Liquid level detection device and water heater

Abstract

This invention discloses a liquid level detection device, comprising: a housing having a closed cavity inside; multiple detection electrodes, each disposed within the cavity, and the multiple detection electrodes being sequentially arranged between a reference electrode and a second end of the cavity; a reference electrode disposed within the cavity and located at a first end of the cavity, the detection value of the reference electrode being used to correct the detection value of the detection electrode; and a processing module disposed within the cavity, the reference electrode and the detection electrodes being connected to the processing module, the processing module being used to determine the liquid level based on the detection values ​​of each detection electrode. The liquid level detection device of this invention, by setting a reference electrode and using the detection value of the reference electrode to correct the detection value of the detection electrode, can offset the influence of water temperature on the capacitance value, improve detection accuracy, and thus improve the accuracy of liquid level determination.

Description

Technical Field

[0001] This invention belongs to the field of detection device technology, specifically, it relates to a liquid level detection device and a water heater. Background Technology

[0002] Liquid level detection devices can detect the height of the liquid level in a container and are widely used.

[0003] For liquid level detection in high-temperature environments, such as solar water heaters, the water tank is constantly exposed to high temperatures. When a certain pressure is accumulated, the water vapor temperature can reach as high as 120℃, and can even reach 140℃ when exposed to direct sunlight. Existing water temperature and level control devices for solar water heaters are mainly electrode-based, utilizing the conductivity of water to detect changes in resistance, thereby discretely detecting multiple water levels.

[0004] Because the sensitive element needs to be in contact with water, prolonged exposure to high temperatures and moisture can cause the moisture to corrode the sensitive element and seep into the internal circuitry, leading to intermittent malfunctions. Furthermore, prolonged use can cause scale buildup, preventing water from contacting the sensitive element and causing the solar water tank's automatic water filling and stopping functions to fail, thus affecting normal operation. Summary of the Invention

[0005] This invention addresses the technical problem that liquid level detection devices in the prior art are prone to malfunction in high-temperature environments, and proposes a liquid level detection device that can solve the above-mentioned problem.

[0006] To achieve the above-mentioned objectives, the present invention employs the following technical solution:

[0007] A liquid level detection device, comprising:

[0008] The outer shell has a closed cavity inside;

[0009] The detection electrodes are multiple and are respectively disposed in the cavity, and the multiple detection electrodes are arranged sequentially between the reference electrode and the second end of the cavity;

[0010] A reference electrode is disposed within the cavity and located at the first end of the cavity. The detection value of the reference electrode is used to correct the detection value of the detection electrode.

[0011] A processing module is disposed within the cavity, and the reference electrode and the detection electrode are respectively connected to the processing module. The processing module is used to determine the liquid level based on the detection values ​​of each detection electrode.

[0012] Furthermore, the reference electrode and the detection electrode are capacitive elements, capable of feeding back their respective capacitance values ​​to the processing module;

[0013] The processing module is configured to perform temperature drift correction on the detection electrode based on the capacitance value detected by the reference electrode.

[0014] Furthermore, the processing module performs temperature drift correction on the detection electrode as follows:

[0015] Calculate the capacitance change of the detection electrode when it is wet and when it is dry: ΔC1=C_ 有水 -C_ 无水 ; Detect and store the capacitance change of the detection electrode at temperature T: ΔC 检测 = a1*T+b1;

[0016] Detect and store the capacitance change of the reference electrode at temperature T: ΔC 参考 = a2*T + b2;

[0017] Calculate the capacitance change caused by the temperature drift of the detection electrode:

[0018] Where a1 is the slope of the capacitance value of the detection electrode as a function of temperature, b1 is the intercept of the capacitance value of the detection electrode as a function of temperature, a2 is the slope of the capacitance value of the reference electrode as a function of temperature, and b2 is the intercept of the capacitance value of the reference electrode as a function of temperature.

[0019] Calculate the capacitance correction value of the nth detection electrode: C n =C′ n -ΔC;

[0020] Among them, C′ n This is the capacitance detection value of the nth detection electrode.

[0021] Furthermore, the parameters a1, b1, a2, and b2 are determined as follows: the capacitance values ​​of the reference electrode and the detection electrode at different temperatures are obtained respectively, the parameters a1, b1, a2, and b2 are fitted, and then stored in the processing module.

[0022] Furthermore, the processing module is also configured to perform scale compensation on the detection electrode:

[0023] Calculate the correction value for the nth detection electrode: C n =C′ n -ΔC-δ;

[0024] δ is the factor that scale affects the capacitance value.

[0025] Furthermore, the processing module is positioned near the second end of the cavity.

[0026] Furthermore, the sensitive surfaces of the reference electrode and the detection electrode are attached to the inner wall of the housing or located at the center of the cavity, and the cavity is filled with a filling layer for sealing it.

[0027] Furthermore, the filler layer is a waterproof adhesive.

[0028] Furthermore, it also includes a temperature sensor, which is disposed within the cavity.

[0029] The present invention also proposes a water heater, including a water tank and a liquid level detection device as described in any of the preceding paragraphs, wherein at least the first end of the outer casing extends vertically into the interior of the water tank.

[0030] Compared with the prior art, the advantages and positive effects of the present invention are as follows: In the liquid level detection device of the present invention, the detection electrode is encapsulated in a cavity and does not come into contact with high-temperature water, thus avoiding corrosion of the device by water and steam, and therefore its function is not affected. By setting a reference electrode, the detection value of the reference electrode is used to correct the detection value of the detection electrode, which can offset the influence of water temperature on the capacitance value, improve the detection accuracy, and thus improve the accuracy of liquid level judgment.

[0031] Other features and advantages of the present invention will become clearer after reading the detailed embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of an embodiment of the liquid level detection device proposed in this invention;

[0034] Figure 2 yes Figure 1 A schematic diagram of a partial structure;

[0035] Figure 3 yes Figure 1 A schematic diagram of a partial structure;

[0036] Figure 4 This is a schematic diagram of an embodiment of the water heater proposed in this invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0038] It should be noted that in the description of this invention, the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," which indicate directional or positional relationships, are based on the directional or positional relationships shown in the accompanying drawings. These are merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0039] Example 1

[0040] This embodiment proposes a liquid level detection device, such as... Figure 1 As shown, the system includes a housing 11, detection electrodes 12, a reference electrode 13, and a processing module 14. The housing 11 has a closed cavity 15 inside. Multiple detection electrodes 12 are disposed within the cavity 15, and are sequentially arranged between the reference electrode 13 and the second end 152 of the cavity 15. The reference electrode 13 is disposed within the cavity 15 and located at the first end 151 of the cavity 15. The detection value of the reference electrode 13 is used to correct the detection values ​​of the detection electrodes 12. The processing module 14 is disposed within the cavity 15, and the reference electrode 13 and detection electrodes 12 are respectively connected to the processing module 14. The processing module 14 is used to determine the liquid level based on the detection values ​​of each detection electrode 12.

[0041] Multiple detection electrodes 12 are arranged along the length of the outer casing 11. The liquid level detection device should be vertically installed in a container that requires liquid level detection to detect the liquid level in the container.

[0042] The detection electrode 12 and the reference electrode 13 are encapsulated in the cavity 15 to isolate the sensitive element from the liquid and prevent scale buildup on the outer surface of the sensitive element from affecting the detection accuracy.

[0043] The detection electrode 12 and the reference electrode 13 can be capacitive elements, which can change their resistance or capacitance value according to changes in the external environment. When the water level does not exceed the detection electrode 12, it outputs a capacitance value. When the water level exceeds the detection electrode 12, the water changes its resistance or capacitance value, and the detection output is a different capacitance value. The processing module 14 compares the detection values ​​of each detection electrode 12 with the reference value to determine whether there is water exceeding the current detection electrode 12, thereby realizing the liquid level determination.

[0044] Since the presence of liquid alters the detection value of the detection electrode 12, temperature also affects the detection value. That is, in the same environment (with or without water), the detection value of the detection electrode 12 changes with temperature. In applications such as water heaters, the temperature environment of the water tank varies extremely complexly, ranging from 0 to 120°C. Therefore, the influence of temperature will significantly affect the detection results. Directly using the detection value to determine the liquid level can easily lead to misjudgment.

[0045] Based on this, a reference electrode 13 is set in this solution. Since the reference electrode 13 and the detection electrode 12 are located in the same temperature environment, the effect of temperature on the detection electrode 13 is related to the effect on the reference electrode 13. Therefore, the reference electrode 13 is set in this solution to correct the detection conclusion of the detection electrode 12, which has high reliability.

[0046] In this embodiment, the reference electrode 13 and the detection electrode 12 are preferably capacitor elements, which can feed back their respective capacitance values ​​to the processing module 14.

[0047] Processing module 14 is configured to perform temperature drift correction on detection electrode 12 based on the capacitance value detected by reference electrode 13.

[0048] To improve the reliability of the reference electrode 13, the environmental factors that cause changes in the detection value of the reference electrode 13 should be minimized. Since temperature changes inside the water heater tank are a fact that cannot be avoided, the reference electrode 13 can be placed in the air or in the liquid at all times. In this way, changes in the reference electrode 13 due to changes in the dry and wet environment can be avoided. That is, the change in the detection value of the reference electrode 13 is only related to temperature changes.

[0049] The method by which the processing module 14 performs temperature drift correction on the detection electrode 12 is as follows:

[0050] Calculate the capacitance change of the detection electrode when it is wet and when it is dry: ΔC1=C_ 有水 -C_ 无水 ;

[0051] ΔC1 generally exhibits a linear relationship with temperature (between 20℃ and 50℃).

[0052] Detect and store the capacitance change of the detection electrode at temperature T: ΔC 检测 = a1*T+b1;

[0053] Detect and store the capacitance change of the reference electrode at temperature T: ΔC 参考 = a2*T + b2;

[0054] Calculate the capacitance change caused by the temperature drift of the detection electrode:

[0055] Where a1 is the slope of the capacitance value of the detection electrode as a function of temperature, b1 is the intercept of the capacitance value of the detection electrode as a function of temperature, a2 is the slope of the capacitance value of the reference electrode as a function of temperature, and b2 is the intercept of the capacitance value of the reference electrode as a function of temperature.

[0056] Calculate the capacitance correction value of the nth detection electrode: C n =C′ n -ΔC;

[0057] Among them, C′ n This is the capacitance detection value of the nth detection electrode.

[0058] n is a positive integer.

[0059] In both air and liquid environments, the capacitance values ​​of the detection electrode 12 and the reference electrode 13 exhibit a linear relationship with temperature, and the linear parameter can be calculated. Since temperature changes have the same effect on both the reference electrode 13 and the detection electrode 12, the temperature drift value of the reference electrode 13 can be calculated, and then this value can be used to calculate the temperature drift value of the detection electrode 12. After removing the temperature effect from the detection electrode 12, if the detected capacitance value changes, it can be determined that the change is due to a change in the gaseous or liquid environment, thus allowing identification of whether the current environment is air or liquid.

[0060] Therefore, the parameters a1, b1, a2, and b2 are determined as follows: obtain the capacitance values ​​of the reference electrode and the detection electrode at different temperatures, fit the values ​​to obtain the parameters a1, b1, a2, and b2, and store them in the processing module. They can be directly called during calculation.

[0061] In many regions, the water quality is hard, making it prone to scaling. Scale adheres to the outer surface of the casing, affecting the sensing sensitivity of the level detection device. To eliminate the impact of scale, the processing module in this embodiment is also configured to compensate for scale buildup on the detection electrodes:

[0062] Calculate the capacitance correction value of the nth detection electrode: C n =C′ n -ΔC-δ;

[0063] δ is the factor that scale affects capacitance, and it can be obtained through laboratory testing.

[0064] Since the water tank no longer contains only air when it is full, this solution preferably places the reference electrode 13 in an environment where it is always filled with water to ensure the stability of the environment. Simply inserting the reference electrode 13 into the bottom of the water tank will, in most cases, result in the water level being higher than the height of the reference electrode 13, unless the water in the tank is intentionally drained and not automatically refilled; this scenario is not within the scope of this solution.

[0065] When using this liquid level detection device, its outer casing 11 is inserted into the container to be detected, and the highest detection electrode 12 should still be at the height that the liquid level may reach. The cavity 15 has a first end 151 and a second end 152 in its length direction. The reference electrode 13 is located at the first end 151 of the cavity 15. When the outer casing 11 is inserted into the container to be detected, the first end 151 should be inserted downwards.

[0066] Because the water tank of a solar water heater is constantly exposed to high temperatures, the water vapor temperature can reach as high as 120°C when pressure is accumulated, and can even reach 140°C when the water is exposed to direct sunlight. If the processing module 14 inside the cavity 15 of this liquid level detection device is exposed to high temperatures for extended periods, its service life will be affected.

[0067] Since the first end 151 is inserted downwards into the container to be tested, the processing module 14 is preferably positioned close to the second end 152 of the cavity 15. The second end 152 does not need to be constantly submerged in the liquid, thus avoiding damage to the processing module 14 from the high-temperature liquid.

[0068] To further protect the processing module 14, it is preferable that after the liquid level detection device is assembled into the container to be tested, the second end 152 is left outside the container to be tested, so as to prevent the processing module 14 from being located in the high-temperature liquid or gas environment inside the container to be tested.

[0069] The sensitive surfaces of the reference electrode 13 and the detection electrode 12 are positioned at the center of the cavity 15, which is attached to the inner wall of the outer shell. The cavity 15 is filled with a filling layer (not shown in the figure) to seal them. The filling layer can seal the reference electrode 13, the detection electrode 12, and the processing module 14, preventing moisture from corroding the sensitive elements and seeping into the internal circuitry under long-term high temperature and moisture conditions, thus preventing intermittent functional failure.

[0070] The preferred filler layer is a high-temperature resistant waterproof adhesive, such as epoxy resin.

[0071] In many applications, in addition to liquid level detection, temperature detection is also required. In order to save packaging costs, there is no need to package a temperature sensor separately. The liquid level detection device of this solution preferably also includes a temperature sensor 16. The temperature sensor is set in the cavity 15 and packaged together with the detection electrode 12 and the reference electrode 13, which expands the temperature detection function and achieves the effect of saving costs.

[0072] like Figure 2 , Figure 3 As shown, the outer shell 11 can be composed of two parts, a first section 111 and a second section 112, which are sealed together to form a closed cavity 15 inside. In this embodiment, the first section 111 and the second section 112 are connected by threads, and a sealing ring 17 is provided at the connection point.

[0073] Example 2

[0074] This embodiment also proposes a water heater, such as... Figure 4 As shown, the system includes a water tank 2 and the liquid level detection device 1 described in Embodiment 1. The top of the water tank 2 has an assembly hole (not shown in the figure), and at least the first end of the outer casing 11 extends vertically into the interior of the water tank 2 through the assembly hole. The liquid level detection device is as follows... Figure 1 As shown, the device includes a housing 11, detection electrodes 12, a reference electrode 13, and a processing module 14. The housing 11 has a closed cavity 15 inside. Multiple detection electrodes 12 are disposed within the cavity 15, and are sequentially arranged between the reference electrode 13 and the second end 152 of the cavity 15. The reference electrode 13 is disposed within the cavity 15 and located at the first end 151 of the cavity 15. The detection value of the reference electrode 13 is used to correct the detection values ​​of the detection electrodes 12. The processing module 14 is disposed within the cavity 15, and the reference electrode 13 and detection electrodes 12 are respectively connected to the processing module 14. The processing module 14 is used to determine the liquid level based on the detection values ​​of each detection electrode 12. For a detailed description of the liquid level detection device, please refer to Embodiment 1, which will not be repeated here.

[0075] In this embodiment, the second end 152 of the cavity 15 is preferably located outside the water tank 2, and the processing module 14 is positioned close to the second end 152 of the cavity 15. This avoids the processing module 14 being located in the high-temperature liquid or gas environment inside the water tank 2, which helps to extend its service life.

[0076] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions claimed by the present invention.

Claims

1. A liquid level detection device, characterized in that, include: The outer shell has a closed cavity inside; The detection electrodes are multiple and are respectively disposed in the cavity, and the multiple detection electrodes are arranged sequentially between the reference electrode and the second end of the cavity; A reference electrode is disposed within the cavity and located at the first end of the cavity. The detection value of the reference electrode is used to correct the detection value of the detection electrode. The reference electrode extends into the bottom of the water tank. A processing module is disposed within the cavity, and the reference electrode and the detection electrode are respectively connected to the processing module. The processing module is used to determine the liquid level based on the detection values ​​of each detection electrode. The reference electrode and the detection electrode are capacitive elements, capable of sending their respective capacitance values ​​to the processing module; The processing module is configured to perform temperature drift correction on the detection electrode based on the capacitance value detected by the reference electrode. The processing module performs temperature drift correction on the detection electrode as follows: Calculate the capacitance change of the detection electrode when it is wet and when it is dry: ΔC1=C_ 有水 -C_ 无水 ; Detect and store the capacitance change of the detection electrode at temperature T: ΔC 检测 =a1*T+b1; Detect and store the capacitance change of the reference electrode at temperature T: ΔC 参考 =a2*T+b2; Calculate the capacitance change caused by the temperature drift of the detection electrode: ΔC = ; Where a1 is the slope of the capacitance value of the detection electrode as a function of temperature, b1 is the intercept of the capacitance value of the detection electrode as a function of temperature, a2 is the slope of the capacitance value of the reference electrode as a function of temperature, and b2 is the intercept of the capacitance value of the reference electrode as a function of temperature. Calculate the capacitance correction value of the nth detection electrode: C n = ; in, This is the capacitance detection value of the nth detection electrode.

2. The liquid level detection device according to claim 1, characterized in that, The parameters a1, b1, a2, and b2 are determined as follows: the capacitance values ​​of the reference electrode and the detection electrode at different temperatures are obtained respectively, the parameters a1, b1, a2, and b2 are fitted, and then stored in the processing module.

3. The liquid level detection device according to claim 1, characterized in that, The processing module is also configured to perform scale compensation on the detection electrode: Calculate the correction value for the nth detection electrode: C n = ; This is the factor affecting the capacitance value due to scaling.

4. The liquid level detection device according to any one of claims 1-3, characterized in that, The processing module is located near the second end of the cavity.

5. The liquid level detection device according to any one of claims 1-3, characterized in that, The sensitive surfaces of the reference electrode and the detection electrode are attached to the inner wall of the housing or located at the center of the cavity, which is filled with a filling layer for sealing it.

6. The liquid level detection device according to claim 5, characterized in that, The filler layer is a waterproof adhesive.

7. The liquid level detection device according to any one of claims 1-3, characterized in that, It also includes a temperature sensor, which is disposed within the cavity.

8. A water heater, comprising a water tank, characterized in that, It also includes the liquid level detection device according to any one of claims 1-7, wherein at least the first end of the housing extends vertically into the interior of the water tank.

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