Bob, I'm not familiar with GR1089 but somewhat with EN61000-4-6 which is a conducted immunity test standard. When calibrating the CDNs or Injection clamps, you have to compensate for the losses in the test fixture. For the CDN, it comprises of a 150 to 50 ohm adaptor at the input and output of the CDN. The fixture acts as a voltage divider, the the measured power levels during calibration would be much lower than what is expected on the CDN output. So you have to account for this loss. In EN61000-4-6 section 6.4.1 "Setting of the output level at the EUT port of the coupling device" it has an equation for calculating the measured power level when you perform the calibration test: Umr = Uo / 6 (in linear quantities) or Umr = Uo - 15.6db (in logarithmic quantities where Uo is the test voltage from table 1. There is a note at the bottom that says, "The factor 6 (15.6db) arises from the e.m.f. value specified for the test level. The matched load level is half the e.m.f. level and the further 3:1 voltage division is caused by the 150 ohm to 50 ohm adaptor terminated by the 50 ohm measuring equipment". For Current Clamps the equation is Umr = Uo / 2 (in linear quantities) or Umr = Uo - 6db (in logarithmic quantities). I am assuming the test fixture acts like a voltage divider so you will only be measuring a fraction of the true voltage at the CDN in the the calibration setup. So yes, if you are not factoring in the fixture losses when you calibrate, you would be testing at too high of level. I hope this is what you are referring to. The Other Brian _____
From: [email protected] [mailto:[email protected]] On Behalf Of Bob Richards Sent: Thursday, June 14, 2007 9:25 AM To: ieee Subject: GR1089 conducted calibration No response from the first post, so I am reposting. Seems like the more complicated the question, the more responses we get. This question must be too simple. :-) The GR1089 Conducted Immunity calibration is to be performed in a 50 ohm fixture, terminated on one side with 50ohms, the other side through an attenuator (also 50ohm impedance) to a measurement device. The test limit at 10khz is listed as 89 dBua. The calibration level, measured at the output of the calibration fixture, should therefore be 123 dBuV ( add 34 dB to convert >from dBuA to dBuV in a 50 ohm system). My question is this: Is there is a 6 dB adjustment in level to be included in the measurement? I have always calibrated without any 6dB adjustment (more severe test), but the question came up recently so I thought I would ask the question here. Bob Richards, NCT - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Notice: This communication may contain confidential information intended for the named recipient(s)only. If you received this by mistake, please destroy it and notify us of the error. Thank you. ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________ - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
