Date: Mon, 14 Apr 1997 14:48:11 -0700 From: John Walker <jorwa@syspac.com> To: cp@opus.hpl.hp.com Message-Id: <aabcdefg1437$foo@default> Subject: Re: TC, Microwaves and Pings
At 03:30 AM 4/12/97 -0700, you wrote:
>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
****************************************
Perry,
I would certainly have to defer to your expertise in this matter. I just
know what works for me. Also, I was not thinking about just putting metal
in the oven i.e. forceps. With no liquid to absorb the microwaves I have no
idea what would happen. I usally have only a little metal and a lot of food
in the oven.
I certainly would not want to be responsible (disclaimer) for someone's
microwave oven being harmed. I just pass along my personal experiences.
Regards,
John in Phoenix
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