X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao12.cox.net ([68.230.241.27] verified) by logan.com (CommuniGate Pro SMTP 4.3c5) with ESMTP id 951639 for flyrotary@lancaironline.net; Fri, 20 May 2005 19:49:39 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.27; envelope-from=dale.r@cox.net Received: from smtp.west.cox.net ([172.18.180.52]) by fed1rmmtao12.cox.net (InterMail vM.6.01.04.00 201-2131-118-20041027) with SMTP id <20050520234854.OJAH550.fed1rmmtao12.cox.net@smtp.west.cox.net> for ; Fri, 20 May 2005 19:48:54 -0400 X-Mailer: Openwave WebEngine, version 2.8.15 (webedge20-101-1103-20040528) From: Dale Rogers To: "Rotary motors in aircraft" Subject: Re: [FlyRotary] Re: More MAP measurement questions Date: Fri, 20 May 2005 19:48:54 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Message-Id: <20050520234854.OJAH550.fed1rmmtao12.cox.net@smtp.west.cox.net> > Why are they at different potentials? Are you using a single point > grounding scheme? Joe, How could you guarantee that the grounds at each end of a long run would be at the same potential? Each connection in a circuit has an associated voltage drop. Each wire has a voltage drop that increases with each foot of length. They are in the millivolt range, but they do add up. If the drops along the ground path are different than the drop across the shield, you have a ground loop circuit. The purpose of the shielding braid is to "trap" signals so that they are not picked up by the wire inside, or be transmitted to adjacent wires. Grounding one end of each shield will accomplish that purpose. Regards, Dale R. COZY MkIV #1254