That's because of near-field effects. You can often get any result you
like (or don't like) when measuring in the near field. And there is no
relationship between the electric and magnetic field strengths. Consider
a dipole - much electric but hardly any magnetic. Then consider a
solenoid - just the opposite.
In a truly unperturbed far field, the levels are predictable. The
problem of interpolation, extrapolation or some other way of processing
the measured results is that, because standards are inconsistent,
whichever way you do the processing, it can be challenged. If all the
standards were consistent, there would be one standardized process and
no possibility of a challenge.
Best wishes
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk
Rayleigh, Essex UK
On 2019-10-28 20:47, Grasso, Charles wrote:
Take the reading. It’s the only way to be sure..
It is not unusual for a product to pass @ 3m and then fail at 10m (or
vice versa).
Thanks!
Charles Grasso
W: 303-706-5467
*From:* John Woodgate [mailto:j...@woodjohn.uk]
*Sent:* Monday, October 28, 2019 1:30 AM
*To:* EMC-PSTC@LISTSERV.IEEE.ORG
*Subject:* Re: [PSES] Reading or Limit Conversion?
This message originated outside of DISH and was sent by:
owner-emc-p...@listserv.ieee.org
<mailto:owner-emc-p...@listserv.ieee.org>
This inconsistency (in the underlying CISPR standards) should be
addressed by CISPR, but it is difficult to get consensus whenever it
is discussed.
Best wishes
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associateswww.woodjohn.uk <http://www.woodjohn.uk>
Rayleigh, Essex UK
On 2019-10-28 07:05, Charlie Blackham wrote:
David
Hmm, different standards appear to deal with this differently:
* EN 55011:2009 section 6.2.2.3 instructs you to normalise the
measured data to the specified distance in the standard
* EN 55032:2015 section 9 instructs you to adjust the limits (in
fact it gives limits for 3 and 10m which are 10 dB apart and
not 10.45dB apart if you extrapolate using 20LogD)
* ANSI 63-4:2014 instructs you to extrapolate the results
If the standard or test method doesn’t specify, I guess the
important thing is to be clear in the report as to what’s been done.
Regards
Charlie
*Charlie Blackham*
*Sulis Consultants Ltd*
*Tel: +44 (0)7946 624317*
*Web: https://sulisconsultants.com/ *
Registered in England and Wales, number 05466247
*From:* itl-emc user group <itl...@itl.co.il>
<mailto:itl...@itl.co.il>
*Sent:* 28 October 2019 06:37
*To:* EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
*Subject:* [PSES] Reading or Limit Conversion?
A number of standards list radiated emission limits in the
frequency range of 30-1000 MHz for test distance greater than 3 or
10 meters.
Testing is normally performed at either 3 meters or 10 meters on
an Open Area Test Site.
A question has arisen concerning reporting the test results in
these cases.
Any opinions concerning which should be converted:
a.Convert the limit to the relevant test distance (3 meters or 10
meters) by adding correction factor or
b.Convert the reading to the unit and test distance listed in the
standard (convert dBµV to µV and add correction factor for distance)
On some occasions I have seen option b. above used.
Which option is preferable?
All opinions welcome
*Regards,*
*David Shidlowsky***| Technical Reviewer
*Address*1 Bat-Sheva St. LOD 7120101 Israel
*Tel*972-8-9186113*Fax* 972-8-9153101
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