Importance

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Abstract

An optical liquid sensor comprises an optical fiber folded back in two, a light-emitting element disposed at one end of the optical fiber, a light-receiving element disposed at the other end, and a detection means comprising a pair of units of a rod lens and/or large-diameter glass optical fiber with a narrow gap interposed therebetween in a linear segment of a folded-back portion of the optical fiber, the folded-back portion being hermetically sealed except at an aperture portion for admitting a liquid into the narrow gap. In this sensor, the loss of light at the narrow gap is minimized. In the manufacture of the sensor, a special jig is used for insuring that a rod lens or the like is accommodated in a metal sheath in such a manner that its forward end is flush with the end face of the sheath or projects slightly beyond the end face. Furthermore, by using the above sensor, there is provided an on oil/battery checker which can be used for determination of the degree of degradation of engine oil and detection of the charge voltage of a car battery.

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First Claim