| 摘要 |
PROBLEM TO BE SOLVED: To obtain a liquid level detecting apparatus, by which a plurality of levels are detected, by arranging light-receiving and light-emitting parts in a row, connecting light- receiving elements in series, and burying light-emitting elements and the light-receiving elements inside a package mace of a transparent material. SOLUTION: Light-receiving elements 33a, 33b, 33c are fixed and bonded with a conductive adhesive to prescribed positions on copper foils 30e, 30f, 30g which correspond to three light- emitting elements 31a, 31b, 31c in such a way that on ende of each of electrodes comes into contact with each of the copper foils, and electrodes on the other side are wired to prescribed parts on the copper foils. A printed-circuit board 30 which is provided with a first light- receiving and light-emitting part, a second light-receiving and light-emitting part and a third light-receiving and light-emitting part which are constituted of the respective light-emitting elements 31a, 31b, 31c and of the respective light-receiving elements 33a, 33b, 33c is loaded into the inside of a package 37 which is formed of a transparent material while its edge on the other side is left. When a level detecting element is situated inside a liquid, a beam of light is not reflected by the surface of the package 37, it is readapted to the outside, and it is not incident on the light-receiving elements. When the level detecting element is situated in the air, the beam of light is reflected by the surface, and it is incident on the light receiving elements. When the light receiving and light-emitting parts come out to the air from the liquid, internal resistances of the light-receiving elements are lowered, and photocurrents flow. When the photocurrents are detected, a level can be discriminated. |
