A major error was made in that attachment. The transfer impedance of a current probe is not a loss. It is a conversion factor. Current passing through the window yields a potential at the probe output, when loaded by its proper termination impedance, typically 50 Ohms, or 34 dB Ohms. That is it. You do not further subtract the 34 dB Ohm of the load from the potential developed by the current probe. So if the test set up injects 107 dBuV into 34 dB Ohms, then 73 dBuA flow in the circuit. The current probe output is then:
V dBuV = 73 dBuA + Zt dB Ohms, where Zt denotes the current probe transfer impedance from the manufacturer's curve. End of story. > From: [email protected] > Reply-To: [email protected] > Date: Thu, 18 Dec 2003 10:48:45 -0500 > To: [email protected] > Subject: CISPR 25 Conducted Emissions (Current Method) > > > > > > All, > > One of my colleagues in town has a question that he would like to post > here, hoping to find an answer. If you have any thoughts, comments, or > suggestions please reply with them, and I will forward them to him. Also, > feel free to email Pete Vander Wel directly (his email address is in the > attached question sheet). > > His question: Does CISPR 25 take a 34dB difference into account in the > tables 8 and 9 of section 6.3.4 (limits)? > > Please read the attached document that he assembled for the details. > > Thank you in advance. > > Best Regards, > > Scott Mee > Johnson Controls Inc. > Automotive Systems Group > EMC Product Compliance > > 616.394.2565 > [email protected] > > > (See attached file: CISPR 25 Conducted Emissions.ZIP) > > > > (See attached file: CISPR 25 Conducted Emissions.zip) This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
