JPH0416720A - Measuring method of liquid surface level - Google Patents

Abstract

PURPOSE:To calculate the level of the liquid surface by a method wherein thin light beams are projected to the liquid surface from above while the liquid surface is oscillated, and the regularly reflected light from the liquid surface is received by a photodetecting part of a laser distance sensor. CONSTITUTION:A liquid M is stored in a tank 1. A light emitting device 2 and a laser distance sensor 3 are provided confronting to each other above the liquid surface of the tank 1 provided with an oscillating means for oscillating the liquid surface. Each image sensor 6 constituting the laser distance sensor 3 is placed along the position where the laser beam from the light emitting device 2 which is regularly reflected by a light spot formed on the vibrated liquid surface forms an image. The laser beam is deflected in various directions according to the vibration of the liquid surface. Therefore, a part of the deflected laser beams enters a lens 5 even when the liquid surface is at such a height that the regularly reflected light does not enter in general. The reflected light at the liquid surface forms an image at the image sensor 6, and the level of the liquid surface can be calculated by an operating device from the position where the image is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for measuring a liquid level in, for example, an oil tank or a water tank.

[Prior Art] Measuring the liquid level in an oil tank, water tank, or gutter is necessary in order to estimate the storage amount and flow rate.

One method for this purpose is to float a float with a wire on the liquid surface and measure the position of the float from the vertical movement of the wire. Furthermore, as a method for remotely detecting the position of an object, there is a method in which a real image of a light spot on the object is formed on a light receiver, and the position of the object is measured from that position. Since the light spot is created by detecting the light diffusely reflected by the microscopic irregularities on the surface of the object using the light receiver, the incident angle of the laser beam with respect to the surface is not particularly limited.

[Problems to be Solved by the Invention] However, in the conventional method as described above, sufficient accuracy cannot be obtained when using a float, and the liquid is high temperature and highly corrosive. In some cases, there have been problems such as short durability, difficulty in stable operation, high wear and tear, and uneconomical performance.

On the other hand, the method of detecting the position of a light spot is easy to automate; however, light usually does not reflect diffusely at the liquid surface, and therefore, by setting the emitter and receiver, the level measurement range covers the area where the light is received. Since the diameter of the lens is limited, for example, as shown in FIG.
2 above the liquid surface to detect specularly reflected light, the reflection angle of the specularly reflected light is always the same, so if the liquid level changes, the reflected light will no longer enter the receiver 12. Put it away.

[Means for Solving the Problems] In order to solve the above problems, the present invention irradiates the liquid surface with a laser beam or a similar narrow light beam from above while shaking the liquid surface, The specularly reflected light from the liquid surface is received by the light receiving part of the laser distance meter, and the liquid level is calculated.

Since specularly reflected light has a higher light intensity than diffusely reflected light, using an appropriate filter to reduce the amount of light received can reduce noise caused by diffusely reflected light and light from other light sources.
Almost only specularly reflected light can be received.

[Operation] In this method of measuring the liquid level, the reflected light from the surface of the liquid is guided to the receiver by giving fluctuations to the liquid level and changing the reflection direction of the specularly reflected light. The liquid level is calculated by determining the position on the image sensor in the light receiver.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, light emitters 2, which are light sources, are placed at mutually opposing positions above the liquid level in a storage tank l that stores liquid M.
and a laser distance meter 3 are installed.

The light emitter 2 is installed so that its tip axis forms a predetermined angle θ with respect to the liquid level.

The laser distance meter 3 consists of a filter 4, a lens 5, and an image sensor 6 which is an assembly of light receiving elements. It is arranged along the position where the laser beam specularly reflected by the lens 4 forms an image. That is, in the figure, A , B on the liquid surface,
Images of the light spots at points C and D are formed through the lens 5 at positions a, b, c, and d on the image sensor, respectively.

The output terminal of the laser distance meter 3 is connected to a calculation device (not shown), and this calculation device calculates the liquid level based on the output of the laser distance meter 3, and displays it on a device such as a display panel or controls the liquid level. input to the device.

This storage tank l is provided with a means for shaking the liquid level (path shown), which can be achieved by using any appropriate means such as a stirring device such as a screw, a device that vibrates the storage tank wall, or a device that blows air onto the liquid surface. It's okay to be.

Next, the laser distance meter 3 configured as described above
Explain how to measure the liquid level.

Since the liquid level is oscillated by the oscillating means, the laser beam from the light emitter 2 swings in various directions according to the oscillation of the liquid level. Therefore, a portion of the deflected light beam enters the lens 5 even at a liquid surface height that would not enter the lens 5 at a normal specular reflection position. Since the image sensor 6 is placed in advance at a position where the reflected light of the laser beam from the light emitter 2 is formed into an image, the reflected light on the liquid surface is reflected by the image sensor 6.
The image is formed in a one-to-one correspondence with the liquid level. Therefore, the level of the liquid level can be calculated from the imaging position.

Inside the "storage tank", the liquid surface oscillates due to the oscillating means and exists as a standing wave, and the direction and height of the waves are also constant, so the direction and height of the waves and the orientation of the laser distance meter 3 must be adjusted appropriately. If set to , detection signals will be obtained at appropriate intervals, allowing continuous level measurement.

Note that the above embodiment was applied to an oil tank or a water tank, but
Needless to say, it can be applied to venereal food solutions and high-temperature metal melting fields.

[Effects of the Invention] As described in detail above, the present invention irradiates a laser beam or a similar narrow light beam onto the liquid surface from above while swinging the liquid surface, and collects specularly reflected light from the liquid surface. is received by the light receiving part of the laser distance meter and the liquid level is calculated, so the surface level of the liquid in a sealed space can be automatically, accurately, and continuously measured. This has excellent effects such as being able to control production and quality based on this measurement data.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing a case where a conventional method is applied to liquid level measurement. 1...Storage tank, 2...Light emitter, 3...
Laser distance meter, 4... Filter 5... Lens, 6... Image sensor, M... Liquid.

Claims (1)

[Claims] While shaking the liquid level, a laser beam or similar narrow light beam is irradiated onto the liquid surface from above, and the specularly reflected light from the liquid surface is received by the receiver of the laser rangefinder to calculate the liquid level. A liquid level measuring method characterized by: