" wrote in
ups.com:

Dave

The defibrillator probably has two field strengths that it was tested
to.
IEC61000-4-3 defines the test proceedure for High Frequency phenomena
(typically 80-1000MHz) and uses units of Volts per Meter.
IEC61000-4-8 defines immunity to Magnetic (Power Frequency) Fields
(50/60Hz)
and uses units of Amps per Meter.

The manufacturer will know what level the device is immune to. I would
cut that level by 3 (which yields half the power) for safety. So if it
complies with say 10V/m keep it below 3V/m.

Note: 10V/m will extend 1 meter from a 5W transmitting antennae.






Dave Isherwood wrote:
Actually, I asked the doctors and they didn't even know how to think
about the problem.

I've tried asking the manufacturer but their 1st response was just
their
standard instructions. Actually, I have a follow-up in a month or so
and I get to meet with a technical representative and I'm hoping to
have some measurements by then.

Given the time of year and the fact that I'll have few needs to enter
the engine room. Combined with the fact that I can just turn
everything off. (Presumption is that there is that there would be a
minimal magnetic fields with only a 12v active for lights - Anybody
think this is a false assumption?). I can spend some time to fully
understand the problem and resolution.

As I make progress I'll make sure to share that with the group as I
cannot believe I'm the only one with the question.

Thanks for the inputs,

Dave

"Lost In Space/Woodchuck" wrote in
message ...
what does your doctor think?

"Dave Isherwood" wrote in message
...
Good Evenin' All,

I've just been fitted with a cardiac defribulator. This device
comes with instructions to avoid using cell phone in right ear and
keep power-tools 12" away from the device. Seems the risk is that
strong magnetic fields may damage the programming and cause the
device to reset.

I currently live on a 53' Carver and the engine room has a lot of
electrical equipment: 50A Charging / Inverter, 2*Starters /
Transformers on the engines and Generator. My concern is that
there is the potential for a sizable magnetic field in the engine
room and I simply don't (short of saving up a few pennies and
getting a crew) know how to avoid or manage the issue.

Questions:

1. Has anybody had to consider this problem? What it a problem?
2. Any clever way I can judge the strength of the magnetic
fields?

Thanks,

Dave





My company repairs medical imaging devices. I ran across this article
just today in a publication called Health Imaging News that is on point.
Apartently it is an extract of an article in another publication called
Heart Rhythm which is turn put out by the Heart Rhythm Society (HRS). The
link to the HRS is at the end of the article. Looks like a subscription
to Heart Rhythm is available for about $131/year. May be a good
investment since this is certainly a subject which is now near and dear
to you. Anyway, if there is anyone who knows something about this
subject, it sounds like it's probably the HRS:

Powerful magnets could impact operation of implanted heart devices
http://www.healthimaging.com/content/view/5487/89/

Magnets could cause dangerous interference with the operation of
pacemakers and implantable cardioverter defibrillators (ICDs), according
to a study published in the December 2006 edition of Heart Rhythm.

The study found that common magnets used in homes and offices are not
high risk. However, stronger magnets made from neodymium-iron-boron
(NdFeB) may cause interference with cardiac devices and pose potential
hazards to patients. NdFeB magnets are increasingly being used in homes
and office products, toys, jewelry and even clothing.

“Physicians should caution patients about the risks associated with these
magnets,” said Thomas Wolber, a cardiologist at the University Hospital
of Zurich in Switzerland and lead author of the study. “We also recommend
that the packaging include information on the potential risks that may be
associated with these types of magnets.”

For the study, two spherical magnets of eight and 10 millimeters in
diameter and one necklace made of 45 spherical magnets were tested on 70
patients, 41 with pacemakers and 29 with ICDs. The magnets were shows to
have an impact on the device operation in each patient. However, the
researchers noted that cardiac devices resumed normal function after the
magnets were removed.

Some researchers who have evaluated magnet interference believe that
manufacturers who use magnets should be required to put warning labels on
their products for optimal patient safety.

Mo www.HRSonline.org