In article ,
wrote:
On Friday, 10 April 2015 19:10:36 UTC+1, Dave Plowman (News) wrote:
In article ,

These days almost any multimeter is good enough for diy. Just dont use
some of them north of the CU's fuses, for that you need a suitable
category rating.

Having had a quite expensive DVM blow up on mains, I'll not use one for
that any more. Have a proper mains test stick one for that - more
convenient too.

BTW, no more volts 'north of the CU' in the average UK house anyway. ;-)

Its the i squared t that's the problem


You using jump leads instead of test leads?

--
*I wished the buck stopped here, as I could use a few*

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

On Saturday, 11 April 2015 00:44:16 UTC+1, Dave Plowman (News) wrote:
In article ,
nt wrote:
On Friday, 10 April 2015 19:10:36 UTC+1, Dave Plowman (News) wrote:
In article ,

These days almost any multimeter is good enough for diy. Just dont use
some of them north of the CU's fuses, for that you need a suitable
category rating.

Having had a quite expensive DVM blow up on mains, I'll not use one for
that any more. Have a proper mains test stick one for that - more
convenient too.

BTW, no more volts 'north of the CU' in the average UK house anyway. ;-)

Its the i squared t that's the problem


You using jump leads instead of test leads?

Are you unfamiliar with how multimeters can kill people?


NT

In article ,
wrote:
On Saturday, 11 April 2015 00:44:16 UTC+1, Dave Plowman (News) wrote:
In article ,
nt wrote:
On Friday, 10 April 2015 19:10:36 UTC+1, Dave Plowman (News) wrote:
In article ,

These days almost any multimeter is good enough for diy. Just dont use
some of them north of the CU's fuses, for that you need a suitable
category rating.

Having had a quite expensive DVM blow up on mains, I'll not use one for
that any more. Have a proper mains test stick one for that - more
convenient too.

BTW, no more volts 'north of the CU' in the average UK house anyway. ;-)

Its the i squared t that's the problem


You using jump leads instead of test leads?

Are you unfamiliar with how multimeters can kill people?

All too familiar which is why I won't use one on mains. ;-) There are far
better designed devices designed specifically for this job.

--
*When cheese gets its picture taken, what does it say? *

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

On Sat, 11 Apr 2015 15:05:18 +0100, Dave Plowman (News) wrote:

In article ,
wrote:
On Saturday, 11 April 2015 00:44:16 UTC+1, Dave Plowman (News) wrote:
In article ,
nt wrote:
On Friday, 10 April 2015 19:10:36 UTC+1, Dave Plowman (News)
wrote:
In article
,

These days almost any multimeter is good enough for diy. Just
dont use some of them north of the CU's fuses, for that you
need a suitable category rating.

Having had a quite expensive DVM blow up on mains, I'll not use
one for that any more. Have a proper mains test stick one for
that - more convenient too.

BTW, no more volts 'north of the CU' in the average UK house
anyway. ;-)

Its the i squared t that's the problem


You using jump leads instead of test leads?

Are you unfamiliar with how multimeters can kill people?

All too familiar which is why I won't use one on mains. ;-) There are
far better designed devices designed specifically for this job.

Last week I picked up a used but in perfect condition high voltage probe
made by AVO. When used in conjunction with my good 'ol British AVO
***ANALOGUE*** meter, I can now measure voltages of up to 32kV.
Try doing that with one of your BnQ ten quid specials.

In article ,
Cursitor Doom wrote:
Last week I picked up a used but in perfect condition high voltage probe
made by AVO. When used in conjunction with my good 'ol British AVO
***ANALOGUE*** meter, I can now measure voltages of up to 32kV.
Try doing that with one of your BnQ ten quid specials.

Pretty useless for measuring things like CRT HT, though. Input impedance
is too low. A similar probe on a 2 quid DVM will be fine. ;-)

--
*Plagiarism saves time *

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

On Saturday, 11 April 2015 15:47:53 UTC+1, Cursitor Doom wrote:
On Sat, 11 Apr 2015 15:05:18 +0100, Dave Plowman (News) wrote:

In article ,
wrote:
On Saturday, 11 April 2015 00:44:16 UTC+1, Dave Plowman (News) wrote:
In article ,
nt wrote:
On Friday, 10 April 2015 19:10:36 UTC+1, Dave Plowman (News)
wrote:
In article
,

These days almost any multimeter is good enough for diy. Just
dont use some of them north of the CU's fuses, for that you
need a suitable category rating.

Having had a quite expensive DVM blow up on mains, I'll not use
one for that any more. Have a proper mains test stick one for
that - more convenient too.

BTW, no more volts 'north of the CU' in the average UK house
anyway. ;-)

Its the i squared t that's the problem


You using jump leads instead of test leads?

Are you unfamiliar with how multimeters can kill people?

All too familiar which is why I won't use one on mains. ;-) There are
far better designed devices designed specifically for this job.

Last week I picked up a used but in perfect condition high voltage probe
made by AVO. When used in conjunction with my good 'ol British AVO
***ANALOGUE*** meter, I can now measure voltages of up to 32kV.
Try doing that with one of your BnQ ten quid specials.

that's easy. string of 3w resistors, bit of coathanger, bit of polystyrene. BTDT.


NT

On Sat, 11 Apr 2015 12:53:44 -0700, tabbypurr wrote:

that's easy. string of 3w resistors, bit of coathanger, bit of
polystyrene. BTDT.


NT

3 watt resistors?? Hmmmm.....And what grade of polystyrene would that be?
I'm sure you know exactly what you're doing, though.

On Saturday, 11 April 2015 21:34:30 UTC+1, Cursitor Doom wrote:
On Sat, 11 Apr 2015 12:53:44 -0700, tabbypurr wrote:

that's easy. string of 3w resistors, bit of coathanger, bit of
polystyrene. BTDT.

3 watt resistors??

Yup, theyre long enough to have a useful voltage rating

Hmmmm.....And what grade of polystyrene would that be?

any grade, its not specced for electrical insulation

I'm sure you know exactly what you're doing, though.

I included a ground shield in the styrene so that if it fails for any reason it arcs to ground, not to the user. And naturally HV kit needs testing before use.


NT

On Sat, 11 Apr 2015 16:49:51 +0100, Dave Plowman (News) wrote:

In article ,
Cursitor Doom wrote:
Last week I picked up a used but in perfect condition high voltage
probe made by AVO. When used in conjunction with my good 'ol British
AVO ***ANALOGUE*** meter, I can now measure voltages of up to 32kV.
Try doing that with one of your BnQ ten quid specials.

Pretty useless for measuring things like CRT HT, though. Input impedance
is too low. A similar probe on a 2 quid DVM will be fine. ;-)

Yeah, go pick on something that has like microscopic source impedance why
don'tcha?
Please note: I still keep a couple of DVMs and the really important thing
is the ***PROBE*** - and having the balls to use it at 32kV (which TBH I
must admit I don't have). But it is *well* out of DIY range, let's face
it.

On Sat, 11 Apr 2015 14:24:37 -0700, tabbypurr wrote:

Yup, theyre long enough to have a useful voltage rating

Ahh. I see. Makes sense in a 'get-you-home' sort of way.

Hmmmm.....And what grade of polystyrene would that be?

any grade, its not specced for electrical insulation

No kidding? :-D

I'm sure you know exactly what you're doing, though.

I included a ground shield in the styrene so that if it fails for any
reason it arcs to ground, not to the user. And naturally HV kit needs
testing before use.

I'm sure readers will be reassured to know it only starts fires rather
than electrocutes the homeowner.

Just discovered another meter in my possession (a Taylor Instruments)
dating back to around 1960 that has a *basic* 2.5kV measurement
capability at 20kopv, giving me the capability to measure EMFs up to 75kV
if I can obtain an even higher rated 30x EHT probe - yeah, baby, yeah!

In article ,
Cursitor Doom wrote:
On Sat, 11 Apr 2015 16:49:51 +0100, Dave Plowman (News) wrote:

In article ,
Cursitor Doom wrote:
Last week I picked up a used but in perfect condition high voltage
probe made by AVO. When used in conjunction with my good 'ol British
AVO ***ANALOGUE*** meter, I can now measure voltages of up to 32kV.
Try doing that with one of your BnQ ten quid specials.

Pretty useless for measuring things like CRT HT, though. Input
impedance is too low. A similar probe on a 2 quid DVM will be fine. ;-)

Yeah, go pick on something that has like microscopic source impedance
why don'tcha? Please note: I still keep a couple of DVMs and the really
important thing is the ***PROBE*** - and having the balls to use it at
32kV (which TBH I must admit I don't have). But it is *well* out of DIY
range, let's face it.

At one time measuring CRT HT would have been DIY for those who fixed or
built tellies. I had a Heathkit valve voltmeter (with HT probe) for that
job. Still got it. But it doesn't get used these days - any more than the
AVO 8. ;-)

--
*Be careful about reading health books. You may die of a misprint.

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

In article , Cursitor Doom
scribeth thus
On Sat, 11 Apr 2015 16:49:51 +0100, Dave Plowman (News) wrote:

In article ,
Cursitor Doom wrote:
Last week I picked up a used but in perfect condition high voltage
probe made by AVO. When used in conjunction with my good 'ol British
AVO ***ANALOGUE*** meter, I can now measure voltages of up to 32kV.
Try doing that with one of your BnQ ten quid specials.

Pretty useless for measuring things like CRT HT, though. Input impedance
is too low. A similar probe on a 2 quid DVM will be fine. ;-)

Yeah, go pick on something that has like microscopic source impedance why
don'tcha?
Please note: I still keep a couple of DVMs and the really important thing
is the ***PROBE*** - and having the balls to use it at 32kV (which TBH I
must admit I don't have). But it is *well* out of DIY range, let's face
it.


Is there anything that most all of us would need to measure up there at
that voltage, seeing that CRT's are almost extinct now?...
--
Tony Sayer

On Sunday, 12 April 2015 00:15:03 UTC+1, Cursitor Doom wrote:
On Sat, 11 Apr 2015 14:24:37 -0700, tabbypurr wrote:

Yup, theyre long enough to have a useful voltage rating

Ahh. I see. Makes sense in a 'get-you-home' sort of way.

No, it makes sense in a basic electrical engineering kinda way. Long resistors tend to have higher voltage specs.

Hmmmm.....And what grade of polystyrene would that be?

any grade, its not specced for electrical insulation

No kidding? :-D

nope

I'm sure you know exactly what you're doing, though.

I included a ground shield in the styrene so that if it fails for any
reason it arcs to ground, not to the user. And naturally HV kit needs
testing before use.

I'm sure readers will be reassured to know it only starts fires rather
than electrocutes the homeowner.

why would it start a fire? You seem to be missing the basic engineering behind this completely.

Just discovered another meter in my possession (a Taylor Instruments)
dating back to around 1960 that has a *basic* 2.5kV measurement
capability at 20kopv, giving me the capability to measure EMFs up to 75kV
if I can obtain an even higher rated 30x EHT probe - yeah, baby, yeah!

upto anything at all if it has enough current delivery. 20 k per v is too often too low of course.


NT

On Sunday, 12 April 2015 11:55:37 UTC+1, tony sayer wrote:
In article , Cursitor Doom
scribeth thus

Please note: I still keep a couple of DVMs and the really important thing
is the ***PROBE*** - and having the balls to use it at 32kV (which TBH I
must admit I don't have). But it is *well* out of DIY range, let's face
it.


Is there anything that most all of us would need to measure up there at
that voltage, seeing that CRT's are almost extinct now?...

There never was, for most people. For electronic folk there's still microwave ovens, occasional HV power transmission, vintage tv, and other occasional/extreme projects. DIY x-rays anyone?


NT

On Sun, 12 Apr 2015 04:33:59 -0700, tabbypurr wrote:

There never was, for most people. For electronic folk there's still
microwave ovens, occasional HV power transmission, vintage tv, and other
occasional/extreme projects. DIY x-rays anyone?

Looking on YT I see quite a lot of nuts who are into indoor lightning. If
you want to mess around with tesla coils and Cockroft-Walton multipliers,
32kV is nowhere near enough!

On Sat, 11 Apr 2015 23:03:04 +0000, Cursitor Doom wrote:

Yeah, go pick on something that has like microscopic source impedance

Sorry, I meant *huge* Zs, not "microscopic" - D'oh!

In article , Cursitor Doom
scribeth thus
On Sun, 12 Apr 2015 04:33:59 -0700, tabbypurr wrote:

There never was, for most people. For electronic folk there's still
microwave ovens, occasional HV power transmission, vintage tv, and other
occasional/extreme projects. DIY x-rays anyone?

Looking on YT I see quite a lot of nuts who are into indoor lightning. If
you want to mess around with tesla coils and Cockroft-Walton multipliers,
32kV is nowhere near enough!

Yep, but do you measure those sort of voltages perhaps you know that a
spark "x" of such a length is equal to "y" volts;?..
--
Tony Sayer

On Sat, 11 Apr 2015 05:46:26 -0700, tabbypurr wrote:

Are you unfamiliar with how multimeters can kill people?

Do go on...?

On Sunday, 12 April 2015 16:03:53 UTC+1, Adrian wrote:
On Sat, 11 Apr 2015 05:46:26 -0700, tabbypurr wrote:

Are you unfamiliar with how multimeters can kill people?

Do go on...?

Arc flash. Circuits after a CU's fuses don't deliver enough current for long enough to cause an explosion, further upstream they surely can.


NT

On Sun, 12 Apr 2015 14:55:51 +0100, tony sayer wrote:

Yep, but do you measure those sort of voltages perhaps you know that a
spark "x" of such a length is equal to "y" volts;?..

Yes, that's how a lot of these kind of measurements are carried out - in
dry air of course.

On Sun, 12 Apr 2015 03:47:08 -0700, tabbypurr wrote:

Well you can't really blame me. Your description is a bit vague, after
all: "string of 3w resistors, bit of coathanger, bit of
polystyrene."

"Engineering" seems rather a grand term for such a sloppy sounding lash-
up.

upto anything at all if it has enough current delivery. 20 k per v is
too often too low of course.

It was the 'gold standard' 50 years ago when this meter was made! Anyhoo,
as I said I keep a couple of modern DVMs with much higher input impedances
so if lack of grunt on the part of the DUT is a problem I can just use
one of them.

On Sun, 12 Apr 2015 10:00:11 -0700, tabbypurr wrote:

On Sunday, 12 April 2015 16:03:53 UTC+1, Adrian wrote:
On Sat, 11 Apr 2015 05:46:26 -0700, tabbypurr wrote:

Are you unfamiliar with how multimeters can kill people?

Do go on...?

Arc flash. Circuits after a CU's fuses don't deliver enough current for
long enough to cause an explosion, further upstream they surely can.

Yes indeedy. You don't want to be using one of those piddly 5 quid meters
off ebay for probing meter tails and whatnot. Just because they claim
they're good for 600V at whatever CAT rating I wouldn't trust 'em for
mains use. NFW.

I experienced an arc flash myself 30 years ago. Won't forget it. Huge
flames shooting up the wall. I instinctively threw myself back away from
the blast but still ended up resembling the typical cartoon character
depiction you see of people who get blown up; black, sooty face except
for white eyes where luckily my specs had protected me. Not nice!

On Sunday, 12 April 2015 18:37:09 UTC+1, Cursitor Doom wrote:
On Sun, 12 Apr 2015 03:47:08 -0700, nt wrote:

Well you can't really blame me. Your description is a bit vague, after
all: "string of 3w resistors, bit of coathanger, bit of
polystyrene."

With your experience/expertise I'd expect you to have no difficulty seeing how that works. Ditto for anyone that would know how to use such a thing safely.

"Engineering" seems rather a grand term for such a sloppy sounding lash-
up.

Not sloppy at all, just basic engineering

upto anything at all if it has enough current delivery. 20 k per v is
too often too low of course.

It was the 'gold standard' 50 years ago when this meter was made! Anyhoo,

A low impedance load can hardly be a gold standard for measuring a normally high impedance voltage. Electrometers would seem better suited, or a VVM. Or even an electrostatic deflection CRT, if one's lab is so equipped.

as I said I keep a couple of modern DVMs with much higher input impedances
so if lack of grunt on the part of the DUT is a problem I can just use
one of them.


NT

wrote:
On Sunday, 12 April 2015 18:37:09 UTC+1, Cursitor Doom wrote:
On Sun, 12 Apr 2015 03:47:08 -0700, nt wrote:

Well you can't really blame me. Your description is a bit vague, after
all: "string of 3w resistors, bit of coathanger, bit of
polystyrene."

With your experience/expertise I'd expect you to have no difficulty seeing how that works. Ditto for anyone that would know how to use such a thing safely.

"Engineering" seems rather a grand term for such a sloppy sounding lash-
up.

Not sloppy at all, just basic engineering

upto anything at all if it has enough current delivery. 20 k per v is
too often too low of course.

It was the 'gold standard' 50 years ago when this meter was made! Anyhoo,

A low impedance load can hardly be a gold standard for measuring a normally high impedance voltage. Electrometers would seem better suited, or a VVM. Or even an electrostatic deflection CRT, if one's lab is so equipped.

as I said I keep a couple of modern DVMs with much higher input impedances
so if lack of grunt on the part of the DUT is a problem I can just use
one of them.


NT
Electrometers were used to 50KV for TV measurements.

In article , Capitol
scribeth thus
wrote:
On Sunday, 12 April 2015 18:37:09 UTC+1, Cursitor Doom wrote:
On Sun, 12 Apr 2015 03:47:08 -0700, nt wrote:

Well you can't really blame me. Your description is a bit vague, after
all: "string of 3w resistors, bit of coathanger, bit of
polystyrene."

With your experience/expertise I'd expect you to have no difficulty seeing how
that works. Ditto for anyone that would know how to use such a thing safely.

"Engineering" seems rather a grand term for such a sloppy sounding lash-
up.

Not sloppy at all, just basic engineering

upto anything at all if it has enough current delivery. 20 k per v is
too often too low of course.

It was the 'gold standard' 50 years ago when this meter was made! Anyhoo,

A low impedance load can hardly be a gold standard for measuring a normally
high impedance voltage. Electrometers would seem better suited, or a VVM. Or
even an electrostatic deflection CRT, if one's lab is so equipped.

as I said I keep a couple of modern DVMs with much higher input impedances
so if lack of grunt on the part of the DUT is a problem I can just use
one of them.


NT

Electrometers were used to 50KV for TV measurements.


I bet theres one hanging around in your shed /shack /office
somewhere;?..

Last one I saw was made by Pye instruments in Cambridge, and that was a
long time ago now;!.

Sort of moving spot light on a scale it was..
--
Tony Sayer

Just incase anyone is still looking for a meter this one looks interesting..

http://www.amazon.co.uk/Extech-EX820...75168&sr=1-638

On Sun, 12 Apr 2015 21:44:08 +0100, tony sayer wrote:

I bet theres one hanging around in your shed /shack /office
somewhere;?..

Last one I saw was made by Pye instruments in Cambridge, and that was a
long time ago now;!.

Sort of moving spot light on a scale it was..

That's a galvanometer I think you mean. I've still got one - and it works!

On Sun, 12 Apr 2015 10:52:08 -0700, tabbypurr wrote:

On Sunday, 12 April 2015 18:37:09 UTC+1, Cursitor Doom wrote:
On Sun, 12 Apr 2015 03:47:08 -0700, nt wrote:

Well you can't really blame me. Your description is a bit vague, after
all: "string of 3w resistors, bit of coathanger, bit of polystyrene."

With your experience/expertise I'd expect you to have no difficulty
seeing how that works. Ditto for anyone that would know how to use such
a thing safely.

I think I can see where you're coming from with your string of resistors,
but the role of the coat-hanger and poly remains unclear. I'm not a mind-
reader.


A low impedance load can hardly be a gold standard for measuring a
normally high impedance voltage.

I was of course referring to the gold standard for moving coil meters.

On Sun, 12 Apr 2015 22:57:11 +0000, Cursitor Doom wrote:

On Sun, 12 Apr 2015 10:52:08 -0700, tabbypurr wrote:

On Sunday, 12 April 2015 18:37:09 UTC+1, Cursitor Doom wrote:
On Sun, 12 Apr 2015 03:47:08 -0700, nt wrote:

Well you can't really blame me. Your description is a bit vague, after
all: "string of 3w resistors, bit of coathanger, bit of polystyrene."

With your experience/expertise I'd expect you to have no difficulty
seeing how that works. Ditto for anyone that would know how to use such
a thing safely.

I think I can see where you're coming from with your string of
resistors,
but the role of the coat-hanger and poly remains unclear. I'm not a
mind-
reader.


A low impedance load can hardly be a gold standard for measuring a
normally high impedance voltage.

I was of course referring to the gold standard for moving coil meters.

I suppose my half century old Japanese moving coil multimeter with its
50K ohm per volt sensitivity rating must have been made to the Platinum
Standard then. :-)

--
Johnny B Good

In article , Cursitor Doom
scribeth thus
On Sun, 12 Apr 2015 21:44:08 +0100, tony sayer wrote:

I bet theres one hanging around in your shed /shack /office
somewhere;?..

Last one I saw was made by Pye instruments in Cambridge, and that was a
long time ago now;!.

Sort of moving spot light on a scale it was..

That's a galvanometer I think you mean. I've still got one - and it works!

Yes, thats the gubbins;!.
--
Tony Sayer

On Sun, 12 Apr 2015 23:29:18 +0000, Johnny B Good wrote:

I suppose my half century old Japanese moving coil multimeter with its
50K ohm per volt sensitivity rating must have been made to the Platinum
Standard then. :-)

Undoubtedly. Well, be good Johnny and post some further particulars on
it. Some pictures would be nice.

On Sunday, 12 April 2015 23:58:10 UTC+1, Cursitor Doom wrote:
On Sun, 12 Apr 2015 10:52:08 -0700, tabbypurr wrote:

On Sunday, 12 April 2015 18:37:09 UTC+1, Cursitor Doom wrote:
On Sun, 12 Apr 2015 03:47:08 -0700, nt wrote:

Well you can't really blame me. Your description is a bit vague, after
all: "string of 3w resistors, bit of coathanger, bit of polystyrene."

With your experience/expertise I'd expect you to have no difficulty
seeing how that works. Ditto for anyone that would know how to use such
a thing safely.

I think I can see where you're coming from with your string of resistors,
but the role of the coat-hanger and poly remains unclear. I'm not a mind-
reader.

OK. A stick of expanded polystyrene makes the insulated handle and the mounting base for the series string of resistors & coathanger offcut. The latter is of course the conductive probe. A 2nd ground wire is wrapped round the poly between resistor string & handle area as a 2nd line of defence against insulation breakdown - this needs grounding of course. The whole is tested to well above working voltage before use. An easy way to do that is hook it up to a CRT anode.

Anyone doing this has to understand the engineering issues, getting it wrong can kill.


A low impedance load can hardly be a gold standard for measuring a
normally high impedance voltage.

I was of course referring to the gold standard for moving coil meters.

in terms of input impedance that would be fet buffered meters


NT

On Mon, 13 Apr 2015 08:20:16 -0700, tabbypurr wrote:

OK. A stick of expanded polystyrene makes the insulated handle and the
mounting base for the series string of resistors & coathanger offcut.
The latter is of course the conductive probe. A 2nd ground wire is
wrapped round the poly between resistor string & handle area as a 2nd
line of defence against insulation breakdown - this needs grounding of
course. The whole is tested to well above working voltage before use. An
easy way to do that is hook it up to a CRT anode.

Anyone doing this has to understand the engineering issues, getting it
wrong can kill.

No kidding? But I can't talk. I stick my fingers into mains sockets to
see if they're on. I guess we're of a different generation. Fearless!

A low impedance load can hardly be a gold standard for measuring a
normally high impedance voltage.

I was of course referring to the gold standard for moving coil meters.

in terms of input impedance that would be fet buffered meters

Well let's wait and see. Maybe he's got some pixie coil-winders.

On Mon, 13 Apr 2015 13:34:39 +0000, Cursitor Doom wrote:

On Sun, 12 Apr 2015 23:29:18 +0000, Johnny B Good wrote:

I suppose my half century old Japanese moving coil multimeter with its
50K ohm per volt sensitivity rating must have been made to the Platinum
Standard then. :-)

Undoubtedly. Well, be good Johnny and post some further particulars on
it. Some pictures would be nice.

Try this:

http://s300.photobucket.com/user/Joh...rary/Japanese%
20Multimeter?sort=9&page=1

I don't know if this is the right way to make image files publically
available (I set it to public so I think that's right).

--
Johnny B Good

On Monday, 13 April 2015 18:30:01 UTC+1, Cursitor Doom wrote:
On Mon, 13 Apr 2015 08:20:16 -0700, tabbypurr wrote:

OK. A stick of expanded polystyrene makes the insulated handle and the
mounting base for the series string of resistors & coathanger offcut.
The latter is of course the conductive probe. A 2nd ground wire is
wrapped round the poly between resistor string & handle area as a 2nd
line of defence against insulation breakdown - this needs grounding of
course. The whole is tested to well above working voltage before use. An
easy way to do that is hook it up to a CRT anode.

Anyone doing this has to understand the engineering issues, getting it
wrong can kill.

No kidding?

For engineer's that business as normal. The design addresses the potential risks effectively.

But I can't talk. I stick my fingers into mains sockets to
see if they're on. I guess we're of a different generation. Fearless!

Crazy.

I was of course referring to the gold standard for moving coil meters.

in terms of input impedance that would be fet buffered meters

Well let's wait and see. Maybe he's got some pixie coil-winders.

an infinite coil perhaps? FET buffered meters & VVMs offer highest input impedance, at least below 1kV.


NT

On Mon, 13 Apr 2015 22:33:28 +0000, Johnny B Good wrote:

Try this:

http://s300.photobucket.com/user/Joh...rary/Japanese%
20Multimeter?sort=9&page=1

I don't know if this is the right way to make image files publically
available (I set it to public so I think that's right).

Nope! Just getting a 400 error message here...

On Mon, 13 Apr 2015 15:48:39 -0700, tabbypurr wrote:

Crazy.

No more so than your contraption for measuring EHT! I should say, though,
as I should have said at the time, "don't try this at home!" - It's just
something I've grown up since the age of 14 with and am confident about,
AND I don't just do it willy-nilly; you won't find me doing it whilst
standing in a puddle, for instance.


I was of course referring to the gold standard for moving coil
meters.

in terms of input impedance that would be fet buffered meters

Well let's wait and see. Maybe he's got some pixie coil-winders.

an infinite coil perhaps? FET buffered meters & VVMs offer highest input
impedance, at least below 1kV.

If the meter has an active device of any sort in it then AFAIC it doesn't
count. I was referring to passive moving coil meters, as I'd assumed JBG
well knew.

On Mon, 13 Apr 2015 15:48:39 -0700, tabbypurr wrote:

But I can't talk. I stick my fingers into mains sockets to see if
they're on. I guess we're of a different generation. Fearless!

Crazy.

A polish electrician I once knew (fully qualified in the UK - honest)
also used to do the same thing to check if a socket was live. It's a lot
better IMV than relying on a neon screwdriver. But I'm NOT suggesting
anyone else do it!

On Tuesday, 14 April 2015 19:36:14 UTC+1, Cursitor Doom wrote:
On Mon, 13 Apr 2015 15:48:39 -0700, tabbypurr wrote:

Crazy.

No more so than your contraption for measuring EHT! I should say, though,

Feel free to point out any engineering flaw in it. Its safer than most EHT probes.

as I should have said at the time, "don't try this at home!" - It's just
something I've grown up since the age of 14 with and am confident about,
AND I don't just do it willy-nilly; you won't find me doing it whilst
standing in a puddle, for instance.


I was of course referring to the gold standard for moving coil
meters.

in terms of input impedance that would be fet buffered meters

Well let's wait and see. Maybe he's got some pixie coil-winders.

an infinite coil perhaps? FET buffered meters & VVMs offer highest input
impedance, at least below 1kV.

If the meter has an active device of any sort in it then AFAIC it doesn't
count.

??


NT

On Tuesday, 14 April 2015 19:40:52 UTC+1, Cursitor Doom wrote:
On Mon, 13 Apr 2015 15:48:39 -0700, tabbypurr wrote:

But I can't talk. I stick my fingers into mains sockets to see if
they're on. I guess we're of a different generation. Fearless!

Crazy.

A polish electrician I once knew (fully qualified in the UK - honest)
also used to do the same thing to check if a socket was live. It's a lot
better IMV than relying on a neon screwdriver. But I'm NOT suggesting
anyone else do it!

Various people used to stick their finger in live things, but its pretty stupid to gamble with your life when nowadays a meter costs £2.


NT