Driver to drive?

[Fred Abse]

On Wed, 31 Oct 2012 10:28:54 -0400, Michael A. Terrell wrote:

Does Tektronix or HP list the vendor in their parts list? They do
for most parts.

Not in the P6015 manual.

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

 

[Fred Abse]

On Mon, 29 Oct 2012 18:07:28 -0800, Robert Baer wrote:

It has been a loooong time; Tektronix made two high voltage probes -
one with a significantly higher voltage rating.
The one i have _did_ have the liquid inside but that has slowly
leaked out over the ages; it is the P6015 rated at 20KV, 40KV peak.
I think that is the top end in voltage.

The Tek probes used 100meg resistors in the probe head, with a 100K
effective load in the termination unit. Much more tractable to compensate.
Any reason for going to 1000meg in your design?

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

 

[tm]

"Fred Abse" <excretatauris@invalid.invalid> wrote in message
newsan.2012.10.31.20.08.38.316417@invalid.invalid...

On Mon, 29 Oct 2012 18:07:28 -0800, Robert Baer wrote:

It has been a loooong time; Tektronix made two high voltage probes -
one with a significantly higher voltage rating.
The one i have _did_ have the liquid inside but that has slowly
leaked out over the ages; it is the P6015 rated at 20KV, 40KV peak.
I think that is the top end in voltage.

The Tek probes used 100meg resistors in the probe head, with a 100K
effective load in the termination unit. Much more tractable to compensate.
Any reason for going to 1000meg in your design?

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

1/10 th the circuit loading.

 

[josephkk]

On Wed, 31 Oct 2012 08:39:30 GMT, Jan Panteltje
<pNaonStpealmtje@yahoo.com> wrote:

On a sunny day (Tue, 30 Oct 2012 20:39:44 -0800) it happened Robert Baer
robertbaer@localnet.com> wrote in <KY1ks.525$TD5.455@newsfe01.iad>:

Personally for a one case, I would take normal coax,
pull the center conductor out,
and insert thinner resistance wire.
Should work for length of 1m or there about.

Not sure if that helps for your case.
That sounds like it may be do-able.
BUT where does that resistance wire come from? Most heaters have a
much larger diameter nichrome wire, and i do not know where one can buy
"plain" resistive wire like that.
Suggestions?
Oh, "insert" might be a bitch..one might be forced to spot-weld the
resistive wire to the existing internal wire.
And it ain't easy to pull out....

Well I just order it from conrad.nl,
several types at several Ohm/meter, some VERY thin.
I have used it to make thermocouples.
I am sure US has many places that sell that wire.
Yes the inner coax does not always come out easy,
I have done it, put one end in the vice, and take an hour to pull it out.
Use gloves, hurt my hands doing it...

Gloves? Like hell. Use a mandrel (or a dowel rod).

?-)

 

[josephkk]

On Wed, 31 Oct 2012 04:39:51 -0400, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:

Not sure if that helps for your case.
That sounds like it may be do-able.
BUT where does that resistance wire come from? Most heaters have a
much larger diameter nichrome wire, and i do not know where one can buy
"plain" resistive wire like that.

It comes on spools- manganin is better than nichrome, but nichrome
isn't all that bad. In a pinch, brass or stainless are pretty awful
tempco-wise, but relatively high resistance.

These guys have 25m lengths of it with Kapton insulation:-

http://www.iceoxford.com/Cryogenic-spares/Wiring.htm

If you need many pounds/kg of it, it's easy to buy.

Suggestions?
Oh, "insert" might be a bitch..one might be forced to spot-weld the
resistive wire to the existing internal wire.
And it ain't easy to pull out....

Except for cable TV coax where it seems pretty easy to pull out (esp
accidentally).. the dielectric is slippery PE, I think, and the center
wire a thick smooth solid wire. But it's awfully stiff for test prod
wire.


Best regards,
Spehro Pefhany

Copper clad steel rather frequently, no good for broadband resistivety.
But that is what you pull out.

I would likely as not try to pull in constantan (perhaps nicked from
thermocouple wire).

?-)

 

[Ralph Barone]

Sum Ting Wong <SumTingWong@thebarattheendoftheVenusianLightningBolt.org>
wrote:

On Tue, 30 Oct 2012 20:41:08 -0800, Robert Baer <robertbaer@localnet.com
wrote:

Sum Ting Wong wrote:

Yeah, like dragging the center conductor out of a meter long piece of
coax is an easy task, much less feeding another back through.

Standard RG-8 center conductor dielectric strength is 1.5kV.and they
are not easy to get out. Fairly tightly bound to the core media.

Probably cheaper to find and get the right stuff.
Reason why center conductors are virtually impossible to pull out,is
that the insulation is hot-cast onto the wire..

Then wrapped even tighter by a Chinese handcuff overbraid of silver
plated copper shielding. So tightly it makes a deep fingerprint
impression of the overbraid onto the core media. It doesn't just slide
off either.

What was the code name for the coax with the helically wound insulation,
leaving mostly air as the dielectric? You might stand a chance replacing
the center conductor on that stuff.

 

On Thu, 01 Nov 2012 01:44:26 GMT, Ralph Barone
<address_is@invalid.invalid> wrote:

Sum Ting Wong <SumTingWong@thebarattheendoftheVenusianLightningBolt.org
wrote:
On Tue, 30 Oct 2012 20:41:08 -0800, Robert Baer <robertbaer@localnet.com
wrote:

Sum Ting Wong wrote:

Yeah, like dragging the center conductor out of a meter long piece of
coax is an easy task, much less feeding another back through.

Standard RG-8 center conductor dielectric strength is 1.5kV.and they
are not easy to get out. Fairly tightly bound to the core media.

Probably cheaper to find and get the right stuff.
Reason why center conductors are virtually impossible to pull out,is
that the insulation is hot-cast onto the wire..

Then wrapped even tighter by a Chinese handcuff overbraid of silver
plated copper shielding. So tightly it makes a deep fingerprint
impression of the overbraid onto the core media. It doesn't just slide
off either.

What was the code name for the coax with the helically wound insulation,
leaving mostly air as the dielectric? You might stand a chance replacing
the center conductor on that stuff.

I've known it as "heliax".

 

[Michael A. Terrell]

Ralph Barone wrote:

What was the code name for the coax with the helically wound insulation,
leaving mostly air as the dielectric? You might stand a chance replacing
the center conductor on that stuff.

RG/62U 93 Ohm, about 3/8" and fairly stiff.

 

[Jeroen Belleman]

On 2012-10-31 18:15, Frank Miles wrote:

On Wed, 31 Oct 2012 17:34:32 +0100, Jeroen Belleman wrote:

On 2012-10-31 15:28, Michael A. Terrell wrote:

Robert Baer wrote:

Jan Panteltje wrote:
On a sunny day (Mon, 29 Oct 2012 18:21:22 -0800) it happened Robert
Baer<robertbaer@localnet.com> wrote
in<%QGjs.66$Ns4.53@newsfe09.iad>:

Perhaps, but us mortals with a limited budget cannot order
umpteen
thousand feet of coax with a resistive center.
The P6015 used ten feet of coax with resistive center (direct
quote
from manual).
Cannot say what its resistance is..i read 657 ohms end-to-end on
the
cable, and the schematic states 150 ohms 10% at probe end, implying
the coax center is about 500 ohms (~5 ohms per foot).

Personally for a one case, I would take normal coax, pull the center
conductor out,
and insert thinner resistance wire.
Should work for length of 1m or there about.

Not sure if that helps for your case.
That sounds like it may be do-able.
BUT where does that resistance wire come from? Most heaters have
a
much larger diameter nichrome wire, and i do not know where one can
buy "plain" resistive wire like that.
Suggestions?
Oh, "insert" might be a bitch..one might be forced to spot-weld
the
resistive wire to the existing internal wire.
And it ain't easy to pull out....


Does Tektronix or HP list the vendor in their parts list? They do
for most parts.

Good suggestiin the P6106 manualon, but no luck. Tektronix lists itself
as manufacturer of most parts, cable included. Interestingly, it lists
the cable as '39 ohm' cable. The resistance of the central conductor of
a 1m P6106 cable is about 130 ohms. The geometry of the cable suggests a
Z0 much higher than 39 ohms, so I don't know what this is supposed to
mean.

Jeroen Belleman

Hmmn. Maybe 39ohms/ft (series resistance)?

Ah yes, exactly. I still get caught sometimes when some
engineering outfit doesn't use metric throughout.

Jeroen Belleman

 

[Sum Ting Wong]

On Wed, 31 Oct 2012 23:14:12 -0400, krw@att.bizzz wrote:

On Thu, 01 Nov 2012 01:44:26 GMT, Ralph Barone
address_is@invalid.invalid> wrote:

Sum Ting Wong <SumTingWong@thebarattheendoftheVenusianLightningBolt.org
wrote:
On Tue, 30 Oct 2012 20:41:08 -0800, Robert Baer <robertbaer@localnet.com
wrote:

Sum Ting Wong wrote:

Yeah, like dragging the center conductor out of a meter long piece of
coax is an easy task, much less feeding another back through.

Standard RG-8 center conductor dielectric strength is 1.5kV.and they
are not easy to get out. Fairly tightly bound to the core media.

Probably cheaper to find and get the right stuff.
Reason why center conductors are virtually impossible to pull out,is
that the insulation is hot-cast onto the wire..

Then wrapped even tighter by a Chinese handcuff overbraid of silver
plated copper shielding. So tightly it makes a deep fingerprint
impression of the overbraid onto the core media. It doesn't just slide
off either.

What was the code name for the coax with the helically wound insulation,
leaving mostly air as the dielectric? You might stand a chance replacing
the center conductor on that stuff.

I've known it as "heliax".

Yes, and it would be even harder to do that job as the elements that
suspend the center conductor would get trashed on the removal, and then
the replacement would no longer be "at the center", especially when you
bend, form, or use the cable.


The 'heliax' is an integrated structure, and breaking the bonds holding
the center will mean the replacement can move about however it gets
pushed. Not good.

 

[Jasen Betts]

On 2012-10-30, Sum Ting Wong <SumTingWong@thebarattheendoftheVenusianLightningBolt.org> wrote:

On Tue, 30 Oct 2012 08:29:45 GMT, Jan Panteltje
pNaonStpealmtje@yahoo.com> wrote:

On a sunny day (Mon, 29 Oct 2012 18:21:22 -0800) it happened Robert Baer
robertbaer@localnet.com> wrote in <%QGjs.66$Ns4.53@newsfe09.iad>:

Perhaps, but us mortals with a limited budget cannot order umpteen
thousand feet of coax with a resistive center.
The P6015 used ten feet of coax with resistive center (direct quote
from manual).
Cannot say what its resistance is..i read 657 ohms end-to-end on the
cable, and the schematic states 150 ohms 10% at probe end, implying the
coax center is about 500 ohms (~5 ohms per foot).

Personally for a one case, I would take normal coax,
pull the center conductor out,
and insert thinner resistance wire.
Should work for length of 1m or there about.

Not sure if that helps for your case.

Yeah, like dragging the center conductor out of a meter long piece of
coax is an easy task, much less feeding another back through.

Use coax with a high tensile steel core weld a piece of
nichrome wire to the other end first

Standard RG-8 center conductor dielectric strength is 1.5kV.and they
are not easy to get out. Fairly tightly bound to the core media.

you may have to ripple it off, like how a caterpillar walks.
the outer is elastic, but the core is not,

Probably cheaper to find and get the right stuff.

probably a few hour's work plus gettign the welds made (perhaps by a
jeweler?)

--
⚂⚃ 100% natural

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

 

[Fred Abse]

On Wed, 31 Oct 2012 17:46:03 -0400, tm wrote:

1/10 th the circuit loading.

There's a problem with that. The proposed 1:1000 single-stage probe
requires a parallel compensating capacitance 1/1000 of the total
scope-plus-cable capacitance, which is likely to be in the order of 50pF,
which implies a compensating capacitor of 50 fF, or 0.05 pF. across the
probe series resistor. This is probably impossible to realize.

The Tektronix 1:100 HV probe used a special "leaf-and-collar" capacitor of
a few pF, across the 100M probe resistor, which is taking things about as
far as they can go, and still withstand the voltage gradient across the
resistor. The capacitor dielectric was Freon, rather than air, giving a
higher dielectric strength. Freons have a permittivity of around 2, which
helps as well. The probe actually had a load of 100K at the scope end of
the cable, not just the 1meg/22pF scope input, giving 1:1000 ratio.
Compensation adjustment was done at the scope end of the cable, as is
ubiquitous in higher-end probes today.


--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

 

[Fred Abse]

On Tue, 30 Oct 2012 20:33:39 -0800, Robert Baer wrote:

Sorry...mistype... cable is about 50 ohms per foot.

Says so on the schematic in the probe manual.

Probe cables, at least modern ones, use foam dielectric, hence lower
capacitance per foot.

I've got some probes with removable cables, I'll TDR one when I get the
time. I'll have a go at open and shorted measurements, too, and calculate
the complex Zo. With a resistive center, Zo will be significantly complex
at higher frequencies than "regular" coax.

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

 

[Fred Abse]

On Tue, 30 Oct 2012 21:31:19 -0400, Michael A. Terrell wrote:

Are you fir real?

He's just taking the pith.

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

 

[tm]

"Fred Abse" <excretatauris@invalid.invalid> wrote in message
newsan.2012.11.03.13.22.37.696696@invalid.invalid...

On Wed, 31 Oct 2012 17:46:03 -0400, tm wrote:

1/10 th the circuit loading.

There's a problem with that. The proposed 1:1000 single-stage probe
requires a parallel compensating capacitance 1/1000 of the total
scope-plus-cable capacitance, which is likely to be in the order of 50pF,
which implies a compensating capacitor of 50 fF, or 0.05 pF. across the
probe series resistor. This is probably impossible to realize.

The Tektronix 1:100 HV probe used a special "leaf-and-collar" capacitor of
a few pF, across the 100M probe resistor, which is taking things about as
far as they can go, and still withstand the voltage gradient across the
resistor. The capacitor dielectric was Freon, rather than air, giving a
higher dielectric strength. Freons have a permittivity of around 2, which
helps as well. The probe actually had a load of 100K at the scope end of
the cable, not just the 1meg/22pF scope input, giving 1:1000 ratio.
Compensation adjustment was done at the scope end of the cable, as is
ubiquitous in higher-end probes today.

Certainly not disagreeing with you Fred. In fact I don't know of any 1000:1
probes that are good at high frequency measurements. But for DC
measurements, you would want a 1Gohm probe for best accuracy measurements.

Also, I think I read somewhere that the Freon 114 used in the 6015 probe had
a permittivity near to 1. There was some discussion of using F-11 as a
replacement but its permittivity is up there and the probe does not work
well with it.

There is some good information on the yahoo tekscopes group archives
concerning this probe.

Regards

 

[Michael A. Terrell]

Fred Abse wrote:

On Tue, 30 Oct 2012 21:31:19 -0400, Michael A. Terrell wrote:

Are you fir real?

He's just taking the pith.

That's just nuts!

 

[tm]

"tm" <No_one_home@white-house.gov> wrote in message
news:k73gve$du6$1@dont-email.me...

"Fred Abse" <excretatauris@invalid.invalid> wrote in message
newsan.2012.11.03.13.22.37.696696@invalid.invalid...
On Wed, 31 Oct 2012 17:46:03 -0400, tm wrote:

1/10 th the circuit loading.

There's a problem with that. The proposed 1:1000 single-stage probe
requires a parallel compensating capacitance 1/1000 of the total
scope-plus-cable capacitance, which is likely to be in the order of 50pF,
which implies a compensating capacitor of 50 fF, or 0.05 pF. across the
probe series resistor. This is probably impossible to realize.

The Tektronix 1:100 HV probe used a special "leaf-and-collar" capacitor
of
a few pF, across the 100M probe resistor, which is taking things about as
far as they can go, and still withstand the voltage gradient across the
resistor. The capacitor dielectric was Freon, rather than air, giving a
higher dielectric strength. Freons have a permittivity of around 2, which
helps as well. The probe actually had a load of 100K at the scope end of
the cable, not just the 1meg/22pF scope input, giving 1:1000 ratio.
Compensation adjustment was done at the scope end of the cable, as is
ubiquitous in higher-end probes today.



Certainly not disagreeing with you Fred. In fact I don't know of any
1000:1 probes that are good at high frequency measurements. But for DC
measurements, you would want a 1Gohm probe for best accuracy measurements.

Also, I think I read somewhere that the Freon 114 used in the 6015 probe
had a permittivity near to 1. There was some discussion of using F-11 as a
replacement but its permittivity is up there and the probe does not work
well with it.

There is some good information on the yahoo tekscopes group archives
concerning this probe.

Regards

I meant to say any 1 G ohm, 1k:1 probes.

 

[josephkk]

On Sat, 03 Nov 2012 18:25:19 -0800, Robert Baer <robertbaer@localnet.com>
wrote:

Fred Abse wrote:
On Tue, 30 Oct 2012 20:33:39 -0800, Robert Baer wrote:

Sorry...mistype... cable is about 50 ohms per foot.

Says so on the schematic in the probe manual.

Probe cables, at least modern ones, use foam dielectric, hence lower
capacitance per foot.

I've got some probes with removable cables, I'll TDR one when I get the
time. I'll have a go at open and shorted measurements, too, and calculate
the complex Zo. With a resistive center, Zo will be significantly complex
at higher frequencies than "regular" coax.

Thought of a way to (perhaps) make resistive coax with element in the
50 ohm per foot region.
Find some Nichrome or other resistive (heater) wire,and use Teflon
sleeving in successive layers or use shrink tubing in successive layers.
Slip braid around that.

Nicrhome is ok for heater uses, but i prefer constantan for electronic
purposes. Check out the properties differences, it will be worth it.

?-)

 

[josephkk]

On Sat, 03 Nov 2012 18:21:07 -0800, Robert Baer <robertbaer@localnet.com>
wrote:

Fred Abse wrote:
On Wed, 31 Oct 2012 17:46:03 -0400, tm wrote:

1/10 th the circuit loading.

There's a problem with that. The proposed 1:1000 single-stage probe
requires a parallel compensating capacitance 1/1000 of the total
scope-plus-cable capacitance, which is likely to be in the order of 50pF,
which implies a compensating capacitor of 50 fF, or 0.05 pF. across the
probe series resistor. This is probably impossible to realize.

The Tektronix 1:100 HV probe used a special "leaf-and-collar" capacitor of
a few pF, across the 100M probe resistor, which is taking things about as
far as they can go, and still withstand the voltage gradient across the
resistor. The capacitor dielectric was Freon, rather than air, giving a
higher dielectric strength. Freons have a permittivity of around 2, which
helps as well. The probe actually had a load of 100K at the scope end of
the cable, not just the 1meg/22pF scope input, giving 1:1000 ratio.
Compensation adjustment was done at the scope end of the cable, as is
ubiquitous in higher-end probes today.


Correct, except it is 1000:1; all else is OK.

I am purposely using a larger capacitance as i am not mechanically
inclined; easy to put plastic tube around resistors, centered with thin
sheet, and wrap adhesive copper foil on outside cut for same length as
resistor.
Easy to calculate capacitance of the resulting coax (resistor / air /
inner tube surface / acrylic / outer tube surface = = floating shield.

Whoosh

?-/

 

[josephkk]

On Sat, 03 Nov 2012 12:55:56 -0400, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

Fred Abse wrote:

On Tue, 30 Oct 2012 21:31:19 -0400, Michael A. Terrell wrote:

Are you fir real?

He's just taking the pith.


That's just nuts!

How squirrely is this going to get?

?-))