As a Product Safety and Process Automation guy (I do not even pretend to be a PS designer), perhaps I am being naive.... But, when I do EMC pre-compliance (as part of a DVT), conducted emissions seems to be the most "repeatable" of all EMC tests. In general, for a static load, with all test equipment and apparatus fixed to pre-defined physical locations, I have found that this test is consistent enough to be used as an informal QA "control point". When our factory makes units having a different conducted emissions profile, it drives me to get more units from this batch and repeat some due-diligence Type Tests.
Is there something that I do not understand about the conduct of this test ? luck, Brian -----Original Message----- From: [email protected] [ mailto:[email protected]] Sent: Wednesday, April 21, 2004 5:35 AM To: [email protected] Subject: Re: EN61000-3-2 repeatability test In response to Kurt's question "It seems that the solution path is to determine why the EUT generates different LF emissions profiles ..." The EUT is a switching power supply, and like all electronics equipment, the components are packed close together. This includes the PFC control circuitry, the PFC boost inductor, and the power transformer. Considering the PFC circuitry has control signals in the tens of microamperes, and it operates in a noisy signal environment of fast switching magnetic fields, it's not had to imagine the measurements varying because of local interference ('jitter' in the digital world). If we had realized this type of 'repeatability' test was to be applied when we designed the product, it would have been taken into account. We thought the PFC design was successful when the emissions were far below the limit line. --- Pat Lawler [email protected] On Tue, 20 Apr 2004 07:42:38 -0700, "Kurt Fischer" <[email protected]> wrote: >I do not have a copy of the standard so I am relying on memory: > >1. The 5% repeatability requirement stated in the standard refers to >Instrumentation repeatability and validation (as Ken referred to in his >email). > >2. The problem stated in Pat's email is that the EUT has different >measurement results when measured at different times. > >It seems that the solution path is to determine why the EUT generates >different LF emissions profiles and determine if these profiles meet the >limits in a reasonable number of cases or trials per the standard. To the >best of my memory, there is no requirement that the repeatability >measurements of the EUT itself be +/- 5%. > >Regards, >Kurt Fischer > >-----Original Message----- >From: Hall, Ken [ mailto:[email protected]] >Sent: Tuesday, April 20, 2004 5:53 AM >To: Kurt Fischer; Pat Lawler; [email protected] >Subject: RE: EN61000-3-2 repeatability test > > >Hello, > >We just purchased the York HFG01for Site reproducibility/RoundRobin testing >and use the HPET ( the for cyclic checks. The HP59510A switch box is >replaced by a solid state relay the load resistors are glowcoils. > >Regards, >Ken Hall > _____ > >From: [email protected] on behalf of Kurt Fischer >Sent: Mon 4/19/2004 7:42 PM >To: 'Pat Lawler'; [email protected] >Subject: RE: EN61000-3-2 repeatability test > >You should use the same EUT (which must be stable and repeatable). If you >are obtaining drastically different results then you do not know if it is >the EUT or the test setup/instrumentation that is effecting the results. > >I would suggest using something like an incandescent light bulb to run the >test and check the repeatability of the instrumentation and test setup. > >Just my 2 cents. > >Good Luck, > >Kurt > >-----Original Message----- >From: [email protected] >[ mailto:[email protected] >< mailto:[email protected]> ]On Behalf Of Pat Lawler >Sent: Monday, April 19, 2004 5:36 PM >To: [email protected] >Subject: EN61000-3-2 repeatability test > > >When the 'Repeatability' clause in EN61000-3-2:2000 (clause 6.3.2.1) is >applied, is the comparison value (reference value) the result from another >test run, or is it the test limit? > >For example, the harmonic test limit is 300mA, and the values from two test >runs are 7.4mA and 13mA. > >1) If the comparision value is from the other test run: >13mA-7.49mA >-----------*100=42.4% (failing the test) > 13mA > >2) If the comparison value is the test limit: >13mA-7.49mA >-----------*100=1.8% (passing the test) > 300mA > >Method 1 seems overly stringent, but I can't find anything in the standard >covering the method. Is this detail covered in another standard (like >61000-4-7?) >--- >Pat Lawler >pat dot lawler at verizon dot net >
