| 摘要 |
A device for optically displaying the pressure of a medium comprises a housing, a piston within the housing which is movable along a longitudinal axis against a restoring force, and an optically transparent element within the housing having a display surface which is visible from outside the housing. An inner wall of the optically transparent element delimits a cavity which is open towards the piston. A surface of a first color, e.g., green, is mounted on the piston and is movable therewith, the colored surface being received within the cavity of the optically transparent element. The optically transparent element includes a circumferential zone of a second color, e.g., red, which colored zone is not directly visible from outside the housing through the display surface. When pressure exerted by the medium on the piston is too low, the restoring force keeps the colored surface away from the inner wall and reflects light rays emanating from the colored zone through the display surface, while reflecting back the light rays from the colored surface. In this condition, the color red is visible through the display surface. When the pressure exerted by the medium overcomes the restoring force so that the colored surface presses against the inner wall, light rays emanating from the colored surface are transmitted through the display surface, while light rays emanating from the colored zone are reflected back onto the housing. In this condition, the color green is visible through the display surface.
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