I got involved with someone who was wiring a external LED Floodlight into
some old wiring.

The light didn't work and from a brief tracing of the cable back to the
switch I suspect it has 2 lives.


Question:

Can I use my cheap digital meter to check between live and earth to prove
this? Could it trip an ELCB if there is one (not checked yet)

On Tue, 18 Jul 2017 10:48:27 GMT, DerbyBorn
wrote:

I got involved with someone who was wiring a external LED Floodlight into
some old wiring.

The light didn't work and from a brief tracing of the cable back to the
switch I suspect it has 2 lives.


Question:

Can I use my cheap digital meter to check between live and earth to prove
this?

Yes (on 240+ AC volts), other than it wouldn't necessarily confirm
either was a real live or the load side of an incandescent lamp in
series.

Could it trip an ELCB if there is one (not checked yet)

On the AC volts range the internal impedance of a DMM is likely to be
pretty high so unlikely to provide a sufficiently high current to trip
an ELCB in any usage combination (even L to E etc).

Cheers, T i m

On 18/07/2017 11:48, DerbyBorn wrote:
I got involved with someone who was wiring a external LED Floodlight into
some old wiring.

The light didn't work and from a brief tracing of the cable back to the
switch I suspect it has 2 lives.


Question:

Can I use my cheap digital meter to check between live and earth to prove
this? Could it trip an ELCB if there is one (not checked yet)

The input impedance on a DVM should be very high, and so it will not
trip a RCD.

(In fact you can see a related problem to this sometimes with DVMs,
where the impedance is so high that you see phantom lives on what are in
reality just floating wires that are being loosely capacitively coupled
to live).


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

DerbyBorn submitted this idea :
Can I use my cheap digital meter to check between live and earth to prove
this? Could it trip an ELCB if there is one (not checked yet)

Normally no, a digital meter has quite a high input resistance so they
draw much less than the 30mA needed to trip an RCD - but if there are
other leaks to ground bring it close to 30mA, a meter might then cause
a trip.

If a neutral is open circuit, it is quite possible for both L and N to
seem to be live. The only certain way to check what is what, is with
something which draws a more sensible load than a digital meter. A test
lamp or similar, might be more suitable.

On Tuesday, 18 July 2017 11:48:31 UTC+1, DerbyBorn wrote:

I got involved with someone who was wiring a external LED Floodlight into
some old wiring.

The light didn't work and from a brief tracing of the cable back to the
switch I suspect it has 2 lives.


Question:

Can I use my cheap digital meter to check between live and earth to prove

yes

this? Could it trip an ELCB if there is one (not checked yet)

no


NT

On 18/07/2017 11:48, DerbyBorn wrote:

I got involved with someone who was wiring a external LED Floodlight into
some old wiring.

The light didn't work and from a brief tracing of the cable back to the
switch I suspect it has 2 lives.

You would expect switched live and a neutral.

Question:

Can I use my cheap digital meter to check between live and earth to prove
this? Could it trip an ELCB if there is one (not checked yet)

It would be wiser to measure from live to neutral if at all possible. I
doubt that a decent high impedance voltmeter would trip an ELCB but you
have to consider the possibility that your leads are less than perfect.

I prefer a good old mains testing neon screwdriver (even though they are
frowned upon these days). If the neon glows it ain't safe to touch.

--
Regards,
Martin Brown

On 18/07/2017 12:47, Martin Brown wrote:

I prefer a good old mains testing neon screwdriver (even though they are
frowned upon these days). If the neon glows it ain't safe to touch.

It's your choice but IMHO that advice is wrong in several ways -
starting with the fact that you have to touch the cable with the
screwdriver and that alone can be dangerous. See
http://wiki.diyfaq.org.uk/index.php/Neon_screwdriver
--
Robin
reply-to address is (intended to be) valid

On 18/07/2017 13:01, Robin wrote:
On 18/07/2017 12:47, Martin Brown wrote:

I prefer a good old mains testing neon screwdriver (even though they
are frowned upon these days). If the neon glows it ain't safe to touch.

It's your choice but IMHO that advice is wrong in several ways -
starting with the fact that you have to touch the cable with the
screwdriver and that alone can be dangerous. See
http://wiki.diyfaq.org.uk/index.php/Neon_screwdriver

If you store it unwisely or hold it in your mouth then all bets are off.

The advice there to test on a known live wire either side is good.

--
Regards,
Martin Brown

On 18/07/2017 12:47, Martin Brown wrote:
On 18/07/2017 11:48, DerbyBorn wrote:

I got involved with someone who was wiring a external LED Floodlight into
some old wiring.

The light didn't work and from a brief tracing of the cable back to the
switch I suspect it has 2 lives.

You would expect switched live and a neutral.

Question:

Can I use my cheap digital meter to check between live and earth to prove
this? Could it trip an ELCB if there is one (not checked yet)

It would be wiser to measure from live to neutral if at all possible. I
doubt that a decent high impedance voltmeter would trip an ELCB but you
have to consider the possibility that your leads are less than perfect.

I prefer a good old mains testing neon screwdriver (even though they are
frowned upon these days). If the neon glows it ain't safe to touch.

With those, if it glows its either live or dead. If it doesn't glow then
its definitely either live or dead.

You call ;-)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Tuesday, 18 July 2017 12:36:33 UTC+1, John Rumm wrote:
On 18/07/2017 11:48, DerbyBorn wrote:


Question:

Can I use my cheap digital meter to check between live and earth to prove
this? Could it trip an ELCB if there is one (not checked yet)

The input impedance on a DVM should be very high, and so it will not
trip a RCD.

Provided it's not on the current metering option, some students to the to see what current is coming out of the power supply. ;-{

Should be obvious I know but a studetn wants to check if 5V is coming out off the PSU and then how much current !.



(In fact you can see a related problem to this sometimes with DVMs,
where the impedance is so high that you see phantom lives on what are in
reality just floating wires that are being loosely capacitively coupled
to live).

Yes I saw this with my DVM when I was trying to check if the old mains wiring was really disconnected, I got volts even though the old wiring wasnlt connected to anything.

DerbyBorn has brought this to us :
Can I use my cheap digital meter to check between live and earth to prove
this? Could it trip an ELCB if there is one (not checked yet)

Be aware that shorting neutral to earth can also trip an RCD. There is
usually some voltage differential between the two, shorting them could
cause more than the 30mA to flow and an RCD to trip.

Robin submitted this idea :
It's your choice but IMHO that advice is wrong in several ways - starting
with the fact that you have to touch the cable with the screwdriver and that
alone can be dangerous. See
http://wiki.diyfaq.org.uk/index.php/Neon_screwdriver

--

Another reason is that the glow can be quite feeble too, improved by
you yourself touching the earth.

On Tuesday, 18 July 2017 12:38:46 UTC+1, Harry Bloomfield wrote:
DerbyBorn submitted this idea :
Can I use my cheap digital meter to check between live and earth to prove
this? Could it trip an ELCB if there is one (not checked yet)

Normally no, a digital meter has quite a high input resistance so they
draw much less than the 30mA needed to trip an RCD - but if there are
other leaks to ground bring it close to 30mA, a meter might then cause
a trip.

If a neutral is open circuit, it is quite possible for both L and N to
seem to be live. The only certain way to check what is what, is with
something which draws a more sensible load than a digital meter. A test
lamp or similar, might be more suitable.

Almost none of that's good advice either. An analogue meters takes typically 50uA at FSD, digitals far less. No ELCB is going to give a damn, even an RCD wouldn't either.

The lamp advice is also bad. It also could electrocute someone else in the building under some circumstances.

This is not an electronics group. Some contributors know what they're talking about, some just think they do.


NT

explained :
Almost none of that's good advice either. An analogue meters takes typically
50uA at FSD, digitals far less. No ELCB is going to give a damn, even an RCD
wouldn't either.

If it were close to the limit?


The lamp advice is also bad. It also could electrocute someone else in the
building under some circumstances.

A test lamp which actually draws some current, is standard electricity
board issue.


This is not an electronics group. Some contributors know what they're talking
about, some just think they do.

Then I would suggest you keep your advice to yourself.

On Tuesday, 18 July 2017 17:39:22 UTC+1, Harry Bloomfield wrote:
tabbypurr explained :

Almost none of that's good advice either. An analogue meters takes typically
50uA at FSD, digitals far less. No ELCB is going to give a damn, even an RCD
wouldn't either.

If it were close to the limit?

If you think a 1+ megohm DMM input is going to make any detectable difference to an ELCB or even a 30mA RCD, you're free to use your brain.

The lamp advice is also bad. It also could electrocute someone else in the
building under some circumstances.

A test lamp which actually draws some current, is standard electricity
board issue.

For people that know how to use them safely & effectively. Not for people that need to ask here how to find out what's wrong with a power feed to a light. Don't tell me you can't see how it could go wrong.

This is not an electronics group. Some contributors know what they're talking
about, some just think they do.

Then I would suggest you keep your advice to yourself.

I'm sure you mean well, but you've not really thought your advice through. This what often happens with threads on a topic where most contributors simply do not have the relevant expertise.

I can see no point wasting further time.


NT

In article , Harry Bloomfield
wrote:
explained :
Almost none of that's good advice either. An analogue meters takes
typically 50uA at FSD, digitals far less. No ELCB is going to give a
damn, even an RCD wouldn't either.

If it were close to the limit?


The lamp advice is also bad. It also could electrocute someone else in
the building under some circumstances.

A test lamp which actually draws some current, is standard electricity
board issue.

We haven't had an Electricity Board in England since 1990. Possibly
technology has moved on in the intervening 27 years.

--
from KT24 in Surrey, England

In article ,
wrote:
On Tuesday, 18 July 2017 17:39:22 UTC+1, Harry Bloomfield wrote:
tabbypurr explained :

Almost none of that's good advice either. An analogue meters takes
typically 50uA at FSD, digitals far less. No ELCB is going to give a
damn, even an RCD wouldn't either.

If it were close to the limit?

If you think a 1+ megohm DMM input is going to make any detectable
difference to an ELCB or even a 30mA RCD, you're free to use your brain.

The lamp advice is also bad. It also could electrocute someone else
in the building under some circumstances.

A test lamp which actually draws some current, is standard electricity
board issue.

For people that know how to use them safely & effectively. Not for people
that need to ask here how to find out what's wrong with a power feed to a
light. Don't tell me you can't see how it could go wrong.

This is not an electronics group. Some contributors know what they're
talking about, some just think they do.

Then I would suggest you keep your advice to yourself.

I'm sure you mean well, but you've not really thought your advice
through. This what often happens with threads on a topic where most
contributors simply do not have the relevant expertise.

or they know the subject so well that they omit things which may be
necessary for other people to know.

--
from KT24 in Surrey, England

On 18/07/2017 16:33, wrote:
On Tuesday, 18 July 2017 12:38:46 UTC+1, Harry Bloomfield wrote:
DerbyBorn submitted this idea :
Can I use my cheap digital meter to check between live and earth
to prove this? Could it trip an ELCB if there is one (not checked
yet)

Normally no, a digital meter has quite a high input resistance so
they draw much less than the 30mA needed to trip an RCD - but if
there are other leaks to ground bring it close to 30mA, a meter
might then cause a trip.

If a neutral is open circuit, it is quite possible for both L and N
to seem to be live. The only certain way to check what is what, is
with something which draws a more sensible load than a digital
meter. A test lamp or similar, might be more suitable.

Almost none of that's good advice either.

No, I disagree.

An analogue meters takes
typically 50uA at FSD, digitals far less. No ELCB is going to give a
damn, even an RCD wouldn't either.

Its not going to trip an RCD, but the current draw on a moving coil
meter is often sufficient to avoid a false live reading on a floating
but capacitively coupled wire.

The lamp advice is also bad. It also could electrocute someone else
in the building under some circumstances.

Since you will connect your lamp from a known good neutral to an unknown
wire, then the risk posed to normal occupants of the building (i.e. not
others carrying out electrical maintenance at the same time) will be
vanishingly small.

This is not an electronics group. Some contributors know what they're
talking about, some just think they do.

and some need to climb down off their high horse...


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

on 18/07/2017, charles supposed :
We haven't had an Electricity Board in England since 1990. Possibly
technology has moved on in the intervening 27 years.

I'm sure you knew what I meant.

was thinking very hard :
If you think a 1+ megohm DMM input is going to make any detectable difference
to an ELCB or even a 30mA RCD, you're free to use your brain.

Camels and straws?

I qualified my statement with - "Normally no, a digital meter has quite
a high input resistance so they draw much less than the 30mA needed to
trip an RCD - but if there are other leaks to ground bring it close to
30mA, a meter might then cause a trip."

Depends on the meter really, Does it have high voltage AC ranges and decent
leads?
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"DerbyBorn" wrote in message
2.236...
I got involved with someone who was wiring a external LED Floodlight into
some old wiring.

The light didn't work and from a brief tracing of the cable back to the
switch I suspect it has 2 lives.


Question:

Can I use my cheap digital meter to check between live and earth to prove
this? Could it trip an ELCB if there is one (not checked yet)

Which is why its often a good idea to wire up a small wattage bulb on a
cable and see if it lights blows the trip or some other strange effect like
light another bulb a bit somewhere else in the house. Don't mock it has
happened.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"John Rumm" wrote in message
...
On 18/07/2017 11:48, DerbyBorn wrote:
I got involved with someone who was wiring a external LED Floodlight into
some old wiring.

The light didn't work and from a brief tracing of the cable back to the
switch I suspect it has 2 lives.


Question:

Can I use my cheap digital meter to check between live and earth to prove
this? Could it trip an ELCB if there is one (not checked yet)

The input impedance on a DVM should be very high, and so it will not trip
a RCD.

(In fact you can see a related problem to this sometimes with DVMs, where
the impedance is so high that you see phantom lives on what are in reality
just floating wires that are being loosely capacitively coupled to live).


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Tue, 18 Jul 2017 12:47:09 +0100, Martin Brown wrote:

I prefer a good old mains testing neon screwdriver (even though they are
frowned upon these days). If the neon glows it ain't safe to touch.

It may be perfectly safe, though. One of the many problems with neon
screwdrivers is that they don't put enough load on the cable to establish
if the current causing the bulb to light is there in sufficient quantity;
as someone else said it may be just coupled from an adjacent live and
completely harmless.

--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

On Tue, 18 Jul 2017 19:14:19 +0100, Brian Gaff wrote:

Depends on the meter really, Does it have high voltage AC ranges and
decent leads?
Brian

I can't believe no one's said anything about this aspect until now. The
OP said he had a cheap and nasty DMM - might be one of these 3.99 jobs
from China - and such a meter is *not* safe to carry out mains
measurements with. You will see on the front what category it is claimed
to be rated for (usually 3 or 4 at a specified voltage). IGNORE that,
throw the ****ing thing over the nearest hedge and buy a meter with the
required proper internal protections for dealing with high energy voltage
sources.



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

On Tue, 18 Jul 2017 13:51:51 +0000, Huge wrote:

Anyone else remember those public information films about working with
HT?

https://www.youtube.com/watch?v=G2RPu4Hs_qo

Wow! More suspense than a Hitchcock film! I'd always thought of Elf &
Safe Tea as a very recent phenomenon and would have expected these power
engineers to be a bit sloppy about such procedures but overall that was
very tight, I thought.
Nice to see the old Tek 555 scopes of the day. Had one once myself.
Beautifully engineered they were. sniff



--
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the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

On Tuesday, 18 July 2017 18:41:31 UTC+1, John Rumm wrote:
On 18/07/2017 16:33, tabbypurr wrote:
On Tuesday, 18 July 2017 12:38:46 UTC+1, Harry Bloomfield wrote:
DerbyBorn submitted this idea :

Can I use my cheap digital meter to check between live and earth
to prove this? Could it trip an ELCB if there is one (not checked
yet)

Normally no, a digital meter has quite a high input resistance so
they draw much less than the 30mA needed to trip an RCD - but if
there are other leaks to ground bring it close to 30mA, a meter
might then cause a trip.

If a neutral is open circuit, it is quite possible for both L and N
to seem to be live. The only certain way to check what is what, is
with something which draws a more sensible load than a digital
meter. A test lamp or similar, might be more suitable.

Almost none of that's good advice either.

No, I disagree.

An analogue meters takes
typically 50uA at FSD, digitals far less. No ELCB is going to give a
damn, even an RCD wouldn't either.

Its not going to trip an RCD,

exactly, it was bull****.

but the current draw on a moving coil
meter is often sufficient to avoid a false live reading on a floating
but capacitively coupled wire.

of course. FWIW the OP asked about a digital meter, not analogue, and they have way higher input impedance, so that advantage does not apply.

The lamp advice is also bad. It also could electrocute someone else
in the building under some circumstances.

Since you will connect your lamp from a known good neutral to an unknown
wire, then the risk posed to normal occupants of the building (i.e. not
others carrying out electrical maintenance at the same time) will be
vanishingly small.

Let's be clear. The light fitting has been miswired but the OP doesn't know what's going on. You can place complete faith in the OP's decision of which wires to connect it to, and the odds are it won't go badly, but I personally don't share that faith. The OP does not demonstrate enough expertise to know how it could electrocute someone and how to avoid it doing so. Yes, it most likely won't, but it can. I would thus suggest the meter rather than the lamp.


This is not an electronics group. Some contributors know what they're
talking about, some just think they do.

and some need to climb down off their high horse...

Some, and I don't mean you, just need to stop wasting other people's time.


NT

On Tuesday, 18 July 2017 18:58:03 UTC+1, Harry Bloomfield wrote:
tabbypurr was thinking very hard :

If you think a 1+ megohm DMM input is going to make any detectable difference
to an ELCB or even a 30mA RCD, you're free to use your brain.

Camels and straws?

I qualified my statement with - "Normally no, a digital meter has quite
a high input resistance so they draw much less than the 30mA needed to
trip an RCD - but if there are other leaks to ground bring it close to
30mA, a meter might then cause a trip."

I see you've not used your brain.

On Tuesday, 18 July 2017 23:41:30 UTC+1, Cursitor Doom wrote:
On Tue, 18 Jul 2017 19:14:19 +0100, Brian Gaff wrote:

Depends on the meter really, Does it have high voltage AC ranges and
decent leads?
Brian

I can't believe no one's said anything about this aspect until now. The
OP said he had a cheap and nasty DMM - might be one of these 3.99 jobs
from China - and such a meter is *not* safe to carry out mains
measurements with. You will see on the front what category it is claimed
to be rated for (usually 3 or 4 at a specified voltage). IGNORE that,
throw the ****ing thing over the nearest hedge and buy a meter with the
required proper internal protections for dealing with high energy voltage
sources.

Does a 5A fused lighting circuit qualify as high energy? A 100A fused incomer certainly would.


NT

On Tuesday, 18 July 2017 23:41:30 UTC+1, Cursitor Doom wrote:
On Tue, 18 Jul 2017 19:14:19 +0100, Brian Gaff wrote:

Depends on the meter really, Does it have high voltage AC ranges and
decent leads?
Brian

I can't believe no one's said anything about this aspect until now. The
OP said he had a cheap and nasty DMM - might be one of these 3.99 jobs
from China - and such a meter is *not* safe to carry out mains
measurements with. You will see on the front what category it is claimed
to be rated for (usually 3 or 4 at a specified voltage). IGNORE that,
throw the ****ing thing over the nearest hedge and buy a meter with the
required proper internal protections for dealing with high energy voltage
sources.

Does a 5A fused lighting circuit qualify as high energy? A 100A fused incomer certainly would.


NT

On 18/07/2017 23:32, Cursitor Doom wrote:
On Tue, 18 Jul 2017 12:47:09 +0100, Martin Brown wrote:

I prefer a good old mains testing neon screwdriver (even though they are
frowned upon these days). If the neon glows it ain't safe to touch.

It may be perfectly safe, though. One of the many problems with neon
screwdrivers is that they don't put enough load on the cable to establish
if the current causing the bulb to light is there in sufficient quantity;
as someone else said it may be just coupled from an adjacent live and
completely harmless.

Or you might be coupled to something live and the thing under test
actually live. The screwdriver will tell you its safe!


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

has brought this to us :
I see you've not used your brain.

I see you are being offensive and for no good reason.

On Wednesday, 19 July 2017 03:43:10 UTC+1, John Rumm wrote:
On 18/07/2017 23:32, Cursitor Doom wrote:
On Tue, 18 Jul 2017 12:47:09 +0100, Martin Brown wrote:

I prefer a good old mains testing neon screwdriver (even though they are
frowned upon these days). If the neon glows it ain't safe to touch.

It may be perfectly safe, though. One of the many problems with neon
screwdrivers is that they don't put enough load on the cable to establish
if the current causing the bulb to light is there in sufficient quantity;
as someone else said it may be just coupled from an adjacent live and
completely harmless.

Or you might be coupled to something live and the thing under test
actually live. The screwdriver will tell you its safe!

And it's trivially easy to be capacitively coupled to something live.


NT

On Tue, 18 Jul 2017 22:37:30 -0000 (UTC), Cursitor Doom
wrote:

On Tue, 18 Jul 2017 19:14:19 +0100, Brian Gaff wrote:

Depends on the meter really, Does it have high voltage AC ranges and
decent leads?
Brian

I can't believe no one's said anything about this aspect until now.

Probably because of a good reason ... (that a left brainer couldn't
believe). ;-)

The
OP said he had a cheap and nasty DMM -

Typical Brexiteer, making sh1t up. He said no such thing ... he
actually said "Can I use my cheap digital meter" and that might mean
that he is aware that some DMMs can cost hundreds and his cost £29.99
(that wouldn't make it 'cheap' by most DIY peoples standards). It may
also mean that it was a £100 DMM that he bought 'cheap' from a friend
or on a special (but that would be less likely from the usage and
context).

ight be one of these 3.99 jobs
from China -

Most DMM's come from China and a £3.99 job could equate to a £19.99
job bought in a UK retail outlet.

and such a meter is *not* safe to carry out mains
measurements with.

But I have done so (many times) and yet somehow I'm still here (except
the DMM actually cost 99p but I did have to supply my own PP9
battery).

That said, 'of course' there is a minimum design / build spec that
most who know what they are doing would consider ideal / acceptable
(and ironically makes them potentially safer for novice use).

to be rated for (usually 3 or 4 at a specified voltage).

To be *formally* rated for such voltages.

snip

Cheers, T i m

In article ,
wrote:
Almost none of that's good advice either. An analogue meters takes typically 50uA at FSD, digitals far less. No ELCB is going to give a damn, even an RCD wouldn't either.

Avo Model 8 is typically 1mA on AC.

--
*OK, so what's the speed of dark? *

Dave Plowman London SW
To e-mail, change noise into sound.

On Wednesday, 19 July 2017 12:17:20 UTC+1, Dave Plowman (News) wrote:
In article ,
tabbypurr wrote:

Almost none of that's good advice either. An analogue meters takes typically 50uA at FSD, digitals far less. No ELCB is going to give a damn, even an RCD wouldn't either.

Avo Model 8 is typically 1mA on AC.

And my 1920s meter takes far more. Of course there are meters that aren't typical. Are you trolling?

In article ,
wrote:
On Wednesday, 19 July 2017 12:17:20 UTC+1, Dave Plowman (News) wrote:
In article ,
tabbypurr wrote:

Almost none of that's good advice either. An analogue meters takes
typically 50uA at FSD, digitals far less. No ELCB is going to give a
damn, even an RCD wouldn't either.

Avo Model 8 is typically 1mA on AC.

And my 1920s meter takes far more. Of course there are meters that aren't typical. Are you trolling?


Just trying to point out to you that a mechanical analogue meter takes
more current measuring AC than DC. So typically not 50uA on a 250v AC
range.

But if you think that trolling, carry on.

--
*Why do the two "sanction"s (noun and verb) mean opposites?*

Dave Plowman London SW
To e-mail, change noise into sound.

On 19/07/2017 10:41, T i m wrote:
On Tue, 18 Jul 2017 22:37:30 -0000 (UTC), Cursitor Doom

and such a meter is *not* safe to carry out mains
measurements with.

But I have done so (many times) and yet somehow I'm still here

I am sure you are well aware of the spectacular holes in that bit of
logic. So far I have never been hit by a car while I am crossing a road.
It does not mean that it can't happen or is necessarily that rare an event.

That said, 'of course' there is a minimum design / build spec that
most who know what they are doing would consider ideal / acceptable
(and ironically makes them potentially safer for novice use).

to be rated for (usually 3 or 4 at a specified voltage).

To be *formally* rated for such voltages.

One of the difficulties with many cheap chinesium meters is that they
may claim Cat II or Cat III certification, and yet even a cursory glance
inside[1] shows that to be wishful thinking.

Now chances are you will be able to measure voltages inside your CU with
one of those many times and get away with it. The problem comes when you
don't because there was a 1kV transient at just the wrong moment.

he further you move from a CU - out to the far reaches of a circuit or
in fact into an appliance, then generally the lower the risk.


[1] Inadequate conductive path separation, lack of low to high voltage
isolation, no HRC fusing, no spark gaps, no input protection MOVs etc.


--
Cheers,

John.

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On Wednesday, 19 July 2017 14:50:30 UTC+1, Dave Plowman (News) wrote:
In article ,
tabbypurr wrote:
On Wednesday, 19 July 2017 12:17:20 UTC+1, Dave Plowman (News) wrote:
In article ,
tabbypurr wrote:

Almost none of that's good advice either. An analogue meters takes
typically 50uA at FSD, digitals far less. No ELCB is going to give a
damn, even an RCD wouldn't either.

Avo Model 8 is typically 1mA on AC.

And my 1920s meter takes far more. Of course there are meters that aren't typical. Are you trolling?


Just trying to point out to you that a mechanical analogue meter takes
more current measuring AC than DC. So typically not 50uA on a 250v AC
range.

But if you think that trolling, carry on.

it's trolling because it has no relevance to the OP's situation, who has a DMM, and no significance to a typical analogue multimeter that takes more than 50uA but way less than 1mA on ac.

So it looks like you trolled successfully.


NT

On Wed, 19 Jul 2017 10:41:15 +0100, T i m wrote:

But I have done so (many times) and yet somehow I'm still here

More's the pity. Why don't you stick your tongue in a 13A outlet and do
us all a favour?

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On Wed, 19 Jul 2017 12:14:13 +0100, Dave Plowman (News) wrote:

In article ,
wrote:
Almost none of that's good advice either. An analogue meters takes typically 50uA at FSD, digitals far less. No ELCB is going to give a damn, even an RCD wouldn't either.

Avo Model 8 is typically 1mA on AC.

Had a Fluke DMM that showed 238V but circuit not working.
AVO 8 showed about 215V; lowered the range and each time the voltage dropped
more.
Cause was RS Octel relay just touching but not making.

I've an old, bodged [1] analogue meter that meets zero standards but is good
for checking where the DMM is no good.

[1]. Casually thrown together from spare parts in the electronics lab at
Plessey Microsystems by, Dog help me, and electronics 'engineer' hysterical
laughter
--
Peter.
The gods will stay away
whilst religions hold sway