high permeability metal to cancel the earth magnetic field

[morrishsu]

I appreciate the responses from IR and hacksaw and sorry for not articulating my question. There are two types of CRT'for products to work in Northern and Southern hemispheres respectively due to the magnetic field of the Earth. Unfortunately my customer deploys my CRT on a CASINO ship as a slot machine. A slot machine has to work 24 hours a day to make the gambling fair(possibility). So here comes the case, when the ship departed from Northern hemisphere to head toward South with the always-on CRT, the colors shifted due to the change of Earth magnetic field. In most cases, the degaussing coil will only work right after you power on the CRT, and it is impossible to frequently degauss the CRT by CPU programming because the gambler will think the slot machine is programmed to cheat (the screen will shake a little bit while degaussing the CRT). The only way is to have the metal shield(like MU metal with high permeability)to block the natural magnetic field coming from the Earth. I'm trying to find if there is cheaper alloy to replace the MU and what the key setup parameters to watch during the metal stamping process.

 

[hacksaw]

you are not just dealing with the earths field, but ship polarization effects. typically the latter are fixed at the time of the ships construction and fitting out. evidently your case is different. the earth field consists of several components, the dominant of which is the earth dipolar field. it has a maximum of about 1/2 oersted ot so. this field by itself does not cause a lot of grief with crt's unless it polarizes adjacent metal parts.

metal chairs and any adjacent metal frame work are characterized by much larger fields, fields that are capable of affecting the crt. you might try demagnetizing these instead of the shielding route.

 

[nbucska]

Use LCD terminals.


<nbucska@pcperipherals.com>