First results are quite encouraging. I was told by the helpful folks
at Boston Scientific that 1 gauss is an acceptable level of field
strength for 60 Hz fields. I don't know if that's RMS or peak to zero,
doubt if it's that precise. Being medical and actually in print, it's
probably quite conservative.

I did two experiments with MIG today. Machine is a Millermatic 210. I
had it set at where it seems to run well on 1/8" mild steel which is
what I mostly MIG. Settings were 3 on voltage knob, 50 on wirespeed.
I'll have Mary read an ampclamp tomorrow while I'm welding, but
current is whatever it is. I'd guess about 150 amps.

Cables were dressed fairly carefully. The sensor was clipped to my
shirt near my left shoulder. I welded in normal position at normal
distance, which is with my chest maybe 18" from the puddle.

On the first run the peak value recorded was about 1 gauss. I moved
the groundclamp to within 6" of the weld zone. Then the peak value
recorded was about 0.38 gauss.

This setup (or lower current for thinner metal) would do about 90% of
what I do with MIG. I have welded heavier stuff, but not often. Now
I'll get help if/when I need thicker stuff done.

I hope things go as well with TIG. I'll be trying that tomorrow.

Don,
I think you need to know what the susceptability of the device is to
electromagnetic interference to make your tests meaningful. There is a very
good chance that the manufacturer has made these tests for "CE"
certification. I would recommend contacting the manufacturer for this
number. There is an ISO test that these devices must pass for this
certification. The results of this test is PASS or FAIL, so it would be nice
to know what that test limit is. Personally, I would think that 10 gauss or
more is a non-issue, especially at such low frequencies that you are
concerned with. EMF caused malfunctions normally occur at much higher
frequencies.
Steve

"Don Foreman" wrote in message
...

First results are quite encouraging. I was told by the helpful folks
at Boston Scientific that 1 gauss is an acceptable level of field
strength for 60 Hz fields. I don't know if that's RMS or peak to zero,
doubt if it's that precise. Being medical and actually in print, it's
probably quite conservative.

I did two experiments with MIG today. Machine is a Millermatic 210. I
had it set at where it seems to run well on 1/8" mild steel which is
what I mostly MIG. Settings were 3 on voltage knob, 50 on wirespeed.
I'll have Mary read an ampclamp tomorrow while I'm welding, but
current is whatever it is. I'd guess about 150 amps.

Cables were dressed fairly carefully. The sensor was clipped to my
shirt near my left shoulder. I welded in normal position at normal
distance, which is with my chest maybe 18" from the puddle.

On the first run the peak value recorded was about 1 gauss. I moved
the groundclamp to within 6" of the weld zone. Then the peak value
recorded was about 0.38 gauss.

This setup (or lower current for thinner metal) would do about 90% of
what I do with MIG. I have welded heavier stuff, but not often. Now
I'll get help if/when I need thicker stuff done.

I hope things go as well with TIG. I'll be trying that tomorrow.

In article ,
Don Foreman wrote:

First results are quite encouraging. I was told by the helpful folks
at Boston Scientific that 1 gauss is an acceptable level of field
strength for 60 Hz fields. I don't know if that's RMS or peak to zero,
doubt if it's that precise. Being medical and actually in print, it's
probably quite conservative.

It's probably RMS, but the standards they are meeting will say. The
decision to fire will require the condition to endure for something like
ten seconds before anything happens, to cut down on false alarms.

I'm not sure what the frequency of peak sensitivity is, or if 60 Hz is
anywhere near. As I understand it, what triggers the shock is detection
of fibrillation, whose signal is lots of random "high frequency" noise
combined with no heartbeat pulse. The details are probably best
documented in patents and articles in medical journals. Perhaps the
engineering fellows can suggest which patents and articles to read.

A google search on the names of the various fellows may also be
productive.


I did two experiments with MIG today. Machine is a Millermatic 210. I
had it set at where it seems to run well on 1/8" mild steel which is
what I mostly MIG. Settings were 3 on voltage knob, 50 on wirespeed.
I'll have Mary read an ampclamp tomorrow while I'm welding, but
current is whatever it is. I'd guess about 150 amps.

Cables were dressed fairly carefully. The sensor was clipped to my
shirt near my left shoulder. I welded in normal position at normal
distance, which is with my chest maybe 18" from the puddle.

On the first run the peak value recorded was about 1 gauss. I moved
the groundclamp to within 6" of the weld zone. Then the peak value
recorded was about 0.38 gauss.

It strikes me that one can turn this around: Using that magnetic field
sensor as the core, make a high-field warning device that beeps loudly
when threshold is exceeded. The patents and articles can inform the
design of the trigger circuit, so the warning device has the same
sensitivity profile as the real ICD, but with enough margin to allow one
to avoid triggering the ICD by accident.


Joe Gwinn

Joseph Gwinn wrote:

In article ,
Don Foreman wrote:

First results are quite encouraging. I was told by the helpful folks
at Boston Scientific that 1 gauss is an acceptable level of field
strength for 60 Hz fields. I don't know if that's RMS or peak to zero,
doubt if it's that precise. Being medical and actually in print, it's
probably quite conservative.

It's probably RMS, but the standards they are meeting will say. The
decision to fire will require the condition to endure for something like
ten seconds before anything happens, to cut down on false alarms.

I'm not sure what the frequency of peak sensitivity is, or if 60 Hz is
anywhere near. As I understand it, what triggers the shock is detection
of fibrillation, whose signal is lots of random "high frequency" noise
combined with no heartbeat pulse. The details are probably best
documented in patents and articles in medical journals. Perhaps the
engineering fellows can suggest which patents and articles to read.

A google search on the names of the various fellows may also be
productive.

I did two experiments with MIG today. Machine is a Millermatic 210. I
had it set at where it seems to run well on 1/8" mild steel which is
what I mostly MIG. Settings were 3 on voltage knob, 50 on wirespeed.
I'll have Mary read an ampclamp tomorrow while I'm welding, but
current is whatever it is. I'd guess about 150 amps.

Cables were dressed fairly carefully. The sensor was clipped to my
shirt near my left shoulder. I welded in normal position at normal
distance, which is with my chest maybe 18" from the puddle.

On the first run the peak value recorded was about 1 gauss. I moved
the groundclamp to within 6" of the weld zone. Then the peak value
recorded was about 0.38 gauss.

It strikes me that one can turn this around: Using that magnetic field
sensor as the core, make a high-field warning device that beeps loudly
when threshold is exceeded. The patents and articles can inform the
design of the trigger circuit, so the warning device has the same
sensitivity profile as the real ICD, but with enough margin to allow one
to avoid triggering the ICD by accident.

Joe Gwinn

That's a good idea, make a EMF data logger to keep on you when welding
so that in the event you do get a bogus mule kick you can review the
data and determine the conditions when it occurred to avoid them in the
future.

In article ,
Joseph Gwinn wrote:

In article ,
Don Foreman wrote:

First results are quite encouraging. I was told by the helpful folks
at Boston Scientific that 1 gauss is an acceptable level of field
strength for 60 Hz fields. I don't know if that's RMS or peak to zero,
doubt if it's that precise. Being medical and actually in print, it's
probably quite conservative.

It's probably RMS, but the standards they are meeting will say. The
decision to fire will require the condition to endure for something like
ten seconds before anything happens, to cut down on false alarms.

I'm not sure what the frequency of peak sensitivity is, or if 60 Hz is
anywhere near. As I understand it, what triggers the shock is detection
of fibrillation, whose signal is lots of random "high frequency" noise
combined with no heartbeat pulse. The details are probably best
documented in patents and articles in medical journals. Perhaps the
engineering fellows can suggest which patents and articles to read.

A google search on the names of the various fellows may also be
productive.

I did a little looking. One useful item is this:
http://www.spectrum.ieee.org/nov08/6921/3.

There are lots of patents from Medtronic: 5,464,430; 5,330,508; et al.

Haven't found anything on Boston Scientific, but haven't looked either.

Joe Gwinn


I did two experiments with MIG today. Machine is a Millermatic 210. I
had it set at where it seems to run well on 1/8" mild steel which is
what I mostly MIG. Settings were 3 on voltage knob, 50 on wirespeed.
I'll have Mary read an ampclamp tomorrow while I'm welding, but
current is whatever it is. I'd guess about 150 amps.

Cables were dressed fairly carefully. The sensor was clipped to my
shirt near my left shoulder. I welded in normal position at normal
distance, which is with my chest maybe 18" from the puddle.

On the first run the peak value recorded was about 1 gauss. I moved
the groundclamp to within 6" of the weld zone. Then the peak value
recorded was about 0.38 gauss.

It strikes me that one can turn this around: Using that magnetic field
sensor as the core, make a high-field warning device that beeps loudly
when threshold is exceeded. The patents and articles can inform the
design of the trigger circuit, so the warning device has the same
sensitivity profile as the real ICD, but with enough margin to allow one
to avoid triggering the ICD by accident.


Joe Gwinn

On Sat, 17 Jan 2009 10:08:01 +0100, "Steve Lusardi"
wrote:

Don,
I think you need to know what the susceptability of the device is to
electromagnetic interference to make your tests meaningful.

Indeed! I have data from Boston Scientific: "suggested guidelines
for limiting peak exposure to power freqency and static fields" that
suggests static B field be limited to 10 gauss or less, 60Hz B field
to 1 gauss or less. After the expected disclaimers, it notes that "no
published documentation of pacemaker or defibrillator interference at
those levels [has been] found [to date]." A footnote cites the EPRI
reference.

I think these guidlines are probably quite conservative.

On Fri, 16 Jan 2009 22:30:33 -0600, Don Foreman
wrote:

I didn't get to TIG today. I'll do that tomorrow. Today I did more MIG
tests. I was surprised at how low the fields were. My findings
indicate that anything within the capacity of the machine (Millermatic
210) will be well below the 1 gauss guidline, given careful dressing
of cables -- torch lead and ground cable.

My test coupon started out as 1/8" steel but it's over an inch thick
now!

I got to doubting the sensor so I did a calibration sanity check of
sorts. I wound a coil, 15 turns of 18-gage magnet wire, 1.8" ID, 2"
OK, .22" wide. When I modelled that in a magnetic fields FEA program
I found that 1 amp would produce 3.6 gauss in the center of the coil.
The sensor, place in the center of the coil, read 3.5 gauss;
definitely close enough for this exercise.

I'm really glad I bothered to do this testing to drill a little deeper
than the one-size-fits-all guidance of "not recommended".

I'll still be a bit antsy about welding at first, but things do look
promising.

We'll see about TIG. Current levels are similar so the results may be
too. I hope. We'll see. The HF could present an E-field issue but
that's easily managed with Faraday shielding. The E-field spec is 1
kilovolt per meter.

Don Foreman wrote:
On Fri, 16 Jan 2009 22:30:33 -0600, Don Foreman
wrote:

I didn't get to TIG today. I'll do that tomorrow. Today I did more MIG
tests. I was surprised at how low the fields were. My findings
indicate that anything within the capacity of the machine (Millermatic
210) will be well below the 1 gauss guidline, given careful dressing
of cables -- torch lead and ground cable.

(...)

Excellent news, Don!

Have you discovered arrangements of cables, settings of the welder,
position of body, etc. that result in unacceptably high field strength?

I'd be leery of HF coupling which might be particularly harmful and
perhaps outside the passband of your sensor. As a first-order test
it might be educational to record a detuned A.M. radio
while welding and see if those steep step functions result in
potentially nasty harmonics in the electrical domain.

--Winston

On Jan 18, 12:33*am, Don Foreman
wrote:
...The HF could present an E-field issue but
that's easily managed with Faraday shielding. The E-field spec is 1
kilovolt per meter. *

Chain mail welding jacket?

On Sun, 18 Jan 2009 07:57:48 -0800, Winston
wrote:

Don Foreman wrote:
On Fri, 16 Jan 2009 22:30:33 -0600, Don Foreman
wrote:

I didn't get to TIG today. I'll do that tomorrow. Today I did more MIG
tests. I was surprised at how low the fields were. My findings
indicate that anything within the capacity of the machine (Millermatic
210) will be well below the 1 gauss guidline, given careful dressing
of cables -- torch lead and ground cable.

(...)

Excellent news, Don!

Have you discovered arrangements of cables, settings of the welder,
position of body, etc. that result in unacceptably high field strength?

Well no, but I've no doubt that such arrangements exist. I was
careful to arrange cables to *minimize* field strength. I then used
body positions and welder settings that I normally use while welding.
I'd be leery of HF coupling which might be particularly harmful and
perhaps outside the passband of your sensor. As a first-order test
it might be educational to record a detuned A.M. radio
while welding and see if those steep step functions result in
potentially nasty harmonics in the electrical domain.

--Winston

I'm not too concerned about that. Shielding is effective at RF
frequencies, and the inputs of cardiac devices are subjected to both
low-level analog filtering and then digital filtering. 60Hz magnetic
fields are of concern because of their possible magnitudes with 100
amps flowing, and because they are much closer to the passband of the
ICD's.

On Fri, 16 Jan 2009 22:30:33 -0600, Don Foreman
wrote:


Don, maybe this will show a lack of understanding of magnetism on my
part, but couldn't you put a metallic shield of some sort over your
clothing between you and the pacer and leads and create a Gaussian
shield of sorts?

RWL

Don Foreman wrote:
On Sun, 18 Jan 2009 07:57:48 -0800, Winston
wrote:

Don Foreman wrote:
On Fri, 16 Jan 2009 22:30:33 -0600, Don Foreman
wrote:

I didn't get to TIG today. I'll do that tomorrow. Today I did more MIG
tests. I was surprised at how low the fields were. My findings
indicate that anything within the capacity of the machine (Millermatic
210) will be well below the 1 gauss guidline, given careful dressing
of cables -- torch lead and ground cable.
(...)

Excellent news, Don!

Have you discovered arrangements of cables, settings of the welder,
position of body, etc. that result in unacceptably high field strength?

Well no, but I've no doubt that such arrangements exist. I was
careful to arrange cables to *minimize* field strength. I then used
body positions and welder settings that I normally use while welding.

If you discover that you cannot generate a field anywhere near
the guideline even with cable dress that *looks* like it
would be dangerous to an ICD user, that would be useful info for
you, post-op. You need to discover what kinds
of arrangements and settings you'll need to avoid, post-op, if any.

Maybe that 'common mode' mitigation is as important as you and I
think it is. Perhaps not. Post-op is not the time to uncover the
critical variable.

You've seen the FCC EMI passband charts, I'm sure.
Clearly there must be an equivalent susceptibility chart for the
ICD in question. 'Static field' and '60 Hz' field strengths are useful
info but it would be much more useful for you to know the field strengths
that could be troublesome for all the other frequencies as well.



--Winston

On Fri, 16 Jan 2009 22:30:33 -0600, Don Foreman
wrote:

I hope things go as well with TIG. I'll be trying that tomorrow.

Update: TIG looks good to go. I'm grinnin'.

On Sun, 18 Jan 2009 11:57:37 -0500, GeoLane at PTD dot NET GeoLane at
PTD dot NET wrote:

On Fri, 16 Jan 2009 22:30:33 -0600, Don Foreman
wrote:


Don, maybe this will show a lack of understanding of magnetism on my
part, but couldn't you put a metallic shield of some sort over your
clothing between you and the pacer and leads and create a Gaussian
shield of sorts?

RWL

Shielding against low-frequency magnetic fields is impractical, but a
metallic shield could indeed protect against E-fields as from HF.

On Mon, 19 Jan 2009 00:02:15 -0600, Don Foreman
wrote:

On Fri, 16 Jan 2009 22:30:33 -0600, Don Foreman
wrote:

I hope things go as well with TIG. I'll be trying that tomorrow.

Update: TIG looks good to go. I'm grinnin'.


Ill bet there is a paper...and a government grant in your research.

G

Gunner

Whenever a Liberal utters the term "Common Sense approach"....grab your
wallet, your ass, and your guns because the sombitch is about to do
something damned nasty to all three of them.

On Mon, 19 Jan 2009 00:14:28 -0600, Don Foreman
wrote:



Shielding against low-frequency magnetic fields is impractical, but a
metallic shield could indeed protect against E-fields as from HF.




I'd have thought that meat was a reasonable E-field screen :-)


Mark Rand
RTFM

On Mon, 19 Jan 2009 00:02:15 -0600, the infamous Don Foreman
scrawled the following:

On Fri, 16 Jan 2009 22:30:33 -0600, Don Foreman
wrote:

I hope things go as well with TIG. I'll be trying that tomorrow.

Update: TIG looks good to go. I'm grinnin'.

Excellent! Just remember La Mula in your chest before you go tiggin'
with a cubic yard of Airco dinosaur, eh? I'm sure that won't be hard
to do.

Have fun on Thursday, Don.

--
Even with the best of maps and instruments,
we can never fully chart our journeys.
-- Gail Pool

Keywords:
In article , Don Foreman wrote:
On Fri, 16 Jan 2009 22:30:33 -0600, Don Foreman
wrote:

I hope things go as well with TIG. I'll be trying that tomorrow.

Update: TIG looks good to go. I'm grinnin'.

Way to go! It's really wonderful when somebody decides to apply their
skills to advancing the global knowledge base instead of just rolling
over & playing along with "the system". Not only will this help you
continue with your enjoyment of life, but it will probably help others
in the same boat, especially if you get the results back to the folks at
Boston Scientific.

A friend of mine went through kidney cancer last year, and got VERY
involved in his treatment, reading everything he could, grilling his
doctors, and communicating on-line with friends & folks who'd been
through it. He was ready to cave when the early doctors & nurses told
him he had something like a 10% chance of survival, until he discovered
that statistic came from a 15 year old study that didn't involve ANY of
the modern treatments. He got pretty ticked off at that point, and
started devouring all of the more recent research papers he could get his
hands on. I'm sure his attitude was a big help in a successful outcome.
He was fortunate that his oncologist was encouraging and enjoyed the
extra input and interaction. The two of them are now heavily involved in
the "e-patient" movement, and my friend is making a second career out of
telling folks to get involved in their treatment. Unfortunately, there
are a lot of doctors out there who either can't be bothered to deal with
intelligent questions from patients, or feel threatened if anyone
questions them.

My hats off to you, and good luck with the surgery!

Doug White

Keywords:
In article , Don Foreman wrote:
On Sun, 18 Jan 2009 11:57:37 -0500, GeoLane at PTD dot NET GeoLane at
PTD dot NET wrote:

On Fri, 16 Jan 2009 22:30:33 -0600, Don Foreman
wrote:


Don, maybe this will show a lack of understanding of magnetism on my
part, but couldn't you put a metallic shield of some sort over your
clothing between you and the pacer and leads and create a Gaussian
shield of sorts?

RWL

Shielding against low-frequency magnetic fields is impractical, but a
metallic shield could indeed protect against E-fields as from HF.

I suspect you could do an OK job if you replaced the metal plates in an
old style flak jacket with mu metal, but it sounds like you are good to
go without that sort of heroics.

Don, I have a roll of thin (15 mil?) mu metal in my junk box. I haven't
fished it out in years, but I suspect I've got about a square foot (or
more) of the stuff. I have no idea how helpful it might be, or if it has
been damaged and has lost some of its effectiveness. It has to be at
least 30 (probably more like 40) years old. If you want it, it's yours.
With your measuring widget, you could even test and see if it helps at
all.

Doug White

On Sat, 17 Jan 2009 11:35:57 -0500, Joseph Gwinn
wrote:

snip
I did a little looking. One useful item is this:
http://www.spectrum.ieee.org/nov08/6921/3.

There are lots of patents from Medtronic: 5,464,430; 5,330,508; et al.

Haven't found anything on Boston Scientific, but haven't looked either.

Joe Gwinn

This stuff is a bit over my head and interest... but I can
poke around the patent site pretty well. The following long
link my be of some interest:

http://patft1.uspto.gov/netacgi/nph-...%2F4&d=PTX Tg

The key to finding stuff of interest is to search via
Classifications. The link above is just a simple search on
Class 607/4. Which translates to:

US Patent Class 607:

SURGERY: LIGHT, THERMAL, AND ELECTRICAL APPLICATION

1 LIGHT, THERMAL, AND ELECTRICAL APPLICATION
2 .~ Electrical therapeutic systems
3 .~.~ Combined with nonelectrical therapy
4 .~.~ Combined cardioverting/defibrillating and pacing
5 .~.~ Cardioverting/defibrillating
6 .~.~.~ Sensing body condition or signal other than
electrocardiographic signal
7 .~.~.~ Controlling or indicating stimulation level
8 .~.~.~ Computing energy required or contact impedance
9 .~.~ Heart rate regulating (e.g., pacing)
10 .~.~.~ With nonimplanted generator
11 .~.~.~ Regulating or compensating stimulus level
12 .~.~.~ Stimulation raised above energy source level
13 .~.~.~ Reducing output recovery time
14 .~.~.~ Treating or preventing abnormally high heart rate

and so on...

The easiest way to find stuff is by looking at the classes
of other devices like you want to find more of.

Not knowing exactly what my be of help to/for Don I can't do
much more. He may be able to peruse the above link and find
items of interest to read up on.

Google patent interface is a lot more user friendly once you
narrow things down a bit. Using the patent suggested by
Joseph, a simple Google patent search would look like this:

http://www.google.com/patents?q=5,46...Patents&num=20


--
Leon Fisk
Grand Rapids MI/Zone 5b
Remove no.spam for email

On Mon, 19 Jan 2009 09:55:42 +0000, Mark Rand
wrote:

On Mon, 19 Jan 2009 00:14:28 -0600, Don Foreman
wrote:



Shielding against low-frequency magnetic fields is impractical, but a
metallic shield could indeed protect against E-fields as from HF.




I'd have thought that meat was a reasonable E-field screen :-)


Mark Rand
RTFM

It is.

On Mon, 19 Jan 2009 15:53:18 GMT, (Doug White)
wrote:

Keywords:
In article , Don Foreman wrote:
On Sun, 18 Jan 2009 11:57:37 -0500, GeoLane at PTD dot NET GeoLane at
PTD dot NET wrote:

On Fri, 16 Jan 2009 22:30:33 -0600, Don Foreman
wrote:


Don, maybe this will show a lack of understanding of magnetism on my
part, but couldn't you put a metallic shield of some sort over your
clothing between you and the pacer and leads and create a Gaussian
shield of sorts?

RWL

Shielding against low-frequency magnetic fields is impractical, but a
metallic shield could indeed protect against E-fields as from HF.

I suspect you could do an OK job if you replaced the metal plates in an
old style flak jacket with mu metal, but it sounds like you are good to
go without that sort of heroics.

Don, I have a roll of thin (15 mil?) mu metal in my junk box. I haven't
fished it out in years, but I suspect I've got about a square foot (or
more) of the stuff. I have no idea how helpful it might be, or if it has
been damaged and has lost some of its effectiveness. It has to be at
least 30 (probably more like 40) years old. If you want it, it's yours.
With your measuring widget, you could even test and see if it helps at
all.

Doug White

Thanks, Doug, that's very generous of you. I'll decline but I do
appreciate the offer. Mu-metal must be hydrogen annealed after any
shaping in order to retain its properties. In any event, I don't seem
to have a B-field issue in my particular setup and situation.

On Sun, 18 Jan 2009 23:36:07 -0800, Gunner Asch
wrote:

On Mon, 19 Jan 2009 00:02:15 -0600, Don Foreman
wrote:

On Fri, 16 Jan 2009 22:30:33 -0600, Don Foreman
wrote:

I hope things go as well with TIG. I'll be trying that tomorrow.

Update: TIG looks good to go. I'm grinnin'.


Ill bet there is a paper...and a government grant in your research.

G

Gunner

Not for me.

I'd gladly write or help with a paper pro bono and I've sent all of my
findings to techical folks at Boston Scientific because they've been
so helpful to me. Geez, the guy returning Ken's call from the ski
slopes at Taos, wow! These people are my kind of professionals.

Being funded by the gummint to do research would have far more hassle
factor than it's worth to me now. Ah'm retired and grinning. Stress
is not nearly as heart-healthy as gunsmoke while shooting for fun.

We don't need much cash flow to do everything we want to do.

Don Foreman wrote:

On Fri, 16 Jan 2009 22:30:33 -0600, Don Foreman
wrote:

I hope things go as well with TIG. I'll be trying that tomorrow.

Update: TIG looks good to go. I'm grinnin'.

Sweet. Good luck with the surgery. Thanks for the email.

Wes