PRESSURE SENSOR

PURPOSE:To improve detecting accuracy, by providing light emitting elements, light receiving elements, which receive light from said light emitting elements, a diaphragm, which converts the change in pressure into mechanical displacement, and a light shielding plate, which is associatively moved with the operation of said diaphragm. CONSTITUTION:Three pairs of a light emitting element 49a and a light receiving element 50a, a light emitting element 49b and a light receiving element 50b, and a light emitting element 49c and a light receiving element 50c are provided so as to face each other on one plane, which is in parallel with the diaphragm, through a light shielding plate 45. A light shielding plate having a slit 51, which passes only the light beams in front of the light receiving elements 50a, 50b, and 50c, is provided between the light receiving elements 50a, 50b, and 50c and the light shielding plate 45. When pressure, which is applied on the diaphragm, is a preset pressure, all the light beams from the light emitting elements 49a-49c do not reach the light receiving elements 50a-50c. In this constitution, the following property to pressure fluctuation and the detecting accuracy of the pressure can be improved.