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Mark rainess
I am building a machine that uses a microwave oven. I need a simple and
cheap way to reliably determine 1) that the magnetron is operating, and
2) that the oven cavity is not empty.
My first attempt was a diode RF sensor on a board mounted outside the
cavity with a short probe projecting inside through a hole. The food
item being heated moves relative to the probe and causes the response to
increase and decrease as it acts on the E field. When I see the changing
response I know the magnetron is working and the oven is not empty. This
works fine if the food is by itself; but, the food rests on ceramic
which moves. The ceramic material influences the E field to a large
degree and makes it impossible to detect the food item. I can't
eliminate the ceramic or change to another material. It seems I need an
entirely different approach.
If I put two RF probes in the waveguide spaced one-quarter wavelength
apart, I think the phase relationship between the two probes will change
when the oven is empty.
I want to avoid the expense of adding a secondary waveguide in order to
make a directional coupler.
Does anyone have an idea for a simple cheap way to detect that the oven
is empty.
Mark
cheap way to reliably determine 1) that the magnetron is operating, and
2) that the oven cavity is not empty.
My first attempt was a diode RF sensor on a board mounted outside the
cavity with a short probe projecting inside through a hole. The food
item being heated moves relative to the probe and causes the response to
increase and decrease as it acts on the E field. When I see the changing
response I know the magnetron is working and the oven is not empty. This
works fine if the food is by itself; but, the food rests on ceramic
which moves. The ceramic material influences the E field to a large
degree and makes it impossible to detect the food item. I can't
eliminate the ceramic or change to another material. It seems I need an
entirely different approach.
If I put two RF probes in the waveguide spaced one-quarter wavelength
apart, I think the phase relationship between the two probes will change
when the oven is empty.
I want to avoid the expense of adding a secondary waveguide in order to
make a directional coupler.
Does anyone have an idea for a simple cheap way to detect that the oven
is empty.
Mark