A liquid level measuring device based on temperature difference demarcation point

Abstract

The application relates to a liquid level measuring device based on a temperature difference demarcation point, which realizes real-time measurement of the liquid level height in a corresponding application background. The inside of an elongated structural member is filled with heat-conducting liquid, which is installed vertically to the surface of a liquid to be measured and extends to the bottom of the liquid to be measured; a control device controls a heating wire immersed in the heat-conducting liquid to heat the heat-conducting liquid until the value measured by a first temperature-sensitive resistor reaches a set temperature; the temperature difference demarcation point of the elongated structural member with small thermal inertia is consistent with the liquid level height because the elongated structural member is partially immersed in the liquid; the value measured by a second temperature-sensitive resistor is the temperature value of the liquid to be measured; the length of a first temperature-sensitive material resistor wire is consistent with the length of the elongated structural member, the first temperature-sensitive material resistor wire is immersed in the heat-conducting liquid, and the two ends of the first temperature-sensitive material resistor wire are fixed at the top end and the bottom end of the elongated structural member respectively; the resistance value of the first temperature-sensitive material resistor wire changes with the liquid level height; and the liquid level height of the liquid to be measured can be determined according to the temperature value measured by the first temperature-sensitive resistor, the temperature value measured by the second temperature-sensitive resistor and the measured resistance value of the first temperature-sensitive material resistor wire.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of liquid level measurement, in particular to a liquid level measurement device based on temperature difference demarcation point. BACKGROUND

[0002] Liquid level measurement has a wide range of applications in modern social production and life, covering multiple industries and fields. For example, liquid level measurement technology is widely used in industries such as oil, natural gas, and food processing for liquid level monitoring of equipment such as storage tanks and reaction kettles; in water treatment, liquid level measurement is used for liquid level monitoring of water bodies such as pools and tanks, providing accurate data support for water resource management and water quality control; in hydrological measurement, real-time monitoring and early warning of water level changes are used to timely detect and respond to abnormal changes in water level, providing technical support for flood control and drought resistance and water resource management; liquid level measurement is also widely used in liquid level monitoring of rivers, lakes, seas, urban water supply systems, drainage pipe networks, and household water tanks to ensure the rational allocation and use of water resources and prevent urban waterlogging; in addition, liquid level sensors are also used in household appliances such as intelligent toilets, water heaters, and coffee machines to automatically detect water level and control water quantity, improving the intelligence of the equipment and user experience.

[0003] With the rapid development of industrial automation and intelligent manufacturing, the precision and reliability of liquid level measurement are increasingly required. Traditional liquid level measurement methods, such as water gauge measurement, buoyancy measurement, pressure measurement, capacitance method, microwave reflection measurement, ultrasonic reflection measurement, infrared reflection measurement, and magnetic float and bubble method, can meet the measurement requirements to some extent, but these methods are limited in applications such as rivers, urban water supply, and drainage pipelines that are not suitable for human operation. SUMMARY

[0004] The present application provides a liquid level measurement device based on temperature difference demarcation point, which can be used for liquid level measurement in applications requiring automatic collection of liquid level data.

[0005] The technical solution of the present application is as follows:

[0006] A liquid level measurement device based on temperature difference demarcation point, comprising:

[0007] an elongated structural member for partial insertion into the liquid to be measured, the inner cavity of the elongated structural member being filled with a heat-conducting liquid;

[0008] a control device, a heating wire and a first temperature-sensitive material resistance wire connected to the control device passing through the elongated structural member and immersed into the heat-conducting liquid, and the ends of the heating wire and the first temperature-sensitive material resistance wire being in contact with the bottom of the inner cavity of the elongated structural member;

[0009] a first temperature-sensitive resistor and a second temperature-sensitive resistor connected to the control device, the first temperature-sensitive resistor being arranged at the top of the heat-conducting liquid, and the second temperature-sensitive resistor being arranged at the bottom of the heat-conducting liquid;

[0010] In the liquid level measurement, one end of the elongated structural member is inserted into the liquid to be measured, and the control device controls the heating wire to heat the heat-conducting liquid. After the heat-conducting liquid is heated, the real-time temperature detected by the first temperature-sensitive resistor and the second temperature-sensitive resistor and the measured resistance of the first temperature-sensitive material resistor wire are used to determine the liquid level of the liquid to be measured.

[0011] Preferably, the step of determining the liquid level of the liquid to be measured according to the real-time temperature detected by the first temperature-sensitive resistor and the second temperature-sensitive resistor and the measured resistance of the first temperature-sensitive material resistor wire comprises:

[0012] According to the formula:

[0013]

[0014] The liquid level l of the liquid to be measured is calculated.

[0015] Wherein, R1 is the measured resistance of the first temperature-sensitive material resistor wire, R2 is the resistance of the first temperature-sensitive material resistor wire calculated at the temperature detected by the first temperature-sensitive resistor, R3 is the resistance of the first temperature-sensitive material resistor wire calculated at the temperature detected by the second temperature-sensitive resistor, and L is the length of the first temperature-sensitive material resistor wire.

[0016] Preferably, the second temperature-sensitive material resistor wire connected to the control device by a wire is installed at the top end of the elongated structural member and immersed in the heat-conducting liquid.

[0017] The second temperature-sensitive material resistor wire has the same material and diameter as the first temperature-sensitive material resistor wire.

[0018] In the liquid level measurement, one end of the elongated structural member is inserted into the liquid to be measured, and the control device controls the heating wire to heat the heat-conducting liquid. After the heat-conducting liquid is heated, the real-time temperature detected by the first temperature-sensitive resistor and the second temperature-sensitive resistor and the measured resistance of the first temperature-sensitive material resistor wire are used to determine the liquid level of the liquid to be measured.

[0019] Preferably, the second temperature-sensitive material resistor wire has the same length as the first temperature-sensitive material resistor wire, and the step of determining the liquid level of the liquid to be measured according to the real-time temperature detected by the first temperature-sensitive resistor and the second temperature-sensitive resistor and the measured resistance of the first temperature-sensitive material resistor wire comprises:

[0020] According to the formula:

[0021]

[0022] The liquid level of the liquid to be measured is calculated according to the measured resistance of the first temperature-sensitive material resistance wire, the measured resistance of the second temperature-sensitive material resistance wire, the measured resistance of the third temperature-sensitive material resistance wire, and the measured resistance of the fourth temperature-sensitive material resistance wire.

[0023] Preferably, the second temperature-sensitive material resistance wire connected with the control device is installed at the top end of the elongated structural member and immersed in the heat-conducting liquid; the second temperature-sensitive material resistance wire has the same material and diameter as the first temperature-sensitive material resistance wire.

[0024] The third temperature-sensitive material resistance wire connected with the control device is inserted into the heat-conducting liquid through the elongated structural member, and the end of the third temperature-sensitive material resistance wire is arranged at the bottom of the inner cavity of the elongated structural member.

[0025] The fourth temperature-sensitive material resistance wire connected with the control device is installed at the top end of the elongated structural member and immersed in the heat-conducting liquid; the fourth temperature-sensitive material resistance wire has the same material and diameter as the first temperature-sensitive material resistance wire.

[0026] When measuring the liquid level, one end of the elongated structural member is inserted into the liquid to be measured, and the control device controls the heating wire to heat the heat-conducting liquid; after the heat-conducting liquid is heated, the liquid level of the liquid to be measured is determined according to the measured resistance of the first temperature-sensitive material resistance wire, the second temperature-sensitive material resistance wire, the third temperature-sensitive material resistance wire, and the fourth temperature-sensitive material resistance wire.

[0027] Preferably, the liquid level of the liquid to be measured is determined according to the measured resistance of the first temperature-sensitive material resistance wire, the second temperature-sensitive material resistance wire, the third temperature-sensitive material resistance wire, and the fourth temperature-sensitive material resistance wire:

[0028] by the formula:

[0029]

[0030] The output voltage V of the bridge in which the first temperature-sensitive material resistance wire, the second temperature-sensitive material resistance wire, the third temperature-sensitive material resistance wire, and the fourth temperature-sensitive material resistance wire are arranged is determined; wherein R1 is the measured resistance of the first temperature-sensitive material resistance wire, R2 is the measured resistance of the second temperature-sensitive material resistance wire, R3 is the measured resistance of the third temperature-sensitive material resistance wire, R4 is the measured resistance of the fourth temperature-sensitive material resistance wire, and U0 is the power supply voltage of the bridge in which the first temperature-sensitive material resistance wire, the second temperature-sensitive material resistance wire, the third temperature-sensitive material resistance wire, and the fourth temperature-sensitive material resistance wire are arranged.

[0031] by the formula:

[0032] l=kV

[0033] calculating the liquid level height l of the liquid to be measured; wherein k is a preset proportion coefficient.

[0034] The application also provides a liquid level measuring device based on temperature difference demarcation point, comprising:

[0035] an elongated structural member for partially inserting into the liquid to be measured, a heat-conducting liquid being injected into the inner cavity of the elongated structural member, and the whole having small thermal inertia;

[0036] a control device, a heating wire connected with the control device penetrating through the elongated structural member and being immersed into the heat-conducting liquid;

[0037] a plurality of infrared shielding rings being uniformly and spacedly sleeved outside the elongated structural member;

[0038] an infrared thermal imaging device being arranged outside the liquid to be measured, and collecting infrared images towards the elongated structural member, and determining the position of the liquid level temperature demarcation line according to the infrared images collected by the infrared thermal imaging device and in combination with the shielding rings, so as to obtain the liquid level of the liquid to be measured;

[0039] The spacing between the infrared shielding rings corresponds to the millimeter number of the imaging pixel number of the infrared thermal imaging device.

[0040] Preferably, the heating wire is a silica gel heating wire or a carbon fiber heating wire.

[0041] Preferably, the heat-conducting liquid is fluorinated liquid or transformer oil, and the elongated structural member is a thin-walled stainless steel pipe.

[0042] Preferably, the first temperature-sensitive material resistance wire, the second temperature-sensitive material resistance wire, the third temperature-sensitive material resistance wire and the fourth temperature-sensitive material resistance wire adopt positive temperature coefficient or negative temperature coefficient materials.

[0043] The application has the following beneficial effects:

[0044] The liquid level measuring device is characterized in that: the measuring body is an elongated structure, a heat-conducting liquid is injected into the inner cavity of the measuring body, and the heat-conducting liquid is heated and temperature monitored by the heating wire and the temperature-sensitive material resistance wire in the control device, so as to realize the accurate and automatic measurement of the liquid level, especially suitable for the environment such as rivers, urban water supply and drainage pipelines which are not suitable for human operation. These liquid level measuring devices do not depend on light conditions, so they can maintain stable liquid level measuring performance in any lighting environment. In addition, since the temperature-sensitive material resistance wire, the heating wire and the temperature-sensitive resistance are arranged inside the elongated structure, they are not directly exposed to the measured liquid, and the working of the devices inside the elongated structure will not be affected by the interference in the measured liquid, so the liquid level measuring device has good anti-interference ability. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 is a schematic diagram of the liquid level measuring principle;

[0046] Figure 2 is a schematic diagram of the liquid level measuring principle; Figure 1 is a partial enlarged schematic diagram of

[0047] Figure 3 is a schematic diagram of the liquid level measuring principle based on the temperature-sensitive effect;

[0048] Figure 4 is a schematic diagram of the liquid level measuring device based on the temperature difference demarcation point involved in the first embodiment of the application;

[0049] Figure 5 is a schematic diagram of the liquid level measuring device based on the temperature difference demarcation point involved in the second embodiment of the application;

[0050] Figure 6 is a schematic diagram of the liquid level measuring device based on the temperature difference demarcation point involved in the third embodiment of the application;

[0051] Figure 7 is a schematic diagram of the liquid level measuring device based on the temperature difference demarcation point involved in the fourth embodiment of the application;

[0052] Figure 8 is a schematic diagram of the circuit principle involved in the fifth embodiment of the application;

[0053] Figure 9 is a schematic diagram of the liquid level measuring device based on the temperature difference demarcation point involved in the fifth embodiment of the application. DETAILED DESCRIPTION

[0054] In order to facilitate the understanding of those skilled in the art, the present application is further described and explained below by means of the accompanying drawings. The description is relatively detailed, but should not be understood as limiting the scope of the present application. The obvious modifications and substitutions of the following examples are all within the protection scope of the present application.

[0055] Reference Figure 3 and Figure 4 In the embodiment one of the present application, a liquid level measuring device based on temperature difference demarcation point is provided, comprising:

[0056] an elongated structure 1, a heat-conducting liquid 11 is injected into the inner cavity of the elongated structure 1;

[0057] a control device 2, a heating wire 21 and a first temperature-sensitive material resistance wire 22 connected in the control device 2 are inserted into the heat-conducting liquid 11 through the elongated structure 1, and the ends of the heating wire 21 and the first temperature-sensitive material resistance wire 22 are in contact with the bottom of the inner cavity of the elongated structure 1;

[0058] a first temperature-sensitive resistance 23 and a second temperature-sensitive resistance 24 connected with the control device 2, the first temperature-sensitive resistance 23 is arranged at the top of the heat-conducting liquid 11, and the second temperature-sensitive resistance 24 is arranged at the bottom of the heat-conducting liquid 11;

[0059] In the liquid level measurement, one end of the elongated structure 1 is inserted into the liquid to be measured 3, the control device 2 controls the heating wire 21 to heat the heat-conducting liquid 11, and the temperature value measured by the first temperature-sensitive resistance 23 reaches the set temperature (i.e. the temperature measured by the first temperature-sensitive resistance 23 is more than 30℃ higher than the temperature of the second temperature-sensitive resistance 24); after the heat-conducting liquid 11 is heated, the real-time temperature detected by the first temperature-sensitive resistance 23 and the second temperature-sensitive resistance 24 and the measured resistance of the first temperature-sensitive material resistance wire 22 are used to determine the liquid level of the liquid to be measured 3.

[0060] In the embodiment one, the overall length of the elongated structure 1 is greater than the liquid level range of the liquid to be measured 3, therefore, it is necessary to verify the elongated structure 3 higher than the historical measurement liquid level of the liquid to be measured 3, and the elongated structure 1 is made of stainless steel pipe. Its inside is hollow, the bottom end is sealed, and the top end is not sealed, which can be used for cable passing; when the heating wire 21 and the first temperature-sensitive material resistance wire 22 are assembled, the top end of the elongated structure 1 is closed by an insulating part (such as a sealing plug, a sealing cover, etc.). The hollow inner cavity of the elongated structure 1 is injected with the heat-conducting liquid 11, so that the elongated structure 1 has small thermal inertia and can be quickly heated to a predetermined temperature higher than the ambient temperature under the heating of the built-in heating wire 21.

[0061] The control device 2 is internally provided with a power supply circuit and a related control circuit, and the control device 2 is connected with the heating wire 21 and the first temperature-sensitive material resistance wire 22 through conductive wires with good temperature stability.

[0062] In the assembly, one end of the heating wire 21 and the first temperature-sensitive material resistance wire 22 is fixed on the insulating part assembled on the top end of the elongated structural member 1 and extends axially along the elongated structural member 1 to the bottom sealing end of the elongated structural member 1 and is fixed (the fixing mode is, for example, the adhesive bonding and fixing mode), and the heating wire 21 and the first temperature-sensitive material resistance wire 22 are integrally immersed in the heat-conducting liquid 11.

[0063] When the liquid level measurement is needed to be measured by the liquid level measuring device, the elongated structural member 1 is inserted into the liquid 3 to be measured in the state perpendicular to the liquid surface of the liquid 3 to be measured, and the bottom end of the elongated structural member 1 is consistent with the bottom height of the liquid 3 to be measured, and when the liquid level height of the liquid 3 to be measured is not zero, the elongated structural member 3 is partially or entirely immersed in the liquid 3 to be measured. The top end of the elongated structural member 1 is fixed on the device floating in the liquid 3 to be measured, or the top end of the elongated structural member 1 is fixed on the fixed environment object (such as a tree, a bridge pier, etc.) in the environment around the liquid 3 to be measured.

[0064] The first temperature-sensitive resistance 23 is installed on the sealing part arranged on the unsealed end of the elongated structural member 1, and the second temperature-sensitive resistance 24 is installed on the internal sealing end of the elongated structural member 1.

[0065] The control device 2 controls the heating wire 21 to heat the heat-conducting liquid 11, and the first temperature-sensitive resistance 23 and the second temperature-sensitive resistance 24 respectively detect the real-time temperature inside the two ends of the elongated structural member 1. Since the lower end of the elongated structural member 1 is immersed in the liquid 3 to be measured, it has a small thermal inertia, and the heat-conducting liquid 11 inside the elongated structural member 1 has a temperature difference boundary point substantially consistent with the liquid level height of the liquid 3 to be measured, and the measured temperature value of the second temperature-sensitive resistance 24 is equivalent to the temperature value of the liquid 3 to be measured. The measured resistance value of the first temperature-sensitive material resistance wire 22 changes with the change of the liquid level height, so that the liquid level of the liquid 3 to be measured can be determined by the measured temperature value of the first temperature-sensitive resistance 23, the measured temperature value of the second temperature-sensitive resistance 24 and the measured resistance value of the first temperature-sensitive material resistance wire 22.

[0066] When not heated, the measured values of the first temperature-sensitive resistance 23 and the second temperature-sensitive resistance 24 are both the ambient temperature values.

[0067] The liquid level of the liquid to be measured 3 is measured accurately by injecting the heat-conducting liquid 11 into the elongated structure 1, heating the heat-conducting liquid 11 by the heating wire 21 connected to the control device 2, and monitoring the temperature of the heat-conducting liquid 11 by the first temperature-sensitive material resistance wire 22. When the elongated structure 1 is inserted into the liquid to be measured 3, the heating wire 21 heats the heat-conducting liquid 11, and the first temperature-sensitive resistance 23 and the second temperature-sensitive resistance 24 detect the real-time temperature at the top and bottom of the heat-conducting liquid 11 respectively, while the first temperature-sensitive material resistance wire 22 monitors the measured resistance. By comprehensively analyzing these data, the liquid level measuring device can accurately determine the liquid level of the liquid to be measured, thereby providing an efficient and reliable automatic liquid level monitoring solution for industrial process control, environmental monitoring and other applications, especially suitable for environments where human operation is not suitable for liquid level measurement. Moreover, this liquid level measurement method does not depend on light conditions, so it can maintain stable liquid level measurement performance in any lighting environment. In addition, since the first temperature-sensitive material resistance wire 22, the heating wire 21, and the first temperature-sensitive resistance 23 and the second temperature-sensitive resistance 24 are all arranged inside the elongated structure 1, they are not directly exposed to the liquid to be measured 3, and the working of the devices inside the elongated structure 1 will not be affected by the interference in the liquid to be measured 3, so the liquid level measuring device has good anti-interference ability.

[0068] In the first embodiment, a thin-walled stainless steel pipe is used as the main body of the elongated structure 1 according to the measurement range of the liquid level. The excellent heat conduction performance and stable physical properties of the thin-walled stainless steel pipe enable it to quickly respond to the temperature changes of the heat-conducting liquid 11, thereby achieving high-precision liquid level measurement.

[0069] In the first embodiment, the heat-conducting liquid 11 is fluorinated liquid or transformer oil. Both fluorinated liquid and transformer oil have good heat conduction performance, which helps to quickly and uniformly transfer heat, thereby improving the response speed and accuracy of liquid level measurement.

[0070] The control device 2 is responsible for controlling the operation of the heating wire 21, reading the resistance value of the first temperature-sensitive material resistance wire 22, processing the signals of the first temperature-sensitive resistance 23 and the second temperature-sensitive resistance 24, and calculating the liquid level height. The structure of the control device 2 includes:

[0071] A power module provides the power required by the control device 2, for example, a battery;

[0072] A heating control module is responsible for controlling the power output of the heating wire 21 to maintain stable heating of the heat-conducting liquid 11. The heating control module is, for example, a PID controller or other types of feedback control system to accurately control the temperature;

[0073] signal conditioning circuitry receiving the resistance signal from the first temperature sensitive material resistance wire 22 and converting it into a voltage or current signal, for example comprising an amplifier, a filter and an analog to digital converter (ADC);

[0074] temperature sensor interface receiving the signal from the first temperature sensitive resistance 23 and converting it into a usable digital signal;

[0075] a microprocessor or microcontroller as the brain of the control device, responsible for processing all input signals, executing the level calculation algorithm and controlling the operation of the heating wire 21 and the first temperature sensitive material resistance wire 22.

[0076] The first temperature sensitive resistance 23 and the second temperature sensitive resistance 24 are for example temperature sensors, when the elongated structure 1 is inserted into the liquid 3 to be measured, heat exchange occurs between the thermally conductive liquid 11 and the liquid 3 to be measured, causing the temperature at the top and bottom of the thermally conductive liquid 11 to change, by comparing the temperatures detected by the first temperature sensitive resistance 23 and the second temperature sensitive resistance 24, i.e. comparing the temperatures at the top and bottom of the thermally conductive liquid 11, the level height of the liquid 3 to be measured can be inferred.

[0077] The heating wire 21 is arranged along the axis of the elongated structure 1, the heating wire 21 can be selected from a silicone heating wire or a carbon fiber heating wire. After arranging the heating wire 21 and the first temperature sensitive material resistance wire 22, one end of the thin-walled stainless steel tube is sealed, and the high-performance thermally conductive liquid 11 is injected from the other end, so that the entire elongated structure 1 has low thermal inertia.

[0078] In combination with Figure 1 and Figure 2 , when in operation, one end of the elongated structure 1 is immersed in the liquid 3 to be measured vertically to the liquid surface, and the other end is exposed to the external environment outside the liquid, which is usually air. In order to form a temperature difference, the thermally conductive liquid 11 inside the elongated structure 1 is heated to a temperature higher than the temperature of the liquid 3 to be measured by a certain degree. Since the thermally conductive liquid 11 and the external air of the elongated structure 1 have significantly different thermal conductivities, under the condition that the material thermal inertia of the elongated structure 1 is small, the thermally conductive liquid 11 outside the liquid 3 to be measured is higher than the part immersed in the liquid 3 to be measured by a certain temperature, and the thermally conductive liquid 11 inside the liquid 3 to be measured is basically consistent with the temperature of the liquid 3 to be measured, forming a temperature difference demarcation point at the liquid surface.

[0079] Examine the temperature demarcation point, and partially enlarge it as Figure 2The temperature transition zone is located at the position where the elongated structural member 1 is perpendicular to the surface of the liquid 3 to be measured. Above the temperature transition zone is the target temperature T1 of the elongated structural member 1, and below the temperature transition zone is the temperature T2 close to the liquid 3 to be measured. The axial length of the temperature transition zone along the elongated structural member 1 affects the accuracy of the liquid level measurement. Therefore, by selecting appropriate materials for the elongated structural member 1 and controlling the temperature difference, the accuracy of the measurement can be improved.

[0080] In the embodiment of the present application, the step of determining the liquid level of the liquid 3 to be measured according to the real-time temperatures detected by the first temperature-sensitive resistor 23 and the second temperature-sensitive resistor 24 and the measured resistance of the first temperature-sensitive material resistor wire 22 includes:

[0081] According to the formula:

[0082]

[0083] The liquid level l of the liquid to be measured is calculated.

[0084] Wherein R1 is the measured resistance of the first temperature-sensitive material resistor wire, R2 is the resistance of the first temperature-sensitive material resistor wire 22 calculated according to the temperature detected by the first temperature-sensitive resistor 23, R4 is the resistance of the first temperature-sensitive material resistor wire 22 calculated according to the temperature detected by the second temperature-sensitive resistor 24, and L is the length of the first temperature-sensitive material resistor wire 22.

[0085] Within a certain range of temperature difference, the resistivity of the first temperature-sensitive material resistor wire 22 has a linear relationship with temperature. Let the upper half temperature detected by the first temperature-sensitive resistor 23 be T1, and the lower half temperature detected by the second temperature-sensitive resistor 24 be T2. Let the resistance R1 and R2 of the first temperature-sensitive material resistor wire 22 be at temperatures T1 and T2 respectively. Let the length of the first temperature-sensitive material resistor wire be L. Let the length of the liquid in which the elongated structural member 1 is immersed be l. Then the actual resistance value R of the first temperature-sensitive material resistor wire 22 is between R1 and R2. When the first temperature-sensitive material resistor wire 22 is completely immersed in the liquid to be measured 3, R = R2. When the first temperature-sensitive material resistor wire 22 is completely exposed outside the liquid to be measured 3, R = R1. The measured resistance R value of the first temperature-sensitive material resistor wire 22 can be used to calculate the liquid level l of the liquid to be measured 3.

[0086] Wherein the cross-sectional area and length of the first temperature-sensitive material resistor wire 22 are known values.

[0087] The relationship between the resistance R of the temperature-sensitive material resistor wire at different temperatures and the temperature change can be represented by the following formula:

[0088] R = R0 × (1 + α × ΔT)

[0089] Wherein:

[0090] R is the resistance value of the temperature-sensitive material resistance wire at temperature T;

[0091] R0 is the initial resistance at the reference temperature; the resistance value of the first temperature-sensitive material resistance wire 22 is measured at the reference temperature (usually 0℃ or 25℃), which is called the initial resistance R0;

[0092] α is the resistance temperature coefficient of the first temperature-sensitive material resistance wire 22;

[0093] ΔT is the temperature change relative to the reference temperature, i.e. T-T0.

[0094] According to the above formula, the resistance R1 of the first temperature-sensitive material resistance wire 22 can be calculated according to the temperature detected by the first temperature-sensitive resistance 23, and the resistance R2 of the first temperature-sensitive material resistance wire 22 can be calculated according to the temperature detected by the second temperature-sensitive resistance 24.

[0095] Wherein, the first temperature-sensitive material resistance wire 22 adopts a positive resistance temperature coefficient or a negative resistance temperature coefficient material. For example, it adopts nickel-chromium alloy Ni80Cr20, and its resistance temperature coefficient is 0.004 / ℃; according to the size of the resistance temperature coefficient of the nickel-chromium alloy Ni80Cr20, the temperature difference between the high temperature zone and the low temperature zone is 20-50℃, which can achieve higher resolution.

[0096] The above liquid level measuring device of the first embodiment can realize automatic measurement of the liquid level.

[0097] In the liquid level measuring device in the first embodiment, the resistance R2 and the resistance R3 need to be calculated according to the temperature measured by the first temperature-sensitive resistance 23 and the temperature measured by the second temperature-sensitive resistance 24 respectively, and the results obtained by calculation have certain errors. In order to eliminate part of the technical errors, the second temperature-sensitive material resistance wire 25 is additionally arranged in the second embodiment based on the first embodiment. For example, Figure 5 The second temperature-sensitive material resistance wire 25 connected with the control device 2 is installed at the top end of the elongated structural member 1 and is immersed in the heat-conducting liquid 11; the second temperature-sensitive material resistance wire 25 has the same material and diameter as the first temperature-sensitive material resistance wire 22;

[0098] When measuring the liquid level, one end of the elongated structural member 1 is inserted into the liquid to be measured 3, and the control device 2 controls the heating wire 21 to heat the heat-conducting liquid 11; after the heat-conducting liquid 11 is heated, the liquid level of the liquid to be measured 3 is determined according to the temperature measured by the second temperature-sensitive resistance 24, the measured resistance of the first temperature-sensitive material resistance wire 22 and the second temperature-sensitive material resistance wire 25.

[0099] When the liquid level measuring device is in operation, the heating wire 21 is used to heat the slender structure 1. Since the lower part of the slender structure 1 is immersed in the liquid 3 to be measured, the slender structure 1 is divided into two parts with different temperatures. The upper part has a relatively high temperature, which is called high temperature zone. The lower part has a relatively low temperature, which is called low temperature zone. Since the thin-wall stainless steel pipe of the slender structure 1 is filled with high-performance heat-conducting liquid 11, the temperature of the pipe is relatively uniform except for the temperature boundary point. The temperatures of the two parts can be measured by the first temperature-sensitive resistor 23 and the second temperature-sensitive resistor 24. The temperature values detected by the first temperature-sensitive resistor 23 and the second temperature-sensitive resistor 24 are used to control the heating temperature of the heating wire 21. When the temperature difference between the first temperature-sensitive resistor 23 and the second temperature-sensitive resistor 24 reaches 30° or more, the temperature heating of the heating wire 21 is completed.

[0100] According to actual requirements, the length of the second temperature-sensitive material resistor wire 25 can be the same as or different from that of the first temperature-sensitive material resistor wire 22.

[0101] When the length of the second temperature-sensitive material resistor wire 25 is the same as that of the first temperature-sensitive material resistor wire 22, the second temperature-sensitive material resistor wire 25 is wound into a coil with a small volume. At this time, the liquid level l of the liquid to be measured is calculated by the formula:

[0102]

[0103] The liquid level l of the liquid to be measured is calculated by the formula: l = (R3 - R1) / (R4 - R3) * L, where R1 is the measured resistance of the first temperature-sensitive material resistor wire 22, R3 is the resistance of the first temperature-sensitive material resistor wire 22 calculated at the temperature measured by the second temperature-sensitive resistor 24, R4 is the measured resistance of the second temperature-sensitive material resistor wire 25, and L is the length of the first temperature-sensitive material resistor wire 22.

[0104] When the length of the second temperature-sensitive material resistor wire 25 is different from that of the first temperature-sensitive material resistor wire 22, the liquid level l of the liquid to be measured is calculated according to the relationship between the length of the second temperature-sensitive material resistor wire 25 and the length of the first temperature-sensitive material resistor wire 22. For example, when the length of the second temperature-sensitive material resistor wire 25 is 1 / 2 of the length of the first temperature-sensitive material resistor wire 22, the liquid level l of the liquid to be measured is calculated by the formula:

[0105]

[0106] The liquid level l of the liquid to be measured is calculated by the formula: l = (R3 - R1) / (R4 - R3) * L, where R1 is the measured resistance of the first temperature-sensitive material resistor wire 22, R3 is the resistance of the first temperature-sensitive material resistor wire 22 calculated at the temperature measured by the second temperature-sensitive resistor 24, R4 is the measured resistance of the second temperature-sensitive material resistor wire 25, and L is the length of the first temperature-sensitive material resistor wire 22.

[0107] When the length of the second temperature-sensitive material resistance wire 25 is 1 / 4 of the first temperature-sensitive material resistance wire 22, at this time, the liquid level l of the liquid to be measured is calculated by the formula:

[0108]

[0109] The liquid level l of the liquid to be measured is calculated, wherein R1 is the measured resistance of the first temperature-sensitive material resistance wire 22, R3 is the resistance of the first temperature-sensitive material resistance wire 22 calculated at the temperature measured by the second temperature-sensitive resistance 24, R4 is the measured resistance of the second temperature-sensitive material resistance wire 25, and L is the length of the first temperature-sensitive material resistance wire 22.

[0110] This calculation method requires only one value of the resistance R3 of the first temperature-sensitive material resistance wire 22 calculated at the temperature measured by the second temperature-sensitive resistance 24, compared with the calculation method in the first embodiment, which reduces one resistance value calculation, eliminates part of the calculation error, and improves the liquid level measurement accuracy.

[0111] The second temperature-sensitive material resistance wire 25 is made of a positive temperature coefficient or a negative temperature coefficient material. For example, a nickel-chromium alloy Cr20Ni80 or Cr20Ni35 with a positive temperature coefficient is used.

[0112] Although part of the calculation error can be eliminated in the second embodiment, one resistance value still needs to be calculated. Therefore, in the third embodiment of the present application, a third temperature-sensitive material resistance wire 26 is additionally provided on the basis of the second embodiment. As shown in FIG. 3, the third temperature-sensitive material resistance wire 26 is connected to the control device 2. Figure 6 The third temperature-sensitive material resistance wire 26 connected to the control device 2 passes through the elongated structural member 1 and is immersed in the heat-conducting liquid 11, and the end of the third temperature-sensitive material resistance wire 26 is arranged at the bottom of the inner cavity of the elongated structural member 1. At this time, an insulating wire with good temperature stability needs to be extended into the inner cavity of the elongated structural member 1 to connect the third temperature-sensitive material resistance wire 26.

[0113] The third temperature-sensitive material resistance wire 26, the second temperature-sensitive material resistance wire 25, and the first temperature-sensitive material resistance wire 21 are made of the same material and have the same diameter.

[0114] Similarly, the length of the third temperature-sensitive material resistance wire 26 can be set to be the same as or different from the length of the first temperature-sensitive material resistance wire 22 according to requirements.

[0115] When the length of the third temperature-sensitive material resistance wire 26 is set to be the same as the length of the first temperature-sensitive material resistance wire 22, the third temperature-sensitive material resistance wire 26 is wound into a smaller coil, so that the liquid level l of the liquid to be measured is calculated by the formula:

[0116]

[0117] The liquid level l of the liquid to be measured 3 is calculated, wherein R1 is the measured resistance of the first temperature-sensitive material resistance wire 22, R4 is the measured resistance of the second temperature-sensitive material resistance wire 25, R5 is the measured resistance of the third temperature-sensitive material resistance wire 26, and L is the length of the first temperature-sensitive material resistance wire 22.

[0118] In this embodiment three, each parameter required for calculating the liquid level l of the liquid to be measured 3 is a measured value, which can completely eliminate the error caused by calculation and reduce the processing process.

[0119] Referring to Figure 7 , the application provides another configuration of the liquid level measuring device based on the temperature difference demarcation point, which comprises:

[0120] The second temperature-sensitive material resistance wire 25 connected with the control device 2 is installed at the top end of the elongated structural member 11 and is immersed in the heat-conducting liquid 11; the second temperature-sensitive material resistance wire 25 has the same material and diameter as the first temperature-sensitive material resistance wire 22.

[0121] The third temperature-sensitive material resistance wire 26 connected with the control device 2 passes through the elongated structural member 1 and is immersed in the heat-conducting liquid 11, and the end of the third temperature-sensitive material resistance wire 26 is arranged at the bottom of the inner cavity of the elongated structural member 1.

[0122] The fourth temperature-sensitive material resistance wire 27 connected with the control device 3 is installed at the top end of the elongated structural member 2 and is immersed in the heat-conducting liquid 11; the fourth temperature-sensitive material resistance wire 27 has the same material and diameter as the first temperature-sensitive material resistance wire 22.

[0123] When measuring the liquid level, one end of the elongated structural member 1 is inserted into the liquid to be measured 3, and the control device 2 controls the heating wire 21 to heat the heat-conducting liquid 11; after the heat-conducting liquid 11 is heated, the liquid level of the liquid to be measured 3 is determined according to the measured resistances of the first temperature-sensitive material resistance wire 22, the second temperature-sensitive material resistance wire 25, the third temperature-sensitive material resistance wire 26 and the fourth temperature-sensitive material resistance wire 27.

[0124] The first temperature sensitive resistance 23 is installed at the inner top of the elongated structure 1, and the second temperature sensitive resistance 24 is installed at the inner bottom of the elongated structure 1. In operation, the heat conducting liquid 11 inside the elongated structure 1 is heated by the heating wire 21. Since the elongated structure 1 is partially immersed in the liquid 3 to be measured, the whole elongated structure 1 is divided into two parts with different temperatures, the upper part with relatively high temperature, referred to as high temperature zone, and the lower part with relatively low temperature, referred to as low temperature zone. Since the thin-walled stainless steel tube of the elongated structure 1 is filled with high performance heat conducting liquid 11, the temperature of the rest of the tube is relatively uniform except the temperature dividing point. The temperatures of the two parts are measured by the first temperature sensitive resistance 23 and the second temperature sensitive resistance 24 respectively. In operation, the temperature of the high temperature zone is T1, and the temperature of the low temperature zone is T2, and the temperature difference between them is kept at 30-50℃.

[0125] Referring to Figure 8 , the liquid level measuring device in Example Five uses four temperature sensitive resistance wires. The second temperature sensitive resistance wire 25 and the fourth temperature sensitive resistance wire 27 are installed at the top of the elongated structure 1, and the installation position is higher than the maximum liquid level measuring height and is immersed in the heat conducting liquid 11. The second temperature sensitive resistance wire 25 and the fourth temperature sensitive resistance wire 27 are R1 and R4 in Figure 8 respectively. The third temperature sensitive resistance wire 26 is installed at the bottom of the elongated structure 1 and is immersed in the heat conducting liquid 11. The third temperature sensitive resistance wire 26 is R3 in Figure 8 . The first temperature sensitive resistance wire 22 has the same length as the elongated structure 1 and is immersed in the heat conducting liquid 11. The two ends of the first temperature sensitive resistance wire 22 are fixed at the top and bottom of the elongated structure 1 respectively, and the resistance value changes with the liquid level height, which is R2 in Figure 8 .

[0126] The four temperature sensitive resistance wires have the same material, the same length and the same diameter. The second temperature sensitive resistance wire 25, the third temperature sensitive resistance wire 26 and the fourth temperature sensitive resistance wire 27 are wound into small coils.

[0127] The output voltage V of the bridge can be determined by the calculation formula of the output voltage V of the bridge:

[0128]

[0129] wherein U0 is the power supply voltage of the bridge, R1 is the measured resistance of the first temperature sensitive resistance wire 22, R2 is the measured resistance of the second temperature sensitive resistance wire 25, R3 is the measured resistance of the third temperature sensitive resistance wire 26, and R4 is the measured resistance of the fourth temperature sensitive resistance wire 27.

[0130] When the liquid level height of the liquid 3 to be measured is zero, R2 = R3, and at this time V = 0.

[0131] When the liquid level of the liquid to be measured 3 reaches the maximum, R2 = R1, at which time V reaches the maximum value:

[0132]

[0133] The direct current is used for power supply, U0 is the power supply voltage, V is the output voltage of the bridge, which has a linear relationship with the liquid level l of the liquid to be measured 3, that is:

[0134] l = kV

[0135] Wherein, k is the proportional coefficient, which can be obtained by calibration; therefore, after determining the output voltage of the bridge, the liquid level l of the liquid to be measured 3 can be determined.

[0136] Referring to Figure 9 , another configuration of the liquid level measuring device based on the temperature difference demarcation point is provided in the fifth embodiment of the present application, which comprises:

[0137] An elongated structural member 1 for partially inserting into the liquid to be measured, a heat-conducting liquid 11 is injected into the inner cavity of the elongated structural member, and the whole has small thermal inertia;

[0138] A control device 2, a heating wire 21 connected with the control device 2 passes through the elongated structural member 1 and is immersed into the heat-conducting liquid 11;

[0139] A plurality of infrared shielding rings 4 are uniformly and spacedly sleeved outside the elongated structural member 1, and the spacing between the shielding rings is equivalent to the millimeter corresponding to the number of imaging pixels of the infrared thermal imaging device used;

[0140] An infrared thermal imaging device 5 is arranged outside the liquid to be measured 3, which collects infrared images towards the elongated structural member 1, and the liquid level of the liquid to be measured 3 is obtained by determining the position of the temperature demarcation line of the liquid level according to the infrared images collected by the infrared thermal imaging device 5 and combining the shielding rings.

[0141] The heating wire inside the elongated structural member 1 heats the heat-conducting liquid 11, which makes its temperature rise, and the elongated structural member 1 itself serves as a light source to emit infrared light outward; when the elongated structural member 1 is inserted into the liquid to be measured 3, the heat exchange between the liquid to be measured 3 and the heat-conducting liquid 11 will form a temperature demarcation line on the inside of the elongated structural member 1. Because the heat capacity and the thermal conductivity of the liquid to be measured 3 are different from those of the heat-conducting liquid 11, the position of the temperature demarcation line will change with the change of the liquid level.

[0142] The infrared thermography device captures the thermal image of the surface of the elongated structure 1. Since the temperature at the temperature boundary is different from the surrounding area, a clear contrast is formed on the thermal image. By controlling the rotation angle of the holder, the camera of the infrared thermography device 5 can be positioned to the segment of the elongated structure where the image is located, and a clear image of the segment can be obtained.

[0143] By adjusting the camera of the infrared thermography device 5, the camera sequentially captures infrared images of the heat-conducting liquid 11 between the two infrared shielding rings 4 from top to bottom. In the captured infrared images, the liquid level temperature boundary can be clearly shown. After the liquid level temperature boundary is determined, the liquid level of the liquid to be measured 3 can be quickly confirmed. For example, if the elongated structure 1 is evenly divided into 10 segments, each segment representing a 10% liquid level height, and the temperature boundary is located in the third segment from top to bottom, the height of the liquid level boundary in the third segment is determined first. The height of the liquid level boundary obtained is added to the height of the remaining 7 segments, and the liquid level height of the liquid to be measured 3 is obtained.

[0144] The liquid level measurement method in this embodiment five does not depend on light conditions, so it can maintain stable liquid level measurement performance in any lighting environment. The liquid level measurement device does not need to be manually operated, and only needs to be placed in the liquid to be measured to automatically measure the liquid level. It is especially suitable for environments such as rivers, urban water supply, and drainage pipelines that are not suitable for human operation. In addition, since the heating wire 21 is arranged inside the elongated structure 1 and is not directly exposed to the liquid to be measured 3, and the infrared thermography device 5 is arranged above the liquid surface and is not affected by the interference in the liquid to be measured 3, the liquid level measurement device has good anti-interference ability.

[0145] The liquid level measurement device in the foregoing embodiments of the present application can be used for liquid level measurement in environments such as rivers, urban water supply, drainage pipelines, various water pools, water tanks, and storage tanks, oil tanks, and the like in the petroleum, natural gas, and food industries that are not suitable for human operation. It has good anti-interference ability and can work in dark environments.

[0146] It should be noted that each of the embodiments in the present specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other.

[0147] Although the preferred embodiments of the embodiments of the present application have been described, those skilled in the art can make further changes and modifications to the embodiments once they know the basic creative concept. Therefore, the appended claims are intended to include the preferred embodiments and all changes and modifications falling within the scope of the embodiments of the present application.

[0148] It should also be noted that, in this article, the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are used for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or component referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, relational terms such as "first" and "second" are used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations, nor can they be understood as indicating or implying relative importance. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or terminal device including a series of elements does not include those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or terminal device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of another identical element in the process, method, article or terminal device including the element.

[0149] The above describes the technical solutions provided by the present application in detail, and the principles and implementation modes of the present application are described by applying specific examples. The above example is only used to help understand the present application, and the content of the description should not be understood as limiting the present application. Meanwhile, for those skilled in the art, according to the present application, different forms of changes in specific implementation modes and application scope will be made, which do not need and cannot be exhausted here, and the obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A liquid level measuring device based on a temperature difference boundary point, characterized in that, include: The elongated structure (1) is used to partially insert into the liquid to be tested (3), and the inner cavity of the elongated structure (1) is filled with a heat-conducting liquid (11). The heating wire (21) and the first temperature-sensitive material resistance wire (22) connected to the control device (2) by a wire pass through the elongated structure (1) and are immersed in the heat-conducting liquid (11), and the ends of the heating wire (21) and the first temperature-sensitive material resistance wire (22) are in contact with the bottom of the inner cavity of the elongated structure (1); A first temperature-sensitive resistor (23) and a second temperature-sensitive resistor (24) are connected to the control device (2). The first temperature-sensitive resistor (23) is disposed at the top of the heat-conducting liquid (11), and the second temperature-sensitive resistor (23) is disposed at the bottom of the heat-conducting liquid (11). When measuring the liquid level, one end of the slender structural member (1) is inserted into the liquid to be measured (3), and the control device (2) controls the heating wire (21) to heat the heat-conducting liquid (11); after the heat-conducting liquid (11) is heated, the liquid level of the liquid to be measured (3) is determined according to the real-time temperature detected by the first temperature-sensitive resistor (23) and the second temperature-sensitive resistor (24) respectively and the measured resistance of the first temperature-sensitive material resistance wire (22); The steps for determining the liquid level of the liquid to be measured (3) based on the real-time temperatures detected by the first temperature-sensitive resistor (23) and the second temperature-sensitive resistor (24) and the measured resistance of the first temperature-sensitive material resistance wire (22) include: According to the formula: Calculate the liquid level l of the liquid to be tested (3); Wherein, R1 is the measured resistance of the first temperature-sensitive material resistance wire (22), R2 is the resistance of the first temperature-sensitive material resistance wire (22) calculated at the temperature measured by the first temperature-sensitive resistor (23), R3 is the resistance of the first temperature-sensitive material resistance wire (22) calculated at the temperature measured by the second temperature-sensitive resistor (24), and L is the length of the first temperature-sensitive material resistance wire (22).

2. The liquid level measuring device based on the temperature difference boundary point according to claim 1, characterized in that, A second temperature-sensitive material resistance wire (25), which is connected to the control device (2) by a wire, is installed at the top of the elongated structural member (1) and immersed in the heat-conducting liquid (11); The second temperature-sensitive material resistance wire (25) is the same as the first temperature-sensitive material resistance wire (22) in terms of material and diameter; When measuring the liquid level, one end of the slender structural member (1) is inserted into the liquid to be measured (3), and the control device (2) controls the heating wire (21) to heat the heat conduction liquid (11). After the heat conduction liquid (11) is heated, the liquid level of the liquid to be measured (3) is determined according to the real-time temperature detected by the second temperature-sensitive resistor (24), the measured resistance of the first temperature-sensitive material resistance wire (22) and the second temperature-sensitive material resistance wire (25).

3. The liquid level measuring device based on the temperature difference boundary point according to claim 2, characterized in that, The second temperature-sensitive material resistance wire (25) has the same length as the first temperature-sensitive material resistance wire (22). The steps for determining the liquid level of the liquid to be measured (3) based on the real-time temperature detected by the second temperature-sensitive resistor (24), the measured resistance of the first temperature-sensitive material resistance wire (22), and the second temperature-sensitive material resistance wire (25) include: Through the formula: Calculate the liquid level l of the liquid to be tested (3), where R1 is the measured resistance of the first temperature-sensitive material resistance wire (22), R3 is the resistance of the first temperature-sensitive material resistance wire (22) calculated at the temperature measured by the second temperature-sensitive resistor (24), R4 is the measured resistance of the second temperature-sensitive material resistance wire (25), and L is the length of the first temperature-sensitive material resistance wire (22).

4. The liquid level measuring device based on the temperature difference boundary point according to claim 1, characterized in that, A second temperature-sensitive material resistance wire (25) connected to the control device (2) by a wire is installed at the top of the slender structural member (1) and immersed in the heat-conducting liquid (11); the second temperature-sensitive material resistance wire (25) is the same as the first temperature-sensitive material resistance wire (22) in terms of material and diameter; A third temperature-sensitive material resistance wire (26) connected to the control device (2) by a wire passes through the elongated structure (1) and is immersed in the heat-conducting liquid (11), and the end of the third temperature-sensitive material resistance wire (26) is located at the bottom of the inner cavity of the elongated structure (1); The fourth temperature-sensitive material resistance wire (27), which is connected to the control device (2) by a wire, is installed at the top of the slender structural member (1) and immersed in the heat-conducting liquid (11); the fourth temperature-sensitive material resistance wire (27) is the same as the first temperature-sensitive material resistance wire (22) in terms of material and diameter. When measuring the liquid level, one end of the slender structural member (1) is inserted into the liquid to be measured (3), and the control device (2) controls the heating wire (21) to heat the heat-conducting liquid (11). After the heat-conducting liquid (11) is heated, the liquid level of the liquid to be measured (3) is determined according to the measured resistance of the first temperature-sensitive material resistance wire (22), the second temperature-sensitive material resistance wire (25), the third temperature-sensitive material resistance wire (26) and the fourth temperature-sensitive material resistance wire (27).

5. The liquid level measuring device based on the temperature difference boundary point according to claim 4, characterized in that, The liquid level of the liquid to be tested (3) is determined based on the measured resistances of the first temperature-sensitive material resistance wire (22), the second temperature-sensitive material resistance wire (25), the third temperature-sensitive material resistance wire (26), and the fourth temperature-sensitive material resistance wire (27). Through the formula: Determine the output voltage V of the bridge circuit containing the first temperature-sensitive material resistance wire (22), the second temperature-sensitive material resistance wire (25), the third temperature-sensitive material resistance wire (26), and the fourth temperature-sensitive material resistance wire (27); wherein R1 is the measured resistance of the first temperature-sensitive material resistance wire (22), R2 is the measured resistance of the second temperature-sensitive material resistance wire (25), R3 is the measured resistance of the third temperature-sensitive material resistance wire (26), R4 is the measured resistance of the fourth temperature-sensitive material resistance wire (27), and U0 is the supply voltage of the bridge circuit containing the first temperature-sensitive material resistance wire (22), the second temperature-sensitive material resistance wire (25), the third temperature-sensitive material resistance wire (26), and the fourth temperature-sensitive material resistance wire (27); Through the formula: Calculate the liquid level l of the liquid to be tested (3); where k is a preset proportional coefficient.

6. The liquid level measuring device based on the temperature difference boundary point according to claim 1, 3, or 5, characterized in that, The heating wire (21) is a silicone heating wire or a carbon fiber heating wire.

7. The liquid level measuring device based on the temperature difference boundary point according to claim 1, 3, or 5, characterized in that, The heat-conducting liquid (11) is a fluorinated liquid or transformer oil, and the slender structural component (1) is a thin-walled stainless steel tube.

8. The liquid level measuring device based on the temperature difference boundary point according to claim 5, characterized in that, The first temperature-sensitive material resistance wire (22), the second temperature-sensitive material resistance wire (25), the third temperature-sensitive material resistance wire (26) and the fourth temperature-sensitive material resistance wire (27) are made of materials with positive or negative temperature coefficient of resistance.

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