[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Magnetic Field Surveys
RE>> Magnetic Field Surveys 5/2/96
I once saw a CRT's image listing due to the magnetic field created when
someone left a magnet in a desk drawer and removed it. The residual from the
magnetized soft steel was enough. The field at the screen was in the range of
a gauss or less. It was also a big screen.
There is a tendency to lump static fields with ELF with rf/microwaves. This
is equivalent to saying U238 and Co60 are the same or that iron and lead are
the same.
--------------------------------------
Date: 5/1/96 4:18 PM
To: GORDON MILLER
From: radsafe@romulus.ehs.uiuc.edu
> Subject: Re: Magnetic Field Surveys
>
> Bernard L Cohen wrote:
>
> > There may be a confusion here between AC and DC magnetic
> > fields.
>
> You are correct that these are DC fields...
>
> However, the problem is that "the public" does not make the
> distinction between AC and DC magnetic fields.
That's my experience also. Note that "the public" also does not know the
difference between 60-Hz and RF. The use of the generic "EMF" by the media
and even some science journals does not help.
> By extension, the people in those
> offices assumed that if the fields can affect their monitors, there is
> no telling what damage it is doing to their long-term health.
> Radiation Safety was unable to allay their fears.
I'd suggest that you demonstrate to the users that even the Earth field
affects a computer monitor. When you subject a large screen color monitor to
a static field of as little as 50 microT (500 mG) you get distortions,
particularly color distortions at the corners. The Earth field doesn't cause
such distortions because the monitor compensates. Turn the monitor on its
side, so that the compensation is wrong, and you will usually (always?) see
the same distortion. [I don't know how the Radius Pivot monitor solved this].
You can also get great distortions with a refrigerator magnet.
We found that these demonstrations solved the problem.
------------------------------------
John Moulder (jmoulder@its.mcw.edu)
Maintainer: Powerlines & Cancer FAQs,
Static EM Fields and Cancer FAQs
USENET: sci.med.physics, sci.answers, news.answers.
ftp://ftp.mcw.edu/pub/emf-and-cancer
ftp://rtfm.mit.edu/pub/usenet-by-group/sci.answers
http://www.cs.ruu.nl/wais/html/na-dir/powerlines-cancer-FAQ
http://www.cis.ohio-state.edu/hypertext/faq/usenet
------------------ RFC822 Header Follows ------------------
Received: by quickmail.llnl.gov with SMTP;1 May 1996 16:16:21 -0700
Received: from romulus.ehs.uiuc.edu (romulus.ehs.uiuc.edu [128.174.74.24]) by
postoffice.cso.uiuc.edu (8.6.12/8.6.12) with SMTP id SAA122554; Wed, 1 May
1996 18:07:46 -0500
Received: from localhost by romulus.ehs.uiuc.edu (NX5.67d/NeXT-2.0)
id AA13387; Wed, 1 May 96 18:06:49 -0500
Date: Wed, 1 May 96 18:06:49 -0500
Message-Id: <9605011804.AA52400@admin-one.radbio.mcw.edu>
Errors-To: melissa@romulus.ehs.uiuc.edu
Reply-To: radsafe@romulus.ehs.uiuc.edu
Originator: radsafe@romulus.ehs.uiuc.edu
Sender: radsafe@romulus.ehs.uiuc.edu
Precedence: bulk
From: "John Moulder" <jmoulder@post.its.mcw.edu>
To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
Subject: Re: Magnetic Field Surveys
X-Listserver-Version: 6.0 -- UNIX ListServer by Anastasios Kotsikonas
X-Comment: Radiation Safety Distribution List