Hi Rick, we experienced similar problems in our company. The magnetic field may be produced in two ways: 1. Power cable in the wall. The sum of the currents is not zero because a (high) percentage of the current flows to protective ground (multiple bonding or capacitors, mainly in power line filters (sic!!) 2. The current you miss in the cables flows back to the source (another bonding point) through the steel in the wall. green yellow PE conductors etc. They cause a magnetic field.
We measured the field intensity but even after having the figures we could not eliminate the cause. Try following (helps only if fields are not strong) Set the vertical frequency to 90 Hz (as far as possible from 60 Hz, 120 Hz, 180 Hz etc.). Thus the perceived frequency of disturbance would be 30 Hz, to high for normal eyes. You will perceive only a slight unfocus. If it does not help, try moving the monitor to another position, rotate the monitor or get another monitor ( like Nokia) If this does not help you'll have to by some very expensive and very ugly magnetic shielding (looks like a telephone cell). We bought about 60 in our company. Good luck George rbus...@es.com wrote: > Sender: owner-emc-p...@majordomo.ieee.org > Received: from ruebert.ieee.org (ruebert.ieee.org [199.172.136.3]) > by dub-img-12.compuserve.com (8.8.6/8.8.6/2.18) with ESMTP id > MAA00426; > Tue, 1 Jun 1999 12:14:45 -0400 (EDT) > Received: by ruebert.ieee.org (8.8.8+Sun/8.8.8) > id MAA28463; Tue, 1 Jun 1999 12:08:16 -0400 (EDT) > From: rbus...@es.com > Message-ID: <8a431c080f0dd211837100805fea6754050e1...@torino.corp.es.com> > To: emc-p...@majordomo.ieee.org > Subject: 60Hz in PC Monitor > Date: Tue, 1 Jun 1999 10:09:26 -0600 > MIME-Version: 1.0 > X-Mailer: Internet Mail Service (5.5.2448.0) > Content-Type: text/plain; > charset="iso-8859-1" > Sender: owner-emc-p...@majordomo.ieee.org > Precedence: bulk > Reply-To: rbus...@es.com > X-Resent-To: Multiple Recipients <emc-p...@majordomo.ieee.org> > X-Listname: emc-pstc > X-Info: Help requests to emc-pstc-requ...@majordomo.ieee.org > X-Info: [Un]Subscribe requests to majord...@majordomo.ieee.org > X-Moderator-Address: emc-pstc-appro...@majordomo.ieee.org > > I have in my company, several people asking for help with swimming in their > monitors. There systems are connected to a half wall (windows on top, power > and heat on the bottom). The head is steam radiation via baseboard > radiators. These monitors are NOT next to any known magnetic fields. I have > verified that if the monitors are physically moved away from the wall/heater > the noise diminishes. In the row of multiple cubicles only selective people > have the problem (perhaps 3 out of 15 or so). The noise appears to be 60 Hz > in nature although no color purity problems were noted. > > I'm assuming that I am now looking for magnetic fields, possibly from the > electrical feed line, or could it be the radiators? Is it possible for these > to be nodal or selective along a common wall? > > Has anyone else had similar problems? Would it make sense to obtain a meter > to measure the magnetics? Any suggestions appreciated. > > Rick Busche > Evans & Sutherland > rbus...@es.com > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to majord...@ieee.org > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to ed.pr...@cubic.com, > jim_bac...@monarch.com, ri...@sdd.hp.com, or > roger.volgst...@compaq.com (the list administrators). -- ************************************************************** * Dr. Georg M. Dancau * HAUNI MASCHINENBAU AG * * g.m.dan...@ieee.org * Manager EMC Lab * * TEL: +49 40 7250 2102 * Kampchaussee 8..32 * * FAX: +49 40 7250 3801 * 21027 Hamburg, Germany * ************************************************************** * home: Tel: +49 4122 99451 * Hauptstr. 60a * * Fax: +49 4122 99454 * 25492 Heist, Germany * ************************************************************** --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
