Brian, The "nearest part of the boundary of the equipment under test in one rotation" would usually be the corners (for rectangular equipment). Picture the smallest circle that just touches the equipment. Measure the antenna distance from the outside of that circle.
The imaginary circle should be concentric with the turntable. Scott B. Lacey On 16 May 2008 at 9:21, Kunde, Brian wrote: > > Grace, > > You bring up an interesting subject and one I have never had a clear > understanding of. I think > most labs center the test table on the turntable andline up the EUT and > peripherals along the > back edge of the table. They also place the antenna 10 (or 3) meter away > measured from the > center of the turntable, not the EUT. I know this is not what the standard > says but this is how most > do it for repeatability. If you are moving your table around and antenna mast > for each setup you > will never be able to repeat that setup at other labs. Many labs cannot move > the table or the mast > for they are hard mounted. > > Whether the table is positioned center on the turntable OR so the EUT is > centered shouldn't make > that much difference in the measurement values, especially if you are testing > at a 10 meter > distance. At 3 meter it will have more of an affect but not more thana couple > db at best and that > is why we have margin. The difference between 10 and 11 meter distanceis only > .83db. The > difference between 3 and 4 meter distance is 2.5db. The few centimeter > difference you are > talking able cannot have much difference in the test results. > > The distance between the EUT and the antennachanges more drasticallyduring > the test as the > turntable turns. When the antenna travels up on the mast it gets farther away > from the EUT > especially when testingat a 3 meter distance. > > The EN 55011 standard says the following: > "7.2.2 Disposition of equipment under test (9 kHz to 1 GHz) > If it is possible to do so, the equipment under test shall be placed on a > turntable. The separation > between the equipment under test and the measuring antenna shall be the > horizontal distance > between the measuring antenna and the nearest part of the boundary of the > equipment > under test in one rotation." > I have no idea what "nearest part of the boundary of the equipment under test > in one rotation" > means. Maybe someone can explain it to me. > > I guess technically, you could maximize your turntable angle, then move your > antenna so it is > exactly 10 (or 3) meter away from the EUT and then record that value, but who > really has time for > that. > > Tell your engineers and manager that a few hundred centimeters will not have > more than 1db > difference and moving the test table to different locations on the turntable > jeopardizes > repeatability. > > The Other Brian > > > From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Grace Lin > Sent: Thursday, May 15, 2008 2:40 PM > To: emc-p...@ieee.org > Subject: Table Location for RE Measurement > Dear Members, > > Is there any test standardindicating the location of 1-meter by 1.5-meter > table in the (2-meter) > turntable? Legend 6) of Figure 11a of ANSI C63.4: 2003states: > > "Rear of EUT, including peripherals, shall all be aligned and flush with rear > of tabletop". > > I assume this legend appliesto all tabletop equipment, including non-computer > devices. Our > engineers align the EUT flush with rear of tabletop. However, some engineers > feel the EUT > should be in the center of the 2m turntable and they move the 1mx1.5m table > forthe EUT to be in > the centerof the2m turntable. Some engineers leave the 1mx1.5m table in the > center of the 2m > turntable.Due to each engineer's preference, the 1mx1.5m table is moved > frequently. Some > engineers took data in different table location and confused by the data > taken. The complaint > arises and brings to the managers' attention. > > Thank you and look forward to your input. > > Best regards, > Grace > > > - ---------------------------------------------------------------- This > message is from the IEEE Product Safety > Engineering Society emc-pstc discussion list. Website: > http://www.ieee-pses.org/ > To post a message to the list, send your e-mail to emc-p...@ieee.org > Instructions: http://listserv.ieee.org/request/user-guide.html > List rules: http://www.ieee-pses.org/listrules.html > For help, send mail to the list administrators: > Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org > For policy questions, send mail to: > Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc > _________________________ > > LECO Corporation Notice: This communication may contain confidential > information intended > for the named recipient(s) only. If you received this by mistake, please > destroy it and notify us of > the error. Thank you.- > ---------------------------------------------------------------- This message > is from the > IEEE Product Safety Engineering Society emc-pstc discussion list. Website: > http://www.ieee- > pses.org/ > To post a message to the list, send your e-mail to emc-p...@ieee.org > Instructions: http://listserv.ieee.org/request/user-guide.html > List rules: http://www.ieee-pses.org/listrules.html > For help, send mail to the list administrators: > Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org > For policy questions, send mail to: > Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
