Microwave oven temperature probe port grounding

[Tom Del Rosso]

Just wondering what would happen if a metal container was used in a
microwave, but grounded to the phono jack for the temperature probe.
Assuming the connection was good, of course.

 

[bz]

Just wondering what would happen if a metal container was used in a
microwave, but grounded to the phono jack for the temperature probe.
Assuming the connection was good, of course.

The 'grounding' would not help.

A 'good ground' at microwave frequencies would be much less than 1/4 wave.
The wavelength is about 3 cm.

A good ground would thus need to be much less than 1/2 cm.

A metal container is probably going to arc to the inside of the oven in
several places.

It may detune the cavity badly enough to present a high SWR to the magnetron
and damage or destroy the magnetron.

--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

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[Michael A. Terrell]

Just wondering what would happen if a metal container was used in a
microwave, but grounded to the phono jack for the temperature probe.
Assuming the connection was good, of course.

The wavelength is too short for any effective grounding, and that is
a 1/4" Phone jack, not a phono jack.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Tom Del Rosso]

The 'grounding' would not help.

A 'good ground' at microwave frequencies would be much less than 1/4
wave. The wavelength is about 3 cm.

A good ground would thus need to be much less than 1/2 cm.

A metal container is probably going to arc to the inside of the oven
in several places.

It may detune the cavity badly enough to present a high SWR to the
magnetron and damage or destroy the magnetron.

Very interesting. I thought the wavelength was a few inches.

So how does the probe get away with it?

 

[Sam Goldwasser]

Very interesting. I thought the wavelength was a few inches.

He meant to say 1/4 wavelength is around 3 cm. The wavelength is
a few inches, like around 5 inches.

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[bz]

He meant to say 1/4 wavelength is around 3 cm. The wavelength is
a few inches, like around 5 inches.

Actually, I was thinking x-band radar was very close to the microwave oven
frequency. I was wrong.

The X band ranges from 7 to 12.5 GHz.
The microwave ovens actually operate in the S band, the 10 cm radar band. The
S band covers from 2 to 4 GHz.

According to http://hypertextbook.com/facts/1998/HowardCheung.shtml
most microwave ovens operate on 2.45 GHz which gives 11.8 cm wavelength, 4.6
inches, for a quarter wave of a little over one inch or 2.95 cm

In any case, it is still a bad idea to put any metal bowls into your
microwave over, unless the metal object has been designed for use in a
microwave oven.



--
bz 73 de N5BZ k
I fixed radars for a living in the mid 70's. I had a 1st class radiotelephone
license, second class radio telegraph license with ship radar endorsements.

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

[email protected] remove ch100-5 to avoid spam trap

 

[Tom Del Rosso]

He meant to say 1/4 wavelength is around 3 cm. The wavelength is
a few inches, like around 5 inches.

Ok, but the probe is over 6 inches long without the plug, so why doesn't it
collect a charge? I always assumed it was because of the grounded plug.