Mac, I have witnessed significant variations in measurements depending on if the OATS was wet or not. It was several dB, and that amount varied a lot over the frequency range. Additionally, IIRC the way it varied over frequency was also not particularly constant rain storm to rain storm. I don’t have any solid numbers or plots to share though, just that we avoided it whenever scheduling allowed.
These days, I only have a semi-anechoic chamber; however, once we have results that we are happy with and that meet internal guidelines, we send the EUT to a third party test lab for official verification where they use an OATS. It has a tent that covers just the EUT area, not the entire 10 meter site, so there is plenty of area for water to puddle up. We have them test rain or shine, whatever they are comfortable with, which I think as long as there is no lightning posing a safety hazard they will run the test. If my margins are where I want them to be, 6dB+, I’m pretty confident it will pass. The EUT has been thoroughly tested in my chamber, so I have results that reflect normal conditions; I just need some results from an accredited laboratory to show that I am passing, to put in my final report, and to base my conformity statements on. Best Regards, Adam Rudd Electrical Engineer (EMC) NCR Corporation, RHSS Duluth, GA (770) 495-2825 ________________________________ From: [email protected] [mailto:[email protected]] On Behalf Of Elliott Mac-FME001 Sent: Wednesday, June 18, 2008 11:20 AM To: [email protected] Subject: OATS tests after rain Hello Colleagues After rain on an OATS, what are your typical guidelines for the resumption of test? I worked with one great engineer on this board at one time who had seen dramatic differences on his OATS after rain and would shut down until the next day when the site was dry. We are trying to run two shifts here and in S. Florida have afternoon rains that are frequently short in duration. I have done a few experiments that shows that it seems OK as long once the rain has stopped and any standing water has run off. There are some damp spots under the ground mesh and maybe some residual moisture on the mesh. Thoughts? Experiences? Regards, Mac Elliott - ---------------------------------------------------------------- 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 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
