Date: Sat, 12 Apr 1997 06:26:05 -0400 (EDT) From: Perry Malouf <pmalouf@access.digex.net> To: cp@opus.hpl.hp.com Message-Id: <aabcdefg1393$foo@default> Subject: Re: TC, Microwaves and Pings
John Walker wrote:
> I regularly put metal... in the microwave while it is operating...
>
> The rules you have to follow are simple:
>
> 1) Do not let any metalic object come into contact with the inside
> surface of the oven. Electrical arcing will result if you do!
>
> 2) Cover the meal (or what ever your heating that contains metal) with
> a paper towel. Electrical arcing will result if you do not!
>
> If you follow these two rules, and do not allow an unblocked path for the
> electricity to arc from the metal utensil to the inside of the oven,
> electrical arcing will not occur and you will be free to enjoy your meal or
> what ever your heating.
Well, John, I feel obliged to address these observations for the
benefit of all concerned parties. I'm an electrical engineer,
specializing in microwaves.
Your described observations, above, are not general phenomena.
In fact I've seen the opposite of what you described. I've
seen arcing from one point to another on the same metallic
trace (independent of covering with a paper towel) and I've
never seen arcing from an object to the side of a microwave oven
(although I'm confident that it does happen).
There are microwave ovens that come with metal shelves inside,
and they do fine.
Unless the microwave oven is designed for it, though, it's
a good idea to avoid putting metal inside for a couple of
reasons.
The lesser reason is that the arcing can cause cosmetic damage
to the metal object. For example, some coffee mugs have metal
traces on the lip for decoration. The arcing along that trace
will cause cosmetic damage.
The greater reason is that it is possible to damage the oven
itself. The magnetron tube in a microwave is supposed to
deliver power to a "load". A "load" is something that absorbs
microwaves, like food (mostly the water contained therein).
The favored operating condition is for the magnetron to
produce high power microwaves and send them into the oven,
never to see them again.
Metals reflect microwaves. So the magnetron sees high
power microwaves coming back at it. It doesn't like
that.
But the ovens must be designed to handle varying loads.
The range can extend from a small muffin to a large
roast beef. The ovens must be able to handle the
varying loads, so the designers put in various things
to keep the magnetron happy over a wide range.
That's why a lot of people get away with putting
metal inside their ovens.
BUT IT'S NEVER _GUARANTEED_ to be harmless to an oven.
Regards,
Perry Malouf
This archive was generated by hypermail 2b30 : Tue Jan 02 2001 - 17:31:01 PST