Homebrew HV hiZ scope probe

Robert Baer

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Oct 20, 2012, 4:42:11 PM10/20/12

to

See similar title in a.b.s.electronic for PDF.
Almost took longer to document than to build..

Jan Panteltje

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Oct 20, 2012, 3:48:33 PM10/20/12

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On a sunny day (Sat, 20 Oct 2012 12:42:11 -0800) it happened Robert Baer
<rober...@localnet.com> wrote in <J8Dgs.1184$aW7....@newsfe24.iad>:

> See similar title in a.b.s.electronic for PDF.
> Almost took longer to document than to build..

Nobody can get that group.

TheGlimmerMan

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Oct 20, 2012, 3:53:32 PM10/20/12

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On Sat, 20 Oct 2012 12:42:11 -0800, Robert Baer <rober...@localnet.com>
wrote:

> See similar title in a.b.s.electronic for PDF.
> Almost took longer to document than to build..

This HV load bank took a while to build.

http://www.mediafire.com/view/?r7mxc48guymk9#o19a4alp8vk1kkb

HV Probes are easy. A sealed dry AIR based (or gas) container for a
precision HV resistor string. Potted versions lose accuracy and are
harder to make calibration adjustments on.

Martin Riddle

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Oct 20, 2012, 9:01:30 PM10/20/12

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"Jan Panteltje" <pNaonSt...@yahoo.com> wrote in message
news:k5uv6l$6vf$1...@news.albasani.net...

alt.binaries.schematics.electronic ?
I get that group, but I don't see the post.

Cheers

Robert Baer

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Oct 21, 2012, 1:29:53 AM10/21/12

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TheGlimmerMan wrote:
> On Sat, 20 Oct 2012 12:42:11 -0800, Robert Baer<rober...@localnet.com>
> wrote:
>
>> See similar title in a.b.s.electronic for PDF.
>> Almost took longer to document than to build..
>
> This HV load bank took a while to build.
>
> http://www.mediafire.com/view/?r7mxc48guymk9#o19a4alp8vk1kkb

* Bet it took a fair amount of time for that labeling in the image.

>
>
> HV Probes are easy. A sealed dry AIR based (or gas) container for a
> precision HV resistor string. Potted versions lose accuracy and are
> harder to make calibration adjustments on.

Would adding heat shrink on the 1% resistors mess them up at high (up
to 20KV) voltage?
As an alternate, what about wrapping them with Kapton(TM)?

John Larkin

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Oct 21, 2012, 12:48:09 AM10/21/12

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A scope probe needs high frequency compensation, too, like a cap
across each resistor and a variable cap at the bottom to tweak the
step response.

--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

legg

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Oct 21, 2012, 2:22:02 PM10/21/12

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Ditto

RL

Jim Thompson

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Oct 21, 2012, 1:44:29 PM10/21/12

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Yep. For some reason I _never_ see any posts by Panteltje >:-}

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

legg

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Oct 21, 2012, 4:52:40 PM10/21/12

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On Sun, 21 Oct 2012 10:44:29 -0700, Jim Thompson
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:

>On Sun, 21 Oct 2012 13:22:02 -0500, legg <le...@nospam.magma.ca> wrote:
>
>>On Sat, 20 Oct 2012 21:01:30 -0400, "Martin Riddle"
>><marti...@verizon.net> wrote:
>>
>>>
>>>"Jan Panteltje" <pNaonSt...@yahoo.com> wrote in message
>>>news:k5uv6l$6vf$1...@news.albasani.net...
>>>> On a sunny day (Sat, 20 Oct 2012 12:42:11 -0800) it happened Robert
>>>> Baer
>>>> <rober...@localnet.com> wrote in <J8Dgs.1184$aW7....@newsfe24.iad>:
>>>>
>>>>> See similar title in a.b.s.electronic for PDF.
>>>>> Almost took longer to document than to build..
>>>>
>>>> Nobody can get that group.
>>>
>>>alt.binaries.schematics.electronic ?
>>>I get that group, but I don't see the post.
>>>
>>>Cheers
>>>
>>Ditto
>>
>>RL
>
>Yep. For some reason I _never_ see any posts by Panteltje >:-}
>
> ...Jim Thompson

I believe its Baer's post that's gone astray.
RL

Jim Thompson

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Oct 21, 2012, 3:55:52 PM10/21/12

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I was being facetious >:-}

Jasen Betts

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Oct 22, 2012, 3:22:02 AM10/22/12

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freenews.netfront.net carries ABSE but only the smaller posts (not
large binaries)

For the binaries Astraweb.com 180GB $25 never expires. Since march
ABSE has used aboiut 0.68GB, so at that rate I'll be putting it in
my will.

--
⚂⚃ 100% natural

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

Jan Panteltje

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Oct 22, 2012, 4:24:17 AM10/22/12

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On a sunny day (22 Oct 2012 07:22:02 GMT) it happened Jasen Betts
<ja...@xnet.co.nz> wrote in <k62s6q$jd4$1...@reversiblemaps.ath.cx>:

>freenews.netfront.net carries ABSE but only the smaller posts (not
>large binaries)

OK I see that group, but not his pdf.

>For the binaries Astraweb.com 180GB $25 never expires.

Well, I do not need it that much.

Robert Baer

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Oct 23, 2012, 2:04:28 AM10/23/12

to

Somehow the post vaporized, so i put it up on my corporate site at
http://www.oil4lessllc.org/HV%20probes/ .
That probe was a "quick and dirty"; rise time seems to be better than
20nSec (my "pulse generator" is a HP3312A function generator).
However, the output step only goes up 70% then a slow rise to max
with a time constant of about 600nSec.
*
Am using SPICE to help design a 40KV probe and i seem to be homing
into a design with values.
The listing is below (and on that site).
The attenuation ratio is 2500 and is "protected" to ground like the
Tektronix probes.
Why 2500? Because it takes two 1Gohm resistors to withstand the 40KV
(target rating is 30KV with some "elbow room").
Note the resistance ratio is exactly 2500:1 and (now) the capacitance
ratio is close also.

Physical layout is to have a floating ring around each resistor,to
provide a controllable input coupling and capacitive divider (which is
the secret of a (theoretical) infinite risetime.
Now around this whole assembly will be a grounded shield (to isolate
input from external bazzzz fazzzz).
I think that five sections is a reasonable division of each resistor
for emulation of the actual distributed part.

Risetime seems to be infinite, but there is this slow "hump" that i
am fighting.
Any ideas as how to solve?

Version 4
SHEET 1 2064 680
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SYMATTR Value {Cs}
SYMBOL cap 768 160 R0
SYMATTR InstName C22
SYMATTR Value {Cs}
TEXT 264 256 Left 2 !.tran 0 10m 0 10n
TEXT 264 -208 Left 4 ;40KV 2E9 ohms HV scope probe
TEXT -144 -120 Left 2 ;Ohmite MOX2-131007FE\nin pi net distributed form
TEXT 168 160 Left 2 !.PARAM Cr=10p, Cs=7.9p, Rp=200Meg
TEXT 672 -120 Left 2 ;Ohmite MOX2-131007FE\nin pi net distributed form

legg

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Oct 23, 2012, 10:53:30 AM10/23/12

to

On Mon, 22 Oct 2012 22:04:28 -0800, Robert Baer
<rober...@localnet.com> wrote:

<snip>

It's conventional to include a 'tip' resistor, that will absorb
contact (arc) surges safely.

The hardest thing about HV probe structure, is getting practical
values that are physically possible, to do the job. Look at physical
embodiments, make a few measurements, then go to the model.

Not much point in speculating over something that you can't build.
Sizing the capacitive divider is a real physical issue. Your Cr/Cs
ratio may be impractical.

As to risetime, an intentional RCseries, paralleling C22 position can
act on leading edges. Look at the current midpoint voltage (jn
C10/C11). Also, run an ac sweep.......the LF and HF gains will meet at
some point that will look like a can of worms, and is just as easily
manipulated, given physical constraints.

RL

Jon Elson

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Oct 23, 2012, 3:51:30 PM10/23/12

to

Robert Baer wrote:

>
> Physical layout is to have a floating ring around each resistor,to
> provide a controllable input coupling and capacitive divider (which is
> the secret of a (theoretical) infinite risetime.
> Now around this whole assembly will be a grounded shield (to isolate
> input from external bazzzz fazzzz).
> I think that five sections is a reasonable division of each resistor
> for emulation of the actual distributed part.
>
> Risetime seems to be infinite, but there is this slow "hump" that i
> am fighting.
> Any ideas as how to solve?

High-Ohm resistors have been reported to be non-linear, possibly that is
what you are getting. You may need some more poles of RC compensation
to try to fix this.

Jon

legg

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Oct 23, 2012, 5:58:39 PM10/23/12

to

On Mon, 22 Oct 2012 22:04:28 -0800, Robert Baer
<rober...@localnet.com> wrote:

Have you attempted a spice simulation of the part you've actually
built and tested? This would be more than just instructive and assist
in developing the newer iteration and an understanding of the spice
derivative.

RL

Robert Baer

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Oct 24, 2012, 12:02:20 AM10/24/12

to

* The only guides i have so far,are the Tektronix P6015 probe and the
"quick and dirty" 1Gohm probe i built.
Unfortunately, i have no way to making reasonable guesses related to
capacitances involved in their construction. The few P6015 drawings
leave a lot to be desired, and measurements on my Q&D probe would be
extremely difficult to do due to some of the very low values.

>
> Not much point in speculating over something that you can't build.
> Sizing the capacitive divider is a real physical issue. Your Cr/Cs
> ratio may be impractical.

* But i have one working one, and the model for it.
And as far as sizing the capacitive divider, as long as there is a
simple capacitor from tip to output, and its ratio to a total
corresponding capacitance from there to ground, there is no problem;
that is simple - for a simple model.

>
> As to risetime, an intentional RCseries, paralleling C22 position can
> act on leading edges. Look at the current midpoint voltage (jn
> C10/C11). Also, run an ac sweep.......the LF and HF gains will meet at
> some point that will look like a can of worms, and is just as easily
> manipulated, given physical constraints.
>
> RL

* The Cs was tweaked for "best looks", and could be easily done
mechanically. The Cr is done via floating coaxial "shield" around the
resistor (see the aluminum foil wrap on the Q&D probe i built).

Robert Baer

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Oct 24, 2012, 12:09:44 AM10/24/12

to

"non-linear" can mean many things..voltage coefficient, temperature
coefficient, and resistance per unit across the length (i assume that is
what you are referring to).
Where is that "report"? What date?
I do not think the resistance per unit length varies much, certainly
not so much as to give the waveform seen in the simulation.
That can be varied by quite a bit by changing Cs and/or Cr.
However, it might be a GOOD THING (as Martha Stewart would say) to
use ten pi pads instead of five for the resistor.

Robert Baer

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Oct 24, 2012, 12:15:27 AM10/24/12

to

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Oct 25, 2012, 9:14:52 PM10/25/12

to

On Thu, 25 Oct 2012 09:36:51 GMT, Jan Panteltje
<pNaonSt...@yahoo.com> wrote:

>
>Safe to touch 7kV high power with that?

You're an idiot.

First, you have no clue what "high power" is.

>For TV maybe (<5 mA).

You have no concept of stored energy.

Robert Baer

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Oct 26, 2012, 1:32:51 AM10/26/12

to

Yep; cheap, small, does the job.

legg

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Oct 26, 2012, 11:28:06 PM10/26/12

to

On Tue, 23 Oct 2012 20:15:27 -0800, Robert Baer

<rober...@localnet.com> wrote:

>legg wrote:
>> On Mon, 22 Oct 2012 22:04:28 -0800, Robert Baer
>> <rober...@localnet.com> wrote:
>>

<snip

>>> Somehow the post vaporized, so i put it up on my corporate site at
>>> http://www.oil4lessllc.org/HV%20probes/ .
>>> That probe was a "quick and dirty"; rise time seems to be better than
>>> 20nSec (my "pulse generator" is a HP3312A function generator).
>>> However, the output step only goes up 70% then a slow rise to max
>>> with a time constant of about 600nSec.
>>> *
>>> Am using SPICE to help design a 40KV probe and i seem to be homing
>>> into a design with values.
>>> The listing is below (and on that site).
>>
>> Have you attempted a spice simulation of the part you've actually
>> built and tested? This would be more than just instructive and assist
>> in developing the newer iteration and an understanding of the spice
>> derivative.
>>
>> RL
> Yes, but i started with a very simple C across the 1G resistor and
>one to ground; it was plain that i needed (so to speak) more cable
>capacitance,and better adjust-ability of that.
> Made no refinements.
> Basically, that probe was an exercise of "can it be done"?
> And it has the noted deficiency of no ground return inside (hence the
>big fat warnings).

Does the model act as the physical part scopes out?

RL

Message has been deleted

Robert Baer

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Oct 28, 2012, 11:11:03 PM10/28/12

to

Fred Abse wrote:

> On Mon, 22 Oct 2012 22:04:28 -0800, Robert Baer wrote:
>
>> Am using SPICE to help design a 40KV probe and i seem to be homing
>> into a design with values.
>> The listing is below (and on that site). The attenuation ratio is 2500
>> and is "protected" to ground like the
>> Tektronix probes.
>> Why 2500? Because it takes two 1Gohm resistors to withstand the 40KV
>> (target rating is 30KV with some "elbow room").
>> Note the resistance ratio is exactly 2500:1 and (now) the capacitance
>> ratio is close also.
>>
>> Physical layout is to have a floating ring around each resistor,to
>> provide a controllable input coupling and capacitive divider (which is the
>> secret of a (theoretical) infinite risetime.
>> Now around this whole assembly will be a grounded shield (to isolate
>> input from external bazzzz fazzzz).
>> I think that five sections is a reasonable division of each resistor
>> for emulation of the actual distributed part.
>>
>> Risetime seems to be infinite, but there is this slow "hump" that i
>> am fighting.
>> Any ideas as how to solve?
>

> Takes forever to converge.
>
> I softened the analysis a bit by making the pulse risetime 20ns, similar
> to your HP3312A, but it's still excruciatingly slow.
>
> How sure are you of the resistor model? Have you considered making it a
> uniform RC line (U) model? I'll try that in a while, it might converge
> faster.
>
> There's a pole at around 67 Hz that needs addressing.
>
> I added 3 feet of RG179, which i have a model for, which is similar to
> RG175, for which I don't. The inevitable quarter-wave spikes appear at
> around 46MHz, et seq. 60 ohms in series with each end of the coax tames
> this, and we now have a 3dB rolloff around 70MHz, making risetime about
> 5ns. That's why resistive cable is used in commercial probes.
>
> I'd do what Tektronix do, and do all compensation at the 'scope end.
>
> Bear in mind that Tek's 40kV probes used to run their HV resistor in an
> atmosphere of Fluorcarbon 114 vapor, which needed topping up from time to
> time. I don't know what they use these days in HV probes, but I doubt it's
> FC.
>
> Try this, it's your circuit with 3 feet of coax. Do an .ac analysis, with
> and without the 60 ohm resistors.
>
** This is what i have, before i saw your response; not too bad
considering simple compensation and implicit coax of indeterminate (but
limited) length to scope end.
Also posted at: http://www.oil4lessllc.org/HV%20probes/ .

Version 4
SHEET 1 2064 680

WIRE 1488 -64 1488 -240

WIRE -352 -16 -448 -16
WIRE -208 -16 -272 -16
WIRE -64 -16 -128 -16
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WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value PULSE(0 250 0 1p 1p 10 20 1)

SYMBOL cap 1184 160 R180
WINDOW 0 -37 59 Left 2
WINDOW 3 28 4 Left 2
SYMATTR InstName C91
SYMATTR Value 1170p
SYMBOL res 1424 48 R0
WINDOW 3 -89 120 Left 2
WINDOW 0 -49 70 Left 2
SYMATTR Value 4.008Meg
SYMATTR InstName R33
SYMATTR SpiceLine tol=0.1 pwr=1
SYMBOL cap 1600 80 R0

SYMATTR InstName C32
SYMATTR Value 22p

SYMBOL res 1584 160 R180

SYMBOL res 1184 0 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R91
SYMATTR Value 1200
SYMBOL cap 1328 272 R180

WINDOW 0 24 56 Left 2
WINDOW 3 24 8 Left 2

SYMATTR InstName C92
SYMATTR Value 900p
SYMBOL res 1296 64 R0
WINDOW 3 -56 49 Left 2
WINDOW 0 -40 8 Left 2
SYMATTR Value 590K
SYMATTR InstName R92
TEXT 264 256 Left 2 !.tran 0 10m 0 10u
TEXT 264 -232 Left 4 ;40KV 2E9 ohms HV scope probe 2500:1
TEXT -144 -120 Left 2 ;Ohmite MOX2-131007FE\nin pi pad distributed form
TEXT 168 160 Left 2 !.PARAM Cr=2.048p, Cs=0.1p, Rp=200Meg
TEXT 672 -120 Left 2 ;Ohmite MOX2-131007FE\nin pi pad distributed form
TEXT 1536 -152 Left 2 ;[SCOPE]
TEXT 1320 -152 Left 2 ;[PROBE]
TEXT 336 -184 Left 3 ;Tr~27nSec; 2% overshoot at 1mSec

Robert Baer

unread,

Oct 28, 2012, 11:51:16 PM10/28/12

to

Fred Abse wrote:
> On Mon, 22 Oct 2012 22:04:28 -0800, Robert Baer wrote:
>

>> Am using SPICE to help design a 40KV probe and i seem to be homing
>> into a design with values.
>> The listing is below (and on that site). The attenuation ratio is 2500
>> and is "protected" to ground like the
>> Tektronix probes.
>> Why 2500? Because it takes two 1Gohm resistors to withstand the 40KV
>> (target rating is 30KV with some "elbow room").
>> Note the resistance ratio is exactly 2500:1 and (now) the capacitance
>> ratio is close also.
>>
>> Physical layout is to have a floating ring around each resistor,to
>> provide a controllable input coupling and capacitive divider (which is the
>> secret of a (theoretical) infinite risetime.
>> Now around this whole assembly will be a grounded shield (to isolate
>> input from external bazzzz fazzzz).
>> I think that five sections is a reasonable division of each resistor
>> for emulation of the actual distributed part.
>>
>> Risetime seems to be infinite, but there is this slow "hump" that i
>> am fighting.
>> Any ideas as how to solve?
>

> Takes forever to converge.
>
> I softened the analysis a bit by making the pulse risetime 20ns, similar
> to your HP3312A, but it's still excruciatingly slow.
>
> How sure are you of the resistor model? Have you considered making it a
> uniform RC line (U) model? I'll try that in a while, it might converge
> faster.
>
> There's a pole at around 67 Hz that needs addressing.
>
> I added 3 feet of RG179, which i have a model for, which is similar to
> RG175, for which I don't. The inevitable quarter-wave spikes appear at
> around 46MHz, et seq. 60 ohms in series with each end of the coax tames
> this, and we now have a 3dB rolloff around 70MHz, making risetime about
> 5ns. That's why resistive cable is used in commercial probes.
>
> I'd do what Tektronix do, and do all compensation at the 'scope end.
>
> Bear in mind that Tek's 40kV probes used to run their HV resistor in an
> atmosphere of Fluorcarbon 114 vapor, which needed topping up from time to
> time. I don't know what they use these days in HV probes, but I doubt it's
> FC.
>
> Try this, it's your circuit with 3 feet of coax. Do an .ac analysis, with
> and without the 60 ohm resistors.

I see you made Cs, capacitance from floating shields, a lot larger =
8pf instead of my wild guesstimate of 0.1pf.
Those floating shields allow defined and predictable capacitive
coupling across the resistors; the capacitance from them to "outer
space" ground seems to be undefinable: coax capacitance runs
(log(D/d))^-1 and with a theoretically infinite D (or very large D in
reality),the capacitance is rather close to zero.
I picked 0.1pf as an estimate to that "zero"; seems you picked a huge
8pf.
*
I did not know of that uniform RC line (U) model; it would be an
excellent choice; better than the pi-pad scheme.
Values can easily be calculated on basis of resistor diameter,
dielectric material and floating shield diameter.
Seems that an eXplicit shield around the floating shield makes for
more trouble.

Message has been deleted

Jeroen Belleman

unread,

Oct 29, 2012, 6:35:46 AM10/29/12

to

On 2012-10-29 10:33, Fred Abse wrote:

> On Sun, 28 Oct 2012 19:11:03 -0800, Robert Baer wrote:
>
>> ** This is what i have, before i saw your response; not too bad
>> considering simple compensation and implicit coax of indeterminate (but
>> limited) length to scope end.
>

> You can't ignore the effect of what is, in effect, an open-circuit quarter
> wave line, at a frequency within the intended bandwidth of the probe.
>
> 3 feet of 0,66 velocity coax, terminated in a large resistance will
> resonate at about 54MHz, and ring like a bell. That's why resistive cables
> are used.
>

Do you have any idea where one can buy resistive cable?

Jeroen Belleman

TheGlimmerMan

unread,

Oct 29, 2012, 7:00:04 AM10/29/12

to

Modern automotive "spark plug wire". Has a "graphite core". Specific
R per foot value. Meant to be an emission suppressive passage for HV
pulses being fed to the plugs, something which generally causes a pretty
big magnetic spike to emanate.

There were folks in the '50s and '60s (hams) who even went so far as to
fully ground shield each of their spark plug wires to reduce the problem.
Then they (those 'they' people) came out with the better, resistive wire
and the problem sufficiently subsided..

May not be exactly what you seek, but that is the only version I am
aware of.

Jamie

unread,

Oct 29, 2012, 10:47:50 AM10/29/12

to

We had an old car here once that I decided to tackle a blower problem
in the heating and ventilation system. THe problem, no blower operation.

After tearing out the blower box under the glove compartment, which
was a big job getting to, I found there was nothing wrong with the
blower motor. The plug was too hard to get to so it wasn't an easy
option to simply test it before hand. So I went to the control switch,
that worked ok. So I then started ripping apart the harness, they had
put a resistor wire in the harness for the blower to reduce the brush
noise in the electrical system.

At that point, I really didn't care much for the car, it was getting
old, so I just hung a copper wire outside of the harness.. I can say
this, not only was that wire there to reduce noise, it also served as a
voltage drop to the blower, that thing was like a wind tunnel afterwards :)

Jamie

unread,

Oct 29, 2012, 6:51:02 PM10/29/12

to

Don't know. The entire cabin is knotty pine, inside and out. But pine
trees are mostly farmed, a renewable resource.

The cabin is sort of a small-scale ripoff of a Frank Lloyd Wright
church in Madison, Wisconsin. Go see it if you're even in the
neighborhood. The church, I mean.

http://www.bc.edu/bc_org/avp/cas/fnart/fa267/flw/unitarian01.jpg

The baer was done by an elementary school kid, part of a fund raiser
up in Truckee. My other birthday present was the snow.

--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

Robert Baer

unread,

Oct 29, 2012, 10:06:30 PM10/29/12

to

Oops..now i see an unreasonable Cr of 10pf; that would total to 50pf
on a resistor; VERY hard to implement.
Dimensions:

+++ +++
| |++++++++++++++++++++++++++| |
----| |----
| |++++++++++++++++++++++++++| |
+++ +++
^-------metal end caps-------^

Metal end caps 0.285 dia, body 0.265 dia, end cap width 0.180, and
end-to-end width 2.085 inches
Most plastics (for insulation and support of the floating shield)
have roughly 3 for dielectric constant, and a tube minimum diameter
would contact only the end caps at best; 1/16 wall thickness at smallest.

Robert Baer

unread,

Oct 29, 2012, 10:07:28 PM10/29/12

to

> Version 4
> SHEET 1 2064 680

> WIRE -352 -16 -448 -16
> WIRE -208 -16 -272 -16
> WIRE -64 -16 -128 -16
> WIRE 80 -16 16 -16
> WIRE 224 -16 160 -16
> WIRE 448 -16 304 -16
> WIRE 592 -16 528 -16
> WIRE 736 -16 672 -16
> WIRE 880 -16 816 -16
> WIRE 1024 -16 960 -16

> WIRE 1280 -16 1104 -16
> WIRE 1328 -16 1280 -16
> WIRE 1408 -16 1328 -16
> WIRE 1568 -16 1488 -16
> WIRE 1760 -16 1664 -16
> WIRE 1952 -16 1840 -16
> WIRE 1984 -16 1952 -16

> WIRE -352 16 -352 -16
> WIRE -272 16 -272 -16
> WIRE -208 16 -208 -16
> WIRE -128 16 -128 -16
> WIRE -64 16 -64 -16
> WIRE 16 16 16 -16
> WIRE 80 16 80 -16
> WIRE 160 16 160 -16
> WIRE 224 16 224 -16
> WIRE 304 16 304 -16
> WIRE 448 16 448 -16
> WIRE 528 16 528 -16
> WIRE 592 16 592 -16
> WIRE 672 16 672 -16
> WIRE 736 16 736 -16
> WIRE 816 16 816 -16
> WIRE 880 16 880 -16
> WIRE 960 16 960 -16
> WIRE 1024 16 1024 -16
> WIRE 1104 16 1104 -16

> WIRE 1568 16 1552 16
> WIRE 1680 16 1664 16
> WIRE 1280 32 1280 -16
> WIRE 1328 64 1328 -16
> WIRE 1952 64 1952 -16
> WIRE 2000 64 1952 64
> WIRE 2000 80 2000 64

> WIRE 1280 144 1280 96
> WIRE 2000 144 1952 144

> WIRE -448 160 -448 -16
> WIRE -32 160 -32 112
> WIRE 784 160 784 112

> WIRE 2000 192 2000 144
> WIRE 1328 224 1328 144
> WIRE 1552 224 1552 16
> WIRE 1680 224 1680 16

> WIRE -448 272 -448 240
> WIRE -32 272 -32 224
> WIRE 784 272 784 224

> FLAG 1328 224 0
> FLAG 2000 192 0
> FLAG 1984 -16 scope
> FLAG 1280 144 0

> FLAG -448 272 0
> FLAG 784 272 0
> FLAG -32 272 0

> FLAG 1680 224 0
> FLAG 1552 224 0

> SYMBOL voltage -448 144 R0
> WINDOW 0 8 7 Left 2
> WINDOW 3 11 105 Left 2

> WINDOW 123 11 123 Left 2
> WINDOW 39 11 141 Left 2
> SYMATTR InstName V2
> SYMATTR Value PULSE(0 250 0 20n 20n 1m 2m 10)
> SYMATTR Value2 AC 1
> SYMATTR SpiceLine Rser=50
> SYMBOL cap 1296 96 R180

> WINDOW 0 24 56 Left 2
> WINDOW 3 24 8 Left 2

> SYMATTR InstName C31
> SYMATTR Value 2478p
> SYMBOL res 1312 48 R0
> WINDOW 3 30 126 Left 2
> SYMATTR Value 4.008Meg
> SYMATTR InstName R31
> SYMATTR SpiceLine tol=0.1 pwr=1
> SYMBOL cap 1984 80 R0

> SYMATTR InstName C32
> SYMATTR Value 22p

> SYMBOL res 1968 160 R180

> SYMBOL ltline 1616 0 R0
> SYMATTR InstName O1
> SYMATTR Value RG179
> SYMBOL res 1504 0 M270

> WINDOW 0 32 56 VTop 2
> WINDOW 3 0 56 VBottom 2

> SYMATTR InstName R11
> SYMATTR Value {R}
> SYMBOL res 1856 0 M270

> WINDOW 0 32 56 VTop 2
> WINDOW 3 0 56 VBottom 2

> SYMATTR InstName R12
> SYMATTR Value {R}
> TEXT 264 256 Left 2 !.ac dec 1000 1 200meg
> TEXT 264 -208 Left 4 ;40KV 2E9 ohms HV scope probe
> TEXT -144 -120 Left 2 ;Ohmite MOX2-131007FE\nin pi net distributed form
> TEXT 168 160 Left 2 !.PARAM Cr=10p, Cs=7.9p, Rp=200Meg
> TEXT 672 -120 Left 2 ;Ohmite MOX2-131007FE\nin pi net distributed form
> TEXT 272 384 Left 2 !.model RG179 LTRA (\n+ len=3\n+ L=.1u\n+ C=19.5p\n+ R=252.5e-3\n+)
> TEXT 272 328 Left 2 !;.step param R 10 100 10m \n.param R = 60
> TEXT 272 -176 Left 2 ;3 feet RG179 (similar to RG175) added to model\nBelden 83265 data used.
>
>
>
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.

Robert Baer

unread,

Oct 29, 2012, 10:21:22 PM10/29/12

to

> *Almost* the same effect can be got by putting a small (tens to hundreds
> of ohms) in series with each end, if all you want is to damp resonances in
> a probe.

* Check.

Robert Baer

unread,

Oct 29, 2012, 11:05:31 PM10/29/12

to

That is exactly what was used as a reference by Fred Abse in his
Spice listing (Belden 83265 is RG-178B/U 50 ohms) .. but data used was
for the RG179 which is 75 ohms but otherwise rather similar.

Sjouke Burry

unread,

Oct 29, 2012, 11:07:24 PM10/29/12

to

Robert Baer <rober...@localnet.com> wrote in
news:_SGjs.67$Ns4...@newsfe09.iad:

> Jeroen Belleman wrote:
>> On 2012-10-29 10:33, Fred Abse wrote:
>>> On Sun, 28 Oct 2012 19:11:03 -0800, Robert Baer wrote:
>>>
>>>> ** This is what i have, before i saw your response; not too bad
>>>> considering simple compensation and implicit coax of indeterminate
>>>> (but limited) length to scope end.
>>>
>>> You can't ignore the effect of what is, in effect, an open-circuit
>>> quarter
>>> wave line, at a frequency within the intended bandwidth of the
>>> probe.
>>>
>>> 3 feet of 0,66 velocity coax, terminated in a large resistance will
>>> resonate at about 54MHz, and ring like a bell. That's why resistive
>>> cables
>>> are used.
>>>
>>
>> Do you have any idea where one can buy resistive cable?

CUT

Any car repair shop.
Used to hook up spark plugs.

Michael A. Terrell

unread,

Oct 30, 2012, 12:40:38 AM10/30/12

to

He's just another sap...

Jan Panteltje

unread,

Oct 30, 2012, 4:29:45 AM10/30/12

to

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

Sum Ting Wong

unread,

Oct 30, 2012, 5:08:49 AM10/30/12

to

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.

Message has been deleted

John Larkin

unread,

Oct 30, 2012, 7:16:12 AM10/30/12

to

It's not nice to needle people like that.

TheGlimmerMan

unread,

Oct 30, 2012, 7:46:43 AM10/30/12

to

On Tue, 30 Oct 2012 02:45:03 -0700, Fred Abse
<excret...@invalid.invalid> wrote:

>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.
>

>Not any more. It has derated itself to about 12kV. It won't do 40kV
>anymore without the fluorocarbon.
>
>If you can get the 114 from somewhere, you can recharge it. See the manual.

DuPont (Ithought)(apperently 3M now) FC-40 also works. "Fluorinert"

http://multimedia.3m.com/mws/mediawebserver?66666UuZjcFSLXTtnxTEo8s6EVuQEcuZgVs6EVs6E666666%E2%80%94

TheGlimmerMan

unread,

Oct 30, 2012, 7:48:23 AM10/30/12

to

On Tue, 30 Oct 2012 04:16:12 -0700, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>On Tue, 30 Oct 2012 00:40:38 -0400, "Michael A. Terrell"
><mike.t...@earthlink.net> wrote:
>
>>
>>Robert Baer wrote:
>>>
>>> Jamie wrote:
>>> > John Larkin wrote:
>>> >
>>> >> On Sat, 20 Oct 2012 12:42:11 -0800, Robert Baer
>>> >> <rober...@localnet.com> wrote:
>>> >>
>>> >>
>>> >>> See similar title in a.b.s.electronic for PDF.
>>> >>> Almost took longer to document than to build..
>>> >>
>>> >>
>>> >>
>>> >> This is my best birthday present.
>>> >>
>>> >> https://dl.dropbox.com/u/53724080/Truckee/Birthday_Baer.jpg
>>> >>
>>> >>
>>> >> grrrrrrrr.
>>> >>
>>> >>
>>> >>
>>> > how many pine trees had to be cut down to build that wall for you?
>>> >
>>> > Jamie
>>> >
>>> If you were a true tree huger, you _would_ "pine" for them..
>>
>>
>> He's just another sap...
>
>It's not nice to needle people like that.

Is "people like that" referring to the needling method or the "way" the
person is?

John Fields

unread,

Oct 30, 2012, 7:56:41 AM10/30/12

to

On Tue, 30 Oct 2012 04:16:12 -0700, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>On Tue, 30 Oct 2012 00:40:38 -0400, "Michael A. Terrell"
><mike.t...@earthlink.net> wrote:
>
>>
>>Robert Baer wrote:
>>>
>>> Jamie wrote:
>>> > John Larkin wrote:
>>> >
>>> >> On Sat, 20 Oct 2012 12:42:11 -0800, Robert Baer
>>> >> <rober...@localnet.com> wrote:
>>> >>
>>> >>
>>> >>> See similar title in a.b.s.electronic for PDF.
>>> >>> Almost took longer to document than to build..
>>> >>
>>> >>
>>> >>
>>> >> This is my best birthday present.
>>> >>
>>> >> https://dl.dropbox.com/u/53724080/Truckee/Birthday_Baer.jpg
>>> >>
>>> >>
>>> >> grrrrrrrr.
>>> >>
>>> >>
>>> >>
>>> > how many pine trees had to be cut down to build that wall for you?
>>> >
>>> > Jamie
>>> >
>>> If you were a true tree huger, you _would_ "pine" for them..
>>
>>
>> He's just another sap...
>
>It's not nice to needle people like that.

---
Still barking, I see.

--
JF

John Larkin

unread,

Oct 30, 2012, 7:59:27 AM10/30/12

to

If you follow the logical tree, I guess the answer is "both."

John Larkin

unread,

Oct 30, 2012, 8:29:19 AM10/30/12

to

Don't be such a conehead.

amdx

unread,

Oct 30, 2012, 8:37:17 AM10/30/12

to

Root around long enough, and we'll find a pun.
Mikek

John Fields

unread,

Oct 30, 2012, 9:24:08 AM10/30/12

to

On Tue, 30 Oct 2012 05:29:19 -0700, John Larkin

---
Trying to branch out of your area of expertise?

--
JF

Michael A. Terrell

unread,

Oct 30, 2012, 10:01:24 AM10/30/12

to

John Larkin wrote:
>
> Michael A. Terrell wrote:
> ?
> ?Robert Baer wrote:
> ?? ?
> ?? If you were a true tree huger, you _would_ "pine" for them..
> ?
> ? He's just another sap...

>
> It's not nice to needle people like that.

Do you think we should just leaf them alone?

John Larkin

unread,

Oct 30, 2012, 10:26:33 AM10/30/12

to

On Tue, 30 Oct 2012 08:24:08 -0500, John Fields

Knot necessarily so.

John Larkin

unread,

Oct 30, 2012, 10:28:06 AM10/30/12

to

On Tue, 30 Oct 2012 07:37:17 -0500, amdx <am...@knologynotthis.net>
wrote:

That stems from our basic need for humor.

Phil Hobbs

unread,

Oct 30, 2012, 10:47:33 AM10/30/12

to

Yew guys conifer control yourselves.

Cheers

Phil Hobbs

JW

unread,

Oct 30, 2012, 10:57:00 AM10/30/12

to

On Tue, 30 Oct 2012 10:01:24 -0400 "Michael A. Terrell"
<mike.t...@earthlink.net> wrote in Message id:
<vNOdnTmmh4AmQBLN...@earthlink.com>:

I Woodn't.

unread,

Oct 31, 2012, 12:33:39 AM10/31/12

to

Robert Baer wrote:
> Fred Abse wrote:
>> On Sun, 28 Oct 2012 19:11:03 -0800, Robert Baer wrote:
>>
>>> ** This is what i have, before i saw your response; not too bad
>>> considering simple compensation and implicit coax of indeterminate (but
>>> limited) length to scope end.
>>
>> You can't ignore the effect of what is, in effect, an open-circuit
>> quarter
>> wave line, at a frequency within the intended bandwidth of the probe.
>>
>> 3 feet of 0,66 velocity coax, terminated in a large resistance will
>> resonate at about 54MHz, and ring like a bell. That's why resistive
>> cables
>> are used.
>>

> 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).
>

> Since you specified 75 ohm cable, the R should then be 75 ohms instead
> of 60 ohms (pickie).
>
Sorry...mistype... cable is about 50 ohms per foot.

Robert Baer

unread,

Oct 31, 2012, 12:35:14 AM10/31/12

to

Resistance is about an order of magnitude higher than desired.

Robert Baer

unread,

Oct 31, 2012, 12:35:39 AM10/31/12

to

OOooo!

Robert Baer

unread,

Oct 31, 2012, 12:39:44 AM10/31/12

to

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....

unread,

Oct 31, 2012, 1:25:14 AM10/31/12

to

On Tue, 30 Oct 2012 20:41:08 -0800, Robert Baer <rober...@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.

Jan Panteltje

unread,

Oct 31, 2012, 4:39:30 AM10/31/12

to

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

Spehro Pefhany

unread,

Oct 31, 2012, 4:39:51 AM10/31/12

to

On Tue, 30 Oct 2012 20:39:44 -0800, the renowned Robert Baer
<rober...@localnet.com> wrote:

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

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
--
"it's the network..." "The Journey is the reward"
sp...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

Jan Panteltje

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Oct 31, 2012, 4:53:18 AM10/31/12

to

On a sunny day (Wed, 31 Oct 2012 04:39:51 -0400) it happened Spehro Pefhany
<spef...@interlogDOTyou.knowwhat> wrote in
<2io198hvid0hv2gjn...@4ax.com>:

>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.

The satellite cables (to the LNB) also have single core,
and mine are flexible (those are the ones with the F-type? connectors you just
screw over the folded back screen / outside plastic, inner solid core is the 'pin').

Michael A. Terrell

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Oct 31, 2012, 10:28:54 AM10/31/12

to

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

Jeroen Belleman

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Oct 31, 2012, 12:34:32 PM10/31/12

to

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

Frank Miles

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Oct 31, 2012, 1:15:20 PM10/31/12

to

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

Michael A. Terrell

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Oct 31, 2012, 1:28:02 PM10/31/12

to

Jeroen Belleman wrote:
>
> Michael A. Terrell wrote:
> >

> > 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.

How asking someone who makes probes?

http://www.probemaster.com/index.php

Message has been deleted

tm

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Oct 31, 2012, 5:46:03 PM10/31/12

to

"Fred Abse" <excret...@invalid.invalid> wrote in message
news:pan.2012.10.31....@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.

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Oct 31, 2012, 11:14:12 PM10/31/12

to

I've known it as "heliax".

Michael A. Terrell

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Oct 31, 2012, 11:40:40 PM10/31/12

to

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

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Nov 1, 2012, 3:37:03 AM11/1/12

to

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

Jeroen Belleman

Sum Ting Wong

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Nov 1, 2012, 8:08:31 AM11/1/12

to

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

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Nov 1, 2012, 8:40:38 AM11/1/12

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On 2012-10-30, Sum Ting Wong <SumTi...@thebarattheendoftheVenusianLightningBolt.org> wrote:
> On Tue, 30 Oct 2012 08:29:45 GMT, Jan Panteltje

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

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