Shorting chassis to ground at the I/O is a very effective way of fixing EMI on
the cables.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On ;
Behalf Of leeritchey@xxxxxxxxxxxxx
Sent: Wednesday, May 09, 2018 11:12 AM
To: joel@xxxxxxxxxx; gurushankara@xxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Logic ground and chassis/safety ground
This message originated outside of DISH and was sent by:
si-list-bounce@xxxxxxxxxxxxx
There is no electrical reason why you need to connect these two. If you do
connect them, do it in only one place and do it with a DC connection. I make
that connection on the side of the PCB where the unshielded wires exit as a way
to minimize potential EMI escaping on those unshielded wires.
Don't know where all of the rules of thumb come from about capacitors and
multiple connections.
Lee RItchey
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx <si-list-bounce@xxxxxxxxxxxxx> On Behalf Of
Joel Brown
Sent: Wednesday, May 9, 2018 9:47 AM
To: gurushankara@xxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Logic ground and chassis/safety ground
Unless you have a requirement or other reason to keep them isolated It would be
best to connect them together.
If you decide to keep them them isolated then add multiple capacitors between
signal and chassis ground at each chassis connection point that can be
populated with different value capacitors or zero ohm resistors. Another option
is to have a chassis ground plane layer in your PCB that is connected to signal
ground at multiple points with capacitors. If you don't have a solid RF
connection between signal and chassis ground then there can be an RF potential
between the two grounds that can radiate if you have antenna structures such as
slots in your enclosure or external cables.
Joel
On Wed, May 9, 2018 at 9:16 AM, Guru Shankara <gurushankara@xxxxxxxxxxx>
wrote:
Hi Experts,chassis.
I am working on a modem design that is powered by an AC/DC supply
(isolated).
The design includes a base board that hosts a mezzanine/daughter card
and both the baseboard and the mezzanine cards are powered by 12V DC.
The chassis walls and misc. mechanical hardware have a conductive
coating on the inside and will be connected to the
chassis/safety/earth ground of the AC/DC power supply.
As the name implies, the chassis/safety/earth ground provides for
safety of the operator if there is a situation where the higher
voltage side line of the AC/DC supply rips off and makes contact with
the
So, I prefer NOT to connect the board logic ground to the
chassis/safety/earth ground of the supply.
Any thoughts on if I should connect them together or not?
Also, if they need to be connected, is there a recommended method?
Really appreciate your help.
Thank you,
Gurushankar
------------------------------------------------------------------
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 forum is accessible at:
http://tech.groups.yahoo.com/group/si-list
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
