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.