For what it's worth I fully agree with Derek. The site calibrator is a good start but if I remember the breakdown correctly a little more than half of the measurement error is from personnel training and equipment setup. Pretty much all of that is completely eliminated with the site calibration - a one box - zero cable (battery operation) device. It doesn't even really matter if you rotate this device. Using such a simple device as the sole arbitrator of "goodness" eliminates the personnel and equipment setup variable - the highest contributor of measurement error. Even a small setup with interconnecting cables etc is a "must" in my opinion. Then document the heck out of it, what software modules are running the exact positioning of all parts of the EUT, contrast settings (more important with CRT's that LCD's). Etc. One might even consider doing this twice at the other lab - once without only general setup instructions - allowing the other test lab to use their procedures and process to set up the gear, and then with an exact replica of your setup.
Shopping for a "better" test site isn't new to your engineers, but it says at least as much about their designs as it does about how the equipment is measured. If they are constantly fighting a 2 -3 dB and think that finding another lab will resolve the they are likely shooting themselves in the foot because they will continue to fight the same problems. This presumes that your test and test facility are truly not in error though. Gary McInturff 208 635 8306 From: Derek Walton [mailto:[email protected]] Sent: Tuesday, November 24, 2009 8:19 AM To: [email protected] Subject: Re: [PSES] 3-meter Chamber Site Comparison Hi Grace, I reaffirm my stance that you should test a real EUT. To start, one with minimum cables, but a real EUT nonetheless. Sincerely, Derek. Grace Lin wrote: > Site comparison is requested by our design group. They feel it is too > difficult to obtain a passing data from my lab. -Grace > > On 11/23/09, Grasso, Charles <[email protected]> wrote: > >> Hello Grace, >> >> >> >> The first question is - what do you mean by a site comparison? If by >> that you mean >> how well a site performs to established site attenuation - well then all >> you need is >> to have the site run the test. >> >> >> >> If, by site comparison, you mean comparing one site against another then >> you actually >> have a more difficult problem as there are several variables that you >> will need to account for. >> >> >> >> What has proved very successful is to use a standard calibrated source >> and provide the test >> lab with a detailed set of instructions on how to take the measurement. >> This methodology >> focuses on the site quality only! (Dell and HP are examples) >> >> >> >> NIST has a very precise site source (the original design was done by >> Galen Koepke from NIST I believe) HP developed their own source and >> reported that >> they reduced site to site variability to about 2dB!! I cannot remember >> the >> individual that designed the source and did the work maybe someone from >> this list >> can help! >> >> >> >> Best Regards >> Charles Grasso >> Compliance Engineer >> Echostar Communications >> (w) 303-706-5467 >> (c) 303-204-2974 >> (t) [email protected] <mailto:[email protected]> >> (e) [email protected] <mailto:[email protected]> >> (e2) [email protected] <mailto:[email protected]> >> >> ________________________________ >> >> From: [email protected] [mailto:[email protected]] On Behalf Of >> [email protected] >> Sent: Friday, November 20, 2009 11:06 AM >> To: [email protected] >> Subject: Re: [PSES] 3-meter Chamber Site Comparison >> >> >> >> >> If you can spare time why not try both an EUT and a 'comb' RF source? >> It would make a nice cross-check. >> ________________________________________________________________________ >> _____________ >> >> Ralph McDiarmid | Schneider Electric | Renewable Energies Business >> | CANADA | >> >> >> >> >> From: >> >> Grace Lin <[email protected]> >> >> To: >> >> [email protected] >> >> Date: >> >> 11/20/2009 04:56 AM >> >> Subject: >> >> [PSES] 3-meter Chamber Site Comparison >> >> >> >> ________________________________ >> >> >> >> >> Dear Members, >> >> I am asked to perform site comparison and would like to hear your >> comments. >> >> Should I purchase a signal source? If yes, do you have any reference? >> I do have a COM-POWER comb generator and don't know if it is good enough >> for the purpose. >> >> Should I use an EUT for site comparison? >> >> Thank you. >> >> Best regards, >> Grace Lin >> >> >> >> >> >> >> - >> ---------------------------------------------------------------- >> 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 <[email protected]> >> >> All emc-pstc postings are archived and searchable on the web at >> http://www.ieeecommunities.org/emc-pstc >> Graphics (in well-used formats), large files, etc. can be posted to that >> URL. >> >> Website: http://www.ieee-pses.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 <[email protected]> >> Mike Cantwell <[email protected]> >> >> For policy questions, send mail to: >> Jim Bacher <[email protected]> >> David Heald <[email protected]> >> >> >> ________________________________________________________________________ >> This email has been scanned for SPAM content and Viruses by the MessageL >> abs Email Security System. >> ________________________________________________________________________ >> >> >> - >> ---------------------------------------------------------------- >> 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 <[email protected]> >> >> All emc-pstc postings are archived and searchable on the web at >> http://www.ieeecommunities.org/emc-pstc >> Graphics (in well-used formats), large files, etc. can be posted to that >> URL. >> >> Website: http://www.ieee-pses.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 <[email protected]> >> Mike Cantwell <[email protected]> >> >> For policy questions, send mail to: >> Jim Bacher <[email protected]> >> David Heald <[email protected]> >> >> >> - >> ---------------------------------------------------------------- >> 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 >> <[email protected]> >> >> All emc-pstc postings are archived and searchable on the web at: >> http://www.ieeecommunities.org/emc-pstc >> Graphics (in well-used formats), large files, etc. can be posted to that >> URL. >> >> Website: http://www.ieee-pses.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 <[email protected]> >> Mike Cantwell <[email protected]> >> >> For policy questions, send mail to: >> Jim Bacher: <[email protected]> >> David Heald: <[email protected]> >> >> > > - > ---------------------------------------------------------------- > 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 <[email protected]> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc > Graphics (in well-used formats), large files, etc. can be posted to that URL. > > Website: http://www.ieee-pses.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 <[email protected]> > Mike Cantwell <[email protected]> > > For policy questions, send mail to: > Jim Bacher: <[email protected]> > David Heald: <[email protected]> > > - 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 <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]> - 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 <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
