Some comments to Neven: -When you use BCI clamp you can measure and limit the current as you describe. -The impedance is not >150 ohms but with +/- tolerance, see Table 3. -The EUT needs to have 150 ohms from chassis to earth so the impedance is not as low as you say
Regards Ari > -----Original Message----- > From: [email protected] > [mailto:[email protected]]On Behalf Of ext > [email protected] > Sent: 23 January, 2004 07:08 > To: [email protected] > Subject: Clamp Injection EN61000-4-3 Question > > > > I have a question for experts on details of Conducted > Immunity testing per EN61000-4-3 using Current Clamp (NOT EM > clamp) injection method. > > I am reading BS EN61000-4-6, 1996 with Amendments 1 and 2. > > Section 7.2 (Procedure for clamp injection application) says > that the Auxiliary Equipment (AE) impedance should meet the > requirement from 6.2 as close as possible. Section 6.2 > requires the input impedance (including the decoupling > network - a line of ferrite in my case) to have the input > common-mode impedance higher than 260 or 150 Ohm (depending > on frequency). I can do it easily by lining the cable under > test with ferrites on the AE-side of the injection clamp. > > Section 7.3 (Procedure for clamp injection when the > common-mode impedance requirements cannot be met) states that > "When using clamp injection and the common-mode impedance > cannot be met at the AE side, it is necessary that the > common-mode impedance of the AE is less then or equal to the > of the EUT port being tested." > > While I can meet the input impedance requirement (>150 ohm) > looking into the AE, the input common-mode impedance of the > EUT port I have is much lower than 150 Ohm, on the order of > 20-40 ohm. That is because at my EUT input I have > center-tapped transformer, with the center-tap capacitively > connected to GND, which is effectively a low impedance for > common-mode. > > It seems that formally the section 7.3 doesn't apply for my > device (because I can meet the AE-impedance requirement), but > then I question why is it stated that it is important that > the EUT input impedance (common mode) is higher than the AE > input common-mode impedance only if the AE input impedance > cannot be met. I believe it is important in any case. > > It seems I might likely overtest, because most current will > flow into the EUT port. Am I out of luck, or can I use the > clause of 7.3 which allows for measuring current into the EUT > using a current-measuring clamp and limit the testing level > to no more than I= Uo/150? I have a product that is allegedly > failing (not by much) a 10 V level, and I want to be sure > that it is being tested correctly (and not over-tested). > > Thank you very much, > > Neven > > > ------------------------------------------- > 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 > 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
