The 20J may be overkill but all you safety experts posting here already know where that number came from.
Hmmm. Is it because that is about the energy used in a defibrillator or because it matches up with the output of an electric fence charger (a powerful one)?
You may not agree but hopefully you at least now have some understanding why I will continue to call my transients low energy.
Thanks for the detailed explanation. Low is a relative term, of course, and relative to MOV ratings, IEC transients, etc, 20J is obviously much lower. The comment I responded to was talking about damage to semiconductors, etc and there 20J will pop the lid on quite a few devices. I think the low energy events he was referring to are the sorts of noise, ESD or spikes that might get through normal filtering for reasons other than that they overwhelm the protection systems by simply exceeding their voltage or energy limitations. Piezo igniters and 220MHz RF come to mind....
Also thanks for the explanation Joe, but I was also talking similar small energy surges, where basically only the fast rise time is what counts, and the only interesting parameter of the protection circuit is how fast they act, and what is the max voltage with the small energy spikes which will be let through.
The Up parameter is mostly the only thing specified at all, but that is at the max amp. rating so usualy no info about the reaction to the much weaker stuff.
Because even if a surge protector meets its Ka and thousend joule specs, there is no word about how it filters out the small surges which eventually leads to failures in electronics.
The surge protector manufacturer is not interested in building a circuit which clamps everything all the time, because than the MOVs etc eventually wear out, so I suppose most of the small spikes will hit the protection circuits of the electronics. But this is only a theory because not much testing going on on ACTUAL surge arrestors and input protection circuits on the net. But I understand if you are not interested in using the... Joe-gen for it.
And here is an important announcment for The Uni-t Ut60e Protection Circuit Variations Collector Society:
(short: TUUPCVCS)
There is a possibly really unique version aviable in Sweden, the Clas Ohlsson edition. Which is a kind of store chain. Being a swedish version I suppose maybe it comes with REAL fuses from the Nobel factories.
(Note for the Fluke test guys: Reinforce the blast shield if testing those!)
Being a rarity and a collectors item soon, I consider sending it to anyone for a symbolic 2000 Euro price. (Shipping included) It would be a solid investmen in these hectic days! (No I don't have it yet, so can't post pictures.)