 10 - 1000us is another. They are usually referenced as tests done on electrical equipment to prove said equipment is capable of withstanding surges associated with lightning strikes or similar phenomenon.

Here is a good article from Wiki EIG (electrical installation guide)

  • \$\begingroup\$ hmm.. I just found an answer, but I can't verify it. It's apparently conflicting with yours. It states, overall pulse width is 20uS with rise time (0 - 100%) of 8us. Can you point to me your references (like Standard Documents or Ratings Document)? \$\endgroup\$ – Choe Apr 24 '13 at 7:23
  • \$\begingroup\$ Great source! Thanks for the update! Where did you get the image of yours from by the way for the above answer? \$\endgroup\$ – Choe Apr 24 '13 at 7:39
  • \$\begingroup\$ Google "8/20μs waveform" \$\endgroup\$ – Andy aka Apr 24 '13 at 7:40
  • \$\begingroup\$ This answer is not in conflict with the first comment. See en.wikipedia.org/wiki/Full_width_at_half_maximum \$\endgroup\$ – JJohnston2 Sep 15 '16 at 17:21

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