Re: Correction factors
I'm not familiar with the software in question, but most spectrum analyzer displays are linear, with some processing taking the spectrum analyzer display and plotting it out as log scale. If you have dense enough info about the transducer factor such that no significant interpolation is necessary, then it doesn't matter if you list it linearly and plot log, or vice versa. As long as you have a limit such as the FCC RE limit which is flat with discontinuous steps log or linear doesn't matter either. Ditto for the old FCC CE limit which was 48 dBuV from 450 kHz to 30 MHz. But the new FCC/CISPR CE limit has a non-zero slope plotted on a log scale, so there you need either an equation or list it as you plot it. From: Franck GALVIN franck.gal...@e-labs.fr Reply-To: Franck GALVIN franck.gal...@e-labs.fr List-Post: emc-pstc@listserv.ieee.org List-Post: emc-pstc@listserv.ieee.org List-Post: emc-pstc@listserv.ieee.org List-Post: emc-pstc@listserv.ieee.org Date: Tue, 6 May 2003 17:35:49 +0200 To: emc-p...@majordomo.ieee.org Subject: Correction factors Dear all, I perform conducted or radiated emission test with HP8594EM spectrum analyser or HP8656A receiver. To not have measurements errors I must enter correction factors (antenna or LISN, cable and other Š). My questions are: 1/ When you enter data to antenna factors for example, you write Œ¹frequency¹¹, Œ¹amplitude¹¹ and what about Œ¹frequency scale¹¹ (log or lin) ? 2/ Does frequency scale depend of correction type (cable, amplifier, antenna, LISN, transient limiterŠ)? Thanks in advance for your answers. Franck GALVIN eLAbs (France)
RE: Correction factors
From: Franck GALVIN [mailto:franck.gal...@e-labs.fr] Sent: Tuesday, May 06, 2003 8:36 AM To: emc-p...@majordomo.ieee.org Subject: Correction factors Dear all, I perform conducted or radiated emission test with HP8594EM spectrum analyser or HP8656A receiver. To not have measurements errors I must enter correction factors (antenna or LISN, cable and other ...). My questions are: 1/ When you enter data to antenna factors for example, you write ''frequency'', ''amplitude'' and what about ''frequency scale'' (log or lin) ? 2/ Does frequency scale depend of correction type (cable, amplifier, antenna, LISN, transient limiter...)? Thanks in advance for your answers. Franck GALVIN eLAbs (France) Franck: I have somewhat older HP hardware software than your setup, but here's how the HP software works for me. When you are creating an equipment calibration table, you are asked to declare the number of data pairs (frequency amplitude) that define a curve which represents the response of the equipment. For example, an external attenuator might be defined by only two pairs, say, 0.01 / 20 18000 / 20 (data units are MHz dB). However, for something like a current probe or antenna, you might have a file of 50 pairs or so. You also choose LIN or LOG, which specifies the interpolation method used between the data points. I always choose LOG, since the completed emission plots usually use a logarithmic frequency scale. I don't think this makes any practical difference, but then I always enter enough data pairs so that the delta dB from one pair to another is 1 dB or less. After setting up a calibration file (you need a transducer, cable and limit set of files), be sure to test the expected accuracy by injecting a known signal into the coax cable head-end to verify that the factors are being added correctly to the raw spectrum analyzer data. IIRC, the HP convention was to always subtract the correction factor value from the raw data. Thus, you have to make the attenuator data a negative number, so that subtracting a negative yields adding a positive! (Hope you don't think I'm joking!!! Read you software manual very carefully.) Regards, Ed Ed Price ed.pr...@cubic.com NARTE Certified EMC Engineer Technician Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military Avionics EMC Is Our Specialty
Re: Correction factors
On Tue, 6 May 2003 17:35:49 +0200, Franck GALVIN franck.gal...@e-labs.fr wrote: I perform conducted or radiated emission test with HP8594EM spectrum analyser or HP8656A receiver. To not have measurements errors I must enter correction factors (antenna or LISN, cable and other .). My questions are: 1/ When you enter data to antenna factors for example, you write ''frequency'', ''amplitude'' and what about ''frequency scale'' (log or lin) ? 2/ Does frequency scale depend of correction type (cable, amplifier, antenna, LISN, transient limiter.)? I'm familiar with the 8590-series analyzers, so I'll comment about that one. The 'Frequency Scale' feature allows you to accurately specify a limit line/correction factor that is linear with log(frequency) by using only two data points. Without this feature, you have to interpolate many data points between the start and stop frequency for an accurate limit line. The scale mode has no benefit if the limit line/correction factor is flat with frequency. The obvious example is to draw the CISPR 11/CISPR 22 Class B Conducted emission limit line from 0.15-0.50MHz. The limit line entries using the 'log' scale mode: 0.15 66dBuV SLOPE 0.50 56dBuV FLAT The limit line entries using the 'linear' scale mode (2dB increments in amplitude): 0.150 66dBuV SLOPE 0.191 64dBuV SLOPE 0.243 62dBuV SLOPE 0.309 60dBuV SLOPE 0.393 58dBuV SLOPE 0.500 56dBuV SLOPE As far as correction factors are concerned, use the scale mode that best fits your accuracy/data point requirements. This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
