Muriel and group: I agree with Helge's comments. The use of a ground choke is now deprecated. In fact a recent UK report recommends the removal of the choke and switch and replacement by a solid connection. The actual wording is:
"The inductor is not now a requirement of any international standards. Since its inclusion compromises the HF impedance from EUT earth connection to ground reference plane (because of the need for a switch), best engineering practice would dictate that it is left out of modern designs of AMN/LISNs." Regards to all, Bill. __ Bill Lyons - [email protected] / [email protected] In message <[email protected]> hknudsen writes: > Hello Muriel and group, > > I believe, Ground Choke "OUT" means that the choke is short circuited. > Unless the standard you are using specify measurement with ground choke, you > must always use this setting. > As far as I know, no standard except this old VDE test specifies use of this > ground choke. > The use of ground is not described in CISPR standards. > > Best regards > > Helge Knudsen > Jyske EMC > > > [email protected] > > ---------- > From: Muriel Bittencourt de Liz[SMTP:[email protected]] > Sent: 7. december 1998 12:46 > To: Helge Knudsen > Cc: 'EMC-PSTC - IEEE' > Subject: Re: Doubt on LISN utilization > > <<File: fig1.gif>><<File: fig2.gif>> > Hello Group, > > Thanks for all that answered my question. This question was due to some > measurements of conducted emissions that i've made. First, i've done > measurements with the Ground Choke in position "OUT". Then, the ambient > interference diminished a lot, as shows Fig. 1. Then i've switched the > ground choke to "IN" position, as shows Fig. 2. The standards i'm using > are based on European Standards ( CISPR 22, CISPR 15). Figs. 1 and 2 are > attached. > > So, when i try to do measurements, the spectra of conducted emissions > change according to switch position (ground choke on or off). > > My questions are: > > => Which emission measurement should i trust: the one with switch "IN" > or the one in "OUT" position (ground choke "in" or "out") > > => Could somebody make clear to me if CISPR requires this ground choke? > > => the ground choke is a must only in VDE measurements? > > I Think that's all... > > Thanks in advance! > > Muriel > > > Helge Knudsen wrote: > > > > Dear group, > > The use of ground choke in conducted measurements was specified in > > "Verfugerung 1046/1982" when testing to comply with VDE 0871 if the > > measured noise was closer to the limit than 5 dB. > > This second measurement must then also comply with the limit. > > The value of this ground conductor choke was specified to 1.6 mH. > > > > I believe the reason for this sophisticated measurement were required > > because the inductance in ground lead in really live may increase the noise > > level with several dB's. > > I hope this clarified the matter. > > > > Best regards > > Helge Knudsen > > Jyske EMC > > Denmark > > [email protected] > > > > -----Original Message----- > > From: Cortland Richmond [SMTP:[email protected]] > > Sent: lordag, december 05, 1998 05:43 > > To: Gary McInturff; ieee pstc list > > Subject: RE: Doubt on LISN utilization > > > > As I recall, when testing conducted emissions to VDE 0871, it was required > > to observe noise in the two powered lines with the switch both open and > > closed, and use the higher result. Some power supplies would in fact give > > different results if the ground was opened. > > > > Cortland --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
