Conducted Emissions PK/AVG
Hi Guys, I had a product tested that failed the conducted emissions. The switch mode power supply was the problem. It runs at approx. 200KHz. The failed readings were in the 150KHz to 600KHz band. The peaks were over the Avg and below the QPk, so the Avg test was done. This resulted in the failures. However, after close examination of the Test lab results, the printout showed IF BW 9KHz AND AVG BW 30KHz below the graphical and tabulated results. The tests were done on a SA. I have a receiver here and my test results for PK are the same as the Test Lab but for the Avg my test results are significantly lower than the Test House. Is the problem that the Test House may have used “AVG BW 30KHz” and this should have been “AVG BW 9KHz” the problem or am I missing something here? Thank you for your time, it is always appreciated. Kind Regards ALEX This email has been scanned for all known viruses and appropriate content by the Messagelabs mail service. 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/listserv/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 For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Conducted Emissions PK/AVG
I assume the time-constant of the AVG Detector is specific in CISPR 16 and that this standard is called out in FCC Part 15. I think if the VBW was placed before the LOG amplifier in the signal chain, it would yield the correct response. If placed after the LOG amp, the BW limit would not provide the desired effect. The UL EMC software we use has tick-boxes for AVG detection, but they have no noticeable affect on the receiver actions nor on the screen plot. Updated versions of this program from UL have also failed to provide a AVG detection function. It could be that this is not available on our 8568B. So, in the rather rare instance where we need to do an AVG conducted scan, we simply reduce the VBW in the test setup file to 10Hz. Ralph McDiarmid, ASc Compliance Engineering Group Xantrex Technology Inc. From: Brent DeWitt [mailto:bdew...@ix.netcom.com] Sent: December 18, 2004 8:02 PM To: Ken Javor; Ralph McDiarmid; ieee pstc list Subject: RE: Conducted Emissions PK/AVG Your point is well taken Ken, and this certainly is interesting. My approach to the concept of "average" does indeed run afoul of the limitations of measurement devices and the potential for instrument dependent results. To the best of my knowledge, the FCC is the most ill-defined with respect to the averaging time constant. That is what initially lead me to my stated empirical method. Other thoughts are welcomed! Brent > -Original Message- > From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On > Behalf Of Ken Javor > Sent: Friday, December 17, 2004 8:14 PM > To: bdew...@ix.netcom.com; Ralph McDiarmid; ieee pstc list > Subject: Re: Conducted Emissions PK/AVG > > > Now this is getting interesting. If you arbitrarily reduce the VBW > until you see no time dependent amplitude variation, I think that > leads to non-repeatability. That is, if my spectrum analyzer has a 1 > Hz VBW, and yours has a 10 Hz VBW, we could get different answers. At > least at one time, there was a specified time interval over which the > averaging was to occur, which is another way of saying the the video > bandwidth was specified. > > I think the idea of average detection is to be able to get an accurate > assessment of the value of a cw or near cw (AM) signal, possibly in > the presence of broadband noise. Considering that "pulsed cw" was > considered by the military to be a narrow-band signal, it would seem > that the specific averaging time period would be very important. On > the other hand, MIL-STD-461 has for almost forty years required peak > detection of all signals, whether NB or BB. Go figure. > > > I'm rambling on, but the point I am trying to make is that I believe > average detection should have an associated time constant, somehow > relating to the information content of the communication link > protected by the radiated emission limit in question. > > > > From: "Brent DeWitt" > > Reply-To: > > Date: Fri, 17 Dec 2004 18:39:11 -0800 > > To: "Ralph McDiarmid" , "ieee pstc > > list" > > Subject: RE: Conducted Emissions PK/AVG > > > > Hi Ralph, > > > > The HP 8568 and 8566 have a "video averaging" function, which > > averages multiple digital traces (up to 100 if I remember > > correctly). > It can be used > > in conjunction with a narrow VBW to get very close to a true > > "average" measurement. I've always been rather empirical about the > > averaging criterion. On a spectrum analyzer in zero span and linear > > detection, I simply reduce the VBW and possibly add video averaging > > until I > don't see any > > more variation in the screen trace and call it done. > > > > Brent G DeWitt > > Laboratory Manager > > CKC Laboratories > > Redmond, WA > > email: brent.dew...@ckc.com > > phone: 425-883-4757 > > cell: 425-417-8228 > > > > > >> -Original Message- > >> From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On > >> Behalf Of Ralph McDiarmid > >> Sent: Friday, December 17, 2004 11:51 AM > >> To: ieee pstc list > >> Subject: RE: Conducted Emissions PK/AVG > >> > >> > >> I suggest there is an important distinction between "video > >> averaging" and "average detection using limited VBW". > >> > >> If this is correct, can someone enlighten those of us who are > >> unsure? > >> > >> Ralph McDiarmid, ASc > >> Compliance Engineering Group > >> Xantrex Technology Inc. > >> > >> > >> -Original Message- > >> From: owner-emc-p...@ieee.o
RE: Conducted Emissions PK/AVG
Sorry to post a second response, but I hit send before I finished my thoughts. Ken's stated concept of the rational of averaging is a bit different from mine. This may be a MIL vs. FCC background related thing (me being the latter). I've always viewed the FCC's switch to average detection above 1GHz as more of a rough approximation to a spectral density measurement. If my approach is correct, the idea is that receivers of potential interference above 1GHz have relatively wide resolution bandwidths, and that something closer to the 1MHz RBW in combination with an average detector could measure the "annoyance factor". Again, other thoughts are welcomed! Brent > -Original Message- > From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On Behalf > Of Ken Javor > Sent: Friday, December 17, 2004 8:14 PM > To: bdew...@ix.netcom.com; Ralph McDiarmid; ieee pstc list > Subject: Re: Conducted Emissions PK/AVG > > > Now this is getting interesting. If you arbitrarily reduce the VBW until > you see no time dependent amplitude variation, I think that leads to > non-repeatability. That is, if my spectrum analyzer has a 1 Hz VBW, and > yours has a 10 Hz VBW, we could get different answers. At least at one > time, there was a specified time interval over which the averaging was to > occur, which is another way of saying the the video bandwidth was > specified. > > I think the idea of average detection is to be able to get an accurate > assessment of the value of a cw or near cw (AM) signal, possibly in the > presence of broadband noise. Considering that "pulsed cw" was > considered by > the military to be a narrow-band signal, it would seem that the specific > averaging time period would be very important. On the other hand, > MIL-STD-461 has for almost forty years required peak detection of all > signals, whether NB or BB. Go figure. > > > I'm rambling on, but the point I am trying to make is that I > believe average > detection should have an associated time constant, somehow relating to the > information content of the communication link protected by the radiated > emission limit in question. > > > > From: "Brent DeWitt" > > Reply-To: > > Date: Fri, 17 Dec 2004 18:39:11 -0800 > > To: "Ralph McDiarmid" , "ieee pstc list" > > > > Subject: RE: Conducted Emissions PK/AVG > > > > Hi Ralph, > > > > The HP 8568 and 8566 have a "video averaging" function, which averages > > multiple digital traces (up to 100 if I remember correctly). > It can be used > > in conjunction with a narrow VBW to get very close to a true "average" > > measurement. I've always been rather empirical about the averaging > > criterion. On a spectrum analyzer in zero span and linear detection, I > > simply reduce the VBW and possibly add video averaging until I > don't see any > > more variation in the screen trace and call it done. > > > > Brent G DeWitt > > Laboratory Manager > > CKC Laboratories > > Redmond, WA > > email: brent.dew...@ckc.com > > phone: 425-883-4757 > > cell: 425-417-8228 > > > > > >> -Original Message- > >> From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On Behalf > >> Of Ralph McDiarmid > >> Sent: Friday, December 17, 2004 11:51 AM > >> To: ieee pstc list > >> Subject: RE: Conducted Emissions PK/AVG > >> > >> > >> I suggest there is an important distinction between "video averaging" > >> and "average detection using limited VBW". > >> > >> If this is correct, can someone enlighten those of us who are unsure? > >> > >> Ralph McDiarmid, ASc > >> Compliance Engineering Group > >> Xantrex Technology Inc. > >> > >> > >> -Original Message- > >> From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org] > On Behalf > >> Of Cortland Richmond > >> Sent: December 16, 2004 1:04 PM > >> To: Alex McNeil; ieee pstc list > >> Subject: Re: Conducted Emissions PK/AVG > >> > >> > >> Alex McNeil asked: > >>>> Is the problem that the Test House may have used "AVG BW 30KHz" and > >>>> this > >> should have been "AVG BW 9KHz" the problem << > >> > >> Sure looks like it from what you posted. There've been discussions here > >> -- it comes up every so often -- how to to do averaging on a SA. > >> Without knowing how they did, it's hard to say for sure, but it
RE: Conducted Emissions PK/AVG
Your point is well taken Ken, and this certainly is interesting. My approach to the concept of "average" does indeed run afoul of the limitations of measurement devices and the potential for instrument dependent results. To the best of my knowledge, the FCC is the most ill-defined with respect to the averaging time constant. That is what initially lead me to my stated empirical method. Other thoughts are welcomed! Brent > -Original Message- > From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On Behalf > Of Ken Javor > Sent: Friday, December 17, 2004 8:14 PM > To: bdew...@ix.netcom.com; Ralph McDiarmid; ieee pstc list > Subject: Re: Conducted Emissions PK/AVG > > > Now this is getting interesting. If you arbitrarily reduce the VBW until > you see no time dependent amplitude variation, I think that leads to > non-repeatability. That is, if my spectrum analyzer has a 1 Hz VBW, and > yours has a 10 Hz VBW, we could get different answers. At least at one > time, there was a specified time interval over which the averaging was to > occur, which is another way of saying the the video bandwidth was > specified. > > I think the idea of average detection is to be able to get an accurate > assessment of the value of a cw or near cw (AM) signal, possibly in the > presence of broadband noise. Considering that "pulsed cw" was > considered by > the military to be a narrow-band signal, it would seem that the specific > averaging time period would be very important. On the other hand, > MIL-STD-461 has for almost forty years required peak detection of all > signals, whether NB or BB. Go figure. > > > I'm rambling on, but the point I am trying to make is that I > believe average > detection should have an associated time constant, somehow relating to the > information content of the communication link protected by the radiated > emission limit in question. > > > > From: "Brent DeWitt" > > Reply-To: > > Date: Fri, 17 Dec 2004 18:39:11 -0800 > > To: "Ralph McDiarmid" , "ieee pstc list" > > > > Subject: RE: Conducted Emissions PK/AVG > > > > Hi Ralph, > > > > The HP 8568 and 8566 have a "video averaging" function, which averages > > multiple digital traces (up to 100 if I remember correctly). > It can be used > > in conjunction with a narrow VBW to get very close to a true "average" > > measurement. I've always been rather empirical about the averaging > > criterion. On a spectrum analyzer in zero span and linear detection, I > > simply reduce the VBW and possibly add video averaging until I > don't see any > > more variation in the screen trace and call it done. > > > > Brent G DeWitt > > Laboratory Manager > > CKC Laboratories > > Redmond, WA > > email: brent.dew...@ckc.com > > phone: 425-883-4757 > > cell: 425-417-8228 > > > > > >> -Original Message- > >> From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On Behalf > >> Of Ralph McDiarmid > >> Sent: Friday, December 17, 2004 11:51 AM > >> To: ieee pstc list > >> Subject: RE: Conducted Emissions PK/AVG > >> > >> > >> I suggest there is an important distinction between "video averaging" > >> and "average detection using limited VBW". > >> > >> If this is correct, can someone enlighten those of us who are unsure? > >> > >> Ralph McDiarmid, ASc > >> Compliance Engineering Group > >> Xantrex Technology Inc. > >> > >> > >> -Original Message- > >> From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org] > On Behalf > >> Of Cortland Richmond > >> Sent: December 16, 2004 1:04 PM > >> To: Alex McNeil; ieee pstc list > >> Subject: Re: Conducted Emissions PK/AVG > >> > >> > >> Alex McNeil asked: > >>>> Is the problem that the Test House may have used "AVG BW 30KHz" and > >>>> this > >> should have been "AVG BW 9KHz" the problem << > >> > >> Sure looks like it from what you posted. There've been discussions here > >> -- it comes up every so often -- how to to do averaging on a SA. > >> Without knowing how they did, it's hard to say for sure, but it looks > >> like you are close enough to hit the target with a hand grenade anyway. > >> But are you sure it doesn't say 30 *Hz*? Narrowing the bandwidth 'way > >> down is a method used to get averaging on a SA. (I will specula
Re: Conducted Emissions PK/AVG
Now this is getting interesting. If you arbitrarily reduce the VBW until you see no time dependent amplitude variation, I think that leads to non-repeatability. That is, if my spectrum analyzer has a 1 Hz VBW, and yours has a 10 Hz VBW, we could get different answers. At least at one time, there was a specified time interval over which the averaging was to occur, which is another way of saying the the video bandwidth was specified. I think the idea of average detection is to be able to get an accurate assessment of the value of a cw or near cw (AM) signal, possibly in the presence of broadband noise. Considering that "pulsed cw" was considered by the military to be a narrow-band signal, it would seem that the specific averaging time period would be very important. On the other hand, MIL-STD-461 has for almost forty years required peak detection of all signals, whether NB or BB. Go figure. I'm rambling on, but the point I am trying to make is that I believe average detection should have an associated time constant, somehow relating to the information content of the communication link protected by the radiated emission limit in question. > From: "Brent DeWitt" > Reply-To: > Date: Fri, 17 Dec 2004 18:39:11 -0800 > To: "Ralph McDiarmid" , "ieee pstc list" > > Subject: RE: Conducted Emissions PK/AVG > > Hi Ralph, > > The HP 8568 and 8566 have a "video averaging" function, which averages > multiple digital traces (up to 100 if I remember correctly). It can be used > in conjunction with a narrow VBW to get very close to a true "average" > measurement. I've always been rather empirical about the averaging > criterion. On a spectrum analyzer in zero span and linear detection, I > simply reduce the VBW and possibly add video averaging until I don't see any > more variation in the screen trace and call it done. > > Brent G DeWitt > Laboratory Manager > CKC Laboratories > Redmond, WA > email: brent.dew...@ckc.com > phone: 425-883-4757 > cell: 425-417-8228 > > >> -Original Message- >> From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On Behalf >> Of Ralph McDiarmid >> Sent: Friday, December 17, 2004 11:51 AM >> To: ieee pstc list >> Subject: RE: Conducted Emissions PK/AVG >> >> >> I suggest there is an important distinction between "video averaging" >> and "average detection using limited VBW". >> >> If this is correct, can someone enlighten those of us who are unsure? >> >> Ralph McDiarmid, ASc >> Compliance Engineering Group >> Xantrex Technology Inc. >> >> >> -Original Message- >> From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org] On Behalf >> Of Cortland Richmond >> Sent: December 16, 2004 1:04 PM >> To: Alex McNeil; ieee pstc list >> Subject: Re: Conducted Emissions PK/AVG >> >> >> Alex McNeil asked: >>>> Is the problem that the Test House may have used "AVG BW 30KHz" and >>>> this >> should have been "AVG BW 9KHz" the problem << >> >> Sure looks like it from what you posted. There've been discussions here >> -- it comes up every so often -- how to to do averaging on a SA. >> Without knowing how they did, it's hard to say for sure, but it looks >> like you are close enough to hit the target with a hand grenade anyway. >> But are you sure it doesn't say 30 *Hz*? Narrowing the bandwidth 'way >> down is a method used to get averaging on a SA. (I will speculate that >> someone might have "learned" to -- incorrectly -- use video averaging in >> dB mode then increase BW to compensate for the error that causes.) >> >> Cortland Richmond >> >> >> 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/listserv/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 >> >> For policy questions, send mail to: >> >> Richard Nute: ri...@ieee.org >> Jim Bacher: j.bac...@ieee.org >> >> All emc-pstc postings are archived and searchable on the web at: >> >> http://www.ieeecommunities.org/emc-pstc >> >> ---
RE: Conducted Emissions PK/AVG
Hi Ralph, The HP 8568 and 8566 have a "video averaging" function, which averages multiple digital traces (up to 100 if I remember correctly). It can be used in conjunction with a narrow VBW to get very close to a true "average" measurement. I've always been rather empirical about the averaging criterion. On a spectrum analyzer in zero span and linear detection, I simply reduce the VBW and possibly add video averaging until I don't see any more variation in the screen trace and call it done. Brent G DeWitt Laboratory Manager CKC Laboratories Redmond, WA email: brent.dew...@ckc.com phone: 425-883-4757 cell: 425-417-8228 > -Original Message- > From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On Behalf > Of Ralph McDiarmid > Sent: Friday, December 17, 2004 11:51 AM > To: ieee pstc list > Subject: RE: Conducted Emissions PK/AVG > > > I suggest there is an important distinction between "video averaging" > and "average detection using limited VBW". > > If this is correct, can someone enlighten those of us who are unsure? > > Ralph McDiarmid, ASc > Compliance Engineering Group > Xantrex Technology Inc. > > > -Original Message- > From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org] On Behalf > Of Cortland Richmond > Sent: December 16, 2004 1:04 PM > To: Alex McNeil; ieee pstc list > Subject: Re: Conducted Emissions PK/AVG > > > Alex McNeil asked: > >> Is the problem that the Test House may have used "AVG BW 30KHz" and > >> this > should have been "AVG BW 9KHz" the problem << > > Sure looks like it from what you posted. There've been discussions here > -- it comes up every so often -- how to to do averaging on a SA. > Without knowing how they did, it's hard to say for sure, but it looks > like you are close enough to hit the target with a hand grenade anyway. > But are you sure it doesn't say 30 *Hz*? Narrowing the bandwidth 'way > down is a method used to get averaging on a SA. (I will speculate that > someone might have "learned" to -- incorrectly -- use video averaging in > dB mode then increase BW to compensate for the error that causes.) > > Cortland Richmond > > > 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/listserv/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 > > For policy questions, send mail to: > > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > 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/listserv/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 > > For policy questions, send mail to: > > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > 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/listserv/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 For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Conducted Emissions PK/AVG
I suggest there is an important distinction between "video averaging" and "average detection using limited VBW". If this is correct, can someone enlighten those of us who are unsure? Ralph McDiarmid, ASc Compliance Engineering Group Xantrex Technology Inc. From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org] On Behalf Of Cortland Richmond Sent: December 16, 2004 1:04 PM To: Alex McNeil; ieee pstc list Subject: Re: Conducted Emissions PK/AVG Alex McNeil asked: >> Is the problem that the Test House may have used "AVG BW 30KHz" and >> this should have been "AVG BW 9KHz" the problem << Sure looks like it from what you posted. There've been discussions here -- it comes up every so often -- how to to do averaging on a SA. Without knowing how they did, it's hard to say for sure, but it looks like you are close enough to hit the target with a hand grenade anyway. But are you sure it doesn't say 30 *Hz*? Narrowing the bandwidth 'way down is a method used to get averaging on a SA. (I will speculate that someone might have "learned" to -- incorrectly -- use video averaging in dB mode then increase BW to compensate for the error that causes.) Cortland Richmond 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/listserv/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 For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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/listserv/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 For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Conducted Emissions PK/AVG
Alex McNeil asked: >> Is the problem that the Test House may have used "AVG BW 30KHz" and this should have been "AVG BW 9KHz" the problem << Sure looks like it from what you posted. There've been discussions here -- it comes up every so often -- how to to do averaging on a SA. Without knowing how they did, it's hard to say for sure, but it looks like you are close enough to hit the target with a hand grenade anyway. But are you sure it doesn't say 30 *Hz*? Narrowing the bandwidth 'way down is a method used to get averaging on a SA. (I will speculate that someone might have "learned" to -- incorrectly -- use video averaging in dB mode then increase BW to compensate for the error that causes.) Cortland Richmond 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/listserv/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 For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Conducted Emissions PK/AVG
>>>scale set to LOG, <<< OOPS, that should have been LINEAR Sorry. Bob Richards wrote: Alex, It is very common that the emissions plots will be made with the RBW and VBW that you mentioned. The actual QP and AV measurements should have the instrument set with the appropriate detector and bandwidths. The RBW should always be 9kHz, and for the average measurement the VBW should be significantly lower than the pulse repetition frequency, the detector should be SAMPLE, scale set to LOG, etc. Also, the frequency span should be set to zero for a compliance measurement. I've seen commercial automated software that does a very poor job of this. Bob Richards, NCT Square D. Alex McNeil wrote: Hi Guys, I had a product tested that failed the conducted emissions. The switch mode power supply was the problem. It runs at approx. 200KHz. The failed readings were in the 150KHz to 600KHz band. The peaks were over the Avg and below the QPk, so the Avg test was done. This resulted in the failures. However, after close examination of the Test lab results, the printout showed IF BW 9KHz AND AVG BW 30KHz below the graphical and tabulated results. The tests were done on a SA. I have a receiver here and my test results for PK are the same as the Test Lab but for the Avg my test results are significantly lower than the Test House. Is the problem that the Test House may have used “AVG BW 30KHz” and this should have been “AVG BW 9KHz” the problem or am I missing something here? Thank you for your time, it is always appreciated. Kind Regards ALEX 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/listserv/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 For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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/listserv/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 For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Conducted Emissions PK/AVG
Alex, It is very common that the emissions plots will be made with the RBW and VBW that you mentioned. The actual QP and AV measurements should have the instrument set with the appropriate detector and bandwidths. The RBW should always be 9kHz, and for the average measurement the VBW should be significantly lower than the pulse repetition frequency, the detector should be SAMPLE, scale set to LOG, etc. Also, the frequency span should be set to zero for a compliance measurement. I've seen commercial automated software that does a very poor job of this. Bob Richards, NCT Square D. Alex McNeil wrote: Hi Guys, I had a product tested that failed the conducted emissions. The switch mode power supply was the problem. It runs at approx. 200KHz. The failed readings were in the 150KHz to 600KHz band. The peaks were over the Avg and below the QPk, so the Avg test was done. This resulted in the failures. However, after close examination of the Test lab results, the printout showed IF BW 9KHz AND AVG BW 30KHz below the graphical and tabulated results. The tests were done on a SA. I have a receiver here and my test results for PK are the same as the Test Lab but for the Avg my test results are significantly lower than the Test House. Is the problem that the Test House may have used “AVG BW 30KHz” and this should have been “AVG BW 9KHz” the problem or am I missing something here? Thank you for your time, it is always appreciated. Kind Regards ALEX 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/listserv/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 For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Conducted Emissions PK/AVG
Alex, You are on the right track. However, even a VBW of 9 kHz will not yield a true average measurement in this frequency range. First of all, it is not likely that the spectrum analyzer meets CISPR requirements as a test receiver. Second, using video averaging as a substitute for an actual average detector requires a VBW that is significantly less than the RBW, and the amplitude scale must be linear instead of log (the average of the log is different than the average). This is a highlight of the most important settings - CISPR 16 will have the detailed requirements from which suitable and/or reasonable instrument settings can be determined. It is not surprising to hear of these differences - the receiver measurement definitely takes precedence over the spectrum analyzer. Thanks, Mike From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On Behalf Of Alex McNeil Sent: Thursday, December 16, 2004 8:19 AM To: emc-p...@ieee.org Subject: Conducted Emissions PK/AVG Hi Guys, I had a product tested that failed the conducted emissions. The switch mode power supply was the problem. It runs at approx. 200KHz. The failed readings were in the 150KHz to 600KHz band. The peaks were over the Avg and below the QPk, so the Avg test was done. This resulted in the failures. However, after close examination of the Test lab results, the printout showed IF BW 9KHz AND AVG BW 30KHz below the graphical and tabulated results. The tests were done on a SA. I have a receiver here and my test results for PK are the same as the Test Lab but for the Avg my test results are significantly lower than the Test House. Is the problem that the Test House may have used “AVG BW 30KHz” and this should have been “AVG BW 9KHz” the problem or am I missing something here? Thank you for your time, it is always appreciated. Kind Regards ALEX This email has been scanned for all known viruses and appropriate content by the Messagelabs mail service. 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/listserv/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 For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org 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/listserv/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 For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Conducted Emissions PK/AVG
Are you sure it says AVG BW 30kHz, and not AVG BW 30 Hz? Is this a typo? Also, quasi-peak should always be at or below the peak measurement. This is why a peak measurement can be made (quickly) and compared to the quasi-peak limit line, and if all the peaks are below the quasi-peak limit, the measurement is a "pass". If you have quasi-peak measurements higher than the peaks measurements, then either something is wrong with the test equipment/software, or the emissions of the EUT changed between the time the two measurements were made. Don Borowski Schweitzer Engineering Labs Pullman, WA, USA "Alex McNeil" wrote on 12/16/2004 08:19:08 AM: > Hi Guys, > I had a product tested that failed the conducted emissions. The > switch mode power supply was the problem. It runs at approx. 200KHz. > The failed readings were in the 150KHz to 600KHz band. The peaks > were over the Avg and below the QPk, so the Avg test was done. This > resulted in the failures. However, after close examination of the > Test lab results, the printout showed IF BW 9KHz AND AVG BW 30KHz > below the graphical and tabulated results. The tests were done on a > SA. I have a receiver here and my test results for PK are the same > as the Test Lab but for the Avg my test results are significantly > lower than the Test House. > > Is the problem that the Test House may have used “AVG BW 30KHz” and > this should have been “AVG BW 9KHz” the problem or am I missing > something here? > > Thank you for your time, it is always appreciated. > > Kind Regards > ALEX 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/listserv/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 For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
