PURPOSE: To make operability and responsibility satisfactory by employing an optical fiber as vibrating members, leading the rays of light in the interior of the optical fiber, emitting it out of the other end and detecting optically the displacement amount of the vibrating members as the displacement of a luminescent spot due to the light.
CONSTITUTION: When an electrode 6 applies a voltage at the same frequency as the inherent vibration number of the fiber 3, it is made in the resonance state, and a fiber tip 15 vibrates at an amplitude (x). An array photosensor 5 can detect the position of the fiber tip 15 as the movement of the luminescent spot due to the light led to the fiber from a fiber end 2. The amplitude (x) of the fiber tip 15 depends deeply on the pressure of atmosphere, and a vacuum degree can be obtained from the amplitude (x) by a control arithmetic circuit 12 with the aid of the relationship between the vacuum degree and the amplitude (x).
SATO KAZUO
TERASAWA TSUNEO
TANAKA SHINJI
KONDO YATARO
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