Driver to drive?

[John Larkin]

On Wed, 24 Oct 2012 14:55:10 -0700 (PDT),
bloggs.fredbloggs.fred@gmail.com wrote:

On Wednesday, October 24, 2012 4:11:21 PM UTC-4, John Larkin wrote:
On Wed, 24 Oct 2012 12:06:01 -0700 (PDT),

bloggs.fredbloggs.fred@gmail.com wrote:



On Wednesday, October 24, 2012 1:24:45 PM UTC-4, John Larkin wrote:

On Wed, 24 Oct 2012 09:38:44 -0700 (PDT),



bloggs.fredbloggs.fred@gmail.com wrote:







On Monday, October 22, 2012 3:30:23 PM UTC-4, John Larkin wrote:



On Mon, 22 Oct 2012 11:31:31 -0700 (PDT),







bloggs.fredbloggs.fred@gmail.com wrote:















On Monday, October 22, 2012 11:50:37 AM UTC-4, John Larkin wrote:































I can't believe an engineer wrote the above. You are an engineer, right?































Obviously not.























What's obvious is that you and that other simpleton are not very good at engineering. In the real world, outside your sheltered little lab environment, there are a multitude of effects that degrade predicted performance. Until the price of Si flat panles dropped, the Solyndra design was best in class.







http://www.solyndra.com/technology-products/cylindrical-module/















What electronics have you designed lately? Show us.











What have you designed is more pertinent. We see a lot of trial and error hacking but little else.







Look at my web site. We do very little breadboarding, no prototypes.



We go directly from engineering design to manufacturing and the first



article usually works.







This works, with a couple of resistor value changes (unexpected ADC



behavior) and one jumper (a charge pump worked, but the ceramic caps



screamed at 14 KHz and annoyed folks, so I bumped the frequency up.)







https://dl.dropbox.com/u/53724080/PCBs/T680_PCB.JPG







It's a 5-channel TDC/time stamper with 12 picosecond resolution and 48



bit range.







This week's project is a 32-channel magnetic field mapper with USB



interface.







Show us something you've designed.





And just exactly how is any of that design? Sounds more like self-amusement.



Why do you post to s.e.d.? You don't seem to admit that electronic

design actually exists.

Why do you post to s.e.d.- other than to brag about these non-design things you work on?

I like to talk about electronics. And I've met some interesting and
useful people.

What do you do? Is it fun?


--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation

 

On Wednesday, October 24, 2012 4:11:21 PM UTC-4, John Larkin wrote:

On Wed, 24 Oct 2012 12:06:01 -0700 (PDT),

bloggs.fredbloggs.fred@gmail.com wrote:



On Wednesday, October 24, 2012 1:24:45 PM UTC-4, John Larkin wrote:

On Wed, 24 Oct 2012 09:38:44 -0700 (PDT),



bloggs.fredbloggs.fred@gmail.com wrote:







On Monday, October 22, 2012 3:30:23 PM UTC-4, John Larkin wrote:



On Mon, 22 Oct 2012 11:31:31 -0700 (PDT),







bloggs.fredbloggs.fred@gmail.com wrote:















On Monday, October 22, 2012 11:50:37 AM UTC-4, John Larkin wrote:































I can't believe an engineer wrote the above. You are an engineer, right?































Obviously not.























What's obvious is that you and that other simpleton are not very good at engineering. In the real world, outside your sheltered little lab environment, there are a multitude of effects that degrade predicted performance. Until the price of Si flat panles dropped, the Solyndra design was best in class.







http://www.solyndra.com/technology-products/cylindrical-module/















What electronics have you designed lately? Show us.











What have you designed is more pertinent. We see a lot of trial and error hacking but little else.







Look at my web site. We do very little breadboarding, no prototypes.



We go directly from engineering design to manufacturing and the first



article usually works.







This works, with a couple of resistor value changes (unexpected ADC



behavior) and one jumper (a charge pump worked, but the ceramic caps



screamed at 14 KHz and annoyed folks, so I bumped the frequency up.)







https://dl.dropbox.com/u/53724080/PCBs/T680_PCB.JPG







It's a 5-channel TDC/time stamper with 12 picosecond resolution and 48



bit range.







This week's project is a 32-channel magnetic field mapper with USB



interface.







Show us something you've designed.





And just exactly how is any of that design? Sounds more like self-amusement.



Why do you post to s.e.d.? You don't seem to admit that electronic

design actually exists.

Why do you post to s.e.d.- other than to brag about these non-design things you work on?

But yes, designing electronics is amusing, and the pay's not bad

either. The mapper schematic is almost done, just 7 sheets (hand

drawn, on D-size vellum!)



What do you do? Is it amusing? You don't seem to be very cheerful.





--



John Larkin Highland Technology, Inc



jlarkin at highlandtechnology dot com

http://www.highlandtechnology.com



Precision electronic instrumentation

Picosecond-resolution Digital Delay and Pulse generators

Custom laser drivers and controllers

Photonics and fiberoptic TTL data links

VME thermocouple, LVDT, synchro acquisition and simulation

 

[josephkk]

On Wed, 24 Oct 2012 07:13:13 -0700 (PDT), dagmargoodboat@yahoo.com wrote:

Nobody is doing route clearance by picking up IEDs with their bare hands.

Actually, they do. And, they walk the route, in front of their
vehicles. Not always, but as conditions require.

I was similarly appalled. My pal explained that in many places their
Buffaloes (armored vehicles) don't give good enough visibility, often
they can just turn you into a blind target. And, the IEDs are *very*
hard to see. Better to be out where you can see.

They have certain precautions in their favor (which shall go
unposted). But yes, manually, especially to disarm. The Buffalo has
an extensible arm; they use that too where they can.

I asked if he actually found any. "Oh yeah. Constantly. Several,
the hard way."

It changed him. He saw things men should not see.

I must disagree that last one. Some must see, to make sure that the

knowledge (and sometimes the horror) is not lost. Just like some (a few
every few years) must see Dr. Mengele's work. See also Holocaust museums
and the early nuclear museums in Hiroshima and Nagasaki (the nuclear
museums have recently been toned down, wrongly in my view).

James Arthur

 

[Robert Baer]

See http://www.oil4lessllc.org/HV%20probes/ for updated PDF.
Have added two more scope pictures and modified closing notes.

This shows that the fundamental risetime is faster than 20nSec.

 

[Fred Bartoli]

Robert Baer a écrit :

See http://www.oil4lessllc.org/HV%20probes/ for updated PDF.
Have added two more scope pictures and modified closing notes.

This shows that the fundamental risetime is faster than 20nSec.

Wow, you're advertising the use of a mutilmeter (pun) probe for 7kV usage...


--
Thanks,
Fred.

 

[Jan Panteltje]

On a sunny day (Wed, 24 Oct 2012 22:17:26 -0800) it happened Robert Baer
<robertbaer@localnet.com> wrote in <1Y3is.1527$lD4.780@newsfe24.iad>:

See http://www.oil4lessllc.org/HV%20probes/ for updated PDF.
Have added two more scope pictures and modified closing notes.

This shows that the fundamental risetime is faster than 20nSec.

Safe to touch 7kV high power with that?
For TV maybe (<5 mA).
The waveform compensation is nice.

 

[P E Schoen]

"Bill Sloman" wrote in message
news:3bb1c30a-9913-420f-ba9d-356cd745167d@o3g2000pbk.googlegroups.com...

[big snip]

You can't spend yoiur way to prosperity, but you can spend your
way out of recession, which isn't quite the same thing.
It's a subtle distinction, but crucial. James Arhur believes iin the
prefection of the free market, and therfore thinks that people make
exactly the same choices - to invest or not to invest - when the
economy is expanding normally, or when it's expanding slowly or in
recession.

This is nonsense - as Keynes pointed out a long time ago - and
stimulus spending creates the illusion that the economy is expanding
which in turn prompts investors to take their money out from under
thoer mattresses and invest it in really expanding the economy. It's a
confidence trick, but a confidence trick that works. Once you've
foolled enogh people for enough of the itme, you can stop the stimulus
spending - and in fact have to stop the stimulus spending if you want
to avoid an over-heated economy and the consequent inflation as too
much investment money goes affter too few investment opportunities -
another problem that James Arthur doesn't understand or appreciate,
since he believes the free market to be perfect and as incapable of
over-investment as it is incapable of under-investment.

I agree with much of what you are saying, but I believe there is a more
fundamental problem at play. Here is something I recently posted on:
http://www.diyelectriccar.com/forums/showthread.php/your-opinion-foreign-policy-debate-80138p7.html

Something to ponder is the fact that businesses are not based on providing
jobs for workers, but to make a profit. From the beginnings of the
Industrial Age in the 1800s up until the dawn of the Technological Age in
the 1960s, big business was mostly manufacturing, along with wholesale and
retail and service companies which at that time employed a lot of people.
There were seemingly endless natural resources and sources of energy and the
jobs were very labor-intensive and required only basic education and skills,
so anyone who wanted or needed a job could easily find one, and most
companies were stable enough that it was a reasonable expectation to stay 30
years with one company and be rewarded with a generous pension.

There was an ominous glitch when the Great Depression crippled our economy
at the end of the 1920s, and it showed the deleterious effects of corporate
excesses, greed, and speculation, as well as the dependence of the economy
on the general optimism and confidence of the people. We were able to crawl
out from that sinkhole because of inspiring leadership as well as the
still-abundant resources on our own soil, and those in many other countries
where they could be extracted for a mere pittance.

We also saw, in Germany, an example of what can happen to a nation where the
economy is in free-fall and money becomes worthless and people are
struggling just to survive. They rallied behind a powerful leader who was
able to provide jobs and hope for the future, albeit in a ruthless and evil
quest for world power and genocide. The ensuing World War also helped grow
our own economy, and the Cold War that followed helped it continue through
the 1980s.

By that time, Technology was becoming King, and traditional manufacturing
jobs diminished as they were established overseas or used more automation to
produce goods. As originally promised in the Industrial Revolution, most
work could be done by machines and computers that required only a few highly
skilled technicians to keep them running and that eliminated millions of
jobs. By the end of the 1990s, the Internet and automated virtual stores
changed the face of retail from local small businesses that employed many
people, to large megastores and on-line operations that could be run by a
handful of tech-savvy individuals.

The on-line and cell-phone connected civilization saw the virtual
obsolescence of previously profitable enterprises such as newspapers,
magazines, and books in printed form. I just found out that my Newsweek
subscription will morph into a paperless format at the end of this year. It
is good for the environment, using less trees and energy to process them,
but also it results in less jobs.

The most recent economic growth was largely the result of stock market
speculation and deceptive and predatory loan practices that artificially
fueled a construction and housing boom, along with de facto temporary jobs
that supported the bubble. Irresponsible and short-sighted expectations for
continued expansion caused more people, and businesses, to engage in deficit
spending and huge debt, while top level speculators and manipulators took
advantage of the situation to amass huge profits and then distance
themselves from the inevitable collapse. Meanwhile, people have been
brainwashed into "needing" an ever-increasing number of technological
gadgets, as well as cars, SUVs, and larger houses ever further from cities,
which has supported an ever-expanding demand that often requires families to
have two wage-earners. And many families are broken, which results in twice
as many households for the same population.

So, now we have a situation where the economy can produce all the goods and
services that are actually needed, with far fewer workers. The perceived
"needs" for individual displays of wealth and inefficient homes and vehicles
have been promoted by those who have profited from such demand. But the fact
is that there has been a growing population with decreasing levels of
education, job skills, work ethics, and even intelligence, with unrealistic
expectations of great individual wealth obtained with little work. So,
realistically, there cannot be enough jobs of that caliber to sustain the
fantasy.

There are still many jobs that require hard physical labor, but they are
mostly filled by immigrants (and illegals) who are willing and ABLE to
perform the work. And at the other end, there are many high-tech jobs and
opportunities for clever entrepreneurs, technicians, engineers, doctors, and
scientists, but there are few US citizens who are qualified. So, again,
these jobs may be filled by foreigners, or the businesses that provide such
jobs may relocate overseas or be lost to foreign businesses who can compete
because highly qualified workers are willing to work harder and smarter for
less.

We face a true crisis, and none of the "economic plans" proposed will
actually correct the problems. The situation is becoming ripe for a true
revolution, which will happen when people continue to spiral into financial
ruin and unmanageable debt and homelessness and despair - or anger. The
government has become powerless to effect any real change because of
unprecedented stonewalling and stagnation, to the point where the wishes of
the general population are blocked by representatives of the top 1% who have
siphoned off the wealth, leaving the masses with very little except
frustration.

We may survive for another five to ten years on our present track, but
ultimately major change will become necessary. We will all need to accept a
downsizing of our expectations of personal material wealth and instead
embrace a paradigm of cooperation and consolidation. We will need to learn
how to deal with each other on a real face-to-face basis, and live in
communities based on efficiency and sustainability. This, ultimately, will
be an improvement in lifestyle, as it will provide much more individual
leisure time as well as the opportunity to establish rewarding group
dynamics and sharing of responsibilities as well as resources and
pleasurable activities that promote learning and peace.

Paul

 

[MrTallyman]

On Thu, 25 Oct 2012 09:36:51 GMT, Jan Panteltje
<pNaonStpealmtje@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]

Fred Bartoli wrote:

Robert Baer a écrit :
See http://www.oil4lessllc.org/HV%20probes/ for updated PDF.
Have added two more scope pictures and modified closing notes.

This shows that the fundamental risetime is faster than 20nSec.


Wow, you're advertising the use of a mutilmeter (pun) probe for 7kV
usage...


Yep; cheap, small, does the job.

 

[Bill Sloman]

On Oct 26, 6:58 am, "P E Schoen" <p...@peschoen.com> wrote:

"Bill Sloman"  wrote in message

news:3bb1c30a-9913-420f-ba9d-356cd745167d@o3g2000pbk.googlegroups.com...

[big snip]



You can't spend yoiur way to prosperity, but you can spend your
way out of recession, which isn't quite the same thing.
It's a subtle distinction, but crucial. James Arhur believes iin the
prefection of the free market, and therfore thinks that people make
exactly the same choices - to invest or not to invest - when the
economy is expanding normally, or when it's expanding slowly or in
recession.
This is nonsense - as Keynes pointed out a long time ago - and
stimulus spending creates the illusion that the economy is expanding
which in turn prompts investors to take their money out from under
thoer mattresses and invest it in really expanding the economy. It's a
confidence trick, but a confidence trick that works. Once you've
foolled enogh people for enough of the itme, you can stop the stimulus
spending - and in fact have to stop the stimulus spending if you want
to avoid an over-heated economy and the consequent inflation as too
much investment money goes affter too few investment opportunities -
another problem that James Arthur doesn't understand or appreciate,
since he believes the free market to be perfect and as incapable of
over-investment as it is incapable of under-investment.

I agree with much of what you are saying, but I believe there is a more
fundamental problem at play. Here is something I recently posted on:http://www.diyelectriccar.com/forums/showthread.php/your-opinion-fore...

Something to ponder is the fact that businesses are not based on providing
jobs for workers, but to make a profit.

<snip>

Australia's rural population has been dropping since the 1890's, while
agricultural production has been rising.

The economy has coped with this. In general increasing productivity
hasn't thrown people out of work, but rather moved them into different
kinds of work in new industries.

In more enlightened economies this has been helped by retraining
programs, and Will Hutton made the point - in his book "The World
We're In" - that countries that spent more social security, notably
Germany and Sweden - did this rather better than the UK and the US.

Presumably there's going to be a point where robots are going to be so
good and so adaptable that there won't be any jobs for the dim and
hard-to-train, but it doesn't seem to have happened yet.

--
Bill Sloman, Sydney

 

[legg]

On Tue, 23 Oct 2012 20:15:27 -0800, Robert Baer
<robertbaer@localnet.com> wrote:

legg wrote:
On Mon, 22 Oct 2012 22:04:28 -0800, Robert Baer
robertbaer@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

 

[josephkk]

On Thu, 25 Oct 2012 15:57:59 -0400, "P E Schoen" <paul@peschoen.com>
wrote:

"Bill Sloman" wrote in message
news:3bb1c30a-9913-420f-ba9d-356cd745167d@o3g2000pbk.googlegroups.com...

[big snip]

You can't spend yoiur way to prosperity, but you can spend your
way out of recession, which isn't quite the same thing.
It's a subtle distinction, but crucial. James Arhur believes iin the
prefection of the free market, and therfore thinks that people make
exactly the same choices - to invest or not to invest - when the
economy is expanding normally, or when it's expanding slowly or in
recession.

This is nonsense - as Keynes pointed out a long time ago - and
stimulus spending creates the illusion that the economy is expanding
which in turn prompts investors to take their money out from under
thoer mattresses and invest it in really expanding the economy. It's a
confidence trick, but a confidence trick that works. Once you've
foolled enogh people for enough of the itme, you can stop the stimulus
spending - and in fact have to stop the stimulus spending if you want
to avoid an over-heated economy and the consequent inflation as too
much investment money goes affter too few investment opportunities -
another problem that James Arthur doesn't understand or appreciate,
since he believes the free market to be perfect and as incapable of
over-investment as it is incapable of under-investment.

I agree with much of what you are saying, but I believe there is a more
fundamental problem at play. Here is something I recently posted on:
http://www.diyelectriccar.com/forums/showthread.php/your-opinion-foreign-policy-debate-80138p7.html

Something to ponder is the fact that businesses are not based on providing
jobs for workers, but to make a profit. From the beginnings of the
Industrial Age in the 1800s up until the dawn of the Technological Age in
the 1960s, big business was mostly manufacturing, along with wholesale and
retail and service companies which at that time employed a lot of people.
There were seemingly endless natural resources and sources of energy and the
jobs were very labor-intensive and required only basic education and skills,
so anyone who wanted or needed a job could easily find one, and most
companies were stable enough that it was a reasonable expectation to stay 30
years with one company and be rewarded with a generous pension.

There was an ominous glitch when the Great Depression crippled our economy
at the end of the 1920s, and it showed the deleterious effects of corporate
excesses, greed, and speculation, as well as the dependence of the economy
on the general optimism and confidence of the people. We were able to crawl
out from that sinkhole because of inspiring leadership as well as the
still-abundant resources on our own soil, and those in many other countries
where they could be extracted for a mere pittance.

We also saw, in Germany, an example of what can happen to a nation where the
economy is in free-fall and money becomes worthless and people are
struggling just to survive. They rallied behind a powerful leader who was
able to provide jobs and hope for the future, albeit in a ruthless and evil
quest for world power and genocide. The ensuing World War also helped grow
our own economy, and the Cold War that followed helped it continue through
the 1980s.

By that time, Technology was becoming King, and traditional manufacturing
jobs diminished as they were established overseas or used more automation to
produce goods. As originally promised in the Industrial Revolution, most
work could be done by machines and computers that required only a few highly
skilled technicians to keep them running and that eliminated millions of
jobs. By the end of the 1990s, the Internet and automated virtual stores
changed the face of retail from local small businesses that employed many
people, to large megastores and on-line operations that could be run by a
handful of tech-savvy individuals.

The on-line and cell-phone connected civilization saw the virtual
obsolescence of previously profitable enterprises such as newspapers,
magazines, and books in printed form. I just found out that my Newsweek
subscription will morph into a paperless format at the end of this year. It
is good for the environment, using less trees and energy to process them,
but also it results in less jobs.

The most recent economic growth was largely the result of stock market
speculation and deceptive and predatory loan practices that artificially
fueled a construction and housing boom, along with de facto temporary jobs
that supported the bubble. Irresponsible and short-sighted expectations for
continued expansion caused more people, and businesses, to engage in deficit
spending and huge debt, while top level speculators and manipulators took
advantage of the situation to amass huge profits and then distance
themselves from the inevitable collapse. Meanwhile, people have been
brainwashed into "needing" an ever-increasing number of technological
gadgets, as well as cars, SUVs, and larger houses ever further from cities,
which has supported an ever-expanding demand that often requires families to
have two wage-earners. And many families are broken, which results in twice
as many households for the same population.

So, now we have a situation where the economy can produce all the goods and
services that are actually needed, with far fewer workers. The perceived
"needs" for individual displays of wealth and inefficient homes and vehicles
have been promoted by those who have profited from such demand. But the fact
is that there has been a growing population with decreasing levels of
education, job skills, work ethics, and even intelligence, with unrealistic
expectations of great individual wealth obtained with little work. So,
realistically, there cannot be enough jobs of that caliber to sustain the
fantasy.

There are still many jobs that require hard physical labor, but they are
mostly filled by immigrants (and illegals) who are willing and ABLE to
perform the work. And at the other end, there are many high-tech jobs and
opportunities for clever entrepreneurs, technicians, engineers, doctors, and
scientists, but there are few US citizens who are qualified. So, again,
these jobs may be filled by foreigners, or the businesses that provide such
jobs may relocate overseas or be lost to foreign businesses who can compete
because highly qualified workers are willing to work harder and smarter for
less.

We face a true crisis, and none of the "economic plans" proposed will
actually correct the problems. The situation is becoming ripe for a true
revolution, which will happen when people continue to spiral into financial
ruin and unmanageable debt and homelessness and despair - or anger. The
government has become powerless to effect any real change because of
unprecedented stonewalling and stagnation, to the point where the wishes of
the general population are blocked by representatives of the top 1% who have
siphoned off the wealth, leaving the masses with very little except
frustration.

We may survive for another five to ten years on our present track, but
ultimately major change will become necessary. We will all need to accept a
downsizing of our expectations of personal material wealth and instead
embrace a paradigm of cooperation and consolidation. We will need to learn
how to deal with each other on a real face-to-face basis, and live in
communities based on efficiency and sustainability. This, ultimately, will
be an improvement in lifestyle, as it will provide much more individual
leisure time as well as the opportunity to establish rewarding group
dynamics and sharing of responsibilities as well as resources and
pleasurable activities that promote learning and peace.

Paul

Interesting Paul, my dad foresaw much of this in the 1960s. Notably the
changes in the job market and the changes in effective productivity to
where a few could produce enough for all; the upsets in the workforce,
both in number and skill requirements, and leisure choices. Just the same
he did not predict Internet though he embraced the changes it brought. He
under scoped offshoring and artificial exchange rates. A bit over 50%
prediction from back then. Beats the hell out of almost all long term
prognosticators.

?-)

 

[Fred Abse]

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.

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
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FLAG 2000 192 0
FLAG 1984 -16 scope
FLAG 1280 144 0
FLAG -448 272 0
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FLAG 1680 224 0
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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
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SYMATTR Value PULSE(0 250 0 20n 20n 1m 2m 10)
SYMATTR Value2 AC 1
SYMATTR SpiceLine Rser=50
SYMBOL cap 1296 96 R180
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WINDOW 3 24 8 Left 2
SYMATTR InstName C31
SYMATTR Value 2478p
SYMBOL res 1312 48 R0
WINDOW 3 30 126 Left 2
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SYMBOL cap 1984 80 R0
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SYMATTR Value 22p
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SYMATTR Value 1Meg
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WINDOW 0 20 11 Left 2
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SYMATTR Value {Cr}
SYMBOL cap -288 16 R0
SYMATTR InstName C2
SYMATTR Value {Cr}
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WINDOW 3 68 60 VBottom 2
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SYMBOL cap -224 16 R0
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SYMATTR Value {Cr}
SYMBOL cap -144 16 R0
SYMATTR InstName C4
SYMATTR Value {Cr}
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SYMATTR Value {Rp}
SYMBOL cap -80 16 R0
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SYMATTR InstName C5
SYMATTR Value {Cr}
SYMBOL cap 0 16 R0
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SYMATTR Value {Cr}
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WINDOW 3 68 60 VBottom 2
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SYMATTR Value {Rp}
SYMBOL cap 64 16 R0
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SYMATTR Value {Cr}
SYMBOL cap 144 16 R0
SYMATTR InstName C8
SYMATTR Value {Cr}
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WINDOW 0 -24 71 VTop 2
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SYMATTR Value {Rp}
SYMBOL cap 208 16 R0
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SYMATTR InstName C9
SYMATTR Value {Cr}
SYMBOL cap 288 16 R0
SYMATTR InstName C10
SYMATTR Value {Cr}
SYMBOL res 208 0 R270
WINDOW 0 -24 71 VTop 2
WINDOW 3 68 60 VBottom 2
SYMATTR InstName R5
SYMATTR Value {Rp}
SYMBOL cap 432 16 R0
WINDOW 0 20 11 Left 2
SYMATTR InstName C11
SYMATTR Value {Cr}
SYMBOL cap 512 16 R0
SYMATTR InstName C12
SYMATTR Value {Cr}
SYMBOL res 432 0 R270
WINDOW 0 -24 71 VTop 2
WINDOW 3 68 60 VBottom 2
SYMATTR InstName R6
SYMATTR Value {Rp}
SYMBOL cap 576 16 R0
WINDOW 0 20 11 Left 2
SYMATTR InstName C13
SYMATTR Value {Cr}
SYMBOL cap 656 16 R0
SYMATTR InstName C14
SYMATTR Value {Cr}
SYMBOL res 576 0 R270
WINDOW 0 -24 71 VTop 2
WINDOW 3 68 60 VBottom 2
SYMATTR InstName R7
SYMATTR Value {Rp}
SYMBOL cap 720 16 R0
WINDOW 0 20 11 Left 2
SYMATTR InstName C15
SYMATTR Value {Cr}
SYMBOL cap 800 16 R0
SYMATTR InstName C16
SYMATTR Value {Cr}
SYMBOL res 720 0 R270
WINDOW 0 -24 71 VTop 2
WINDOW 3 68 60 VBottom 2
SYMATTR InstName R8
SYMATTR Value {Rp}
SYMBOL cap 864 16 R0
WINDOW 0 20 11 Left 2
SYMATTR InstName C17
SYMATTR Value {Cr}
SYMBOL cap 944 16 R0
SYMATTR InstName C18
SYMATTR Value {Cr}
SYMBOL res 864 0 R270
WINDOW 0 -24 71 VTop 2
WINDOW 3 68 60 VBottom 2
SYMATTR InstName R9
SYMATTR Value {Rp}
SYMBOL cap 1008 16 R0
WINDOW 0 20 11 Left 2
SYMATTR InstName C19
SYMATTR Value {Cr}
SYMBOL cap 1088 16 R0
SYMATTR InstName C20
SYMATTR Value {Cr}
SYMBOL res 1008 0 R270
WINDOW 0 -24 71 VTop 2
WINDOW 3 68 60 VBottom 2
SYMATTR InstName R10
SYMATTR Value {Rp}
SYMBOL cap -48 160 R0
SYMATTR InstName C21
SYMATTR Value {Cs}
SYMBOL cap 768 160 R0
SYMATTR InstName C22
SYMATTR Value {Cs}
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.



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

 

[Bill Sloman]

On Oct 29, 4:00 am, josephkk <joseph_barr...@sbcglobal.net> wrote:

On Thu, 25 Oct 2012 15:57:59 -0400, "P E Schoen" <p...@peschoen.com
wrote:



"BillSloman"  wrote in message
news:3bb1c30a-9913-420f-ba9d-356cd745167d@o3g2000pbk.googlegroups.com...

[big snip]

You can't spend yoiur way to prosperity, but you can spend your
way out of recession, which isn't quite the same thing.
It's a subtle distinction, but crucial. James Arhur believes iin the
prefection of the free market, and therfore thinks that people make
exactly the same choices - to invest or not to invest - when the
economy is expanding normally, or when it's expanding slowly or in
recession.

This is nonsense - as Keynes pointed out a long time ago - and
stimulus spending creates the illusion that the economy is expanding
which in turn prompts investors to take their money out from under
thoer mattresses and invest it in really expanding the economy. It's a
confidence trick, but a confidence trick that works. Once you've
foolled enogh people for enough of the itme, you can stop the stimulus
spending - and in fact have to stop the stimulus spending if you want
to avoid an over-heated economy and the consequent inflation as too
much investment money goes affter too few investment opportunities -
another problem that James Arthur doesn't understand or appreciate,
since he believes the free market to be perfect and as incapable of
over-investment as it is incapable of under-investment.

I agree with much of what you are saying, but I believe there is a more
fundamental problem at play. Here is something I recently posted on:
http://www.diyelectriccar.com/forums/showthread.php/your-opinion-fore...

Something to ponder is the fact that businesses are not based on providing
jobs for workers, but to make a profit. From the beginnings of the
Industrial Age in the 1800s up until the dawn of the Technological Age in
the 1960s, big business was mostly manufacturing, along with wholesale and
retail and service companies which at that time employed a lot of people..
There were seemingly endless natural resources and sources of energy and the
jobs were very labor-intensive and required only basic education and skills,
so anyone who wanted or needed a job could easily find one, and most
companies were stable enough that it was a reasonable expectation to stay 30
years with one company and be rewarded with a generous pension.

There was an ominous glitch when the Great Depression crippled our economy
at the end of the 1920s, and it showed the deleterious effects of corporate
excesses, greed, and speculation, as well as the dependence of the economy
on the general optimism and confidence of the people. We were able to crawl
out from that sinkhole because of inspiring leadership as well as the
still-abundant resources on our own soil, and those in many other countries
where they could be extracted for a mere pittance.

We also saw, in Germany, an example of what can happen to a nation where the
economy is in free-fall and money becomes worthless and people are
struggling just to survive. They rallied behind a powerful leader who was
able to provide jobs and hope for the future, albeit in a ruthless and evil
quest for world power and genocide. The ensuing World War also helped grow
our own economy, and the Cold War that followed helped it continue through
the 1980s.

By that time, Technology was becoming King, and traditional manufacturing
jobs diminished as they were established overseas or used more automation to
produce goods. As originally promised in the Industrial Revolution, most
work could be done by machines and computers that required only a few highly
skilled technicians to keep them running and that eliminated millions of
jobs. By the end of the 1990s, the Internet and automated virtual stores
changed the face of retail from local small businesses that employed many
people, to large megastores and on-line operations that could be run by a
handful of tech-savvy individuals.

The on-line and cell-phone connected civilization saw the virtual
obsolescence of previously profitable enterprises such as newspapers,
magazines, and books in printed form. I just found out that my Newsweek
subscription will morph into a paperless format at the end of this year. It
is good for the environment, using less trees and energy to process them,
but also it results in less jobs.

The most recent economic growth was largely the result of stock market
speculation and deceptive and predatory loan practices that artificially
fueled a construction and housing boom, along with de facto temporary jobs
that supported the bubble. Irresponsible and short-sighted expectations for
continued expansion caused more people, and businesses, to engage in deficit
spending and huge debt, while top level speculators and manipulators took
advantage of the situation to amass huge profits and then distance
themselves from the inevitable collapse. Meanwhile, people have been
brainwashed into "needing" an ever-increasing number of technological
gadgets, as well as cars, SUVs, and larger houses ever further from cities,
which has supported an ever-expanding demand that often requires families to
have two wage-earners. And many families are broken, which results in twice
as many households for the same population.

So, now we have a situation where the economy can produce all the goods and
services that are actually needed, with far fewer workers. The perceived
"needs" for individual displays of wealth and inefficient homes and vehicles
have been promoted by those who have profited from such demand. But the fact
is that there has been a growing population with decreasing levels of
education, job skills, work ethics, and even intelligence, with unrealistic
expectations of great individual wealth obtained with little work. So,
realistically, there cannot be enough jobs of that caliber to sustain the
fantasy.

There are still many jobs that require hard physical labor, but they are
mostly filled by immigrants (and illegals) who are willing and ABLE to
perform the work. And at the other end, there are many high-tech jobs and
opportunities for clever entrepreneurs, technicians, engineers, doctors, and
scientists, but there are few US citizens who are qualified. So, again,
these jobs may be filled by foreigners, or the businesses that provide such
jobs may relocate overseas or be lost to foreign businesses who can compete
because highly qualified workers are willing to work harder and smarter for
less.

We face a true crisis, and none of the "economic plans" proposed will
actually correct the problems. The situation is becoming ripe for a true
revolution, which will happen when people continue to spiral into financial
ruin and unmanageable debt and homelessness and despair - or anger. The
government has become powerless to effect any real change because of
unprecedented stonewalling and stagnation, to the point where the wishes of
the general population are blocked by representatives of the top 1% who have
siphoned off the wealth, leaving the masses with very little except
frustration.

We may survive for another five to ten years on our present track, but
ultimately major change will become necessary. We will all need to accept a
downsizing of our expectations of personal material wealth and instead
embrace a paradigm of cooperation and consolidation. We will need to learn
how to deal with each other on a real face-to-face basis, and live in
communities based on efficiency and sustainability. This, ultimately, will
be an improvement in lifestyle, as it will provide much more individual
leisure time as well as the opportunity to establish rewarding group
dynamics and sharing of responsibilities as well as resources and
pleasurable activities that promote learning and peace.

Paul

Interesting Paul, my dad foresaw much of this in the 1960s.  Notably the
changes in the job market and the changes in effective productivity to
where a few could produce enough for all; the upsets in the workforce,
both in number and skill requirements, and leisure choices.  Just the same
he did not predict Internet though he embraced the changes it brought.  He
under scoped offshoring and artificial exchange rates.  A bit over 50%
prediction from back then.  Beats the hell out of almost all long term
prognosticators.

Accurate prediction should have allowed him to invest strategically
and profitably. Did he?

People made a lot of money out if investing in IBM stock when they
first got into computers. They should have got out when IBM got into
the habit of sabotaging standards committees as a way of sustaining
market share.

--
Bill Sloman, Sydney

 

[Tim Williams]

"P E Schoen" <paul@peschoen.com> wrote in message
news:k6c5ki$ofr$1@dont-email.me...

There was an ominous glitch when the Great Depression crippled our
economy
at the end of the 1920s, and it showed the deleterious effects of
corporate
excesses, greed, and speculation, as well as the dependence of the
economy on the general optimism and confidence of the people. We were
able to crawl
out from that sinkhole because of inspiring leadership as well as the
still-abundant resources on our own soil, and those in many other
countries
where they could be extracted for a mere pittance.

Don't forget to include previous recessions in your narrative. The 1930s
were nothing new to the US, take the 1870s for instance. 1839-43 before
that, and 1807-1810, plus recessions after pretty much every single war
we've ever had until more recent history.

I expect 1930s stands in our minds because it was only three generations
ago, and has the most articles about it, as well as unprecedented audio
and video, and brand new economic data. But remember, just as you might
hear from a grandparent today about the '30s, , some of them would've
likewise heard about the '70s from their grandparents, and so on.
Remember, "business as usual" is not a modern invention, only its
automation.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

 

[Robert Baer]

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
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WIRE 1616 176 1568 176
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WIRE -448 272 -448 240
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WIRE 1312 336 1312 272
FLAG 1440 224 0
FLAG 1616 192 0
FLAG 1600 -16 scope
FLAG 1168 224 0
FLAG -448 272 0
FLAG 784 272 0
FLAG -32 272 0
FLAG 1312 336 0
SYMBOL voltage -448 144 R0
WINDOW 0 8 7 Left 2
WINDOW 3 11 105 Left 2
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
WINDOW 0 36 76 Left 2
WINDOW 3 36 40 Left 2
SYMATTR InstName R32
SYMATTR Value 1Meg
SYMBOL cap -368 16 R0
WINDOW 0 20 11 Left 2
SYMATTR InstName C1
SYMATTR Value {Cr}
SYMBOL cap -288 16 R0
SYMATTR InstName C2
SYMATTR Value {Cr}
SYMBOL res -368 0 R270
WINDOW 0 -24 71 VTop 2
WINDOW 3 68 60 VBottom 2
SYMATTR InstName R1
SYMATTR Value {Rp}
SYMBOL cap -224 16 R0
WINDOW 0 20 11 Left 2
SYMATTR InstName C3
SYMATTR Value {Cr}
SYMBOL cap -144 16 R0
SYMATTR InstName C4
SYMATTR Value {Cr}
SYMBOL res -224 0 R270
WINDOW 0 -24 71 VTop 2
WINDOW 3 68 60 VBottom 2
SYMATTR InstName R2
SYMATTR Value {Rp}
SYMBOL cap -80 16 R0
WINDOW 0 20 11 Left 2
SYMATTR InstName C5
SYMATTR Value {Cr}
SYMBOL cap 0 16 R0
SYMATTR InstName C6
SYMATTR Value {Cr}
SYMBOL res -80 0 R270
WINDOW 0 -24 71 VTop 2
WINDOW 3 68 60 VBottom 2
SYMATTR InstName R3
SYMATTR Value {Rp}
SYMBOL cap 64 16 R0
WINDOW 0 20 11 Left 2
SYMATTR InstName C7
SYMATTR Value {Cr}
SYMBOL cap 144 16 R0
SYMATTR InstName C8
SYMATTR Value {Cr}
SYMBOL res 64 0 R270
WINDOW 0 -24 71 VTop 2
WINDOW 3 68 60 VBottom 2
SYMATTR InstName R4
SYMATTR Value {Rp}
SYMBOL cap 208 16 R0
WINDOW 0 20 11 Left 2
SYMATTR InstName C9
SYMATTR Value {Cr}
SYMBOL cap 288 16 R0
SYMATTR InstName C10
SYMATTR Value {Cr}
SYMBOL res 208 0 R270
WINDOW 0 -24 71 VTop 2
WINDOW 3 68 60 VBottom 2
SYMATTR InstName R5
SYMATTR Value {Rp}
SYMBOL cap 432 16 R0
WINDOW 0 20 11 Left 2
SYMATTR InstName C11
SYMATTR Value {Cr}
SYMBOL cap 512 16 R0
SYMATTR InstName C12
SYMATTR Value {Cr}
SYMBOL res 432 0 R270
WINDOW 0 -24 71 VTop 2
WINDOW 3 68 60 VBottom 2
SYMATTR InstName R6
SYMATTR Value {Rp}
SYMBOL cap 576 16 R0
WINDOW 0 20 11 Left 2
SYMATTR InstName C13
SYMATTR Value {Cr}
SYMBOL cap 656 16 R0
SYMATTR InstName C14
SYMATTR Value {Cr}
SYMBOL res 576 0 R270
WINDOW 0 -24 71 VTop 2
WINDOW 3 68 60 VBottom 2
SYMATTR InstName R7
SYMATTR Value {Rp}
SYMBOL cap 720 16 R0
WINDOW 0 20 11 Left 2
SYMATTR InstName C15
SYMATTR Value {Cr}
SYMBOL cap 800 16 R0
SYMATTR InstName C16
SYMATTR Value {Cr}
SYMBOL res 720 0 R270
WINDOW 0 -24 71 VTop 2
WINDOW 3 68 60 VBottom 2
SYMATTR InstName R8
SYMATTR Value {Rp}
SYMBOL cap 864 16 R0
WINDOW 0 20 11 Left 2
SYMATTR InstName C17
SYMATTR Value {Cr}
SYMBOL cap 944 16 R0
SYMATTR InstName C18
SYMATTR Value {Cr}
SYMBOL res 864 0 R270
WINDOW 0 -24 71 VTop 2
WINDOW 3 68 60 VBottom 2
SYMATTR InstName R9
SYMATTR Value {Rp}
SYMBOL cap 1008 16 R0
WINDOW 0 20 11 Left 2
SYMATTR InstName C19
SYMATTR Value {Cr}
SYMBOL cap 1088 16 R0
SYMATTR InstName C20
SYMATTR Value {Cr}
SYMBOL res 1008 0 R270
WINDOW 0 -24 71 VTop 2
WINDOW 3 68 60 VBottom 2
SYMATTR InstName R10
SYMATTR Value {Rp}
SYMBOL cap -48 160 R0
SYMATTR InstName C21
SYMATTR Value {Cs}
SYMBOL cap 768 160 R0
SYMATTR InstName C22
SYMATTR Value {Cs}
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]

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.

 

[Bill Sloman]

On Oct 29, 1:05 pm, "Tim Williams" <tmoran...@charter.net> wrote:

"P E Schoen" <p...@peschoen.com> wrote in messagenews:k6c5ki$ofr$1@dont-email.me...

There was an ominous glitch when the Great Depression crippled our
economy
at the end of the 1920s, and it showed the deleterious effects of
corporate
excesses, greed, and speculation, as well as the dependence of the
economy on the general optimism and confidence of the people. We were
able to crawl
out from that sinkhole because of inspiring leadership as well as the
still-abundant resources on our own soil, and those in many other
countries
where they could be extracted for a mere pittance.

Don't forget to include previous recessions in your narrative.  The 1930s
were nothing new to the US, take the 1870s for instance.  1839-43 before
that, and 1807-1810, plus recessions after pretty much every single war
we've ever had until more recent history.

I expect 1930s stands in our minds because it was only three generations
ago, and has the most articles about it, as well as unprecedented audio
and video, and brand new economic data.

And it was international, which was rather new, at the time.

<snip>

--
Bill Sloman, Sydney

 

[Fred Abse]

On Sun, 28 Oct 2012 19:51:16 -0800, Robert Baer wrote:

I see you made Cs, capacitance from floating shields, a lot larger =
8pf instead of my wild guesstimate of 0.1pf.

No, I refer you to your previous post,<Tzphs.1182$gX7.1025@newsfe01.iad>:


"TEXT 168 160 Left 2 !.PARAM Cr=10p, Cs=7.9p, Rp=200Meg"

Cs=7.9pF

Exact copy of your published schematic, with the addition of 3 feet of
cable, and two resistors.

I wondered about that.

The same value occurs in the listing on your website.

I didn't pick it, you did ;-(

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

 

[Fred Abse]

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.

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