| 摘要 |
A contraction monitor includes an optical strain gauge having a frame and a reed flexible with respect to the frame. A light emitting element and a photosensitive element are provided with one of the elements fixed to the frame and the other of the elements carried by the reed to vary the distance separating the elements. The resulting signal from the photosensitive element, which has a magnitude variable with the separation distance, provides an indication of the strain in the reed. Two pair of optical elements can be provided to eliminate common mode variations. The resulting signal can be processed in a differential amplifier having degenerative feedback loops to further swamp temperature sensitive parameters. The sum of the currents from the photosensitive elements can be maintained constant by driving the light emitting elements with the output signal. This provides the output signal with linear characteristics over a relatively wide range of deflections.
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