| 摘要 |
PURPOSE:To detect liquid level irrespectively of whether liquid is transparent or not and to make size small and also to prolong life by the constitution wherein an optically transparent plate having the 1st interface and the 2nd interface, as well as a light emitting element and a photodetector are combined. CONSTITUTION:A shield plate 6 is provided in order to prevent the refracted light in a transparent plate 1 of the time when liquid contact the 1st interface A and 2nd interface B of the plate 1 from advancing to the region D in the 2nd interface B. Now, if the liquid does not contact with the interfaces A, B, the light from a light emitting diode 3 refracts at the point P and the point Q and arrives at a phototransistor 4. On the other hand, if the liquid contacts with the interfaces A, B, the light from the diode 3 refracts in the direction of the point Q' at the point P, is shut off by the plate 6 and does not arrive at the phototransistor 4. Hence, depending upon whether the phototransistor 4 detects the light or not, the liquid level is easily detected. |
