JPS6231856Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to an optical liquid level detector using an optical fiber, and has an extremely simple configuration and excellent reliability.
The purpose of the present invention is to provide an optical liquid level detector that can be safely used in systems that require explosion protection, such as gasoline tanks.

The liquid level detector according to this invention is constructed by bundling a first optical fiber having an optically rough surface and a second optical fiber having a smooth surface with their end surfaces aligned. One embodiment is shown in FIG. Reference numeral 1 denotes a first optical fiber, and a light emitting diode 2, for example, is provided at one end of the fiber as a light source. 3 is a second optical fiber, one end of which is provided with, for example, a photodiode 4 as a photodetector. These first and second
The optical fibers 1 and 3 are bundled with their other ends aligned. The end surface 1a of the first optical fiber 1 is an optically rough surface. These optical fiber bundles are fixed at a certain height in a container containing water, with their end faces facing, for example, the water surface 5 to be detected.

With this configuration, when the end surfaces 1a and 3a are above the water surface 5, the light introduced from the light emitting diode 2 to the first optical fiber 1 is scattered by the optically rough end surface 1a. Some of the light is reflected through the optical fiber 1 toward the light emitting diode 2. Of the reflected light, the reflection angle is optical fiber 1
Optical fiber 1 has a numerical aperture NA larger than
passes through the core and cladding of the optical fiber 2 and leaks into the adjacent optical fiber 2. A part of the light leaking into the optical fiber 2 propagates through the optical fiber 2 toward the photodiode 4 and is detected by the photodiode.

On the other hand, when the water surface 5 rises and the end surface 1a of the optical fiber 1 sinks below the water surface 5 as shown in FIG. It travels straight into the water without scattering, and the photodiode 4 has no output.

Therefore, by monitoring the output of the photodiode 4, the level of the water surface 5 can be known.

This liquid level detector can be used for various purposes. For example, it is useful when automating water supply and drainage in a fully automatic washing machine. That is, in order to automate water supply, the end surfaces 1a and 3a of the optical fibers 1 and 3 are fixed at a constant level, and the water surface is
The change in the output of the photodiode 4 when the temperature reaches a, 3a is taken out and used as a control signal, and the water supply can be controlled to be stopped using this signal.

Furthermore, since this liquid level detector uses an optical fiber as a liquid sensitive surface element, it is useful for application to things that require explosion protection, such as gasoline tanks.

Further, in the embodiment, the optical fibers 1 and 3 are fixed to detect whether or not the water surface 5 has reached a certain level, but it is of course possible to use it as a mobile liquid level gauge. That is, by dropping the optical fibers 1 and 3 from the upper end of the liquid container, the point at which the output of the photodiode 4 disappears is determined, and the liquid level position can be determined from the length of the optical fiber hanging down at this point.

Furthermore, other light sources such as miniature light bulbs may be used instead of the light emitting diode 2, and other photodetectors such as phototransistors and solar cells may be used instead of the photodiode 4.

As explained above, the liquid level detector according to this invention has a very simple structure, 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.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the optical liquid level detector according to this invention, and FIG. 2 is a diagram showing the state in which the tip thereof is submerged under the water surface. DESCRIPTION OF SYMBOLS 1... First optical fiber, 1a... End face (optically rough surface), 2... Light emitting diode, 3... Second optical fiber, 3a... End face (smooth surface), 4... Photodiode, 5 ...Water surface.

Claims (1)

[Scope of utility model registration request] The other ends of first and second optical fibers, each having a light source and a photodetector optically coupled to one end thereof, are aligned and bundled, and the end face of the first optical fiber opposite to the light source is optically coupled. An optical liquid level detector characterized by a rough surface.