JPS5848049B2 - Liquid level detection device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a liquid level detection device.

Conventionally, liquid level detection devices have been considered indispensable for controlling the liquid level, and many methods have been proposed and implemented. The main methods include floating the liquid and detecting it mechanically or electrically, or using a plurality of electrodes and determining the level of the liquid by determining the conduction between the electrodes.

An object of the present invention is to provide a new liquid level detection device that applies the principle of optical catadioptric refraction without relying on such conventional methods.

To explain in detail with reference to the figures below, FIG. 1A shows an embodiment of the present invention, in which light emitted from a light source 2 such as a light emitting diode installed on a fixture 1 changes slightly with respect to the direction of liquid surface displacement. The light reaches the photosensitive element 4 through the light transmitting body 3 having such a structure.

At this time, the optical path cross-sectional area S-S' at the water level 6 of the test liquid 5
limits the light from the light source 2, and in the case of FIG. 1, the amount of light received increases as the water level rises.

In this case, if there is a seat-separated portion 7 inside the light transmitting body 3, the effect will be further enhanced.

FIG. 1B is a side view of the liquid level detecting device shown in FIG. 1A, showing the seated portion 7. FIG.

The measurement principle is not clearly known.

However, one of the assumptions will be explained with reference to FIG. 1C, which shows a schematic sectional view when the liquid level is high, and FIG. 1D, which shows a schematic sectional view when the liquid level is low.

That is, when the liquid level is high, as shown in FIG. The light passes through the test liquid 5 having a refractive index close to 3, and is received by the photosensitive element 4 at a relatively acute angle with respect to the liquid level displacement direction.

However, when the liquid level is low, for example when the light transmitting body 3 is not immersed in the test liquid as shown in FIG. The light travels toward the photosensitive element 4 while being reflected many times at the total reflection surface on the side surface and the interface on the inner surface, but the more times the light is reflected, the more obtuse the angle between the light and the liquid surface displacement direction becomes.
This increases the amount of light that does not reach the photosensitive element 4 and is absorbed around it.

FIG. 2 shows an application example of the present invention, in which the wall 8 of the storage tank for the test liquid 5 is shown.
The same effect can be obtained by using a light transmitting member and providing a portion 7' corresponding to the seat part 7 shown in FIG.

That is, in this case, the optical path cross-sectional area at the water level 6' corresponds to S'', and the amount of light at the photosensitive element 4 changes as the water level changes.

FIG. 3 shows these results in a graph as a relationship between the amount of light and the water level. Based on this, changes in the water level can be easily controlled, and its industrial effects are significant.

[Brief explanation of drawings]

Figures 1A and B are cross-sectional views and side views of the liquid level detection device according to the present invention, Figures 1C and D are schematic cross-sectional views showing the measurement principle of the present invention, and Figure 2 is a schematic cross-sectional view of the liquid level detection device according to the present invention. FIG. 3 is a sectional view of a main part showing an example of an applied case, and is a graph showing the relationship between water level and light amount. 2: light source, 3: light transmitting body, S'/S': optical path cross-sectional area. 4: Photosensitive element, S

Claims (1)

[Claims] 1. In a liquid box detection device in which a light source and a photosensitive element are arranged with a light transmitting body in between, the optical path cross-sectional area of the light transmitting body becomes narrower from the light source to the photosensitive element with respect to the liquid level displacement direction. A liquid level detection device characterized by having a structure that changes slightly.