I do not know what the sensor in my scale really does, I opened the scale
for cleaning, not snooping ;-). The sensors are almost always a movable
horizontal plate coupled with the dish moving parallel with and between
two fixed plates, against a spring. The more accurate springs are
horseshoe-shaped (derived from NIST proving ring shapes ?). I once built a
sensor out of a differential variable capacitor (the kind where the fixed
stack can be sawed through in the middle). It worked by moving (not
turning) the rotor towards one or the other of the fixed stacks.

Peter

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