Well, except for the cold inrush current wear. I always left my lights
off when I wasn't working in the chamber. A camera still allowed me to monitor
equipment activity, which was either on a CRT or indicator lights.
Fluorescents can indeed cause a large problem, but generally changing the tube
every so often (the analyzer will tell you long before your eye) and eventually
the ballast the fluorescents, in my experience will do fine.
I have a current problem with some special ballasts and expensive
spectral output fluorescents that require me to turn them off if I want to see
anything below 100 Mhz, and pretty much anything up to 200 Mhz. Its all nasty
broadband. Very expensive to fix, so I just put in some task lighting so that I
can walk around without killing myself while measuring, and when I need to
troubleshoot or repair I snap the fluorescents back on. Dirty but cheap and
accomplishes the purpose for the prescan chamber.
Gary
-----Original Message-----
From: Ralph McDiarmid [mailto:ralph.mcdiar...@xantrex.com]
Sent: Thursday, October 31, 2002 11:55 AM
To: EMC-PSTC (E-mail)
Subject: RE: Shield Room Lighting
We use four florescent screw-in lights in our 3-metre chamber and detect
some
emission 3dB or so above the "noise floor".
Ralph McDiarmid, AScT
Member Technical Staff
Engineering Services
Xantrex Technology Inc.
-----Original Message-----
From: POWELL, DOUG [mailto:doug.pow...@aei.com]
Sent: Thursday, October 31, 2002 9:49 AM
To: EMC-PSTC (E-mail)
Subject: Shield Room Lighting
Greetings all,
I wanted to share an experience and I hope benefits someone else.
My past experience with shield room lighting is that incandescent bulbs
frequently burn out, about once every 2-3 months. I tried ruggedized lamps
of various sorts, still with the same results. Obviously, I wanted to avoid
florescent lighting because of the huge fields they radiate. After some
investigation and discussions with co-workers, it became apparent that the
problem is the line filter for service power in the room and the tungsten
filament in the bulb. These line filters are typically have a really large
line to neutral capacitance which significantly lowers the source impedance
of the line. Coupled with this, tungsten experiences a fairly high in-rush
current owing to it's very dynamic negative temperature coefficient. I
toyed with idea of using inrush limiters but I thought there had to be a
reliable low-tech solution. And at all costs, whatever solution I used, I
wanted to avoid injecting unwanted RF noise into the room.
I discovered traffic light signal bulbs. Available from a few sources,
these bulbs have at least 5 filament supports, heat dissipaters and
reflectors and are designed for continuous on/off operation in all sorts of
weather conditions. They even keep working when the hanging fixtures bang
into each other in wind storms. I also learned that these bulbs have about
a 1 to 2 year life expectancy in these conditions, so I tried it out in my
room. So far, I've logged a full year of use on 4 x 150W bulbs with no burn
out. And no, I don't just leave them turned on.
If you want to try this, do it soon because it appears that these bulbs may
become a thing of the past and prices may be driven up. Over the last few
years, many cities and counties are replacing their incandescent bulbs with
the new LED bulbs and with great success. As soon as a white LED light
becomes available I may try it out, although I guess I could use red LED
lamps since I used to be in the navy.
Best regards,
-doug
Douglas E. Powell
Compliance Engineer
Advanced Energy Industries, Inc.
Fort Collins, CO 80535 USA
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