What if the design has a serial port that could connect to a laptop or PC that could have a much different chassis ground reference (difference of several volts)? Connecting chassis ground to signal ground could crash the board, right? -Chris > -----Original Message----- > From: si-list-bounce@xxxxxxxxxxxxx=20 > [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of steve weir > Sent: Wednesday, December 15, 2004 12:38 PM > To: leeritchey@xxxxxxxxxxxxx; Peterson, James F (FL51);=20 > si-list@xxxxxxxxxxxxx > Subject: [SI-LIST] Re: Chassis and Signal ground >=20 >=20 > Lee, DC single pointing can work under the right conditions=20 > and may be=20 > required for safety in circumstances as I outlined to Jim. >=20 > That said, DC single point connection does not eliminate AC=20 > paths, and can=20 > greatly reduce the SRF of the resulting structures. For example, the=20 > proximity of a big signal ground plane near a chassis pan=20 > makes a nice big=20 > resonant cavity. More often than not, a low cavity SRF is a=20 > bad thing that=20 > makes for efficient radiation / efficient reception across a=20 > broad range of=20 > frequencies. This makes the folks who sell ferrite cable=20 > clamps happy, but=20 > not usually the poor compliance guy. >=20 > Regards, >=20 > Steve, > At 08:46 AM 12/15/2004 -0800, Lee Ritchey wrote: > >If I connected them at all, and I usually don't, it would be in only=20 > >one place, so that the opportunity for inceased EMI is held to a=20 > >minimum. > > > >Lee W. Ritchey > >Speeding Edge > >P. O. Box 2194 > >Glen Ellen, CA 95442 > >Phone- 707-568-3983 > >FAX- 707-568-3504 > > > >I just used the energy it took to be angry to write some=20 > blues. Count=20 > >Basie > > > > > > > [Original Message] > > > From: Peterson, James F (FL51) <james.f.peterson@xxxxxxxxxxxxx> > > > To: <si-list@xxxxxxxxxxxxx> > > > Date: 12/15/2004 8:26:04 AM > > > Subject: [SI-LIST] Chassis and Signal ground > > > > > > Chassis and Signal ground, what happens to our noise=20 > susceptibility=20 > > > if we connect them together on our cards (some of them are analog=20 > > > cards)? > > > > > > We've always kept chassis ground and signal ground=20 > separate on our=20 > > > cards > >and > > > connected them together on our backplanes. The reason we=20 > even have a > >chassis > > > ground on a board is because we use them as thermal=20 > layers that are=20 > > > used > >to > > > remove heat from boards (that need to operate in the vacuum of=20 > > > space). > > > > > > We are currently evaluating connecting our signal ground on the=20 > > > boards to the "card guides" of the chassis. The benefit=20 > is we don't=20 > > > need thermal layers anymore. The signal ground layers can now=20 > > > conduct the heat out through the guides and onto the=20 > chassis....but=20 > > > what have we done to our radiated noise levels and to our=20 > > > susceptibility to incoming noise? > > > > > > Regards, > > > Jim > > > > > > ------------------------------------------------------------------ > > > To unsubscribe from si-list: > > > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject=20 > > > field > > > > > > or to administer your membership from a web page, go to:=20 > > > //www.freelists.org/webpage/si-list > > > > > > For help: > > > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > > > > List FAQ wiki page is located at: > > > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > > > > > > List technical documents are available at: > > > http://www.si-list.org > > > > > > List archives are viewable at: > > > //www.freelists.org/archives/si-list > > > or at our remote archives: > > > http://groups.yahoo.com/group/si-list/messages > > > Old (prior to June 6, 2001) list archives are viewable at: > > > http://www.qsl.net/wb6tpu > > > > > > > > > > >------------------------------------------------------------------ > >To unsubscribe from si-list: > >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > > >or to administer your membership from a web page, go to:=20 > >//www.freelists.org/webpage/si-list > > > >For help: > >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > >List FAQ wiki page is located at: > > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > > > >List technical documents are available at: > > http://www.si-list.org > > > >List archives are viewable at: > > //www.freelists.org/archives/si-list > >or at our remote archives: > > http://groups.yahoo.com/group/si-list/messages > >Old (prior to June 6, 2001) list archives are viewable at: > > http://www.qsl.net/wb6tpu > > >=20 >=20 > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field >=20 > or to administer your membership from a web page, go to:=20 > //www.freelists.org/webpage/si-list >=20 > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field >=20 > List FAQ wiki page is located at: > http://si-list.org/wiki/wiki.pl?Si-List_FAQ >=20 > List technical documents are available at: > http://www.si-list.org >=20 > List archives are viewable at: =20 > //www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > =20 >=20 >=20 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu