There are two points to be made here. One is that control of cable emissions can be performed separately by making conducted measurements on those cables first before going into the TEM cell. If the cable common mode (cm) conducted emission (CE) meet their requirements, then you know any out of tolerance conditions measured in the TEM cell source >from the equipment enclosure. such cable cm CE measurements can be performed with a current probe, or better yet the CISPR absorbing clamp. Mr. Grasso et al. of this forum have published a simple relationship between cable cm CE and the resultant radiated field at three or ten meters.
The second point is that if you have gone to the trouble and expense of buying GTEM cells, then it might be profitable to investigate their use for radiated immunity testing in lieu of the procedures of 61000-4-3. In the same way that for emissions you control cable cm CE, you can verify cable-immunity via 61000-4-6, perhaps pushing the requirement to 230 MHz or higher, and then the RI results are not so dependent on the cable layout. The smaller the test item, hence the smaller the GTEM cell, the more profitable this is in terms of maximizing field intensity Volts per meter per Watt of rf amplifier, and the field structure (uniformity) is ideal. -- Ken Javor Phone: (256) 650-5261 From: "Farley, John" <[email protected]> List-Post: [email protected] Date: Tue, 28 Aug 2007 09:46:08 -0500 To: <[email protected]> Subject: General question on the use of GTEMs All, I've been reading through past posts on GTEM cells. The limitation that seems to be mentioned the most is the difficulty in cable manipulation/ cabling being part of the finite EUT test volume available limits the accuracy/ correlation of test data below 230 MHz. I'm looking into purchasing GTEM cells as a supplement to our anechoic chamber. They are appealing due to the fact that they are cheaper and we can fit sveral of even the largest TEM cell in the area taken up by one chamber. My first question would be whether practical solutions to the cable manipulation issue have been identified and if so what is it? I also know that the reading from the septum varies depending on location in the test area. What is the group's experience with repeatability from emissions scan doing repeated test on the same product? I'm just trying to get a feel for how practical TEMs are for emissions testing. Any information you could provide me would be appreciated. Thank you. Regards, John P. Farley Senior Compliance Engineer Garmin International 1200 East 151st Street Olathe, KS 66062 P: 913-397-8200 F: 913-397-8282 ------------------------- This e-mail and any attachments may contain confidential material for the sole use of the intended recipient. If you are not the intended recipient, please be aware that any disclosure, copying, distribution or use of this e-mail or any attachment is prohibited. If you have received this e-mail in error, please contact the sender and delete all copies. Thank you for your cooperation - ---------------------------------------------------------------- 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 [email protected] 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 [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________ - ---------------------------------------------------------------- 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 [email protected] 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 [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
