Path: utzoo!attcan!uunet!clyde.concordia.ca!news-server.csri.toronto.edu!rutgers!usc!zaphod.mps.ohio-state.edu!mips!sgi!rpw3@rigden.wpd.sgi.com From: rpw3@rigden.wpd.sgi.com (Rob Warnock) Newsgroups: sci.electronics Subject: Re: question about computer power supply Keywords: computer power supply Message-ID: <64414@sgi.sgi.com> Date: 18 Jul 90 05:40:22 GMT References: <30733@eerie.acsu.Buffalo.EDU> <3852@kitty.UUCP> Sender: rpw3@rigden.wpd.sgi.com Reply-To: rpw3@sgi.com (Rob Warnock) Distribution: sci Organization: Silicon Graphics, Inc., Mountain View, CA Lines: 28 In article <3852@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes: +--------------- | Some well-designed power supplies provide an external sense lead | which is connected to a terminal on the PC-board backplane. This will | automatically compensate for any IR drop between the supply and the | backplane. If your power supply has a multi-pin connector whose pin | functions are not explicitly labeled or otherwise known, it may be that | one or more pins are for sense purposes. | | Failing to connect a voltage sense lead to the power output lead | will result in an incorrect voltage with lack of regulation (usually, but | not always a *lower* voltage). +--------------- And even *more*-well-designed supplies contain internal resistors between the sense leads and the outputs to keep the output from wandering far afield if the sense leads get disconnected. The internal resistor is usually a lot larger than the resistance of the sense wire but small enough to give good regulation if the sense wire is broken/missing. (A typical value is ~20 ohm.) -Rob ----- Rob Warnock, MS-9U/510 rpw3@sgi.com rpw3@pei.com Silicon Graphics, Inc. (415)335-1673 Protocol Engines, Inc. 2011 N. Shoreline Blvd. Mountain View, CA 94039-7311