I read in !emc-pstc that Muriel Bittencourt de Liz <[email protected]> wrote (in <017b01c1adf6$74216430$55ddbfc8@marx>) about 'Conducted noise emission diagnosis device', on Tue, 5 Feb 2002: >I am looking for a device that will differentiate the dominant component >(either >common-mode or differential-mode current) in the total conducted noise >emission >current of a product measuring through its' power cord using a LISN. > > >This device can be called "common/differential mode current separator". In >conducted >noise emission measurement, both common-mode and differential mode noise >current are measured by LISN and the LISN can't tell which mode is the >dominant >current.
If you are referring to the CISPR16-1 LISNs, it is true that they don't separate the common- and differential-mode currents, ***but you can**. If C is the common-mode (CM) component and D is the differential-mode (DM) component (both in linear units, not decibels), then one output of the LISN gives C + D and the other gives C - D. This follows from the definitions of CM and DM. This approach is suitable for wide-band measurements using an r.f. voltmeter or narrow-band measurements using a receiver, but for measurements with a spectrum analyser you need to derive the sum and difference voltages in real time, using a balun transformer, as described in the Armstrong-Williams article in 'EMC and Compliance Journal Issue 34. **Note that the diagram Figure 12 does not show the essential earth/ground connection to the enclosure.*** -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk After swimming across the Hellespont, I felt like a Hero. PLEASE do NOT copy news posts to me by E-MAIL! ------------------------------------------- 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: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [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: No longer online until our new server is brought online and the old messages are imported into the new server.
