Re: [PSES] Fully anechoic chamber vs. Semi-anechoic chamber
It would be helpful, especially if it discloses unexpected deviations, but the cable layouts of different EUTs have a significant influence, so might well show different transfer functions. Data collected from such dual measurements could be helpful to CISPR/A. John Woodgate OOO-Own Opinions Only J M Woodgate and Associates www.woodjohn.uk Rayleigh, Essex UK On 2018-11-12 08:23, Manny Barron wrote: Hi Amund, This approach can get tricky. There are several factors that will influence the results in either chamber and in general are not easily predictable. If I were doing this I would implement a required minimum 10 dB margin when testing in the FAC. But that's just me, I'm typically cautious, sometimes more than necessary. Here's a better approach if it's possible for you to do this. The lab with the SAC most likely has comb generators covering the frequency range of testing in order to do pre-test checks. If you are able to borrow those comb generators it would be great to run them in both chambers and compare the difference. The combs typically contain many unique frequencies throughout the frequency range that can provide a decent data resolution (i.e., maybe hundreds of data points). This can be done for both vertical and horizontal comb polarizations (the horizontal polarization may have some issues but at least you'd get some data instead of no data). In the end you would have a simple transfer function that can be applied to the FAC data to get an idea of how the SAC data would turn out. I used this method about 20 years ago when I managed 2 SAC's for H-P. It wasn't perfect but it helped to correlate the test results between chambers. Hope this is helpful. Manny Barron EMC Lab Mgr -Original Message- From: Amund Westin [mailto:am...@westin-emission.no] Sent: Sunday, November 11, 2018 11:09 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] Fully anechoic chamber vs. Semi-anechoic chamber Doing EMC pre-qual test in Fully anechoic chamber, but ending up doing qualified EMC testing in a Semi-anechoic chamber, that might not be a good approach? ….. There will always be deviation in results from lab to lab. And if the type of chamber is different as well, I assume additional deviations might apply. Will 6-8dB margin in a Fully anechoic chamber be enough, when entering qualified EMC testing in a Semi-anechoic chamber? Any good rule of thumb here? ... Best regards Amund - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald: - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald: - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] Fully anechoic chamber vs. Semi-anechoic chamber
Hi Amund, This approach can get tricky. There are several factors that will influence the results in either chamber and in general are not easily predictable. If I were doing this I would implement a required minimum 10 dB margin when testing in the FAC. But that's just me, I'm typically cautious, sometimes more than necessary. Here's a better approach if it's possible for you to do this. The lab with the SAC most likely has comb generators covering the frequency range of testing in order to do pre-test checks. If you are able to borrow those comb generators it would be great to run them in both chambers and compare the difference. The combs typically contain many unique frequencies throughout the frequency range that can provide a decent data resolution (i.e., maybe hundreds of data points). This can be done for both vertical and horizontal comb polarizations (the horizontal polarization may have some issues but at least you'd get some data instead of no data). In the end you would have a simple transfer function that can be applied to the FAC data to get an idea of how the SAC data would turn out. I used this method about 20 years ago when I managed 2 SAC's for H-P. It wasn't perfect but it helped to correlate the test results between chambers. Hope this is helpful. Manny Barron EMC Lab Mgr -Original Message- From: Amund Westin [mailto:am...@westin-emission.no] Sent: Sunday, November 11, 2018 11:09 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] Fully anechoic chamber vs. Semi-anechoic chamber Doing EMC pre-qual test in Fully anechoic chamber, but ending up doing qualified EMC testing in a Semi-anechoic chamber, that might not be a good approach? ….. There will always be deviation in results from lab to lab. And if the type of chamber is different as well, I assume additional deviations might apply. Will 6-8dB margin in a Fully anechoic chamber be enough, when entering qualified EMC testing in a Semi-anechoic chamber? Any good rule of thumb here? ... Best regards Amund - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald: - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] Fully anechoic chamber vs. Semi-anechoic chamber
Hi Amund, One place to start is looking at the difference in limits in EN 55032 for a SAC and for a FAR (see attached graph). Above 230MHz the chart is 5dB lower to account for the lack of a reflective ground plane. I don't know how the upward-sloping compensation below 230MHz was derived originally and would be interested to find out. I've found that using these limits and applying a 6dB margin that the SAC test is successful nearly all the time. The exceptions have been down to variations in test setups or cabling. Make sure the test setup is consistent between both! There is still variation in the absolute levels that I've measured between chambers of around ±3dB. That's why the 6dB margin comes in handy. For key marginal frequencies, a quick pre-test at the SAC gives you a benchmark by which to gauge your improvements. I've tried to build up a library of test results between my laboratory and the chambers of other laboratories to identify differences in performance but don't have enough data yet to build up a good picture of trends. I hope this is useful. James -Original Message- From: Amund Westin Sent: 12 November 2018 07:09 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] Fully anechoic chamber vs. Semi-anechoic chamber Doing EMC pre-qual test in Fully anechoic chamber, but ending up doing qualified EMC testing in a Semi-anechoic chamber, that might not be a good approach? ….. There will always be deviation in results from lab to lab. And if the type of chamber is different as well, I assume additional deviations might apply. Will 6-8dB margin in a Fully anechoic chamber be enough, when entering qualified EMC testing in a Semi-anechoic chamber? Any good rule of thumb here? ... Best regards Amund - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald: - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
Re: [PSES] Fully anechoic chamber vs. Semi-anechoic chamber
It might well be a great help to CISPR/A if you could collect data on the different results in the two chambers and submit a report. If you don't know how to do that, please ask here. John Woodgate OOO-Own Opinions Only J M Woodgate and Associates www.woodjohn.uk Rayleigh, Essex UK On 2018-11-12 07:09, Amund Westin wrote: Doing EMC pre-qual test in Fully anechoic chamber, but ending up doing qualified EMC testing in a Semi-anechoic chamber, that might not be a good approach? ….. There will always be deviation in results from lab to lab. And if the type of chamber is different as well, I assume additional deviations might apply. Will 6-8dB margin in a Fully anechoic chamber be enough, when entering qualified EMC testing in a Semi-anechoic chamber? Any good rule of thumb here? ... Best regards Amund - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald: - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas Mike Cantwell For policy questions, send mail to: Jim Bacher: David Heald:
