Following up on Brent’s reply, the CM current measured by the probe will be 
partially determined by the CM termination impedance which is 150 ohms in the 
CISPR setups. You can use an IEC 61000-4-6 EM clamp to approximate this with 
reasonably good results.



All the best

James



James Pawson

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Unit 3 Compliance Ltd

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From: Brent DeWitt <bdew...@ix.netcom.com>
Sent: 17 December 2024 21:54
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Conducted emission - LISN vs. current clamp



>From my experience, I would seldom expect the current probe and the LISN to 
>show the same answer. The big difference is that the current probe is looking 
>at a fairly random termination impedance compared to the "Line Impedance 
>Stabilization Network", which is reasonably stable in its design. An 
>interesting experiment is to use the CM/DM choke on a power cord plugged into 
>a LISN and examine the differences,



On 12/17/2024 4:27 PM, Ken Wyatt wrote:

We’ll need a lot more information on what you’re testing, the test setup 
configuration and how you’re measuring DM and CM. Can you share some photos or 
screen captures?



Usually there will be a difference between DM and CM current spectral response. 
Now Line and Neutral from a LISN will like look the same typically.



Kenneth Wyatt

Windsor, CO





On Dec 17, 2024, at 13:46, am...@westin-emission.no 
<mailto:am...@westin-emission.no>  wrote:



Clamp is ok for investigate DM and CM currents. LISN for formal testing at lab.



Right now, the plots of CM and DM currents are almost equal over the whole 
spectrum (10k – 30MHz). Surprise?

In the same setup, using a LISN, the spectrum is quite different regarding 
peaks and waveform.



I know the information from this test is defective, but do you have a first 
thought anyway?



BR

Amund








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