Chris,
I like your innovative thinking! When I once managed our acoustics
lab, we had both a semi-anechoic chamber and a reverberation chamber.
The SAC was similar to those for EMC, in that the walls were designed
to absorb all sound waves striking them, so that sound pressure at a
point near the DUT could be measured.
The reverberation chamber sides (6) were to reflect all sound waves
striking them so the total noise energy emitted from the DUT could
be measured.
This might suggest that your "igloo" EMC chamber not include the
initial absorber layer. With a good conductive inner liner, all
EMC energy would eventually be conducted away by this liner, and
measured with a low impedance meter between the liner and ground.
It really does not matter how many reflections take place, as all
wave energy must eventually leave via the conductive path.
The problem is how to fully electrically isolate this conductive
"collector" from additional outside EMI. Perhaps a very thick
di-electric (low C) between the collector and an outer conductive
layer to absorb in-coming EMI.
If you ever build one that works, just allow me to visit you at
your new house in the Bahamas, bought with your profit from the
"Igloo Chamber".
George
"Chris Maxwell" <chris.maxwell%[email protected]> on 12/12/2001
03:45:52 PM
To: "George_Alspaugh/Lex/Lexmark.LEXMARK"@sweeper.lex.lexmark.com, "Patrick
Lawler" <plawler%[email protected]>
cc: "EMC-PSTC" <emc-pstc%[email protected]> (bcc: George
Alspaugh/Lex/Lexmark)
Subject: RE: Enclosed OATS facilities---detour
Hmmmm,
This conductive layer of snow reminds me of a daydream/ thought
experiment that I had for measuring emissions...
What if you put a DUT inside a chamber that looked like a hemisphere.
The chamber would be hollow (otherwise, how would the DUT get in). The
chamber "skin" would be a sandwich with a thin layer of absorber on the
inside and a good conductor (conductor 1) then a dielectric then another
good conductor (conductor 2) on the outside.
Why these layers?
The inner layer would offer just enough attenuation to reduce
reflections, while letting some energy get to the conductor 1 behind it.
The conductor 1 layer would effectively be a "integrating measurement
antenna" which picks up and integrates all emissions from the DUT.
The dielectric layer would insulate conductor 1 from conductor 2.
(maybe this layer would need to be RF absorbant as well, not sure).
The conductor 2 layer would be grounded all the way around and would
serve to block ambients.
What would happen?
Would conductor 1 capacitively couple to the DUT such that a simple
swept RF voltage measurement between the DUT and conductor 1 would show
the total interference produced by the DUT?
Who's with me? Let's go to K-mart and get:
A large dome tent.
About 50 square yards of tin foil
Some Tokin flexible ferrite stuff **
A DUT.
An RF voltmeter/spectrum analyzer and a stub cable. **
**probably not available at K-mart...maybe Wal-Mart?
Might make a fun experiment, or maybe give the neighbors the idea that
you're building an escape pod to the mother ship.
Any immediate pitfalls that can be foreseen by the collective gurus?
Chris Maxwell | Design Engineer - Optical Division
email [email protected] | dir +1 315 266 5128 | fax +1 315 797
8024
NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA
web www.nettest.com | tel +1 315 797 4449 |
-------------------------------------------
This message is from the IEEE EMC Society Product Safety
Technical Committee emc-pstc discussion list.
Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/
To cancel your subscription, send mail to:
[email protected]
with the single line:
unsubscribe emc-pstc
For help, send mail to the list administrators:
Michael Garretson: [email protected]
Dave Heald [email protected]
For policy questions, send mail to:
Richard Nute: [email protected]
Jim Bacher: [email protected]
All emc-pstc postings are archived and searchable on the web at:
No longer online until our new server is brought online and the old
messages are imported into the new server.
