Re: ELF Effects on VDUs

[grcohn@cats.ucsc.edu (Gregg Cohn)]

>G'day Radsafers
>
>I recently completed an ELF (50Hz) survey in an office which backs onto an
>11000V transformer. As expected, the magnetic flux densities were quite high
>- eg a maximum of 640mG at the closest point to the transformer. The
>magnetic flux density at the point where the VDU is situated is about 30mG.
>This appears to be causing a "wavering" effect in the screen.
>
>My question is does anyone have a feeling for the minimum magnetic flux
>density (50Hz) required to cause such an effect in a VDU screen?
>
>Thanks in advance
>
>regards
>
>
>
>                        Alex Zapantis
>                        Radiation Safety Officer                               
>                        Queensland University of Technology          
>                        Health & Safety Section                             
>                        Locked Bag No.2
>                        Red Hill Qld 4059
>                        AUSTRALIA
>
>                        Ph     : 61 7 864 3566
>                        fax     : 61 7 864 3993
>                        email  : a.zapantis@qut.edu.au
>
>
Alex,

What brand of monitor is it?  Have you tried another monitor in same place
with the same effect? I had similar problem with a monitor and it was due to
a defective deGausser in the power supply.

Good luck,

Gregg R Cohn, RSO
University of California-Santa Cruz
FAX     (408)459-3209
VOICE   (408) 459-3542
E-Mail  grcohn@cats.ucsc.edu