JPS59192921A - Optical liquid level detector - Google Patents

Abstract

PURPOSE:To detect a liquid level with high reliability by bending one optical fiber at one or plural points as bending points, and detecting a leakage of light at the bending points. CONSTITUTION:A light source such as a light emitting diode 2 is provided to one end surface of the optical fiber. Further, a photodiode 5, etc., is provided to the other end surface 4 of the optical fiber. Theose optical fiber parts 1 and 4 are bundled together equally. A part 3 is bending point of the optical fiber and light is easy to leak at this point; and this bending point 3 is fixed facing the surface 6 of water at specific height from a container which contains the water. When the water level rises up to the bending point 3 of the optical fiber, 60% of light admitted into the optical fiber on one side 1 is absorbed in the water, so the water level is known sensitively by a decrease in the output of the photodiode.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical liquid level detector using optical fiber for liquid level detection and liquid level control.

Conventional optical liquid level detectors are susceptible to the effects of ambient light and cannot be used with extremely thin optical fibers. In addition, careful attention and skill were required to process the optical end face and adjust the detection sensitivity.

This invention does not require any skill to manufacture the liquid level detector.
To provide an optical liquid level detector that has a very simple and inexpensive configuration, has excellent reliability, can be applied even with extremely thin optical fibers, and can be used safely regardless of the color or flammability of the liquid. With the goal.

The liquid level detector according to the present invention is constructed by bending one optical fiber at one or several locations, providing a bending point, aligning the other ends, and bundling. An example in which an optical fiber having a diameter of 0.5 sugar and a length of 2 m is applied and has one bending point will be described below with reference to the drawings.

In FIG. 1, 1 is one side of the optical fiber,
For example, a light emitting diode 2 is provided on the end face as a light source. 4 is the other side of the optical fiber, and a photodiode 5, for example, is provided on the end face thereof. These optical fibers 1.4 on both sides are bundled together. 3 is the bending point of the optical fiber, and light easily leaks from this part. These optical fiber bundles are fixed at a certain height in a container containing water, with their bending points 3 facing, for example, the water surface 6 to be detected.

With such a configuration, when the bending point 3 is above the water surface 6, all the light introduced from the light emitting diode 2 to one side 1 of the optical fiber is transmitted to the other side 4 of the optical fiber.
can be detected by the photodiode 5.

On the other hand, when the water surface 6 rises and comes into contact with the bending point 3 of the optical fiber as shown in FIG. decreases by more than half.

Therefore, by monitoring the output of the photodiode 5, the level of the water surface 6 can be known.

The same results were also obtained for liquids such as soy sauce and sewing machine oil. Furthermore, by making three bending points, one liquid level detector can be fixed at a constant level.
We were able to detect liquid levels at three locations.

This liquid level detector can be used for various purposes. This analogy is useful when automating water supply in a fully automatic washing machine. That is, in order to automate water supply, the bending point 3 of the optical fiber is fixed at a constant level, and the change in the output of the photodiode 5 when the water surface touches this bending point 3 is taken out and used as a control signal. All you have to do is control it so that it stops.

Furthermore, since this liquid level detector uses an optical fiber, it is useful as an explosion-proof measure even for flammable liquids such as gasoline.

Further, although an optical fiber with a diameter of about 0.5 mm was used in the embodiment, it is also possible to use a thinner optical fiber, which is also useful for detecting liquid levels in extremely narrow spaces.

Furthermore, instead of the light emitting diode 2, another light source such as a miniature light bulb may be used, and instead of the photodiode 5, a photodetector such as a phototransistor or a solar cell may be used.

As explained above, the liquid level detector according to the present invention has a very simple structure and is inexpensive, has excellent reliability because it does not use mechanical contacts, and is suitable for systems that require explosion protection. It is extremely useful in practice, as it can be applied with confidence, and liquid levels at multiple locations can be easily detected with a single detector.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of an optical liquid level detector according to the present invention, and FIG. 2 is a diagram showing a state in which the tip thereof is in contact with the water surface. 1... Optical fiber on one side, 2... Light emitting diode, 3... Optical fiber bending point, 4...
...Optical fiber on the other side, 5...Photodiode, 6...Water surface, Patent Applicant Seiko Imoto Figure 1

Claims (1)

[Claims] 1 with a light source and a photodetector optically coupled to each end
1. An optical liquid level detector characterized in that an optical fiber of a book is bent at one or several places to provide a bending point, and is equipped with means for detecting light leakage at the bending point.