Pressure sensitive displacement sensor

A pressure-sensitive displacement sensor comprises: (A) a contact portion which includes: a semi-conductive matrix layer containing conductive materials with a predetermined density, wherein the semi-conductive matrix layer is formed with a soft material having elasticity and has a resistance (Rx) under a normal condition without subjecting to a contact pressure, and when the semi-conductive layer is pressed, a density of the conductive materials in the semi-conductive matrix layer is increased due to compression of the soft semi-conductive layer, which results in reduction of the resistance (Rx); a first conductive layer disposed on a first surface of the semi-conductive matrix layer; and a second conductive layer disposed on a second surface of the semi-conductive matrix layer; (B) a first resistor having one side connected to the first conductive layer and the other side connected to a power source; (C) a second resistor having one side connected to the second conductive layer and the other side connected to ground; (D) a first voltage comparator having a plus terminal and a minus terminal, the minus terminal connected to the first conductive layer; (E) a second voltage comparator having a plus terminal and a minus terminal, the plus terminal connected to the second conductive layer; (F) a third resistor having one side connected to the power source and the other side connected to the plus terminal of the first voltage comparator; (G) a fourth resistor having one side connected to the plus terminal of the first voltage comparator and the other side connected to the minus terminal of the second voltage comparator; (H) a fifth resistor having one side connected to ground and the other side connected to the minus terminal of the second voltage comparator; and (I) an OR-gate connected to the outputs of the first and second voltage comparators and operable to output signals in response to the outputs of the first and second voltage comparators.