Hi,
I have some questions. What are the dimension of your loop? Are you
measuring a static field? If so, I suggest you use a Hall-effect type
sensor, I have had good results at powerline frequencies. If you are
measuring the H-field component for anything in the 30 MHz or so region, I
would be more careful about moving away from the source because of the
extremely complex (nonlinear and usually unpredictable) field patterns in
the near-field.
Redesigning the input circuit would help but that would mean that the new
setup have to be calibrated.
:-)
Just my 2 cents worth.
Tim Foo,
(or just call me 'Tim')
E-mail: [email protected]
ECE, School of Engineering,
http://www.np.edu.sg/ece/ Tel: + 65 460 6143
Ngee Ann Polytechnic, Fax: + 65 467 1730
535 Clementi Road,
Singapore 599489
"Robert Macy"
<[email protected]> To: "KC CHAN [PDD]"
<[email protected]>, "<"
Sent by: cc: (bcc: Wan Juang
Foo/ece/staff/npnet)
owner-emc-pstc@majordom Subject: Re: Active loop
antenna overload
o.ieee.org
09/24/01 03:45 PM
Please respond to
"Robert Macy"
Move the antenna further away. then use correction factors to calculate
what it would have been at the original distance.
Magnetic fields decrease as the inverse cube of the distance. So just
apply a correction factor to "boost" the amplitude back up. For example,
twice the distance away means the signal will look 1/8 as much or around
18dB smaller.
Of course, that assumes the source is a magnetic dipole AND your original
measurement distance is at least 3 diameters (diameters of the sensing loop
AND diameters of the source loop) away to begin with.
[ Also, conductive surfaces and magnetic materials need to be out of the
field of interest. Make certain the minimum distance to such
"interference" is at least 3 times the distance between what you're
measuring and your sensing loop. ]
If the above assumptions don't hold, come back at me.
- Robert -
Robert A. Macy, PE [email protected]
408 286 3985 fx 408 297 9121
AJM International Electronics Consultants
619 North First St, San Jose, CA 95112
-----Original Message-----
From: KC CHAN [PDD] <[email protected]>
To: < <[email protected]>
List-Post: [email protected]
Date: Monday, September 24, 2001 12:19 AM
Subject: Active loop antenna overload
Dear All
When doing the magnetic field measurement by a active loop antenna, what we
can do if we find the loop antenna is saturated/overloaded? Is there any
ways that we can do to overcome this?
Best Regards
KC Chan
<snip>
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