JPH07260552A - Magnet float type level gauge - Google Patents

Abstract

PURPOSE:To provide a magnet float type level gauge of high resolution at a low cost by providing plural stages of magnets in a float following the liquid level. CONSTITUTION:A pipe 2 is inserted through the hole 3a of a hollow doughnut shaped float 3, and the float 3 ascends and descends in the axial direction of the pipe 2 following the vertical fluctuation of the liquid level 4. Two magnets A, B are provided in two vertical stages with a space (a) in the float 3, and magnetic flux passes in the pipe 2. Magnetic sensitive switches S are disposed vertically at equal spaces (d) in the pipe 2. The switches S positioned near the magnets A, B are put in the conductive state. The number of the switches S put in the conductive state changes in association with the movement of the magnets A, B, and it is so set that the phase of the change has phase difference among the respective switch groups. The position of each switch group is corrected by an arithmetic circuit to compute the liquid level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnet float type liquid level gauge mainly used in a closed tank.

[0002]

2. Description of the Related Art FIGS. 4 and 5 show an example of a conventional magnet float type liquid level gauge, which penetrates a hollow donut-shaped float 22 having a built-in magnet 21 and a hole 22a at the center of the float and a lower end. It is composed of a closed pipe 23 and a device for detecting the position of the float 22.

This type of level gauge has a large number of magnetic sensitive switches S ₁ , S ₂ , S along the longitudinal direction in the pipe 23.
₃ ... are arranged at equal intervals, magnetically sensitive switch S in the vicinity of the magnet 21 in the float the float 22
(S ₂ , S ₃ , and S _{4 in} FIG. 4) are brought into conduction, and the position of the float is obtained from the position of the switch in conduction.

At this time, when a plurality of magnetic sensitive switches are in the conducting state, the average position of the switches in the conducting state is output as the liquid level.

FIG. 6 shows a case where the liquid level rises by d / 2 from the state of FIG. 5, and in this case, the average position of the switches S ₂ and S ₃ which are in the conductive state is output as the liquid level. . That is, the resolution (measurement accuracy) of the conventional liquid level gauge shown in FIGS. 5 and 6 is 1/2 of the interval d of the magnetic sensitive switches.

[0006]

In the above-mentioned conventional level gauge, in order to improve the resolution, it is necessary to reduce the distance between the magnetic sensitive switches and arrange a larger number of switches. To double the number of magnetic sensitive switches, the number of magnetic sensitive switches was doubled, resulting in high device cost.

It is an object of the present invention to provide a magnet float type liquid level gauge having a high resolution at a low cost.

[0008]

Means for carrying out the present invention and its embodiments are as follows.

<Means> A large number of magnetic sensitive switches, which are hung vertically in the tank and closed at the lower end, are brought into conduction by sensing a magnetic flux density of a certain level or more, are arranged at equal intervals in the longitudinal direction of the pipe. Then, a float that follows the liquid surface is provided so as to be movable in the axial direction of the pipe, and a plurality of stages of magnets are provided in the float along the axial direction of the pipe. The switch groups that are made conductive by discontinuity are set, and the phase of the number of switch groups that are made conductive due to the displacement of the float is set so that there is a phase difference between each switch group. An arithmetic circuit for calculating the liquid level from the combination of the number of switches in the group and its position is provided.

<Embodiment> A large number of magnetic sensitive switches, which are hung vertically in a tank and closed at a lower end thereof, are brought into a conductive state in response to a magnetic flux density of a certain level or more are arranged at equal intervals in a longitudinal direction of the pipe. A float that follows the liquid level is provided so as to be movable in the axial direction of the pipe, and a plurality of stages of magnets are provided in the float along the axial direction of the pipe. Discontinuity between the switch groups that are made conductive by the magnetic flux, and the phase of the change in the number of switch groups that are made conductive due to the displacement of the float is based on the switch interval d and the number of magnet steps n. There is a phase difference of d / (2n) between them, and a calculation circuit for calculating the liquid level from the combination of the number of switches in each switch group and its position is provided.

[0011]

With the magnetic flux from the magnet in the float, a large number of magnetic sensitive switches arranged in the pipe are placed in the vicinity of the magnet.

The number of magnetically responsive switches brought into conduction by each magnet changes with the movement of the magnet, and the phase of the change is set so that there is a phase difference between each switch group. Thus, the position of each switch group is corrected by the combination of the number of switches in each switch group, and the liquid level is calculated.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. A pipe 2 having a closed lower end is vertically provided in a closed tank 1, and a hollow donut-shaped float 3 is provided by inserting the pipe 2 into a hole 3a penetrating the center of the float. The float 3 can be raised and lowered in the axial direction of the pipe 2 by following the vertical fluctuation of the liquid level 4.

There are two magnets A and B in the float 3.
Are provided in upper and lower two steps with a space a, and the magnetic flux passes through the pipe 2 with the upper and lower surfaces of each magnet as N and S poles.

Magnetic sensitive switches S are arranged in the pipe 2 in the vertical direction at equal intervals d, and the magnetic sensitive switches are connected via a power supply line 5 and a signal line 6 to an arithmetic circuit 7 provided outside the tank. Has been done.

When the magnetic sensitive switch S detects a magnetic flux density of a certain level or more, the magnetic sensitive switch S becomes conductive and outputs an ON signal. Its structure is a hall element that generates an electromotive force according to the detected magnetic flux density, and a hall element. And an comparator circuit that outputs an ON signal when a certain amount of power is input from the amplifier circuit.

FIG. 3 shows the measurement principle of the liquid level gauge according to the present invention from the positional relationship between the magnets A and B and the magnetic sensitive switch S.

In the figure, the middle position between the magnets A and B is the liquid surface, and there is no direct correlation between the thickness of the magnets and the magnetic force, but the thickness of the magnets A and B and the magnetic flux of the magnets make the switch conductive. The range of the magnetic flux density that can be set is the same, and the switch in the conductive state is shown in black.

In FIGS. 3A to 3D, the liquid level 8 is d in this order.
It shows a state of rising by / 4, and each magnet A,
A switch group that is made conductive by the magnetic flux of B (hereinafter,
The number of switches in each of the switch groups A'and B ') is 1, 2, 1, 2 ...
・ It turns out that it changes.

However, in the liquid level gauge of the present invention, the magnets A and B'are arranged so that the switch groups A'and B'are not continuous.
The distance between B and the magnets A and B is adjusted so as to shift the phase of the change in the number of switches of each switch group A ′ and B ′ due to the fluctuation of the liquid level by d / 4 minutes. , B ', the vertical fluctuation of d / 4 unit is detected from the combination of the numbers of switches.

The arithmetic circuit 7 obtains an ON signal sent from the magnetic sensitive switch via the signal line 6 to recognize the position of the switch group, and this position is corrected based on the combination of the number of switches of each switch group described above. To be done.

In the case of FIG. 3, the distance from the tank bottom 9 to the switch S _n in the non-conducting state between the switch groups A ′ and B ′ is defined as a reference liquid level L _n, and this is combined with the number of switches in each switch group. Liquid level L by adding the correction term ΔL set based on
To get

Table 1 below shows the correction term ΔL corresponding to (a) to (d) of FIG.

[0024]

[Table 1] Although the reference liquid level L is corrected based on the combination of the number of switches in each switch group in the above embodiment, in the example shown in FIG. 3, the switch groups A ′ and B ′ in the arithmetic circuit 7 are used. Switch number combination (1, 2),
The four combinations of (2,2), (2,1), and (1,1) are judged to be liquid level rises if they change in this order, and liquid level drop if they change in the opposite order. The liquid level may be output by counting as one set and calculating the counted number of times.

In the above embodiment, the magnetic forces of the magnets A and B are the same, but the magnetic forces of the upper and lower magnets do not have to be the same, and the number of switches brought into conduction by the magnetic flux. Also 1, 2,
It is assumed that the number changes with 1, 2, ... If the number changes with every d / 2, for example, 3, 4, 3, 4, ...
.. The magnet may be made to have a strong magnetic force or the setting of the comparator circuit of the magnetic sensitive switch may be changed so as to change to.

Further, the magnets may be provided in three or more stages in the vertical direction. For example, in the case of three stages, the phase of change in the number of switches for bringing each magnet into a conductive state is d / d with respect to the number of stages n of the magnet. (2n) That is, it is shifted by d / 6. Thus, the resolution of the liquid level gauge is d
It becomes / 6.

[0027]

Since the magnet float type liquid level gauge according to the present invention has the above-mentioned construction, the measurement accuracy can be remarkably improved without adding a magnetic sensitive switch.

Further, if the measurement accuracy is the same, the number of magnetic sensitive switches can be reduced to less than half that of the conventional one, and therefore the apparatus cost can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged vertical sectional view showing the float portion of the above.

FIG. 3 is a diagram showing a positional relationship between a magnet and a magnetic sensitive switch.

FIG. 4 is a vertical sectional view showing a float portion of a conventional liquid level gauge.

5 is a vertical cross-sectional view showing a state where the liquid level has risen from the state shown in FIG.

[Explanation of symbols]

 1 Tank 2 Pipe 3 Float 4 Liquid Level 5 Power Line 6 Signal Line 7 Arithmetic Circuit

Claims (1)

[Claims] 1. A large number of magnetic sensitive switches, which are hung vertically in a tank and closed at a lower end thereof, are in a conductive state in response to a magnetic flux density of a certain level or more and are arranged at equal intervals in a longitudinal direction of the pipe. , A float that follows the liquid level is provided so as to be movable in the axial direction of the pipe, and a plurality of stages of magnets are provided in the float along the axial direction of the pipe, and the spacing between the magnets is set by the magnetic flux from each magnet. Set the discontinuity between the switch groups that are made conductive, and set the phase of the number of switch groups that are made conductive to change with the displacement of the float so that there is a phase difference between each switch group. Magnet float type liquid level gauge provided with an arithmetic circuit for calculating the liquid level from the combination of the switch numbers and the positions.