Mains protection

[AudioFile]

The only component I need to hunt down is the power switch.

Good luck with the build. I used a switch like this, but a cheaper, I think £2.79. https://bit.ly/32WnXgP

[vk6zgo]

In the valve era, rubber gloves were conspicuous by their absense.

Commonsense working procedures reduced the likelihood of dangerous contact with high voltages to a miniscule level.
Rubber gloves which are thin enough not to be an encumbrance don't withstand mechanical damage well, & a breach may compromise any insulating capabilities.

Thicker gloves may increase the risk of personal injury or damage to the equipment during mechanically handling.

[nctnico]

With my bench ISOLATED,  ground is out of equation and
I can touch things just fine.

And this is exactly why the advise to use an isolation transformer without this context is so bad. Experienced people forget how much they have learned and what the underlying principles are of a certain approach. Your way of working goes way beyond just an isolation transformer. Your entire work environment is setup to work relatively safe with floating mains voltages. This isn't true for an ordinary bench or maybe even a kitchen table which may even have a metal frame and sit next to a grounded heater. A typical home/commercial environment is (very) likely designed to be protected by a GFI due to modern building regulations. You'd need to adapt the design of an entire room (or at least a significant part of it) in order to use an isolation transformer safely.

[vk6zgo]

With my bench ISOLATED,  ground is out of equation and
I can touch things just fine.

And this is exactly why the advise to use an isolation transformer without this context is so bad. Experienced people forget how much they have learned and what the underlying principles are of a certain approach. Your way of working goes way beyond just an isolation transformer. Your entire work environment is setup to work relatively safe with floating mains voltages. This isn't true for an ordinary bench or maybe even a kitchen table which may even have a metal frame and sit next to a grounded heater. A typical home/commercial environment is (very) likely designed to be protected by a GFI due to modern building regulations. You'd need to adapt the design of an entire room (or at least a significant part of it) in order to use an isolation transformer safely.

Or have a functional brain!

[PKTKS]

(..)
Or have a functional brain!

Unless you have gone through all the fast changes in the
mid 70s/80s when "SOLID STATE" became available and
really fast the VLSI was introduced...

Unless you had lived that changes forcing you to adapt
your methods and procedures and instruments... you will
not realize how easy is to take for granted the things
available today.

By the late 70s early 80s most OSCILLOSCOPES and
vast majority  of instruments were ISOLATED by design.

Like it or not we lived and changed methods and the BRAIN
for that.. LINEAR PSUs (there were no SMPS "supervisors")
were norm and mostly FULLY ISOLATED.

My old archive still have dozens of scopes and instruments
with LINEAR ISOLATED only mains..

so.. unless you have lived with that .. taking these SMPS
and "differential probes" and  fancy scopes of today and
thinking they are safe by default...

just will not fit the kind of hard methods old school forces you

Attached a typical OSCILLOSCOPE FROM 70s MAIN PSU.

FULLY ISOLATED by default CHASSIs NOT GROUNDED
that kind of care was left to the technician as much as
the methods to touch a 600V HOT tube with their instruments...

Not an easy time to start... lessons learned
BTW this was my first scope... w/a COLINE 100x probe
best and safe enough to go

Paul

[2N3055]

(..)
Or have a functional brain!

Unless you have gone through all the fast changes in the
mid 70s/80s when "SOLID STATE" became available and
really fast the VLSI was introduced...

Unless you had lived that changes forcing you to adapt
your methods and procedures and instruments... you will
not realize how easy is to take for granted the things
available today.

By the late 70s early 80s most OSCILLOSCOPES and
vast majority  of instruments were ISOLATED by design.

Like it or not we lived and changed methods and the BRAIN
for that.. LINEAR PSUs (there were no SMPS "supervisors")
were norm and mostly FULLY ISOLATED.

My old archive still have dozens of scopes and instruments
with LINEAR ISOLATED only mains..

so.. unless you have lived with that .. taking these SMPS
and "differential probes" and  fancy scopes of today and
thinking they are safe by default...

just will not fit the kind of hard methods old school forces you

Attached a typical OSCILLOSCOPE FROM 70s MAIN PSU.

FULLY ISOLATED by default CHASSIs NOT GROUNDED
that kind of care was left to the technician as much as
the methods to touch a 600V HOT tube with their instruments...

Not an easy time to start... lessons learned
BTW this was my first scope... w/a COLINE 100x probe
best and safe enough to go

Paul

WHAT was isolated from WHAT?

You think floating equipment without grounding it anywhere makes it safe ?
Grounding chassis became the norm EXACTLY because it is NOT safe...

I made a lot of pocket money as a kid converting stupid tube guitar amplifiers from 2 wire floating to 3 wire grounded chassis wiring to mains because people were getting shocked touching microphones with their mouths while playing a guitar....

It is called "protective ground" because it prevents chassis to become energized to dangerous voltages..

[PKTKS]

WHAT was isolated from WHAT?

You think floating equipment without grounding it anywhere makes it safe ?
Grounding chassis became the norm EXACTLY because it is NOT safe...

I made a lot of pocket money as a kid converting stupid tube guitar amplifiers from 2 wire floating to 3 wire grounded chassis wiring to mains because people were getting shocked touching microphones with their mouths while playing a guitar....

It is called "protective ground" because it prevents chassis to become energized to dangerous voltages..

Never said an ISOLATED (aka floating) is "SAFE"
as a matter of fact even having the so called "SAFE" ground pin
YOU ARE STILL PRONE .. to the same mistakes.
and they do happen.

I will say again just 2 cents of jambo..:
- an isolated DUT is a very clever option.
- on the lack of a "much" better alternative...
  an isolated equipment will do as fine as battery one.
- concerning things like common ground (BNCs) and
  measures between spots not "related" ...
  you are still required to think of that...

And you are still required to use your
best methods to do safe choices.

Always bounded to what you have.

Summary?  Use what you got and get best results.

Bottom line? The isolator transformers are a cheap
affordable and very good method.

Proper gloves (not that crappy silly ones used by mobile techs)
are a very clever option for anything above 100V.

last not least. Mistakes still happen and a BRAND $1000
will not prevent that. Assuming you have a 3rd pin grounded
is some sort of safety may prevent you some reasoning

PUDIM?  I have used them isolated more than 4 decades just fine.

Paul

[2N3055]

WHAT was isolated from WHAT?

You think floating equipment without grounding it anywhere makes it safe ?
Grounding chassis became the norm EXACTLY because it is NOT safe...

I made a lot of pocket money as a kid converting stupid tube guitar amplifiers from 2 wire floating to 3 wire grounded chassis wiring to mains because people were getting shocked touching microphones with their mouths while playing a guitar....

It is called "protective ground" because it prevents chassis to become energized to dangerous voltages..

Never said an ISOLATED (aka floating) is "SAFE"
as a matter of fact even having the so called "SAFE" ground pin
YOU ARE STILL PRONE .. to the same mistakes.
and they do happen.

I will say again just 2 cents of jambo..:
- an isolated DUT is a very clever option.
- on the lack of a "much" better alternative...
  an isolated equipment will do as fine as battery one.
- concerning things like common ground (BNCs) and
  measures between spots not "related" ...
  you are still required to think of that...

And you are still required to use your
best methods to do safe choices.

Always bounded to what you have.

Summary?  Use what you got and get best results.

Bottom line? The isolator transformers are a cheap
affordable and very good method.

Proper gloves (not that crappy silly ones used by mobile techs)
are a very clever option for anything above 100V.

last not least. Mistakes still happen and a BRAND $1000
will not prevent that. Assuming you have a 3rd pin grounded
is some sort of safety may prevent you some reasoning

PUDIM?  I have used them isolated more than 4 decades just fine.

Paul

 
I will repeat this one more time.

Every time this pops up, there are at least few oldtimers that do this for 40 years that say :  IF YOU KNOW WHAT ARE YOU DOING IT IS SAFE..

THAT IS CRETINOUS STATEMENT!!!!

People that ask those questions in a first place DON'T KNOW WHAT THEY ARE DOING !!

That is why they are asking....

So answer to a general population on the Internet is : NO, IT IS NOT SAFE, you will kill yourself...

You do whatever you think is safe for you. Don't give advice to people how to kill themself.


P.S. : Make note this is not addressed to you, but to this general approach... It's not meant to insult YOU personally, but to make statement..

[PKTKS]

100% agreed - no insults taken.
I have learned the hard way however.

I would say that some folk that would fuss around
a 380V or 600V around without knowing ...

well ... the world is full of insane ones.
no matter how much you advice...

That sort of folk fussing around  without the skills
will find it sooner or later...

I  hope my comments will reach a proper brain
The comments are target:
- a SANE  interested in budget alternatives tech
- a clever folk eager to find new alternatives.

Some will do that with the comments just fine
others..  the odds vary
Paul

[2N3055]

100% agreed - no insults taken.
I have learned the hard way however.

I would say that some folk that would fuss around
a 380V or 600V around without knowing ...

well ... the world is full of insane ones.
no matter how much you advice...

That sort of folk fussing around  without the skills
will find it sooner or later...

I  hope my comments will reach a proper brain
The comments are target:
- a SANE  interested in budget alternatives tech
- a clever folk eager to find new alternatives.

Some will do that with the comments just fine
others..  the odds vary
Paul

Take care!

[vk6zgo]

(..)
Or have a functional brain!

Unless you have gone through all the fast changes in the
mid 70s/80s when "SOLID STATE" became available and
really fast the VLSI was introduced...

Unless you had lived that changes forcing you to adapt
your methods and procedures and instruments... you will
not realize how easy is to take for granted the things
available today.

By the late 70s early 80s most OSCILLOSCOPES and
vast majority  of instruments were ISOLATED by design.

Sorry, but this comment doesn't make sense.

Yes, the internal "guts" of 1970s/'80s Oscilloscopes & other instruments was isolated from the Mains, but this wasn't at all new---my old 1930s General Radio VTVM used a power transformer to provide power to the internal parts.

Over many years of experience, I have never seen an old-style "transformerless" PSU (like in AC/DC radios), used in any test equipment at all.
SMPS used in test instruments also fully isolated the internal components, (outside the PSU itself), from the Mains.

Like it or not we lived and changed methods and the BRAIN
for that.. LINEAR PSUs (there were no SMPS "supervisors")
were norm and mostly FULLY ISOLATED.

My old archive still have dozens of scopes and instruments
with LINEAR ISOLATED only mains..

so.. unless you have lived with that .. taking these SMPS
and "differential probes" and  fancy scopes of today andp
thinking they are safe by default...

just will not fit the kind of hard methods old school forces you

Attached a typical OSCILLOSCOPE FROM 70s MAIN PSU.

FULLY ISOLATED by default CHASSIs NOT GROUNDED
that kind of care was left to the technician as much as
the methods to touch a 600V HOT tube with their instruments...

This was not typical of Oscilloscopes of the 1970s, or any other era, for that matter!
The vast majority of 'scopes did, & do, have a power cord with a Protective Earth connection to the chassis, cabinet & common side of all the internal voltages on the non-Mains side of the transformer.

Other versions of the HIOKI you show in your schematic probably also used a PE connection.

Not an easy time to start... lessons learned
BTW this was my first scope... w/a COLINE 100x probe
best and safe enough to go

Paul

[vk6zgo]

(..)
Or have a functional brain!

Unless you have gone through all the fast changes in the
mid 70s/80s when "SOLID STATE" became available and
really fast the VLSI was introduced...

Unless you had lived that changes forcing you to adapt
your methods and procedures and instruments... you will
not realize how easy is to take for granted the things
available today.

By the late 70s early 80s most OSCILLOSCOPES and
vast majority  of instruments were ISOLATED by design.

Like it or not we lived and changed methods and the BRAIN
for that.. LINEAR PSUs (there were no SMPS "supervisors")
were norm and mostly FULLY ISOLATED.

My old archive still have dozens of scopes and instruments
with LINEAR ISOLATED only mains..

so.. unless you have lived with that .. taking these SMPS
and "differential probes" and  fancy scopes of today and
thinking they are safe by default...

just will not fit the kind of hard methods old school forces you

Attached a typical OSCILLOSCOPE FROM 70s MAIN PSU.

FULLY ISOLATED by default CHASSIs NOT GROUNDED
that kind of care was left to the technician as much as
the methods to touch a 600V HOT tube with their instruments...

Not an easy time to start... lessons learned
BTW this was my first scope... w/a COLINE 100x probe
best and safe enough to go

Paul

WHAT was isolated from WHAT?

You think floating equipment without grounding it anywhere makes it safee ?
Grounding chassis became the norm EXACTLY because it is NOT safe...

I made a lot of pocket money as a kid converting stupid tube guitar amplifiers from 2 wire floating to 3 wire grounded chassis wiring to mains because people were getting shocked touching microphones with their mouths while playing a guitar....

It is called "protective ground" because it prevents chassis to become energized to dangerous voltages..

Before "protective ground"(more commonly called "PE"), it was quite possible for several domestic appliances (& they all pretty much had metal bodies back then) to develop shorts between "Active"(A) & the body, or between "Neutral"(N), & the body.
(I'm using the modern terms, even though they are not quite appropriate to the case of a  fully floating Mains supply).

Both A & N shorted to the body is OK, as that would blow a fuse in the building "fusebox".
One device with the case shorted to A & another with the body shorted to N is a deathtrap.

Example would be a toaster & a metal bodied electric kettle:-
"What's for breakfast dear?"
"Electrocution!" came the stern reply!

By providing a PE linked to the N at the building power entry, & connecting the metal bodies to PE, if A is shorted to the body, the Mains fuse will blow.i


If N is shorted to the body, it will not blow a fuse, but the metal body will not be above PE potential,
so personal protection is provided.
in this second scenario  an RCD  if fitted, will operate  isolating the circuit

[Electro Detective]

WHAT was isolated from WHAT?

You think floating equipment without grounding it anywhere makes it safe ?
Grounding chassis became the norm EXACTLY because it is NOT safe...

I made a lot of pocket money as a kid converting stupid tube guitar amplifiers from 2 wire floating to 3 wire grounded chassis wiring to mains
because people were getting shocked touching microphones with their mouths while playing a guitar....

It is called "protective ground" because it prevents chassis to become energized to dangerous voltages..

More than likely most of those stage zaps and unrehearsed barbeques were also or mainly due to flipped polarity extension cables (stoner muso DIY kamikaze power cords)

and everyone including the gunja/coked/cranked sound and lighting crews plugging into scattered power points from a three phase source,
with blunder potentials of 440 not 240, assuming the Neutral was not wonky or a bootleg neutral

This was in the daze before RCDs were installed, I doubt having 2 wire or three wire would have made much difference back then,
musos and tradies would have got zapped regardless

Still happens today, a lot of places don't have RCDs in their switchboards, or they are sort of bypassed 

and musos and tradies will always do stupid sh!t to make an easy setup task difficult and dangerous that isn't necessary 

i.e. if you're a muso or tradie that loves life, buy a proper RCD/MCB orange cube, test it before each gig, and avoid suss DIY cables   


It's not really that simple, but a good start 

[nctnico]

IMHO it is not very wise to rely on properly wired extension cords and outlets. And what if you are connected between 2 phases where both 'neutral' and 'live' are hot?

[2N3055]

WHAT was isolated from WHAT?

You think floating equipment without grounding it anywhere makes it safe ?
Grounding chassis became the norm EXACTLY because it is NOT safe...

I made a lot of pocket money as a kid converting stupid tube guitar amplifiers from 2 wire floating to 3 wire grounded chassis wiring to mains
because people were getting shocked touching microphones with their mouths while playing a guitar....

It is called "protective ground" because it prevents chassis to become energized to dangerous voltages..

More than likely most of those stage zaps and unrehearsed barbeques were also or mainly due to flipped polarity extension cables (stoner muso DIY kamikaze power cords)

and everyone including the gunja/coked/cranked sound and lighting crews plugging into scattered power points from a three phase source,
with blunder potentials of 440 not 240, assuming the Neutral was not wonky or a bootleg neutral

This was in the daze before RCDs were installed, I doubt having 2 wire or three wire would have made much difference back then,
musos and tradies would have got zapped regardless

Still happens today, a lot of places don't have RCDs in their switchboards, or they are sort of bypassed 

and musos and tradies will always do stupid sh!t to make an easy setup task difficult and dangerous that isn't necessary 

i.e. if you're a muso or tradie that loves life, buy a proper RCD/MCB orange cube, test it before each gig, and avoid suss DIY cables   


It's not really that simple, but a good start 

In EU there is no defined which one is Live and Neutral on a single phase socket. You can freely rotate schuko socket, and both conductors are potentially dangerous. You never know which one is which. Only ground is known.  What you said about 3-phase is correct, I'we seen things go boom because Neutral went wonky or lifted and you got inter-phase voltage ... And yes RCDs are godsend....

[PKTKS]

Other versions of the HIOKI you show in your schematic probably also used a PE connection.

That HIOKI is actually (like 99% of instruments in Brazil) a
rebranded clone.. with some minor adjustments for local stuff.

Vast majority of instruments here are just "rebranded" clones

And still today most rebranded clones like ICEL www.icel.com.br
or MINIPA www.minipa.com.br and some others - just have minor adjustments.

That particular HIOKI and all others of that line  are housed in
FULL METALLIC CASE CHASSIs - with a GROUND screw provided.

Well.. grounding that housing and touching the panel while
attached to some hot tubes (even w/a 100x probe) is not clever.

Today vast majority housing is ABS based or some sort of plastic.
While SMPS are indeed "ISOLATED" flybacks the voltages and power
ratings are rather different from those cheap CRTs.

Never trusted to ground such metallic housing while putting
the probes on tubes horizontal drivers or flybacks...
some bad things could happen.

... isolating stuff and thinking a bench gig setup always help
but will never prevent you from making the classic mistakes however...

Paul

[Black Phoenix]

In EU there is no defined which one is Live and Neutral on a single phase socket. You can freely rotate schuko socket, and both conductors are potentially dangerous. You never know which one is which. Only ground is known.  What you said about 3-phase is correct, I'we seen things go boom because Neutral went wonky or lifted and you got inter-phase voltage ... And yes RCDs are godsend....

True and False. Yes you can rotate the plug and it will work, although by norm (I'm citing the Portuguese Electrical Norms, because is the ones I learned on my degree) the Neutral is on the left and the Live is on the right. You can always check of course but no electrical installation is approved and allowed to enter production if they are exchanged, even if it is one plug only. Same way as you can make an ethernet cable anyway you want, just have the colours be equal in both ends if you want a straight cable, but the norm have 2 different methods, EIA/TIA 568A or EIA/TIA 568B. It sure helps a lot to diagnose.

That doesn't happen with the UK Norm, were the Plug only fits one way and only that way. Of course if the socket is incorrectly wired, well nothing can't be done against it. IMHO the UK Electrical Norms are way better, a switch per plug and the plug is always fused. But that's my opinion.

[2N3055]

In EU there is no defined which one is Live and Neutral on a single phase socket. You can freely rotate schuko socket, and both conductors are potentially dangerous. You never know which one is which. Only ground is known.  What you said about 3-phase is correct, I'we seen things go boom because Neutral went wonky or lifted and you got inter-phase voltage ... And yes RCDs are godsend....

True and False. Yes you can rotate the plug and it will work, although by norm (I'm citing the Portuguese Electrical Norms, because is the ones I learned on my degree) the Neutral is on the left and the Live is on the right. You can always check of course but no electrical installation is approved and allowed to enter production if they are exchanged, even if it is one plug only. Same way as you can make an ethernet cable anyway you want, just have the colours be equal in both ends if you want a straight cable, but the norm have 2 different methods, EIA/TIA 568A or EIA/TIA 568B. It sure helps a lot to diagnose.

That doesn't happen with the UK Norm, were the Plug only fits one way and only that way. Of course if the socket is incorrectly wired, well nothing can't be done against it. IMHO the UK Electrical Norms are way better, a switch per plug and the plug is always fused. But that's my opinion.

You are correct, socket is standardized, but since you can rotate plug, devices can receive whatever.
And if you use extension cords, those can be any combination...

I agree that UK plug is better, it is  indexed, and it has built in high break capacity fuse...

[madires]

True and False. Yes you can rotate the plug and it will work, although by norm (I'm citing the Portuguese Electrical Norms, because is the ones I learned on my degree) the Neutral is on the left and the Live is on the right. You can always check of course but no electrical installation is approved and allowed to enter production if they are exchanged, even if it is one plug only.

In Germany it can be both ways. Some sparkies have a preference for left, some for right, and other don't care. There's no requirement for L being left or right. As 2N3055 already has explained, it doesn't matter anyway because we don't have indexed plugs (besides 3 phase connectors).

[nctnico]

That doesn't happen with the UK Norm, were the Plug only fits one way and only that way. Of course if the socket is incorrectly wired, well nothing can't be done against it. IMHO the UK Electrical Norms are way better, a switch per plug and the plug is always fused. But that's my opinion.

That is all nice and dandy in theory but in practice you won't know if a socket is wired correctly or not. A single phase device will work just fine with live/neutral reversed or even 2 phases. Nobody cares about the wiring. So the best way to deal with single phase mains is to assume both wires are dangerous.

[Black Phoenix]

That is all nice and dandy in theory but in practice you won't know if a socket is wired correctly or not. A single phase device will work just fine with live/neutral reversed or even 2 phases. Nobody cares about the wiring. So the best way to deal with single phase mains is to assume both wires are dangerous.

Totally agree with it... When for some reason I need to check some socket I always assume it is energised even if It was me who turned off the circuit breaker. I always check with a DMM to be really sure.

[madires]

Be aware that a DMM without low-Z mode is the wrong tool for mains because the meter's high input impedance and capacitive coupling between wires can screw up the measurement. The best tool for that is a Duspol or a similar tester.

[Black Phoenix]

Be aware that a DMM without low-Z mode is the wrong tool for mains because the meter's high input impedance and capacitive coupling between wires can screw up the measurement. The best tool for that is a Duspol or a similar tester.

I'm sure that between my 87V and my 289 I have one with it. But thank you anyway for the info.

[Electro Detective]

Be aware that a DMM without low-Z mode is the wrong tool for mains because the meter's high input impedance and capacitive coupling between wires can screw up the measurement. The best tool for that is a Duspol or a similar tester.

I'm sure that between my 87V and my 289 I have one with it. But thank you anyway for the info.

no Low-Z mode for 87V, but 289 has it (the first far left switch setting) 

It's a fixed 0 to 1000 volt range only (no auto or manual range) with both AC and DC readouts, and gets it done 
 
 
Take note that in Low-Z mode with any meter, you will trip the RCD/GFCI if probing between a line and earth ground
which may score you nil readings and some nasty vibes from others on the premises,
how do I know this...?   

[madires]

It's not a bug, it's a feature called RCD test.