Strange Problem With Monitor being around Microwave..

[none]

"Jerry G." bravely wrote to "All" (20 Feb 05 22:20:24)
--- on the heady topic of "Re: Strange Problem With Monitor being around
Microwave.."


It could simply be the MWO triac leaving notches in the power line ac
and this harmonic rich waveform is modulating the monitor's supply.
IOW the monitor's line regulation is rather poor. Try it on a
different breaker circuit, that might clear up the problem. I can't
believe the magnetic leakage from the MWO transformer is that great.
However the shielding on many monitors is scant to non-existant so it
wouldn't be too surprising.


JG> From: "Jerry G." <[email protected]>
JG> Xref: aeinews sci.electronics.repair:11081 sci.electronics.misc:3798

JG> The magnetic field from the microwave, and possibly to a smaller
JG> degree, the electrical wiring near the microwave that is supplying it,
JG> is creating a magnetic field that the particular monitor is sensitive
JG> to. This will not have a permanent effect on the monitor, but would be
JG> annoying to someone like me.

JG> If you move them a few more feet apart, you will see the effect
JG> decrease.
JG> If you were to have an LCD type screen, there would be no effect from
JG> magnetic fields, unless they were excessively strong.

JG> --

JG> Jerry G.
JG> ======


JG>
JG> Does anyone know what would cause this to happen :
JG> In my apt, I've got my monitor set up so that it's in my living
JG> room, theres a 'window' to the kitchen where I have my Microwave. They
JG> are around 5' apart. When I turn my microwave on I get a noticable
JG> shaking on my screen. It only has happpened with my new monitor ( Dell
JG> - Sony Trinitron 19" model M991). Do I have anything to worry about as
JG> far as ruining the display ?

JG> tia ,

JG> jason bean

... High Voltage Electronics: Life's a glitch, then you fry.

I have the same problem with mine. Every time the microwave is turned
on I get slight blurring and jitters.
The monitor is in my office opposite the kitchen.(micro is on the
other side of the wall.)
Been doing this for years and hasn't harmed my monitor in any way yet.

 

[Jim Adney]

Not so; you're forgetting the AC power line itself, which
obviously is carrying a fairly high current wheneve the
microwave is operating.

That's true, and I hadn't thought of that, but the amount of magnetic
field it would create really just depends on the amount of area inside
the current loop. Assuming that this is wired in the usual way, that
loop is pretty small, since the two conductors are parallel to each
other and maybe just 1/4" apart.

I don't think that would do it, but if there was some sort of wierd
(and possibly illegal) wiring scheme that created a current loop that
surrounded the room, then that would certainly cause such a problem.

-

 

[jason b]

Does anyone know what would cause this to happen :
In my apt, I've got my monitor set up so that it's in my living
room, theres a 'window' to the kitchen where I have my Microwave. They
are around 5' apart. When I turn my microwave on I get a noticable
shaking on my screen. It only has happpened with my new monitor ( Dell
- Sony Trinitron 19" model M991). Do I have anything to worry about as
far as ruining the display ?

tia ,

jason bean

Thanks all. Good to hear it's not messing up anything that's all I
care really...


jason




--
((¯`'·.¸(¯`'·.((¯`'·.¸ * jason bean* ¸.·'´¯))¸.·'´¯)¸.·'´¯))

For me , said Sherlock Holmes, "there still remains the cocaine bottle,"
and he reached his hand up for it.

http://home.cogeco.ca/~jabean
http://musicpage.kicks-ass.org/

 

[Bob Myers]

That's true, and I hadn't thought of that, but the amount of magnetic
field it would create really just depends on the amount of area inside
the current loop. Assuming that this is wired in the usual way, that
loop is pretty small, since the two conductors are parallel to each
other and maybe just 1/4" apart.

Yes, you'd think it was pretty small - but this happens all the
time. It just doesn't take that much field to affect the typical
CRT display. (I've seen AC fields all the way down to 0.1 Gauss
or a bit less still result in visible movement on the screen, during
mag. susceptibility testing - and just to put that in context, that's
something like a fifth of the strength of the Earth's field typical
in North America.) The problem is that it's an alternating
field; low-level DC fields simply cause a static displacement,
which you'll either ignore or adjust out with the centering controls,
but an AC field results in a very annoying jitter.

Bob M.

 

[Terry]

It's normal. Move them further apart.

Plugged into same or adjacent AC circuit?
Doubt if it is Microwave RF field; they are not supposed to leak that much
if properly buttoned up even though there is several hundred watts of
microwave RF floating around inside to cook/heat the food.
So that means interference either magnetic field and/or distortion of the AC
waveform due to the m.wave transformer saturating each half cycle (120 times
a second?). Read somewhere that those m.wave mains transformers which feed
voltage doubling rectifier circuits for up to 5 to 6 Kv Dc for the magnetron
do operate into saturation, waveform not being important.

 

[Terry]

Hopefully nobody wears a
pacemaker in that house.

Excellent point:
Sometimes see notices in restaurants and lunch rooms where 'customers' may
microwave food themselves
"Microwave in use"; as a warning to pacemaker users! Also at an airport
lunch counter where microwave was in use by serving staff.

 

[NSM]

Excellent point:
Sometimes see notices in restaurants and lunch rooms where 'customers' may
microwave food themselves
"Microwave in use"; as a warning to pacemaker users! Also at an airport
lunch counter where microwave was in use by serving staff.

I've never believed that was more than a stupid warning, i.e. rubber ducky
marked "Not a Flotation Device"!

N

 

[Michael A. Terrell]

The warning is in case the door seal becomes defective. The leaking
high power RF can cause erratic operation or total failure of the
electronics in their pacemaker. Microwave ovens in commercial settings
get a lot of use so the chances of a failed seal are much higher.

I've never believed that was more than a stupid warning, i.e. rubber ducky
marked "Not a Flotation Device"!

N

That's exactly who the warning is for, "The stupid!" On the other
hand, if you cant swim, anything that floats may improve your chances of
keeping your head above water for a few more minutes but the toy maker
doesn't want to be sued if you drown anyway.