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In magnetic circuits we talk about reluctance instead of resistance. A change in the distance between two magnetic devices causes a change in reluctance. In this type of sensor, the pressure acts on a part of the magnetic circuit (movable core) and changes the reluctance between the coils. The amplitude of the displacement is proportional to the output voltage which is used to calculate the applied pressure.
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These sensors use a vibrating element which frequency of vibration depends on the force applied to it. This element is made from ferromagnetic material and induces voltage supplied by a detection coil, between two magnets, which is consecutively amplified and passed to an excitation coilmeasured. This voltage reflects the frequency of vibrations which follow a mathematical model to derive the pressure. The sensing element can be the vibrating element itself or connected to it.
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