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Cydrome Leader Cydrome Leader is offline
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Default Panasonic microwave, blown inverter board transformer

Jeff Liebermann wrote:
On Thu, 18 Jun 2020 23:22:57 +1000, Clifford Heath
wrote:

On 18/6/20 9:50 am, Jeff Liebermann wrote:
On Wed, 17 Jun 2020 06:55:26 +0000 (UTC), Cydrome Leader
wrote:
Lol, I've wondered about the "sensor" in these things. I know can't be
related to any sort of device that measures anything. Must be marketing
speak or a weirdly translated word.

It's a humidity sensor. When whatever you're cooking gets hot enough
to vaporize water, the "sensor" detects the water vapor and shuts off
the oven, usually after a short delay.


The vapor pressure of water rises very rapidly above 60 degrees C.
So presence of vapor is a good indicator of the outside temperature of
your food, even before the water starts to boil.

CH


Yep, but there's a little more to it. The 1978 Panasonic patent
agrees that it's the surface temperature that's important.
"Apparatus for controlling heating time utilizing humidity sensing"
https://patents.google.com/patent/US4097707
See "Description" section:
...it has been known to sense the temperature of the food
or degree of heating by measuring the change of humidity
which takes place as the food is heated. For example, in
most foods, water included therein abruptly evaporates
when the temperature of the food reaches 100? C and a
large amount of water vapor appears in the oven. By
detecting such change of humidity by a humidity sensor,
the time at which the humidity abruptly changes can be
related to the time at which the food has reached 100? C.

Further down the "Description" section, the patent explains how the
cooking time is extrapolated from the 100? C point and the target
temperature. Apparently, the humidity sensor is only interested in a
single point, where the air abruptly transitions from low humidity to
high humidity at 100? C. Everything else is done by temperature curve
extrapolation. Crude, but effective.


Hmm, sort of shocked there wasn't a "fuzzy logic" spin on all of that in
1988 or whenever that annoying as hell fad came out.