KR101568376B1 - Water level sensor and water level sensing system of apparatus using same - Google Patents

Abstract

Disclosed is a water level sensor which can be applied even when the object to be measured is grounded, and which has excellent measurement reliability, and a water level sensing system using the water level sensor. The present invention is characterized in that a flat plate-shaped shield electrode having a predetermined length and at least two sensor electrodes in the longitudinal direction are formed on one surface of the shield electrode with a first insulating layer interposed therebetween, A water level sensor in which the width of the shield electrode is smaller than the width of the other end, and a water level sensing system using the water level sensor

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water level sensor and a water level sensing system for the water level sensor using the water level sensor,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water level sensor and a water level sensing system using the water level sensor and, more particularly, to a water level sensor having a sensor electrode for sensing a change in capacitance according to a liquid level, And a water level sensing system using the water level sensing system.

Generally, the water level sensor is used to measure the level of various liquids in an industrial field. Industrial applications include water traps widely used in various production facilities, industrial and domestic boilers, waterworks, water tanks, as well as devices using liquids such as chemicals in the manufacturing process of semiconductors and PCBs And is widely applied to home appliances such as washing machines, dishwashers, water purifiers, humidifiers, and bidets.

Such a water level sensor can be measured by various methods. In the fields of rainfall measurement and environmental monitoring such as river height measurement, high measurement reliability, small and inexpensive sensors are required for a service combined with a sensor network. In addition, there is an increasing need for a simple and easy-to-install sensor tag.

Recently, household appliances using water have been trying to reduce power consumption and water consumption by regulating water consumption as well as improving power consumption. For this purpose, a more accurate control of the water level is required. For example, in the washing machine, the water level is measured by a mechanical pressure sensor up to now, but a water level sensor capable of accurate water level measurement is required in order to reduce water consumption.

Conventionally, the water level sensor has been commercialized in various forms. The water level sensor includes a capacitance type water level sensor for measuring the liquid level using the difference between the dielectric constants of air and liquid, an ultrasonic level sensor using the ultrasonic wave generator and a sensor, And a water level sensor for measuring a pressure change according to the pressure.

Among them, the capacitance type water level sensor has been spotlighted in terms of precision and economy, and its measurement principle is as shown in Fig. That is, the capacitance type water level sensor 10 is constituted by a double cylindrical shape of the internal electrode 11 and the external electrode 12 (see Fig. 1 (a)), and the capacitance between the internal electrode 11 and the external electrode 12 (C _h ) between the electrodes according to the height (h) of the liquid (l) of the liquid. At this time, the change of the capacitance C _h can be expressed by the capacitance C that can be expressed by the following equation (1), the relative dielectric constant of the air between the electrodes,? _R , about 1 and the relative dielectric constant of the liquid epsilon _r , and about 80 in water).

(C: capacitance,? ₀ : vacuum permittivity,? _R : relative dielectric constant, L: cylinder height, a: internal electrode radius, b: external electrode radius)

When a plate type electrostatic capacitive level sensor (see Fig. 1 (b)) such as a film is used, the electrostatic capacity can be calculated by the following equation (2).

(C: capacitance,? ₀ : vacuum permittivity,? _R : relative dielectric constant, S: electrode area,

Such a capacitance type water level sensor is problematic when it is used in a device in which a liquid container such as a washing machine, a dishwasher, etc., may be made of a metallic material. That is, in the case of a device provided with a container capable of containing liquid, there is a risk of electric shock when the user operates it, so that the capacitance measurement object is generally grounded in many cases. However, in this case, since the liquid contained in the container is regarded as a ground instead of a dielectric, the capacitance type water level sensor using the difference in relative dielectric constant of air and liquid can not measure the capacitance itself.

Accordingly, the electrostatic capacitance type water level sensor can be applied even when the electrostatic capacitance measuring object is grounded. Further, a water level sensor having a new structure that can solve the sensitivity change problem due to the influence of the electrostatic field due to the ground state, System is required.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above problems, and it is an object of the present invention to provide a new water level sensor which can be applied even when the capacitance measurement object is grounded and has excellent measurement reliability and a water level sensing system using the same .

The present invention also provides a water level sensor which is easy to install and economical, and a water level sensing system using the same.

According to an aspect of the present invention, there is provided a plasma display device including: a flat plate-shaped shield electrode having a predetermined length; and at least two sensor electrodes in the longitudinal direction on a surface of the shield electrode, And the shield electrode is formed to have a width smaller than that of the other end.

Further, the shield electrode has a trapezoidal shape.

The ratio of the one end width to the other end width of the shield electrode is 0.5 to 0.8 based on the case where the length is 3.5 times the other end width.

The sensor electrode may include a first electrode and a second electrode arranged in parallel to each other with a structure in which a plurality of protrusions and a plurality of grooves are alternately arranged on at least one surface in a direction orthogonal to the longitudinal direction, The projections of the first electrode correspond to the grooves of the second electrode and the projections of the second electrode correspond to the grooves of the first electrode so as to be engaged with each other and spaced apart from each other by a predetermined distance .

The water level sensor further includes a signal processing unit disposed at an upper end of the first electrode and the second electrode and detecting a water level through a sensing signal generated by the water level sensor and generating a detection signal.

The water level sensor is a wireless type structure having an antenna for transmitting a detection signal of the signal processing unit to the outside and a solar cell or a battery for supplying power to the signal processing unit and the water level sensor. Lt; / RTI >

Also, the water level sensor is a streamlined structure having a connecting line for transmitting a detection signal of the signal processing unit to the outside, and a solar cell or a battery for supplying electric power.

The sensor further includes a second insulating layer on the shield electrode and the sensor electrode, and an adhesive layer on the other surface of the shield electrode.

According to another aspect of the present invention, there is provided a water level sensing system for a device having a container capable of containing a liquid, wherein the liquid in the container or the container is grounded, And a controller for sensing a change in the capacitance value of the water level sensor according to the level of the liquid immersed in the container to sense the water level, Wherein the level sensor is configured to linearly sense a sensor electrode having a predetermined length and a sensor electrode having two or more sensor electrodes in the longitudinal direction on a surface of the shield electrode with a first insulating layer interposed therebetween, And the shield electrode may be a device using a water level sensor whose width is smaller than the width of the other end It provides a level sensing system.

According to the present invention, when the liquid in the container or the container is grounded, since the liquid level sensor having a value larger than 0 in the capacitance immediately before the highest level of the liquid immersed in the container is provided, The sensor of the present invention can sense the level of the sensor by sensing the change in capacitance of the sensor and adjust the width of the upper and lower ends of the electrode to linearly detect the change of the capacitance value. It is possible to provide a device level sensing system.

In addition, it is possible to accurately measure the amount of the liquid to be measured by linearly sensing the change in the capacitance value at the water level, thereby reducing the consumption of the liquid used in the apparatus, thereby saving power energy consumed in the apparatus.

Also, it is economical because it can be manufactured by using film or adhesive film of low plasticity, low cost, and can be easily installed without designing a special mechanism in the structure, thereby providing a water level sensor which is easy to apply in the field and a water level sensing system using the same can do.

1 is an explanatory view showing a measurement principle of a capacitance type water level sensor,
FIG. 2 is a front view (a), a side view (b), and a top view (c) of a water level sensor according to an embodiment of the present invention,
3 is a schematic view illustrating a water level sensing system of a device to which a water level sensor according to the present invention is applied
FIG. 4 is a schematic circuit diagram for explaining a capacitance change according to a water level in a capacitance-decreasing water level sensor;
5 is a graph showing a schematic front view (a), a capacitance change (b), and a sensitivity change (c) of a water level sensor manufactured using a shield electrode formed in a rectangular shape,
FIG. 6 is a graph showing a schematic front view (a), a sensitivity change (b), and a capacitance change (c) of a water level sensor manufactured using a shield electrode whose lower end width is excessively smaller than the upper end width,
7 to 9 are a layout diagram showing an example of a water level sensor according to the present invention,
10 is a side sectional view showing a process sequence for explaining a method of manufacturing a water level sensor according to the present invention,
11 is a front view (a) and sectional views (b) and (d) illustrating dimensions of a water level sensor manufactured according to the embodiment and the comparative example,
12 is a graph showing capacitance measurement results according to a water level of a water level sensor manufactured according to Examples and Comparative Examples.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same reference numerals are used throughout the drawings to refer to the same or like parts. In the drawings, the same reference numerals are used to designate the same or similar parts throughout the drawings. Also, throughout the specification, when an element is referred to as "comprising ", it means that it can include other elements, not excluding other elements, unless specifically stated otherwise.

2 is a front view (a), a side view (b), and a top view (c) schematically showing a water level sensor according to an embodiment of the present invention.

2, a water level sensor 100 according to the present invention includes a flat electrode-shaped shield electrode 110 having a predetermined length L1, The first electrode 121 and the second electrode 122 are formed with the first insulating layer 130 interposed therebetween so that the first electrode 121 and the second electrode 122 act as the sensor electrode 120, The lower end width d1 of the shield electrode 110 is formed to be smaller than the upper end width d2 of the water level sensor 100 for sensing the water level by sensing a change in capacitance according to the water level in the direction.

The present invention basically comprises a sensor (110) for shielding the sensing of the back surface of the sensor electrode (120) to measure a more stable capacitance, a level sensor 100). The first insulation layer 130 may be formed of PET (polyethylene terephthalate) or PI (polyimide) for insulation between the shield electrode 110 and the sensor electrode 120.

3 is a schematic diagram illustrating a water level sensing system of a device to which a water level sensor according to the present invention is applied.

3, the water level sensor 100 according to the present invention is applied to a water level sensing system 200 of a device having a liquid storage tank 210 capable of containing a liquid (l) It is possible to detect a change in capacitance according to the water level even when the storage tank 210 capable of holding the liquid is grounded 220 to prevent the risk of electric shock in the operation of the user . Here, the water level sensor 100 may be manufactured in such a manner that the water level sensor 100 outputs a capacitance value without performing any signal processing. The water level sensor 100 may include a signal processor for detecting a signal from the sensor electrode 120, Or the like, and output the converted signal.

In other words, in general, the capacitance type water level sensor uses the air and the liquid only as the dielectric between the electrodes, and senses the water level by the capacitance difference. According to the present invention, the capacitance of the water level sensor 100 is sufficiently large, That is, the capacitance value is designed to have a capacitance value larger than 0 even before the liquid level (ℓ) of the highest level exists in the storage tank 210, so that the capacitance value decreases as the liquid level increases The water level can be detected by detecting the change of the capacitance value. At this time, if the storage tank 210 of the apparatus or the internal liquid (l) is not grounded 220 or the ground 220 is weakly treated, the liquid (l) is arbitrarily connected to the ground 220 The capacitance change can be sensed by the same principle.

In order to design the capacitance value of the level sensor 100 sufficiently large in advance, for example, as shown in FIG. 3 (b), the dielectric 230 having a dielectric constant higher than that of air is connected to the level sensor The electrodes 121 and 122 may be formed by filling protrusions between the electrodes 121 and 122 constituting the electrodes 121 and 122 so as to increase the area of the electrodes 121 and 122, . However, it goes without saying that the electrostatic capacity reduction type water level sensor function can be exhibited even if the design considering only the relative dielectric constant of air without an artificial design such as filling of the dielectric body 230 is performed.

FIG. 4 shows a schematic circuit diagram for explaining a capacitance change according to the water level in the electrostatic capacity reduction type water level sensor. Here, FIG. 4 (a) is schematically shown for the convenience of understanding.

4, in the water level sensing system 200 according to the present invention, the water level sensor 100 is designed to have a capacitance value of a predetermined magnitude even when there is no liquid (l) (b), a plurality of capacitances can be expressed as a circuit connected in parallel, and the total capacitance can be expressed by Equation (3).

(ε ₀ : vacuum permittivity, ε _r : relative dielectric constant of air, S 1: sensor electrode area, S 2: shield electrode area)

At this time, the electrodes 110, 121, 122 surrounded by the liquid (l) due to the increase of the water level are coupled with the ground 220 (see Fig. 4 (a)) and capacitance, And the capacitance is reduced by the height corresponding to the portion where the water level is increased, thereby making it possible to perform the water level sensing using the principle that the total capacitance is reduced. Therefore, in the case of the capacitance type water level sensor, the liquid (l) as the capacitance measurement object is grounded (220) by the storage tank (210) or the internal liquid (l) Can be overcome. On the other hand, when the water level reaches the maximum height of the water level sensor, the electrostatic capacitance value becomes close to '0'.

In this case, in the case of the water level sensor 300 manufactured using the shield electrode 310 formed in a rectangular shape as shown in FIG. 5 (a), when the capacitance change due to the actual water level increase is measured, , It can be seen that the capacitance decreases non-linearly. In this way, when the capacitance change due to the water level change is detected non-linearly, the measurement accuracy and accuracy as the water level sensor becomes unreliable.

The nonlinear characteristic of the capacitance change according to the water level is caused by the sensitivity (? C /? L) of the water level sensor, that is, the capacitance change? C with respect to the water level variation? L. The main factors affecting the sensitivity of the water level sensor are the distance between the water level sensor and the liquid to be measured, and the area of the sensor electrode and the shield electrode. The closer the distance between the water level sensor and the liquid is, The sensitivity of the water level sensor increases. Therefore, in order to improve the sensitivity or resolution of the water level sensor, it is necessary to design the thickness of the container such as the liquid storage tank to which the water level sensor is attached so that the distance between the water level sensor and the liquid is close, It is necessary to design a wide range. However, when the shield electrode is simply applied to a rectangular shape, as shown in FIG. 5 (c), the sensitivity decreases as the water level gradually increases due to the influence of the electrified field depending on the ground state. As a result, The capacitance due to the water level changes non-linearly due to the shield electrode.

The present inventors paid attention to the sensitivity change characteristic depending on the water level in such a capacitance reduction type water level sensor and linearly sensed the capacitance variation according to the water level by keeping the sensitivity according to the water level constant through the shape modification of the shield electrode The water level sensor was developed.

Accordingly, in the present invention, when the shape of the shield electrode 110 is set to be the direction of increasing the water level, the lower end width d1 is made smaller than the upper end width d2 so that the capacitance according to the water level is changed to be linear do. The shield electrode 110 may have an upper end 111 and a lower end 112 and a lower end 112 and a lower end 112. The shield electrode 110 may be formed in a straight line shape such as a trapezoidal shape, May be formed in a substantially linear shape so that the shape thereof may be somewhat deformed in the case of linearly sensing the change in capacitance according to the water level.

6 (a), in the case of the water level sensor 400 manufactured using the shield electrode 410 whose lower end width d3 is excessively smaller than the upper end width d4, as shown in FIG. 6 as shown in FIG. 6 (b), the sensitivity increases with an increase in the water level, so that the capacitance according to the water level can be non-linearly changed as shown in FIG. 6 (c). Therefore, in the present invention, the ratio d1 / d2 of the lower end width d1 to the upper end width d2 of the shield electrode 110 is set to a ratio of the shield electrode length L1 to the upper end width d2 Is preferably 0.5 to 0.8, more preferably 0.6 to 0.7, most preferably 0.62 to 0.68.

7 to 9 are arrangement views showing an example of a water level sensor according to the present invention. 7 to 9 are provided for the purpose of illustrating the positions and arrangement of the electrodes 121 and 122, the signal processing unit 140 and the solar cell 160 of the water level sensor 100. The completed water level sensor 100 ) And does not show the second insulating layer in the completed structure.

7, the water level sensor 100 according to an embodiment of the present invention includes a shield electrode 110, a first insulation layer 130 formed on the shield electrode 110, A signal processing unit 140, an antenna 150, and a solar cell 160 may be formed on the first electrode 121 and the second electrode 122, which form the sensor electrode 120, have. In addition, a battery 170 may be disposed.

The first electrode 121 and the second electrode 122 may have a predetermined length L2 in the longitudinal direction of the shield electrode 110 and may have a plurality of protrusions and a plurality of protrusions Grooves can be arranged in parallel with each other in a structure in which the grooves are alternately arranged. That is, the protrusion of the first electrode 121 corresponds to the groove of the second electrode 122, the protrusion of the second electrode 122 corresponds to the groove of the first electrode 121, The first electrode 121 and the second electrode 122 may be spaced apart from each other by a predetermined distance.

For example, the first electrode 121 and the second electrode 122 may be formed in a shape in which a plurality of teeth (protrusions) of a quadrangular (or polygonal) shape protruding in the orthogonal direction are arranged at regular intervals The first electrode 121 and the second electrode 122 may be arranged such that the teeth of the second electrode 122 and the teeth of the first electrode 121 are engaged with each other, The first electrode 121 and the second electrode 122 may be spaced apart from each other by a predetermined distance.

Also, the upper ends of the first electrode 121 and the second electrode 122 are electrically connected to the signal processing unit 140 through the electrode pattern. The signal processing unit 140 is disposed at an upper end portion of the first electrode 121 and the second electrode 122 to detect the position of the first electrode 121 and the second electrode 122 constituting the sensor electrode 120, 122 to detect a water level and generate a detection signal.

The arrangement structure of the signal processing unit 140 may be linearly arranged as shown in FIG. 8, may have a circular arrangement structure, and may have various arrangement structures such as 'A' or 'B' character. And may be variously configured according to the shape, size, or arrangement structure of the chips or elements constituting the signal processing unit 140. [

An antenna 150 may be disposed at an upper end of the signal processing unit 140 and a battery 170 may be disposed at a side of the antenna 150. The antenna 150 and the battery 170 may be connected to each other, The solar cell 160 may be disposed at an upper end portion of the solar cell 160.

The antenna 150 supplies power to the signal processing unit 140, the first electrode 121 and the second electrode 122 as well as a general RF tag or outputs a detection signal of the signal processing unit 140 to the outside . The shape of the antenna 150 may have a hollow square shape as shown in FIG. 7, or may be arranged in various shapes such as a rectangle, a circle, and a straight line.

7 shows a water level sensor 100 when the solar cell 160 is provided. However, the water level sensor 100 according to the present invention may be a wireless type having no solar cell 160 And can be manufactured in a wire type.

In the case of the wireless type water level sensor 100 that does not include the solar cell 160, as shown in FIG. 8, A signal processing unit 140, an antenna 150 for communication, and a battery 170. The configuration of the first electrode 121 and the second electrode 122 may be the same as those described with reference to FIG. Or similar.

As another example, the wireless type water level sensor 100 having no solar cell 160 may be a passive type water level sensor 100 that does not include the battery 170.

9, the first electrode 121 and the second electrode 122 constituting the sensor electrode 120 are connected to each other in the case 100 of a streamline water level sensor having no solar cell 160, And a signal processing unit 140. The signal processing unit 140 may include a connection line 180 for transmitting a signal to the outside or supplying power to the signal processing unit 140. [

2, the level sensor 100 includes a second insulating layer 191 on the shield electrode 110 and the sensor electrode 120 and an adhesive layer 192 on the other surface of the shield electrode 110. [ ) Can be further formed. The second insulating layer 191 is coated for insulation with the liquid (l) of the shield electrode 110, the first electrode 121 and the second electrode 122 and is made of polyethylene terephthalate (PET) or polyimide ). In addition, the adhesive layer 192 may be adhered to the other surface of the shield electrode 110 by forming an adhesive material film in the form of a double-sided adhesive so as to adhere or fix the water level sensor 100 to the storage tank to be measured, can do.

The above-described water level sensor according to the present invention can be manufactured simply by combining known methods.

10 is a side sectional view showing a process sequence for explaining a method of manufacturing the water level sensor according to the present invention.

10A, a first conductive film 510 having a trapezoidal shape to form the shield electrode 110 is prepared and a first insulating film 530 is formed on the top surface of the first conductive film 510 And the second conductive film 520 is bonded to the upper surface of the first insulating film 530 using a laminating process. At this time, the first insulating film 530 may be a PET (polyethylene terephthalate) film. The first conductive film 510 and the second conductive film 520 may be formed of a copper film, but the present invention is not limited thereto. For example, copper alloy such as brass, bronze, an alloy film may be used, or a film of another conductive material such as nickel, gold, or silver may be used.

The laminating process may be a rolling coating method using a laminating machine at a preheated temperature of 100 to 120 ° C.

Next, referring to FIG. 10 (b), a first electrode 121 and a second electrode 122 are formed on the upper surface of the second conductive film 520 through exposure, development, and etching according to a predetermined pattern. The sensor electrode pattern 120 and the PCB pattern 123 for circuit connection can be formed in a batch process. The antenna pattern 150 may be formed in a batch process together with the sensor electrode pattern 120 and the PCB pattern 123. The antenna pattern 150 may be formed only when necessary. Hereinafter, it is assumed that the antenna pattern 150 is formed together. According to another example, the sensor electrode pattern 120, the PCB pattern 123, and the antenna pattern 150 may be formed of a metal or a conductive thin film that can be manufactured by a screen printing, a deposition, or a sputtering process. Alternatively, it may be formed by coating gold, silver, platinum, copper, nickel, or the like using a deposition or sputtering process, and then etching. Alternatively, carbon or silver may be formed by screen printing.

Next, referring to FIG. 10 (c), the second insulating film 191 is bonded to only the portion where the sensor electrode pattern 120 is formed using a laminating process, or is coated with a plastic film having a waterproof function. The second insulation film 191 protects the sensor electrode pattern 120 from the liquid (l) to prevent damage, and may be formed of a PET film.

10 (d), an adhesive layer 192 is formed on the lower surface of the first conductive film 510 in the form of a double-sided adhesive by a laminating process, a coating process, or an adhering process. The adhesive layer 192 serves as an adhesive tape, so that the completed water level sensor 100 can be adhered or fixed to a specific site.

Next, referring to FIG. 10 (e), at least one SMD (Surface Mount Dvices) type signal processing device for signal processing is soldered on the PCB pattern 123 or a signal chip for signal processing is bonded to the signal processing part 140 ). The SMD type signal processing element is a general term for elements used for signal processing among electronic components mounted on the surface of a printed board and refers to elements mounted on one or both sides of the printed board by using surface mounting technology (SMT) Lt; / RTI >

Next, referring to FIG. 10 (f), the signal processing unit 140 is molded to protect it from external influences. The material for the molding may be epoxy or the like. The molding portion 193 may include the PCB pattern portion 123 as well as the signal processing portion 140.

Example  And Comparative Example

Based on the above-described water level sensor manufacturing method, a water level sensor was manufactured by the standard (mm) shown in Table 1 below. D1 is the upper end width of the shield electrode, d5 is the sensor electrode width, d6 is the sensor electrode interval, h1 is the thickness of the adhesive layer, h2 is the thickness of the shield electrode, H3 is the thickness of the first insulating layer, h4 is the thickness of the sensor electrode, and h5 is the thickness of the second insulating layer (see Fig. 11). A copper film was used as the material of the shield electrode and the sensor electrode, and PET was used as the material of the insulating layer.

Experimental Example

The water level sensor according to the above Examples and Comparative Examples was attached to the inside of a solution storage tank (polycarbonate material, thickness: 1 mm), and the sensed capacitance was measured while increasing the water level by 1 mm relative to the sensor electrode And the results are shown in FIG.

Referring to FIG. 12, in the case (c) of Comparative Example 1 in which the shield electrode is formed in a rectangular shape and the case (d) of Comparative Example 2 in which the bottom end width of the shield electrode is excessively small, the capacitance value according to the water level is non- However, when the bottom electrode width of the shield electrode is small as in the embodiment (b), it can be confirmed that the capacitance value according to the water level is detected almost linearly. Fig. 12 (a) shows the measurement results according to the examples and the comparative examples, and it can be seen that the capacitance values at the respective water levels are different from each other because the shield electrode area is different.

The preferred embodiments of the present invention have been described in detail with reference to the drawings. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.

Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing detailed description, and all changes or modifications derived from the meaning, range, and equivalence of the claims are included in the scope of the present invention Should be interpreted.

100: Water level sensor 110: Shield electrode
120: sensor electrode 121: first electrode
122: second electrode 130: first insulating layer
140: signal processor 150: antenna
160: Solar cell 170: Battery
180: connecting line 191: second insulating layer
192: adhesive layer 200: water level sensing system
210: storage tank 220: ground
510: first conductive film 520: second conductive film
530: first insulating film 591: second insulating film
L1: Shield electrode length d1: Shield electrode bottom width
d2: Shield electrode top width ℓ: Liquid

Claims (9)

delete delete delete A shield electrode having a predetermined length and at least two sensor electrodes in the longitudinal direction are formed on one surface of the shield electrode with a first insulating layer interposed therebetween, As a water level sensor,
The shield electrode is formed to have a lower end width smaller than an upper end width based on an increase direction of the water level so as to linearly detect a change in capacitance according to a water level while maintaining sensitivity of the sensor according to a water level,
Wherein the sensor electrode comprises a first electrode and a second electrode arranged in parallel to each other with a structure in which a plurality of protrusions and a plurality of grooves are alternately arranged on at least one surface in a direction orthogonal to the longitudinal direction, Wherein protrusions of the second electrode correspond to the grooves of the second electrode, and protrusions of the second electrode correspond to the grooves of the first electrode and are mutually engaged with each other at a predetermined interval. 5. The method of claim 4,
And a signal processing unit disposed at an upper end of the first electrode and the second electrode for detecting a water level through a sensing signal generated by the water level sensor and generating a detection signal. 6. The method of claim 5,
Wherein the water level sensor is a wireless type structure including an antenna for transmitting a detection signal of the signal processing unit to the outside and a solar cell or a battery for supplying power to the signal processing unit and the water level sensor. delete delete A liquid level sensing system for a device having a container capable of containing liquid, wherein the liquid in the container or the container is grounded, and the capacitance just before the highest level of liquid immersed in the container has a value greater than zero A water level sensor for detecting a change in the capacitance value of the water level sensor according to the level of the liquid immersed in the inside of the container to sense the water level and linearly detecting a change in the capacitance value, A water level sensing system for a device using the water level sensor according to any one of claims 4 to 6.

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