---------- Forwarded message ---------- List-Post: [email protected] Date: Wed, 21 Jan 1998 15:08:24 -0800 (PST) From: [email protected] To: John Harrington <[email protected]> Subject: Re: Strange specification
On Wed, 21 Jan 1998, John Harrington wrote: > Dear all > > We have recently been asked to perform magnetic VDT > measurements to MPR II (1990:8). > > Does any one know of this specification or even what a VDT > measurement is? > > Any help or hints greatly appreciated > > John Harrington > EMC Group Manager, KTL > Telephone : +44 (0) 1482 801801 > Fax : +44 (0) 1482 801806 > email : [email protected] > > Sweden instituted these rules regarding VDT's (Visual Display Terminals) As I recall, it covers quite a bit of performance specifications but the one of main interest is the magnetic field emanations, called emf. Back in the late 80's there was tremendous concern that people suddenly sitting in front of terminals would be continuously exposed to "excess" magnetic fields, etc. The bands of interest cover the vertical rates and the horizontal rates of the VDT and measurement techniques and equipment is *very* well defined. It is my understanding that the limits of magnetic field are based upon an epidemiological investigation which correlated cancer rates to field exposures from power lines. This study showed that when fields were less than As I recall, the fields are limited to an rms value of 200 nanoTeslas in the band 5Hz to 2KHz and 20 nanoTeslas in the band of 2KHz to 400KHz. Several measurements are taken around the VDT at specified distances. I've a copy of MPR II if you absolutely need it. But I'm sure the Sweden can send you a copy directly. Also, Combinova (I think it is) makes the equipment capable of making these measurements. - Robert -
