[PSES] FW: [PSES] Calibration practice for EMI test transducers
Several EMC antennas have AF step performance of 1 dB per 5 MHz or so at certain frequencies. If the antenna would have a linear behavior, 2 points would be enough as all other frequencies could be linearly interpolated. But my particular Chase BILOG 6111A has a bump at 14.1 dB at 258 MHz and at both 250 MHz and 266 MHz the antennafactor is 13.0 dB. This is what I read from the calibration graph. The manufacturer however, also has calibration (numeric) data provided as discrete points at comfortable round numbers of 250 (12.9) and 300 MHz. (13.6) These points are in general used for creating a interpolation curve. Linear interpolation using the table provides a antennafactor of 13.1 dB at 258 MHz which is a full -1 dB off from what I read from the graph. The bump has virtually disappeared. Nice result with a 0.2 dB receiver. That is why the output level change and required accuracy should be the driving factor in creating a calibration table. It can easily be automated during a sweep. What complicates this further is that not all manufacturers provide data about their interpolation system. My RS receiver uses quadratic spline (I suppose Lagrange). My RS FSP only uses LIN interpolation (with log option) for the transducers. Regards, Ing. Gert Gremmen, BSc g.grem...@cetest.nl www.cetest.nl Kiotoweg 363 3047 BG Rotterdam T 31(0)104152426 F 31(0)104154953 Before printing, think about the environment. Van: emc-p...@ieee.org [mailto:emc-p...@ieee.org] Namens Ken Javor Verzonden: Tuesday, December 06, 2011 11:12 PM Aan: EMC-PSTC@LISTSERV.IEEE.ORG Onderwerp: Re: [PSES] Calibration practice for EMI test transducers This discussion has gone far a field from the original post. I'm assuming some sort of scan has been run and a continuous sweep is available. The question is, how densely does that sweep need to be digitized? Not as a practical matter, but as a matter of compliance with standards or standard practice. What manner of antenna would have performance as cited below where at 100 MHz the antenna factor is 10 dB and at 120 MHz it is 12 dB, but at 110 MHz it could be 20 dB? Let's generalize the question to any closely spaced frequencies. Let's look at the types of antennas available. 30-200 MHz: A half-wave tuned dipole is nowhere near that sharp. Neither is a biconical. 200 - 1000 MHz: A half-wave tuned dipole is nowhere near that sharp. Neither is a logperiodic, log-spiral, nor a Yagi. 1 GHz+: Logperiodic, log-spiral nor pyramidal horns act the way surmised. My conclusion, and the point here is to invite discussion, not close it out, is that no test-type antenna is a high Q device. Antennas can have arbitrarily high gains, depending on construction, but the high gain is a geometrical quality, not a high quality factor in the frequency domain. Ken Javor Phone: (256) 650-5261 From: ralph.mcdiar...@schneider-electric.com Date: Tue, 6 Dec 2011 11:25:43 -0800 To: ce-test, qualified testing bv - Gert Gremmen g.grem...@cetest.nl Cc: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Calibration practice for EMI test transducers Yet how far would you take that argument? If it's say 11.1db at 110MHz and 11.5dB at 112MHz, would you still worry about factor at 111MHz? At some point surly this all becomes rather silly. _ Ralph McDiarmid | Schneider Electric | Renewable Energies Business | CANADA | Regulatory Compliance Engineering From: ce-test, qualified testing bv - Gert Gremmen g.grem...@cetest.nl To: EMC-PSTC@LISTSERV.IEEE.ORG Date: 12/05/2011 10:06 PM Subject: Re: [PSES] Calibration practice for EMI test transducers If at 100 MHz your sensor indicates during calibration 10 dB and at 120 MHz 12 dB, how are you going to know the value at 110 MHz. It maight be 20 as well as 0 dB, you don't not know as you did not measure/ calibrate. This requires some knowledge about the behavior of the sensor, and the 1/BW is and indication of that. There is another aspect in EMI measurements. As the measuring receiver interpolates between the calibrated samples, the max interpolation error (lin interpolation) is 50% of the vertical differences between calibration points. If the measuring receiver is +/- 0.5 dB you should register a calibration each time the difference between previous and current sample is 0.5 dB. Then the total error will be slightly more than 0.5 dB. There are more sophisticated interpolation methods such as cubic spline and polynomial interpolation, and the error item is subject to higher mathematics. Play with it at: http://terpconnect.umd.edu/~petersd/interp.html http://terpconnect.umd.edu/~petersd/interp.html http://terpconnect.umd.edu/~petersd/interp.html or at http://www.ibiblio.org/e-notes/Splines/Lagrange.htm http
Re: [PSES] Calibration practice for EMI test transducers
The quotation below is a little out-of-context. In the previous statement in that post, it says, ...the point ... is that no test-type antenna is a high ³Q² device. It is true that a tuned loop can be a very high Q antenna, but these are designed solely for communications. No one uses such antennas for EMI testing, precisely because of the sharp tuning involved. And if one were to do so, presumably with a knowledge of the antenna's behavior, the antenna factor would be properly characterized at the frequency (ies) of operation, and not missed because the tuned frequency was interpolated between two untuned frequencies. Ken Javor Phone: (256) 650-5261 From: John Woodgate j...@jmwa.demon.co.uk Date: Wed, 7 Dec 2011 04:52:25 + To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Calibration practice for EMI test transducers In message cb03ef45.c9421%ken.ja...@emccompliance.com, dated Tue, 6 Dec 2011, Ken Javor ken.ja...@emccompliance.com writes: Antennas can have arbitrarily high gains, depending on construction, but the high gain is a geometrical quality, not a high quality factor in the frequency domain. True for electric antennas, I think, but not for magnetic. Tuned loops and ferrite-rod antennas can have high Q. CISPR 16 includes at least one magnetic antenna, although it may well not be high Q. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK Some people who are peeling the finch of the financial crisis are thinking of biting a rook. - 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 emc-p...@ieee.org 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://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 emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com - 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 emc-p...@ieee.org 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://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 emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] Calibration practice for EMI test transducers
An untuned loop should exhibit no resonances in its usable range. See http://www.ets-lindgren.com/page/charts.cfm?i=6511 . Also, A Novel Standard Loop Antenna for Antenna Calibration in the MF and HF Bands, ieeexplore.ieee.org/iel5/10111/32404/01513478.pdf Amateurs have used home-made loops to get pretty accurate measurements of BPL emissions. http://vk1od.net/antenna/SmallUntunedSquareLoop/index.htm One of his loops, 600mm square, has an AF flat within one dB from about 5.5 to 30 MHz ( http://vk1od.net/antenna/SmallUntunedSquareLoop/Loop600.pdf ). Cortland KA5S On 12/6/2011 11:52 PM, John Woodgate wrote: True for electric antennas, I think, but not for magnetic. Tuned loops and ferrite-rod antennas can have high Q. CISPR 16 includes at least one magnetic antenna, although it may well not be high Q. - 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 emc-p...@ieee.org 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://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 emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] Calibration practice for EMI test transducers
Now we get to the heart of the matter that prompted the original post. That spike in the 137 cm tip-to-tip biconical used with a T1 dipole balun (28 200 MHz) behavior might have been objectionable, but you wouldn¹t miss it an analog sweep with even 1% frequency steps. You would only miss it if you calibrated every ten MHz as was done with the biconical antenna design in MIL-STD-461A (1968 when swept performance was difficult to do). There is no need to use frequency steps commensurate with the sorts of BWs used during EMI testing. A 1 - 5 MHz BW would more than suffice to sweep an antenna used above 30 MHz to ensure not missing anything. The following quote is the rationale I have seen a few places with which I take issue: ³Though the sweep may be continuous, if you can read amplitude only by marking pixels, you need to insure .5 BW or less per pixel. That's straight sampling theory, right?² That is straight sampling theory applied to an unknown signal characteristic. If a continuous sweep using 1/2 BW steps as per sampling theory has been performed, then discrete points for an antenna factor file may be chosen by inspection so that in any particular frequency range either of the two following conditions are met: 1. If the data is noisy, with no obvious trend, then frequency points should be listed so that the antenna factor between any two listed points doesn¹t change by more than 1 dB (or whatever delta is deemed necessary for adequate accuracy). 2. If a linear or log-linear approximation can be made over some frequency interval, then only the two endpoints of that interval need be recorded, with the understanding that between those two points the appropriate interpolation will yield the desired accuracy. The interpolation has to be one which the automated software can be instructed to perform on its recorded antenna factor files. One of these two approaches should work when deriving a set of discrete points from a continuous sweep of any test transducer factor¹s performance. The question is whether this is ³cast in stone² anywhere or left up to the person doing the calibration, or the test engineer abstracting a subset of data points for inclusion in his files. Ken Javor Phone: (256) 650-5261 From: Cortland Richmond k...@earthlink.net Reply-To: k...@earthlink.net Date: Tue, 06 Dec 2011 20:43:38 -0500 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Calibration practice for EMI test transducers We might *like* measuring antennas to be low-Q, but remember the bicon shorting bars that were added some years ago? The skeleton bicons lacking them inserted a rather sharp notch that had to be accounted for in transducer tables. Baluns might go off from impact damage, too. And so on. I gave an ebay 50 MHz comb good past 2 GHz to a former employer who later gave all their own EMC lab gear to an NRTL. But you still have to check. For that matter, I've seen coax factors programmed with GAIN at a narrow range at microwave frequencies; that was caused by reflection from a crimped cable*. So we do need to be able to spot them. *This was due to the ignorance of operators collecting the data, IMO. I spoke to them and likely, they won't do it again. But they believed the SA/TG reading because they didn't know what they were measuring. That's another thread. Though the sweep may be continuous, if you can read amplitude only by marking pixels, you need to insure .5 BW or less per pixel. That's straight sampling theory, right? If your analyzer has a 1024 pixel wide screen you can't SEE less than about .1% of the scan width and can rely on less. Does it matter? Often it doesn't. Fun, isn't it? Cortland KA5S On 12/6/2011 5:11 PM, Ken Javor wrote: Re: [PSES] Calibration practice for EMI test transducers This discussion has gone far a field from the original post. I¹m assuming some sort of scan has been run and a continuous sweep is available. The question is, how densely does that sweep need to be digitized? Not as a practical matter, but as a matter of compliance with standards or standard practice. What manner of antenna would have performance as cited below where at 100 MHz the antenna factor is 10 dB and at 120 MHz it is 12 dB, but at 110 MHz it could be 20 dB? Let¹s generalize the question to any closely spaced frequencies. Let¹s look at the types of antennas available. 30-200 MHz: A half-wave tuned dipole is nowhere near that sharp. Neither is a biconical. 200 1000 MHz: A half-wave tuned dipole is nowhere near that sharp. Neither is a logperiodic, log-spiral, nor a Yagi. 1 GHz+: Logperiodic, log-spiral nor pyramidal horns act the way surmised. My conclusion, and the point here is to invite discussion, not close it out, is that no test-type antenna is a high ³Q² device. Antennas can have arbitrarily high gains, depending on construction, but the high gain is a geometrical quality, not a high quality factor
Re: [PSES] Calibration practice for EMI test transducers
In message 4edf523d.4090...@earthlink.net, dated Wed, 7 Dec 2011, Cortland Richmond k...@earthlink.net writes: An untuned loop should exhibit no resonances in its usable range. See http://www.ets-lindgren.com/page/charts.cfm?i=6511 . Also, A Novel Standard Loop Antenna for Antenna Calibration in the MF and HF Bands, ieeexplore.ieee.org/iel5/10111/32404/01513478.pdf Amateurs have used home-made loops to get pretty accurate measurements of BPL emissions. http://vk1od.net/antenna/SmallUntunedSquareLoop/index.htm One of his loops, 600mm square, has an AF flat within one dB from about 5.5 to 30 MHz ( http://vk1od.net/antenna/SmallUntunedSquareLoop/Loop600.pdf ). Thank you; these are very interesting. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK Some people who are peeling the finch of the financial crisis are thinking of biting a rook. - 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 emc-p...@ieee.org 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://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 emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] Calibration practice for EMI test transducers
Yes, and in the real world that is what is done. But it has to meet the accuracy requirement of the test. For example, see MIL-STD461E 4.3.1 (slightly snipped): 4.3.1 Measurement tolerances. Unless otherwise stated for a particular measurement, the tolerance shall be as follows: c. Amplitude, measurement receiver: ±2 dB d. Amplitude, measurement system (includes measurement receivers, transducers, cables, and so forth): ±3 dB If the receiver is already ±2 dB we don't have much to work with. Calibration with X4 TUR might require an accuracy of 0.25 dB. Might settle for less, no? Sooner or later, someone will say their project passes by 0.5 dB; SHIP IT. Same old story. Cortland KA5S On 12/7/2011 6:50 AM, Ken Javor wrote: Now we get to the heart of the matter that prompted the original post. That spike in the 137 cm tip-to-tip biconical used with a T1 dipole balun (28 -- 200 MHz) behavior might have been objectionable, but you wouldn't miss it an analog sweep with even 1% frequency steps. You would only miss it if you calibrated every ten MHz as was done with the biconical antenna design in MIL-STD-461A (1968 -- when swept performance was difficult to do). There is no need to use frequency steps commensurate with the sorts of BWs used during EMI testing. A 1 - 5 MHz BW would more than suffice to sweep an antenna used above 30 MHz to ensure not missing anything. The following quote is the rationale I have seen a few places with which I take issue: Though the sweep may be continuous, if you can read amplitude only by marking pixels, you need to insure .5 BW or less per pixel. That's straight sampling theory, right? That is straight sampling theory applied to an unknown signal characteristic. If a continuous sweep using 1/2 BW steps as per sampling theory has been performed, then discrete points for an antenna factor file may be chosen by inspection so that in any particular frequency range either of the two following conditions are met: 1. If the data is noisy, with no obvious trend, then frequency points should be listed so that the antenna factor between any two listed points doesn't change by more than 1 dB (or whatever delta is deemed necessary for adequate accuracy). 2. If a linear or log-linear approximation can be made over some frequency interval, then only the two endpoints of that interval need be recorded, with the understanding that between those two points the appropriate interpolation will yield the desired accuracy. The interpolation has to be one which the automated software can be instructed to perform on its recorded antenna factor files. One of these two approaches should work when deriving a set of discrete points from a continuous sweep of any test transducer factor's performance. The question is whether this is cast in stone anywhere or left up to the person doing the calibration, or the test engineer abstracting a subset of data points for inclusion in his files. Ken Javor Phone: (256) 650-5261 ** - 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 emc-p...@ieee.org 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://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 emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] Calibration practice for EMI test transducers
In message 4edf7f60.9020...@earthlink.net, dated Wed, 7 Dec 2011, Cortland Richmond k...@earthlink.net writes: Sooner or later, someone will say their project passes by 0.5 dB; SHIP IT. It may be reprehensible, but it's realistic. The vast majority of cases of actual interference occur when the source is 10 dB or more stronger than the immunity of the victim can cope with. If that 'pass by 0.5 dB' is really a 'fail by 2.5 dB', the chances are no-one will ever know. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK Some people who are peeling the finch of the financial crisis are thinking of biting a rook. - 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 emc-p...@ieee.org 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://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 emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] FW: [PSES] Calibration practice for EMI test transducers
But how are those measurements made? At what distance above the ground plane? Surly the calibration setup should match how the antenna is used during emissions measurement, otherwise 1dB here or there becomes meaningless. _ Ralph McDiarmid | Schneider Electric | Renewable Energies Business | CANADA | Regulatory Compliance Engineering From: ce-test, qualified testing bv - Gert Gremmen g.grem...@cetest.nl To: EMC-PSTC@LISTSERV.IEEE.ORG Date: 12/07/2011 12:59 AM Subject: [PSES] FW: [PSES] Calibration practice for EMI test transducers Several EMC antennas have AF step performance of 1 dB per 5 MHz or so at certain frequencies. If the antenna would have a linear behavior, 2 points would be enough as all other frequencies could be linearly interpolated. But my particular Chase BILOG 6111A has a bump at 14.1 dB at 258 MHz and at both 250 MHz and 266 MHz the antennafactor is 13.0 dB. This is what I read from the calibration graph. The manufacturer however, also has calibration (numeric) data provided as discrete points at comfortable round numbers of 250 (12.9) and 300 MHz. (13.6) These points are in general used for creating a interpolation curve. Linear interpolation using the table provides a antennafactor of 13.1 dB at 258 MHz which is a full -1 dB off from what I read from the graph. The bump has virtually disappeared. Nice result with a 0.2 dB receiver. That is why the output level change and required accuracy should be the driving factor in creating a calibration table. It can easily be automated during a sweep. What complicates this further is that not all manufacturers provide data about their interpolation system. My RS receiver uses quadratic spline (I suppose Lagrange). My RS FSP only uses LIN interpolation (with log option) for the transducers. Regards, Ing. Gert Gremmen, BSc g.grem...@cetest.nl www.cetest.nl Kiotoweg 363 3047 BG Rotterdam T 31(0)104152426 F 31(0)104154953 Before printing, think about the environment. Van: emc-p...@ieee.org [mailto:emc-p...@ieee.org] Namens Ken Javor Verzonden: Tuesday, December 06, 2011 11:12 PM Aan: EMC-PSTC@LISTSERV.IEEE.ORG Onderwerp: Re: [PSES] Calibration practice for EMI test transducers This discussion has gone far a field from the original post. I’m assuming some sort of scan has been run and a continuous sweep is available. The question is, how densely does that sweep need to be digitized? Not as a practical matter, but as a matter of compliance with standards or standard practice. What manner of antenna would have performance as cited below where at 100 MHz the antenna factor is 10 dB and at 120 MHz it is 12 dB, but at 110 MHz it could be 20 dB? Let’s generalize the question to any closely spaced frequencies. Let’s look at the types of antennas available. 30-200 MHz: A half-wave tuned dipole is nowhere near that sharp. Neither is a biconical. 200 – 1000 MHz: A half-wave tuned dipole is nowhere near that sharp. Neither is a logperiodic, log-spiral, nor a Yagi. 1 GHz+: Logperiodic, log-spiral nor pyramidal horns act the way surmised. My conclusion, and the point here is to invite discussion, not close it out, is that no test-type antenna is a high “Q” device. Antennas can have arbitrarily high gains, depending on construction, but the high gain is a geometrical quality, not a high quality factor in the frequency domain. Ken Javor Phone: (256) 650-5261 From: ralph.mcdiar...@schneider-electric.com Date: Tue, 6 Dec 2011 11:25:43 -0800 To: ce-test, qualified testing bv - Gert Gremmen g.grem...@cetest.nl Cc: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Calibration practice for EMI test transducers Yet how far would you take that argument? If it's say 11.1db at 110MHz and 11.5dB at 112MHz, would you still worry about factor at 111MHz? At some point surly this all becomes rather silly. _ Ralph McDiarmid | Schneider Electric | Renewable Energies Business | CANADA | Regulatory Compliance Engineering From: ce-test, qualified testing bv - Gert Gremmen g.grem...@cetest.nl To: EMC-PSTC@LISTSERV.IEEE.ORG Date: 12/05/2011 10:06 PM Subject: Re: [PSES] Calibration practice for EMI test transducers If at 100 MHz your sensor indicates during calibration 10 dB and at 120 MHz 12 dB, how are you going to know the value at 110 MHz. It maight be 20 as well as 0 dB, you don't not know as you did not measure/ calibrate. This requires some knowledge about the behavior of the sensor, and the 1/BW is and indication of that. There is another aspect in EMI measurements. As the measuring receiver interpolates between the calibrated samples, the max interpolation error (lin interpolation) is 50% of the vertical differences between calibration points. If the measuring receiver
Re: [PSES] Calibration practice for EMI test transducers
Many times there seems a disconnect between what is required by a standard and what is needed for compatibility. _ Ralph McDiarmid | Schneider Electric | Renewable Energies Business | CANADA | Regulatory Compliance Engineering From: John Woodgate j...@jmwa.demon.co.uk To: EMC-PSTC@LISTSERV.IEEE.ORG Date: 12/07/2011 07:11 AM Subject: Re: [PSES] Calibration practice for EMI test transducers In message 4edf7f60.9020...@earthlink.net, dated Wed, 7 Dec 2011, Cortland Richmond k...@earthlink.net writes: Sooner or later, someone will say their project passes by 0.5 dB; SHIP IT. It may be reprehensible, but it's realistic. The vast majority of cases of actual interference occur when the source is 10 dB or more stronger than the immunity of the victim can cope with. If that 'pass by 0.5 dB' is really a 'fail by 2.5 dB', the chances are no-one will ever know. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK Some people who are peeling the finch of the financial crisis are thinking of biting a rook. - 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 emc-p...@ieee.org 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://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 emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com __ This email has been scanned by the Symantec Email Security.cloud service. __ - 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 emc-p...@ieee.org 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://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 emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] Calibration practice for EMI test transducers
Hello Gert, It was Ken Javor who was asking, but I will note that ETS-Lindgren probe documents specify an accuracy of +/- 2 dB transfer impedance, which for *formal* calibration requires as you say 0.5 dB accuracy. It also takes precision 50 Ohm test fixtures, better loads that I used, and a better instrument, too. Call my process a sanity check, adequate only to get an ad-hoc setup back to readings that more closely approximate what was seen at outside test houses. That's what the customer wanted. However, any deviation from a smooth response may be detected fairly easily, and if I saw a jog in a current probe function I would recommend replacement. I did recommend the customer get their analyzer and probe calibrated. Regards, Cortland Richmond KA5S On 12/6/2011 1:03 AM, ce-test, qualified testing bv - Gert Gremmen wrote: If at 100 MHz your sensor indicates during calibration 10 dB and at 120 MHz 12 dB, how are you going to know the value at 110 MHz. It maight be 20 as well as 0 dB, you don't not know as you did not measure/ calibrate. This requires some knowledge about the behavior of the sensor, and the 1/BW is and indication of that. There is another aspect in EMI measurements. As the measuring receiver interpolates between the calibrated samples, the max interpolation error (lin interpolation) is 50% of the vertical differences between calibration points. If the measuring receiver is ± 0.5 dB you should register a calibration each time the difference between previous and current sample is 0.5 dB. Then the total error will be slightly more than 0.5 dB. There are more sophisticated interpolation methods such as cubic spline and polynomial interpolation, and the error item is subject to higher mathematics. Play with it at: http://terpconnect.umd.edu/~petersd/interp.html or athttp://www.ibiblio.org/e-notes/Splines/Lagrange.htm you can actually move the points on the latter page. Gert Gremmen - 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 emc-p...@ieee.org 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://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 emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] Calibration practice for EMI test transducers
Yet how far would you take that argument? If it's say 11.1db at 110MHz and 11.5dB at 112MHz, would you still worry about factor at 111MHz? At some point surly this all becomes rather silly. _ Ralph McDiarmid | Schneider Electric | Renewable Energies Business | CANADA | Regulatory Compliance Engineering From: ce-test, qualified testing bv - Gert Gremmen g.grem...@cetest.nl To: EMC-PSTC@LISTSERV.IEEE.ORG Date: 12/05/2011 10:06 PM Subject: Re: [PSES] Calibration practice for EMI test transducers If at 100 MHz your sensor indicates during calibration 10 dB and at 120 MHz 12 dB, how are you going to know the value at 110 MHz. It maight be 20 as well as 0 dB, you don't not know as you did not measure/ calibrate. This requires some knowledge about the behavior of the sensor, and the 1/BW is and indication of that. There is another aspect in EMI measurements. As the measuring receiver interpolates between the calibrated samples, the max interpolation error (lin interpolation) is 50% of the vertical differences between calibration points. If the measuring receiver is +/- 0.5 dB you should register a calibration each time the difference between previous and current sample is 0.5 dB. Then the total error will be slightly more than 0.5 dB. There are more sophisticated interpolation methods such as cubic spline and polynomial interpolation, and the error item is subject to higher mathematics. Play with it at: http://terpconnect.umd.edu/~petersd/interp.html or at http://www.ibiblio.org/e-notes/Splines/Lagrange.htm you can actually move the points on the latter page. Gert Gremmen -Oorspronkelijk bericht- Van: emc-p...@ieee.org [mailto:emc-p...@ieee.org] Namens Cortland Richmond Verzonden: dinsdag 6 december 2011 3:01 Aan: emc-p...@ieee.org Onderwerp: RE: Calibration practice for EMI test transducers I recently had occasion to verify on an 8591EM generic factors for an EMCO current clamp during pretest, and used its tracking generator to see if with a short wire the result was a straight line on the screen. That simply called for paying attention to 1/BW. Cortland KA5S On 12/5/2011 5:33 PM, Ken Javor wrote: If an antenna, current probe or other transducer is going to be calibrated over its frequency range of operation, what determines the step sizes between measured frequencies, or if swept, what determines the density of test points reported? - 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 emc-p...@ieee.org 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://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 emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com - 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 emc-p...@ieee.org 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://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 emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com __ This email has been scanned by the Symantec Email Security.cloud service. __ - 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 emc-p...@ieee.org 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
Re: [PSES] Calibration practice for EMI test transducers
This discussion has gone far a field from the original post. I¹m assuming some sort of scan has been run and a continuous sweep is available. The question is, how densely does that sweep need to be digitized? Not as a practical matter, but as a matter of compliance with standards or standard practice. What manner of antenna would have performance as cited below where at 100 MHz the antenna factor is 10 dB and at 120 MHz it is 12 dB, but at 110 MHz it could be 20 dB? Let¹s generalize the question to any closely spaced frequencies. Let¹s look at the types of antennas available. 30-200 MHz: A half-wave tuned dipole is nowhere near that sharp. Neither is a biconical. 200 1000 MHz: A half-wave tuned dipole is nowhere near that sharp. Neither is a logperiodic, log-spiral, nor a Yagi. 1 GHz+: Logperiodic, log-spiral nor pyramidal horns act the way surmised. My conclusion, and the point here is to invite discussion, not close it out, is that no test-type antenna is a high ³Q² device. Antennas can have arbitrarily high gains, depending on construction, but the high gain is a geometrical quality, not a high quality factor in the frequency domain. Ken Javor Phone: (256) 650-5261 From: ralph.mcdiar...@schneider-electric.com Date: Tue, 6 Dec 2011 11:25:43 -0800 To: ce-test, qualified testing bv - Gert Gremmen g.grem...@cetest.nl Cc: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Calibration practice for EMI test transducers Yet how far would you take that argument? If it's say 11.1db at 110MHz and 11.5dB at 112MHz, would you still worry about factor at 111MHz? At some point surly this all becomes rather silly. _ Ralph McDiarmid | Schneider Electric | Renewable Energies Business | CANADA | Regulatory Compliance Engineering From: ce-test, qualified testing bv - Gert Gremmen g.grem...@cetest.nl To: EMC-PSTC@LISTSERV.IEEE.ORG Date: 12/05/2011 10:06 PM Subject: Re: [PSES] Calibration practice for EMI test transducers If at 100 MHz your sensor indicates during calibration 10 dB and at 120 MHz 12 dB, how are you going to know the value at 110 MHz. It maight be 20 as well as 0 dB, you don't not know as you did not measure/ calibrate. This requires some knowledge about the behavior of the sensor, and the 1/BW is and indication of that. There is another aspect in EMI measurements. As the measuring receiver interpolates between the calibrated samples, the max interpolation error (lin interpolation) is 50% of the vertical differences between calibration points. If the measuring receiver is +/- 0.5 dB you should register a calibration each time the difference between previous and current sample is 0.5 dB. Then the total error will be slightly more than 0.5 dB. There are more sophisticated interpolation methods such as cubic spline and polynomial interpolation, and the error item is subject to higher mathematics. Play with it at: http://terpconnect.umd.edu/~petersd/interp.html http://terpconnect.umd.edu/~petersd/interp.html or at http://www.ibiblio.org/e-notes/Splines/Lagrange.htm http://www.ibiblio.org/e-notes/Splines/Lagrange.htm you can actually move the points on the latter page. Gert Gremmen -Oorspronkelijk bericht- Van: emc-p...@ieee.org [mailto:emc-p...@ieee.org mailto:emc-p...@ieee.org ] Namens Cortland Richmond Verzonden: dinsdag 6 december 2011 3:01 Aan: emc-p...@ieee.org Onderwerp: RE: Calibration practice for EMI test transducers I recently had occasion to verify on an 8591EM generic factors for an EMCO current clamp during pretest, and used its tracking generator to see if with a short wire the result was a straight line on the screen. That simply called for paying attention to 1/BW. Cortland KA5S On 12/5/2011 5:33 PM, Ken Javor wrote: If an antenna, current probe or other transducer is going to be calibrated over its frequency range of operation, what determines the step sizes between measured frequencies, or if swept, what determines the density of test points reported? - 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 emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html 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/ http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott
Re: [PSES] Calibration practice for EMI test transducers
Original post answer from here - COST. From: Ken Javor ken.ja...@emccompliance.com To: EMC-PSTC@LISTSERV.IEEE.ORG Sent: Tuesday, December 6, 2011 5:11 PM Subject: Re: [PSES] Calibration practice for EMI test transducers Re: [PSES] Calibration practice for EMI test transducers This discussion has gone far a field from the original post. I’m assuming some sort of scan has been run and a continuous sweep is available. The question is, how densely does that sweep need to be digitized? Not as a practical matter, but as a matter of compliance with standards or standard practice. What manner of antenna would have performance as cited below where at 100 MHz the antenna factor is 10 dB and at 120 MHz it is 12 dB, but at 110 MHz it could be 20 dB? Let’s generalize the question to any closely spaced frequencies. Let’s look at the types of antennas available. 30-200 MHz: A half-wave tuned dipole is nowhere near that sharp. Neither is a biconical. 200 – 1000 MHz: A half-wave tuned dipole is nowhere near that sharp. Neither is a logperiodic, log-spiral, nor a Yagi. 1 GHz+: Logperiodic, log-spiral nor pyramidal horns act the way surmised. My conclusion, and the point here is to invite discussion, not close it out, is that no test-type antenna is a high “Q” device. Antennas can have arbitrarily high gains, depending on construction, but the high gain is a geometrical quality, not a high quality factor in the frequency domain. Ken Javor Phone: (256) 650-5261 From: ralph.mcdiar...@schneider-electric.com Date: Tue, 6 Dec 2011 11:25:43 -0800 To: ce-test, qualified testing bv - Gert Gremmen g.grem...@cetest.nl Cc: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Calibration practice for EMI test transducers Yet how far would you take that argument? If it's say 11.1db at 110MHz and 11.5dB at 112MHz, would you still worry about factor at 111MHz? At some point surly this all becomes rather silly. _ Ralph McDiarmid | Schneider Electric | Renewable Energies Business | CANADA | Regulatory Compliance Engineering From:ce-test, qualified testing bv - Gert Gremmen g.grem...@cetest.nl To:EMC-PSTC@LISTSERV.IEEE.ORG Date:12/05/2011 10:06 PM Subject:Re: [PSES] Calibration practice for EMI test transducers If at 100 MHz your sensor indicates during calibration 10 dB and at 120 MHz 12 dB, how are you going to know the value at 110 MHz. It maight be 20 as well as 0 dB, you don't not know as you did not measure/ calibrate. This requires some knowledge about the behavior of the sensor, and the 1/BW is and indication of that. There is another aspect in EMI measurements. As the measuring receiver interpolates between the calibrated samples, the max interpolation error (lin interpolation) is 50% of the vertical differences between calibration points. If the measuring receiver is +/- 0.5 dB you should register a calibration each time the difference between previous and current sample is 0.5 dB. Then the total error will be slightly more than 0.5 dB. There are more sophisticated interpolation methods such as cubic spline and polynomial interpolation, and the error item is subject to higher mathematics. Play with it at: http://terpconnect.umd.edu/~petersd/interp.htmlhttp://terpconnect.umd.edu/~petersd/interp.html or at http://www.ibiblio.org/e-notes/Splines/Lagrange.htmhttp://www.ibiblio.org/e-notes/Splines/Lagrange.htm you can actually move the points on the latter page. Gert Gremmen -Oorspronkelijk bericht- Van: emc-p...@ieee.org [mailto:emc-p...@ieee.orgmailto:emc-p...@ieee.org ] Namens Cortland Richmond Verzonden: dinsdag 6 december 2011 3:01 Aan: emc-p...@ieee.org Onderwerp: RE: Calibration practice for EMI test transducers I recently had occasion to verify on an 8591EM generic factors for an EMCO current clamp during pretest, and used its tracking generator to see if with a short wire the result was a straight line on the screen. That simply called for paying attention to 1/BW. Cortland KA5S On 12/5/2011 5:33 PM, Ken Javor wrote: If an antenna, current probe or other transducer is going to be calibrated over its frequency range of operation, what determines the step sizes between measured frequencies, or if swept, what determines the density of test points reported? - 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 emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.htmlhttp://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/http://product
Re: [PSES] Calibration practice for EMI test transducers
We might *like* measuring antennas to be low-Q, but remember the bicon shorting bars that were added some years ago? The skeleton bicons lacking them inserted a rather sharp notch that had to be accounted for in transducer tables. Baluns might go off from impact damage, too. And so on. I gave an ebay 50 MHz comb good past 2 GHz to a former employer who later gave all their own EMC lab gear to an NRTL. But you still have to check. For that matter, I've seen coax factors programmed with GAIN at a narrow range at microwave frequencies; that was caused by reflection from a crimped cable*. So we do need to be able to spot them. *This was due to the ignorance of operators collecting the data, IMO. I spoke to them and likely, they won't do it again. But they believed the SA/TG reading because they didn't know what they were measuring. That's another thread. Though the sweep may be continuous, if you can read amplitude only by marking pixels, you need to insure .5 BW or less per pixel. That's straight sampling theory, right? If your analyzer has a 1024 pixel wide screen you can't SEE less than about .1% of the scan width and can rely on less. Does it matter? Often it doesn't. Fun, isn't it? Cortland KA5S On 12/6/2011 5:11 PM, Ken Javor wrote: This discussion has gone far a field from the original post. I'm assuming some sort of scan has been run and a continuous sweep is available. The question is, how densely does that sweep need to be digitized? Not as a practical matter, but as a matter of compliance with standards or standard practice. What manner of antenna would have performance as cited below where at 100 MHz the antenna factor is 10 dB and at 120 MHz it is 12 dB, but at 110 MHz it could be 20 dB? Let's generalize the question to any closely spaced frequencies. Let's look at the types of antennas available. 30-200 MHz: A half-wave tuned dipole is nowhere near that sharp. Neither is a biconical. 200 -- 1000 MHz: A half-wave tuned dipole is nowhere near that sharp. Neither is a logperiodic, log-spiral, nor a Yagi. 1 GHz+: Logperiodic, log-spiral nor pyramidal horns act the way surmised. My conclusion, and the point here is to invite discussion, not close it out, is that no test-type antenna is a high Q device. Antennas can have arbitrarily high gains, depending on construction, but the high gain is a geometrical quality, not a high quality factor in the frequency domain. - 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 emc-p...@ieee.org 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://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 emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] Calibration practice for EMI test transducers
In message cb03ef45.c9421%ken.ja...@emccompliance.com, dated Tue, 6 Dec 2011, Ken Javor ken.ja...@emccompliance.com writes: Antennas can have arbitrarily high gains, depending on construction, but the high gain is a geometrical quality, not a high quality factor in the frequency domain. True for electric antennas, I think, but not for magnetic. Tuned loops and ferrite-rod antennas can have high Q. CISPR 16 includes at least one magnetic antenna, although it may well not be high Q. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK Some people who are peeling the finch of the financial crisis are thinking of biting a rook. - 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 emc-p...@ieee.org 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://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 emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] Calibration practice for EMI test transducers
I sure hope that standard practice and practicality (pardon me) go hand-in-hand. If not, the committees members need to give their head a shake. _ Ralph McDiarmid | Schneider Electric | Renewable Energies Business | CANADA | Regulatory Compliance Engineering From: Ken Javor ken.ja...@emccompliance.com To: EMC-PSTC@LISTSERV.IEEE.ORG Date: 12/06/2011 02:14 PM Subject: Re: [PSES] Calibration practice for EMI test transducers This discussion has gone far a field from the original post. I’m assuming some sort of scan has been run and a continuous sweep is available. The question is, how densely does that sweep need to be digitized? Not as a practical matter, but as a matter of compliance with standards or standard practice. What manner of antenna would have performance as cited below where at 100 MHz the antenna factor is 10 dB and at 120 MHz it is 12 dB, but at 110 MHz it could be 20 dB? Let’s generalize the question to any closely spaced frequencies. Let’s look at the types of antennas available. 30-200 MHz: A half-wave tuned dipole is nowhere near that sharp. Neither is a biconical. 200 – 1000 MHz: A half-wave tuned dipole is nowhere near that sharp. Neither is a logperiodic, log-spiral, nor a Yagi. 1 GHz+: Logperiodic, log-spiral nor pyramidal horns act the way surmised. My conclusion, and the point here is to invite discussion, not close it out, is that no test-type antenna is a high “Q” device. Antennas can have arbitrarily high gains, depending on construction, but the high gain is a geometrical quality, not a high quality factor in the frequency domain. Ken Javor Phone: (256) 650-5261 From: ralph.mcdiar...@schneider-electric.com Date: Tue, 6 Dec 2011 11:25:43 -0800 To: ce-test, qualified testing bv - Gert Gremmen g.grem...@cetest.nl Cc: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Calibration practice for EMI test transducers Yet how far would you take that argument? If it's say 11.1db at 110MHz and 11.5dB at 112MHz, would you still worry about factor at 111MHz? At some point surly this all becomes rather silly. _ Ralph McDiarmid | Schneider Electric | Renewable Energies Business | CANADA | Regulatory Compliance Engineering From: ce-test, qualified testing bv - Gert Gremmen g.grem...@cetest.nl To: EMC-PSTC@LISTSERV.IEEE.ORG Date: 12/05/2011 10:06 PM Subject: Re: [PSES] Calibration practice for EMI test transducers If at 100 MHz your sensor indicates during calibration 10 dB and at 120 MHz 12 dB, how are you going to know the value at 110 MHz. It maight be 20 as well as 0 dB, you don't not know as you did not measure/ calibrate. This requires some knowledge about the behavior of the sensor, and the 1/BW is and indication of that. There is another aspect in EMI measurements. As the measuring receiver interpolates between the calibrated samples, the max interpolation error (lin interpolation) is 50% of the vertical differences between calibration points. If the measuring receiver is +/- 0.5 dB you should register a calibration each time the difference between previous and current sample is 0.5 dB. Then the total error will be slightly more than 0.5 dB. There are more sophisticated interpolation methods such as cubic spline and polynomial interpolation, and the error item is subject to higher mathematics. Play with it at: http://terpconnect.umd.edu/~petersd/interp.html http://terpconnect.umd.edu/~petersd/interp.html or at http://www.ibiblio.org/e-notes/Splines/Lagrange.htm http://www.ibiblio.org/e-notes/Splines/Lagrange.htm you can actually move the points on the latter page. Gert Gremmen -Oorspronkelijk bericht- Van: emc-p...@ieee.org [mailto:emc-p...@ieee.org mailto:emc-p...@ieee.org ] Namens Cortland Richmond Verzonden: dinsdag 6 december 2011 3:01 Aan: emc-p...@ieee.org Onderwerp: RE: Calibration practice for EMI test transducers I recently had occasion to verify on an 8591EM generic factors for an EMCO current clamp during pretest, and used its tracking generator to see if with a short wire the result was a straight line on the screen. That simply called for paying attention to 1/BW. Cortland KA5S On 12/5/2011 5:33 PM, Ken Javor wrote: If an antenna, current probe or other transducer is going to be calibrated over its frequency range of operation, what determines the step sizes between measured frequencies, or if swept, what determines the density of test points reported? - 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 emc-p...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html http
[PSES] Calibration practice for EMI test transducers
If an antenna, current probe or other transducer is going to be calibrated over its frequency range of operation, what determines the step sizes between measured frequencies, or if swept, what determines the density of test points reported? Thank you, Ken Javor Phone: (256) 650-5261 - 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 emc-p...@ieee.org 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://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 emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] Calibration practice for EMI test transducers
I recently had occasion to verify on an 8591EM generic factors for an EMCO current clamp during pretest, and used its tracking generator to see if with a short wire the result was a straight line on the screen. That simply called for paying attention to 1/BW. Cortland KA5S On 12/5/2011 5:33 PM, Ken Javor wrote: If an antenna, current probe or other transducer is going to be calibrated over its frequency range of operation, what determines the step sizes between measured frequencies, or if swept, what determines the density of test points reported? - 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 emc-p...@ieee.org 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://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 emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
Re: [PSES] Calibration practice for EMI test transducers
If at 100 MHz your sensor indicates during calibration 10 dB and at 120 MHz 12 dB, how are you going to know the value at 110 MHz. It maight be 20 as well as 0 dB, you don't not know as you did not measure/ calibrate. This requires some knowledge about the behavior of the sensor, and the 1/BW is and indication of that. There is another aspect in EMI measurements. As the measuring receiver interpolates between the calibrated samples, the max interpolation error (lin interpolation) is 50% of the vertical differences between calibration points. If the measuring receiver is +/- 0.5 dB you should register a calibration each time the difference between previous and current sample is 0.5 dB. Then the total error will be slightly more than 0.5 dB. There are more sophisticated interpolation methods such as cubic spline and polynomial interpolation, and the error item is subject to higher mathematics. Play with it at: http://terpconnect.umd.edu/~petersd/interp.html or at http://www.ibiblio.org/e-notes/Splines/Lagrange.htm you can actually move the points on the latter page. Gert Gremmen -Oorspronkelijk bericht- Van: emc-p...@ieee.org [mailto:emc-p...@ieee.org] Namens Cortland Richmond Verzonden: dinsdag 6 december 2011 3:01 Aan: emc-p...@ieee.org Onderwerp: RE: Calibration practice for EMI test transducers I recently had occasion to verify on an 8591EM generic factors for an EMCO current clamp during pretest, and used its tracking generator to see if with a short wire the result was a straight line on the screen. That simply called for paying attention to 1/BW. Cortland KA5S On 12/5/2011 5:33 PM, Ken Javor wrote: If an antenna, current probe or other transducer is going to be calibrated over its frequency range of operation, what determines the step sizes between measured frequencies, or if swept, what determines the density of test points reported? - 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 emc-p...@ieee.org 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://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 emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com - 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 emc-p...@ieee.org 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://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 emcp...@radiusnorth.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: dhe...@gmail.com
