FreeLists / si-list / [SI-LIST] Re: Question on 60Hz magnetic field strengths

["Nagel Michael-amn029" <Michael.Nagel@xxxxxxxxxxxx>]

Hi Ray,

I do not know the history behind the figure of 3A/m, but an instrument =
where it is specified that
it is compliant with this requirement must work within its =
specifications (in an ideal world).

As ISM (Industrial, scientific and medical) equipment is not in the =
focus of my work, I am not=20
familiar with the corresponding standards.=20
A quick search had CISPR 11 for emission as result which translates to =
EN 55011 for the EU.=20
Standards like IEC/EN 61000-4-xx describe only test methods but not the =
required emission
or immunity levels, these must be specified within the relevant product =
standard. In the ITE=20
(Information Technology Equipment) world it looks like this =
(simplified):
CISPR 22 -> EN 55022: Emission limits and test methods (Reference to =
CISPR 16-1 for instrument=20
                      properties)
CISPR 24 -> EN 55024: Immunity Requirements with reference to test =
methods in the various=20
                      IEC/EN 61000-4-xx standards.

Regarding the measured field close to the TDR, 100mGauss seems a lot to =
me. It is too much for
the TDR, and - applying the precautionary principle - too much for a =
person.
IEEE has a standard covering this:
http://www.osha.gov/SLTC/elfradiation/epri-ieee1-03d.pdf

If you want more than just my opinion, consider asking the same question =
in the IEEE EMC-PSTC forum.

Best regards,
Michael

Michael Nagel
Senior EMC Engineer
Motorola GmbH
ECC Embedded Communications Computing
Lilienthalstrasse 15
85579 Neubiberg/Muenchen - Germany
Ph: +49-89-9608-0
Fax: +49-89-9608-2376
e-mail: Michael.Nagel@xxxxxxxxxxxx
info: http://www.motorola.com/computers=20
=20
=20



-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
On Behalf Of Ray Anderson
Sent: Mittwoch, 7. M=E4rz 2007 20:11
To: si-list@xxxxxxxxxxxxx
Cc: Ray Anderson
Subject: [SI-LIST] Question on 60Hz magnetic field strengths

I've got a question for the EMC guys on the list:
=20

Looking in the spec manual for a Tektronix TDR I find that the =
acceptable EMC environment for the instrument is a reference to IEC =
61000-4-3. Not having a copy of that standard, some snooping on the net =
seems to imply that IEC 61000-4-8 is also relevant with regards to 60 HZ =
magnetic fields.

=20

From some related appnote I find that 3A/m is a relevant magnetic field =
strength spec for domestic, commercial and light industrial =
environments.  Since 80A/m =3D 1Gauss it seems that 3A/m =3D 37.5mGauss.

=20

Since all the above is inferred from 3rd party info and not the actual =
standard, I'd just like to inquire if the 37.5mGauss field strength for =
a 60 Hz field sounds like a reasonable number for an instrument to =
operate properly in?

=20

My lab just got rearranged and the TDR bench got shoved up against a =
wall that adjoins a room that houses some heavy duty power distribution =
transformers. Some measurements with an el-cheapo magnetic field meter
(non-calibrated) seem to imply we are seeing about 100mGauss in the =
vicinity of where the TDR is intended to operate. I'm trying to do a =
sanity check to determine just how serious of an issue this really is.
The wavy display on the TDR CRT and a collocated computer monitor are =
really annoying.

=20

-Ray

=20

=20

Raymond Anderson

Senior Signal Integrity Staff Engineer

Advanced Platforms Group

Advanced Products Division

Product Technology Department

Package Design Engineering

Xilinx Inc.

2100 Logic Drive

San Jose, California  95124

(408) 626-6277

=20

=20


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