I am not sure I really agree with this, the double insulation mark
indicates that there is two levels of insulator (case materials, fiberglass
/ mylar sheeting, cable insulation etc) between the user and anything live.
A double insulated appliance (such as most consumer electronics /
appliances) should* not* need or indeed have an earth connection. For more
info on that, see here : http://www.double-insulated.com/
Now, if you want an *electrically isolated output* the only true way of
doing this is galvanomically - either an old style 50Hz transformer /
rectifier (heavy power brick kind of thing) or a good quality switching
supply with a guaranteed isolation level. You can then pass through the
true earth to your chassis and, since it is isolated, peg the neutral
output to earth as well - though I would argue this actually reduces the
safety somewhat, I would always prefer to leave the isolated supply
floating, that way you can contact either conductor and be safe.
The symbol you really want to see, is two overlapping circles like those
seen on this page : http://sc3c.iec.ch/ap60417/TC96gif.html
Hopefully I have not spread any inaccuracies here, I recently did a large
commercial project involving many 3kva isolating transformers so had to
read up a bit on all this, but that was a few months ago now...
On Sunday, 18 September 2016 20:25:39 UTC+1, nixiebunny wrote:
> The mark that indicates that the input and output are fully isolated
> from each other is a square within another square, called "double
> insulated". If you don't see that mark, and you see a UL or ETL mark,
> then it's reasonable to assume that the barrel is grounded, because
> otherwise the unit wouldn't pass UL or ETL testing.
> On 9/18/16 12:06 PM, Nicholas Stock wrote:
> > Hi Fellow lovers of neon...
> > I have a question from a bit of a novice here (me..). I'm working on a
> > project that involves a dekatron or two and want to make sure that
> > there's some degree of safety when placed inside a metal case and HV is
> > involved. Instead of an IEC inlet and transformer inside the device, I
> > want to use a 12V DC supply with a ground connection or -ve side tied to
> > Earth. I found the following picture in my PSU stash and checked the
> > continuity of the barrel side of the supply and Earth and there's
> > continuity. Can anyone tell me which symbol on the PSU denotes this
> > (instead of it being a truly isolated supply) or if anyone has any other
> > ideas about how to go about a 'safe' 12V DC supply (I looked at the
> > medical grade PSU's with 4 pin DIN and earthed shell, but they're quite
> > expensive).
> > Apologies if this seems like a stupid question...
> > Thanks,
> > Nick
> > image1.JPG
> > --
> > You received this message because you are subscribed to the Google
> > Groups "neonixie-l" group.
> > To unsubscribe from this group and stop receiving emails from it, send
> > To post to this group, send email to neoni...@googlegroups.com
> > To view this discussion on the web, visit
> > <
> > For more options, visit https://groups.google.com/d/optout.
> David Forbes, Tucson AZ
You received this message because you are subscribed to the Google Groups
To unsubscribe from this group and stop receiving emails from it, send an email
To post to this group, send an email to email@example.com.
To view this discussion on the web, visit
For more options, visit https://groups.google.com/d/optout.