阅读说明：本技术 液位检测方法及液位传感器 (Liquid level detection method and liquid level sensor ) 是由 顾一新 于 2021-11-03 设计创作，主要内容包括：本发明公开了一种液位检测方法及液位传感器,属于液位测量技术领域,为解决现有液位检测方法精度低等问题而设计。本发明液位检测方法能沿电子管轴向移动的浮筒中对称布置有两块磁石,两块磁石的同极相对设置形成磁场,在电子管内的PCB上等间距地设置有多个用于采集磁场强度信号的隧道磁电阻元件,磁石的长度大于相邻两个隧道磁电阻元件之间的距离；浮筒移动时位于两块磁石之间的相邻两个隧道磁电阻元件检测到磁场强度变化并输出线性的检测结果,根据检测结果计算得到液位高度值。本发明液位检测方法及液位传感器使用隧道磁电阻元件来采集磁场强度信号,测量精度高,适用范围广,尤其适用于一些对测量精度要求比较高的领域,使用成本低。(The invention discloses a liquid level detection method and a liquid level sensor, belongs to the technical field of liquid level measurement, and is designed for solving the problems of low precision and the like of the existing liquid level detection method. The liquid level detection method can symmetrically arrange two magnets in a buoy moving along the axial direction of an electronic tube, homopolarities of the two magnets are oppositely arranged to form a magnetic field, a plurality of tunnel magneto-resistance elements for acquiring magnetic field intensity signals are arranged on a PCB in the electronic tube at equal intervals, and the lengths of the magnets are larger than the distance between two adjacent tunnel magneto-resistance elements; when the buoy moves, two adjacent tunnel magneto-resistance elements between the two magnets detect the change of the magnetic field intensity and output a linear detection result, and the liquid level height value is obtained through calculation according to the detection result. The liquid level detection method and the liquid level sensor of the invention use the tunnel magneto-resistance element to collect the magnetic field intensity signal, have high measurement precision and wide application range, are particularly suitable for the fields with higher requirements on the measurement precision, and have low use cost.)

1. The liquid level detection method is characterized in that two magnets (4) are symmetrically arranged in a buoy (3) capable of moving along the axial direction of an electronic tube (1), homopolarities of the two magnets (4) are oppositely arranged to form a magnetic field, a plurality of tunnel magneto-resistance elements (2) used for acquiring magnetic field intensity signals are arranged on a PCB (printed circuit board) in the electronic tube (1) at equal intervals, and the length of each magnet (4) is greater than the distance between every two adjacent tunnel magneto-resistance elements (2); be located two when flotation pontoon (3) remove adjacent two between magnetite (4) tunnel magneto resistance element (2) detect the magnetic field intensity change and output linear testing result, according to the testing result calculates and obtains the liquid level height value.

2. The method of claim 1, comprising the steps of:

and a step T1 of marking the output voltage value of the first tunneling magneto-resistance element (21) as V when the first tunneling magneto-resistance element is not influenced by the magnetic field_llnitial；

And T2, the magnets (4) move along with the buoy (3), when the first tunneling magneto-resistance element (21) is positioned between the two magnets (4), the position is recorded as the current position, and the output voltage value of the first tunneling magneto-resistance element (21) is recorded as V₁Current；

Step T3, recording the change value of the voltage detected by the tunnel magneto-resistance element (2) as Vmm when the buoy (3) moves for a set distance value;

step T4, outputting a voltage value V₁Current and V_lDividing the difference value of lnitial by Vmm to obtain the distance H between the first tunneling magneto-resistance element (21) and the plane of the designated position on the magnet (4) along the moving direction of the buoy (3),

a step T5 of adding or subtracting the distance H to or from the position H1 of the first tunneling magnetoresistive element (21) on the valve (1) to obtain a liquid level height value H,

wherein H is negative when the liquid level height is below H1, H is 0 when the liquid level height is equal to H1, and H is positive when the liquid level height is above H1.

3. The method of claim 1, comprising the steps of:

step Sl, when not influenced by the magnetic field, the output voltage value of the first tunneling magneto-resistance element (21) is marked as V_llnitial, the value of the output voltage of the second tunneling magneto-resistance element (22) is represented as V₂1nitial, the first tunneling magneto-resistance element (21) and the second tunneling magneto-resistance element (22) are two adjacent tunneling magneto-resistance elements (2) in the magnetic field range, and the first tunneling magneto-resistance element (21) is positioned above the second tunneling magneto-resistance element (22);

step S2, the magnets (4) move along with the float bowl (3), when the first tunneling magneto-resistance element (21) and the second tunneling magneto-resistance element (22) are both positioned between the two magnets (4), the position is recorded as the current position, and at the moment, the output voltage value of the first tunneling magneto-resistance element (21) is recorded as V₁The Current and the output voltage value of the second tunnel magneto-resistance element (22) are marked as V₂Current；

Step S3, outputting the voltage value V of the first tunnel magneto-resistance element (21)₁Current and V_lThe difference of lnitial is recorded as a first difference, and the output voltage value V of the second tunnel magneto-resistance element (22) is recorded₂Current and V₂The difference value of lnitial is recorded as a second difference value, the ratio of the first difference value to the second difference value is subjected to exponential n correction, and the distance H from the first tunnel magneto-resistance element (21) to the plane where the designated position on the magnet (4) is located along the moving direction of the buoy (3) is obtained after corresponding calculation;

and step S4, adding or subtracting the distance H according to the position H1 of the first tunneling magneto-resistance element (21) on the electronic tube (1) to obtain a liquid level height value, wherein H is negative when the liquid level height is lower than H1, H is 0 when the liquid level height is equal to H1, and H is positive when the liquid level height is higher than H1.

4. The liquid level detection method according to claim 3, wherein when the distance between two adjacent tunnel magnetoresistive elements (2) is L and the length of the magnet (4) is L + and a correction value is set, outputs of the first tunnel magnetoresistive element (21) for detecting the change of the magnetic field strength are all cosine curves, outputs of the second tunnel magnetoresistive element (22) for detecting the change of the magnetic field strength are all sine curves, and the phase difference between the first tunnel magnetoresistive element (21) and the second tunnel magnetoresistive element (22) is 90 degrees; the step S3 calculates the distance H according to the following formula,

wherein the value range of n is between 1.1 and 1.7.

5. A liquid level sensor for realizing the liquid level detection method according to any one of claims 1 to 4, characterized by comprising an electronic tube (1), wherein a plurality of tunnel magneto-resistance elements (2) for measuring the liquid level are sequentially arranged in the electronic tube (1) along the longitudinal direction, a float bowl (3) is rotatably sleeved on the outer side of the electronic tube (1), two magnets (4) are symmetrically arranged in the float bowl (3), the homopolar poles of the two magnets (4) face the tunnel magneto-resistance elements (2), and a magnetic field is formed between the two magnets (4); all tunnel magneto resistor component (2) equidistant setting and adjacent two distance between tunnel magneto resistor component (2) is L, every the length of magnetite (4) equals L + and sets for the correction value.

6. A level sensor according to claim 5, characterized in that a plurality of adjacent said tunneling magnetoresistive elements (2) are connected to a differential multiplexing switch; the plurality of differential multi-way selection switches are connected to a series-to-parallel switch, the series-to-parallel switch is connected to an impedance transformation circuit and a differential amplification circuit, and the differential amplification circuit is connected to a single chip microcomputer processing system (5); and the single chip microcomputer processing system (5) is respectively connected to the series-parallel switch and the output terminal to realize data acquisition, data processing and calculation result output.

7. The liquid level sensor of claim 6, further comprising a calibration device connected to the single-chip processing system through a digital interface; the calibration device is used for recording an initial output voltage value of the tunneling magneto-resistance element (2) and/or an assembly error value of the liquid level sensor.

8. The fluid level sensor according to claim 6, further comprising a micro control unit for correcting the electrical signal output from the output terminal, the micro control unit squaring the electrical signal output from the output terminal by a prescribed factor.

9. Level sensor according to any of claims 5 to 8, wherein the distance between the two magnets (4) is between 21mm and 26 mm.

10. A liquid level sensor according to any one of claims 5 to 8, characterized in that the liquid level sensor comprises a single-tube structure, i.e. the valve (1) provided with the tunnel magnetoresistive element (2), or a multi-tube structure; the multi-tube structure comprises the electronic tube (1), an engine oil suction tube (6) and an engine oil return tube (7).

Technical Field

The invention relates to the technical field of liquid level measurement, in particular to a liquid level detection method and a liquid level sensor for realizing the liquid level detection method.

Background

In some working conditions, liquid needs to be added into the container, and the height of the liquid in the container needs to be monitored in real time during use. Considering that many times the container is made of opaque material, the liquid level height cannot be directly observed, it is necessary to measure the liquid level height by using the change of physical parameters (such as capacitance, resistance, inductance, sound velocity and light velocity) of electricity or electricity caused by the difference of physical properties of media on two sides of the liquid level or the change of the liquid level.

One known detection method is to use the signal change of a magneto-resistive element in a magnetic field to realize liquid level measurement, wherein the magnetic field is provided by a magnet arranged in a buoy. Specifically, the sampling resistance values of the magnetoresistive elements at different positions in the magnetic field are different, so that the output voltages are different, and the height of the liquid level is calculated according to the change of the voltages.

In the prior art, the number of the magnetoresistive elements is often difficult to increase due to control cost, the distance between the magnetoresistive elements is difficult to set as small as possible due to processing difficulty, so that the measurement precision is easy to reduce, the requirements of some high-precision detection fields are difficult to meet, the application range is narrow, and meanwhile, the calculation precision correction of the measurement method is lacked.

Disclosure of Invention

One object of the present invention is to provide a liquid level detection method with high measurement accuracy.

Another object of the present invention is to provide a level sensor with high measurement accuracy.

To achieve the purpose, on one hand, the invention adopts the following technical scheme:

a liquid level detection method comprises the steps that two magnets are symmetrically arranged in a floating barrel capable of moving along the axial direction of an electronic tube, homopolarities of the two magnets are oppositely arranged to form a magnetic field, a plurality of tunnel magneto-resistance elements used for collecting magnetic field intensity signals are arranged on a PCB in the electronic tube at equal intervals, and the lengths of the magnets are larger than the distance between every two adjacent tunnel magneto-resistance elements; the flotation pontoon is located two when removing adjacent two between the magnetite tunnel magneto resistance element detects the change of magnetic field intensity and exports linear testing result, according to testing result calculates and obtains the liquid level height value.

In particular, the liquid level detection method comprises the following steps:

step T1, when the first tunneling magneto-resistance element is not influenced by the magnetic field, the output voltage value of the first tunneling magneto-resistance element is recorded as V_llnitial；

And T2, the magnets move along with the buoy, when the first tunneling magneto-resistance element is positioned between the two magnets, the position is recorded as the current position, and the output voltage of the first tunneling magneto-resistance element is at the momentThe value is denoted as V₁Current；

Step T3, recording the change value of the voltage detected by the tunnel magneto-resistance element as Vmm when the buoy moves a set distance value;

step T4, outputting a voltage value V₁Current and V_lDividing the difference value of lnitial by Vmm to obtain the distance H between the first tunneling magneto-resistance element and the plane where the designated position on the magnet is located along the moving direction of the buoy,

a step T5 of adding or subtracting the distance H to or from the position H1 of the first tunneling magnetoresistive element on the valve tube to obtain a liquid level height value H,

wherein H is negative when the liquid level height is below H1, H is 0 when the liquid level height is equal to H1, and H is positive when the liquid level height is above H1.

In particular, the liquid level detection method comprises the following steps:

step Sl, when the first tunnel magneto-resistance element is not influenced by the magnetic field, the output voltage value of the first tunnel magneto-resistance element is recorded as V_llnitial, the value of the output voltage of the second tunneling magneto-resistance element is denoted as V₂1nitial, the first tunneling magneto-resistance element and the second tunneling magneto-resistance element are two adjacent tunneling magneto-resistance elements in the magnetic field range, and the first tunneling magneto-resistance element is positioned above the second tunneling magneto-resistance element;

step S2, the magnets move along with the float bowl, when the first tunnel magneto-resistance element and the second tunnel magneto-resistance element are both positioned between the two magnets, the position is recorded as the current position, and the output voltage value of the first tunnel magneto-resistance element is recorded as V at the moment₁Current, output of the second tunneling magneto-resistance elementThe voltage value is recorded as V₂Current；

Step S3, outputting the voltage value V of the first tunnel magneto-resistance element₁Current and V_lThe difference value of lnitial is recorded as a first difference value, and the output voltage value V of the second tunnel magneto-resistance element is recorded as a second difference value₂Current and V₂The difference value of lnitial is recorded as a second difference value, the ratio of the first difference value to the second difference value is subjected to exponential n correction, and the distance H from the first tunnel magneto-resistance element to the plane where the designated position on the magnet is located along the moving direction of the buoy is obtained after corresponding calculation;

and step S4, adding or subtracting the distance H according to the position H1 of the first tunneling magneto-resistance element on the electronic tube to obtain a liquid level height value, wherein H is negative when the liquid level height is lower than H1, H is 0 when the liquid level height is equal to H1, and H is positive when the liquid level height is higher than H1.

Particularly, when the distance between two adjacent tunnel magneto-resistance elements is L and the length of the magnet is L + set correction values, the output of the first tunnel magneto-resistance element for detecting the change of the magnetic field strength is a cosine curve, the output of the second tunnel magneto-resistance element for detecting the change of the magnetic field strength is a sine curve, and the phase difference between the first tunnel magneto-resistance element and the second tunnel magneto-resistance element is 90 degrees; the step S3 calculates the distance H according to the following formula,

wherein the value range of n is between 1.1 and 1.7.

On the other hand, the invention adopts the following technical scheme:

a liquid level sensor is used for achieving the liquid level detection method and comprises an electronic tube, a plurality of tunnel magneto-resistance elements used for measuring liquid level are sequentially arranged in the electronic tube along the longitudinal direction, a buoy is rotatably sleeved on the outer side of the electronic tube, two magnets are symmetrically arranged in the buoy, the homopolar poles of the two magnets face the tunnel magneto-resistance elements, and a magnetic field is formed between the two magnets; all tunnel magneto resistor components equidistant setting and adjacent two distance between the tunnel magneto resistor components is L, every the length of magnetite equals L + and sets for the correction value.

In particular, a plurality of adjacent said tunneling magnetoresistive elements are connected to a differential multiplexing switch; the plurality of differential multi-way selection switches are connected to a series-to-parallel switch, the series-to-parallel switch is connected to an impedance transformation circuit and a differential amplification circuit, and the differential amplification circuit is connected to a single chip microcomputer processing system; and the single chip microcomputer processing system is respectively connected to the series-parallel switch and the output terminal to realize data acquisition, data processing and calculation result output.

Particularly, the liquid level sensor also comprises a calibration device, and the calibration device is connected to the single chip microcomputer processing system through a digital interface; the calibration device is used for recording an initial output voltage value of the tunneling magneto-resistance element and/or an assembly error value of the liquid level sensor.

In particular, the liquid level sensor further includes a micro control unit for correcting the electric signal output from the output terminal, and the micro control unit multiplies the electric signal output from the output terminal by a predetermined coefficient.

In particular, the distance between the two magnets is between 21mm and 26 mm.

Particularly, the liquid level sensor comprises a single tube structure or a multi-tube structure, wherein the single tube structure is the electronic tube provided with the tunnel magneto-resistance element; the multi-tube structure comprises the electronic tube, an engine oil suction tube and an engine oil return tube.

The liquid level detection method of the invention uses the tunnel magneto-resistance element to collect the magnetic field intensity signal, has high measurement precision and wide application range, is particularly suitable for the fields with higher requirements on the measurement precision, including but not limited to the liquid level measurement of fuel oil and urea solution, and has convenient use and low use cost.

The electronic tube of the liquid level sensor is internally and sequentially provided with a plurality of tunnel magneto-resistance elements for measuring the liquid level along the longitudinal direction, and the liquid level detection method has the advantages of high measurement precision, wide application range and convenience in use.

Drawings

FIG. 1 is a schematic diagram of a single tube configuration of a level sensor according to an embodiment of the present invention;

FIG. 2 is an axial cross-sectional view of a single tube configuration of a level sensor provided in accordance with an embodiment of the present invention;

FIG. 3 is a schematic diagram of a multi-tube configuration of a level sensor according to an embodiment of the present invention;

fig. 4 is a wiring diagram of an impedance transformation circuit and a differential amplification circuit according to an embodiment of the present invention;

FIG. 5(a) is a schematic view of a magnet according to an embodiment of the present invention at a home position; FIG. 5(b) is a schematic view of a magnet according to an embodiment of the present invention at an intermediate position; FIG. 5(c) is a schematic view of a magnet according to an embodiment of the present invention at the end position.

In the figure:

1. an electron tube; 2. a tunneling magnetoresistive element; 3. a float bowl; 4. a magnet; 5. a single chip processor processing system; 6. an engine oil suction pipe; 7. an engine oil return pipe; 21. a first tunneling magnetoresistive element; 22. a second tunneling magnetoresistive element; 23. a third tunneling magnetoresistive element.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered limiting of the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.

The embodiment provides a liquid level sensor and a liquid level detection method based on the liquid level sensor. As shown in fig. 1 to 4, the liquid level sensor comprises an electronic tube 1, a plurality of tunneling magneto-resistance elements 2(TMR) for measuring liquid level are sequentially arranged in the electronic tube 1 along the longitudinal direction, a buoy 3 is rotatably sleeved outside the electronic tube 1, two magnets 4 are symmetrically arranged in the buoy 3, the same poles of the two magnets 4 face the tunneling magneto-resistance elements 2, and a magnetic field is formed between the two magnets 4; all the tunnel magnetoresistive elements 2 are arranged at equal intervals, the distance between two adjacent tunnel magnetoresistive elements 2 is L, and the length D of each magnet 4 is equal to L + by a set correction value, which is preferably 4 mm. The distance E between the two magnets 4 is not particularly limited, and can be matched with the buoy 3. The value of the distance E is preferably between 21mm and 26mm, the magnetic field is more uniform and appropriate in strength, and the magnetic field can meet the use requirements of various working conditions.

The liquid level detection method comprises the following steps: two magnets 4 are symmetrically arranged in the float bowl 3 capable of moving along the axial direction of the electronic tube 1, homopolarity of the two magnets 4 is oppositely arranged to form a magnetic field, and the position of the magnetic field changes along with the position change of the float bowl 3. A plurality of tunnel magneto-resistance elements 2 used for acquiring magnetic field intensity signals are arranged on a PCB in the electronic tube 1 at equal intervals, all the tunnel magneto-resistance elements 2 are positioned in the moving range of the buoy 3, and the length D of the magnet 4 is larger than the distance between two adjacent tunnel magneto-resistance elements 2; when the buoy 3 moves, the two adjacent tunnel magneto-resistance elements 2 between the two magnets 4 detect the magnetic field intensity change and output linear detection results, and the liquid level height value is calculated according to the detection results.

The tunnel magneto-resistance element 2 is used for collecting magnetic field intensity signals, the measuring precision is high, the application range is wide, and the tunnel magneto-resistance element is particularly suitable for fields with higher requirements on the measuring precision, including but not limited to liquid level measurement of fuel oil and urea solution, the use is convenient, and the use cost is low.

Specifically, fig. 1 and 2 show a single tube liquid level sensor, which includes only one electron tube 1 provided with a tunnel magnetoresistive element 2, and the magnetic field position is changed by moving a float 3 up and down along the electron tube 1. Fig. 3 shows a liquid level sensor of a multi-tube structure, which comprises an electronic tube 1, an engine oil suction tube 6 and an engine oil return tube 7.

The working principle of the liquid level sensor with a single tube structure and the liquid level sensor with a multi-tube structure are the same, and liquid level measurement is carried out through a plurality of tunneling magneto-resistance elements 2 integrated on the electronic tube 1. What is different is that the liquid level sensor with the multi-tube structure comprises an engine oil suction pipe 6 and an engine oil return pipe 7 for the oil suction and return function of the engine, besides the electronic tube 1, a filter screen (not shown) for filtering fuel oil, a device with a fuel oil heating function (such as a heating water pipe, a heating electric pump or a PTC heating sheet and the like), an oil tank air pressure balancing air valve, a turnover safety explosion-proof device, a parking heating oil suction and return device, a temperature alarm, an oil theft alarm and the like. The liquid level sensor with the multi-tube structure has the advantages of higher integration level, good strength, strong anti-vibration capability, low cost and convenient installation.

As shown in fig. 4, a plurality of adjacent tunneling magnetoresistive elements 2 are connected to a differential multiplexing switch; the plurality of differential multi-path selection switches are connected to the series-to-parallel switch, the series-to-parallel switch is connected to the impedance transformation circuit and the differential amplification circuit, and the differential amplification circuit is connected to the single chip microcomputer processing system 5; the single chip microcomputer processing system 5 is connected to the series-parallel switch and the output terminal respectively to achieve data acquisition, data processing and calculation result output. The single chip microcomputer processing system 5 preferably comprises a power supply, an MCU (single chip microcomputer) and a signal output device which are integrated on the same PCB (printed circuit board), and is high in integration level, convenient to use, high in control precision and wide in application range.

The tunnel magneto-resistance elements 2 connected to the same differential multi-way selection switch can be two, four, eight or other numbers, and the specific number is determined according to the bit number of the differential multi-way selection switch; the specific devices of the impedance transformation circuit are not limited, the problem of signal acquisition precision caused by different internal resistances of the analog switch can be solved, and the impedance transformation circuit is preferably a voltage follower; the output terminal comprises at least one of a voltage terminal, an RS485 interface and a CAN bus. The specific structures or devices of the differential multi-path selection switch and the differential amplification circuit are not limited, and the corresponding functions can be realized.

On the basis of the structure, the liquid level sensor also comprises a calibration device (not shown), and the calibration device is connected to the single chip microcomputer processing system through a digital interface; the calibration device is used for recording the initial output voltage value of the tunneling magneto-resistance element 2 and/or the assembly error value of the liquid level sensor.

In addition to the above configuration, the liquid level sensor further includes a Micro Controller Unit (MCU) (not shown) for correcting the electric signal output from the output terminal, and the micro controller Unit multiplies the electric signal output from the output terminal by a predetermined factor.

As shown in fig. 5(a), the upper end of the magnet 4 moving upward with the float 3 reaches a position aligned with the first tunneling magneto-resistive element 21, at which the second tunneling magneto-resistive element 22 is located at a middle position of the magnet 4 and the third tunneling magneto-resistive element 23 is located just apart from the lower end position of the magnet 4.

The float 3 continues to move upward, and as shown in fig. 5(b), the magnet 4 also continues to move upward, the first tunneling magneto-resistive element 21 and the second tunneling magneto-resistive element 22 are both located between the upper end and the lower end of the magnet 4, and the midpoint of the first tunneling magneto-resistive element 21 and the midpoint of the second tunneling magneto-resistive element 22 are located substantially on the same horizontal line as the midpoint of the magnet 4.

The float 3 continues to move upward, and as shown in fig. 5(c), the magnet 4 also continues to move upward, the second tunneling magneto-resistive element 22 is located at the lower end of the magnet 4, and the first tunneling magneto-resistive element 21 is located at the middle of the magnet 4.

The method for detecting the level of a liquid using only one tunnel magnetoresistive element 2 comprises the following steps:

in step T1, when the first tunnel magnetoresistive element 21 is not affected by the magnetic field, the output voltage value is denoted as V_llnitial。

In step T2, the magnets 4 move with the float 3, when the first tunneling magneto-resistance element 21 is located between two magnets 4, the position is recorded as the current position, and the output voltage value of the first tunneling magneto-resistance element 21 is recorded as V₁Current。

In step T3, each time the float 3 moves by the set distance value, the change value of the voltage detected by the tunneling magnetoresistive element 2 is recorded as Vmm. Preferably, the set distance value is 1 mm.

Step T4, outputting a voltage value V₁Current and V_lThe difference between lnitial is divided by Vmm to obtain the distance H from the first tunneling magneto-resistance element 21 to the plane of the magnet 4 (which can be any point on the upper end, the lower end, the middle point or the magnet 4, and can be determined by the user according to the use requirement, and can be detected and calculated conveniently) along the moving direction of the buoy 3,

a step T5 of adding or subtracting the distance H to or from the position H1 of the first tunneling magnetoresistive element 21 on the valve 1 to obtain a liquid level height value H,

wherein H is negative when the liquid level height is below H1, H is 0 when the liquid level height is equal to H1, and H is positive when the liquid level height is above H1.

The liquid level detection method using two tunneling magneto-resistive elements 2 simultaneously comprises the following steps:

step Sl, when the first tunnel magneto-resistance element is not influenced by a magnetic field, the first tunnel magneto-resistance element is connected with the first tunnel magneto-resistance elementThe value of the output voltage of the member 21 is denoted as V_llnitial, the value of the output voltage of the second tunneling magneto-resistive element 22 is denoted as V₂1nitial, the first tunneling magnetoresistive element 21 and the second tunneling magnetoresistive element 22 are two adjacent tunneling magnetoresistive elements 2 in a magnetic field range, and the first tunneling magnetoresistive element 21 is located above the second tunneling magnetoresistive element 22.

Step S2, the magnets 4 move along with the float 3, when the first tunneling magneto-resistance element 21 and the second tunneling magneto-resistance element 22 are both located between the two magnets 4, the position is recorded as the current position, and the output voltage value of the first tunneling magneto-resistance element 21 is recorded as V at the moment₁The value of the output voltage of the Current and second tunneling magnetoresistive element 22 is denoted as V₂Current。

Step S3 is to determine the output voltage V of the first tunneling magneto-resistance element 21₁Current and V_lThe difference of lnitial is recorded as a first difference, and the output voltage value V of the second tunneling magnetoresistive element 22 is expressed as a second difference₂Current and V₂The difference value of lnitial is recorded as a second difference value, the index n of the ratio of the first difference value to the second difference value is corrected, and the distance H from the first tunnel magneto-resistance element 21 to the plane where the designated position on the magnet 4 is located along the moving direction of the buoy 3 is obtained after corresponding calculation; wherein, the ratio of the first difference and the second difference is to eliminate the interference of the factors in the working environment to the detection result.

When the distance between two adjacent tunnel magnetoresistive elements 2 is L and the length D of the magnet 4 is L + a set correction value (the set correction value is preferably 4mm), the outputs of the first tunnel magnetoresistive element 21 for detecting the change of the magnetic field strength are all cosine curves, the outputs of the second tunnel magnetoresistive element 22 for detecting the change of the magnetic field strength are all sine curves, and the phase difference between the first tunnel magnetoresistive element 21 and the second tunnel magnetoresistive element 22 is 90 degrees; step S3 calculates the distance H according to the following equation,

the value range of n is 1.1-1.7, the specific value is related to the distance L of the tunneling magneto-resistance element 2 and the length D of the magnet 4, and n is obtained according to actual tests. The distance E between the two magnets 4 is not particularly limited, and can be matched with the buoy 3, and is preferably 21mm-26 mm.

Step S4, adding or subtracting the distance H to or from the position H1 of the first tunneling magnetoresistive element 21 on the valve 1 to obtain a liquid level height value, wherein H is negative when the liquid level height is lower than H1, H is 0 when the liquid level height is equal to H1, and H is positive when the liquid level height is higher than H1. The distance H is a distance between the first tunneling magneto-resistive element 21 and a plane where a designated position on the magnet 4 is located along the moving direction of the float 3, and the designated position may be any point on the magnet 4, such as the upper end, the lower end, the middle point, or the upper end of the magnet 4.

It should be noted that the foregoing is only a preferred embodiment of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.