VDT interference

["Jeffrey A. Leavey" <certhp@vnet.IBM.COM>]

Being with IBM, I frequently got calls about VDT interference.
Almost all cases were caused by power lines running over, under,
along side, etc. VDT's. Also, electrical closets located next to
offices. I saw no problems with regular outlet wiring but with
feeders and large gauge branch line wiring. The problems really
became noticeable when VGA displays popped up. The better the
resolution of a display, the more sensitive it is to mag
interference. So, in order of increasing sensitivity are
monochrome, CGA, EGA, VGA, etc.

I bought the Holiday 60 Hz survey meter (I can post more info
about this is someone is interested) that checks E and H fields.
I quickly found the H fields were the cause and at levels far
below people safety levels. In fact, people were thinking that
because their display was affected, they must be too. Showing
them the survey results and the IRPA guidelines helped dispel
their fears (well... most of the time :-) )

In most cases fixing the problem simply involved moving the
display to another location. Mag shielding is not easy and
the fix might involve relocating the power lines (also not
easy or cheap). We also offered to relocate some people to
different offices and that worked well for some.

So the moral of the story is: plan new construction to avoid
electrical closets and power line runs near offices, have
a survey meter to show people their levels are below health
and safety standards, and finally offer them an alternative
if they are really upset.

Good luck!

Jeff
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Jeffrey Leavey      certhp@vnet.ibm.com
X-ray Lithography Program - IBM Corp.
East Fishkill, NY  12533 - 914-892-4595
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