Re: Magnetic Field Surveys

["John Moulder" <jmoulder@post.its.mcw.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)
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