KR102476167B1 - Sensor for measuring moisture of soil - Google Patents

Abstract

The present invention relates to a soil moisture content sensor capable of accurately grasping the moisture state in a medium and soil by using a change in permittivity of soil. According to the present invention, the soil moisture content sensor may determine the water content of the soil by measuring the capacitance due to a change in permittivity according to water content of soil located in front of the plurality of electrodes, which are coplanar electrodes, and the water content can be accurately measured with a guard and a shield.

Description

Soil moisture content sensor {SENSOR FOR MEASURING MOISTURE OF SOIL}

The present invention relates to a soil moisture content sensor, and more particularly, to a soil moisture content sensor capable of precisely determining the state of moisture in a medium and soil using a change in permittivity of soil.

Soil information sensors (moisture content, EC, pH) are being used in smart farms, and among them, sensors that measure soil moisture are used for various purposes such as collecting data on soil moisture, building an automatic watering system and monitoring system.

Methods for measuring soil moisture include soil moisture tension method, gravimetry method, gypsum block method, neutron moisture measurement method, permittivity measurement method, and electrical resistance measurement method.

However, most of these measurement methods have low reliability in accuracy or durability due to mechanical characteristics, etc., and lack compatibility or price competitiveness. In addition, the neutron moisture meter has high accuracy, but high price and radioactivity may be problems.

An object of the present invention is to provide a soil moisture content sensor that is easy to install in soil, is not affected by mechanical properties, and can accurately measure moisture in soil.

A soil moisture content sensor according to an embodiment of the present invention includes a plate-shaped body portion extending in a longitudinal direction; a sensing unit that is disposed on one side of the body and changes capacitance according to moisture content in the soil; a driving signal wire connected to the sensing unit and supplying a driving signal to the sensing unit; and a sensing wire for receiving a sensing signal from the sensing unit, wherein the sensing unit includes: an electrode unit having a plurality of electrodes disposed on a substrate; a metallic shield disposed under the substrate; an upper coating layer protecting the plurality of electrodes; and a shield coating layer protecting the shield.

In addition, the plurality of electrodes are arranged in a horizontal direction, some of the plurality of electrodes, the electrodes of the first group are alternately arranged with the rest of the electrodes of the second group, and any one of the first group and the second group A group is connected to the driving signal wiring, the remaining groups are connected to the sensing wiring, and the plurality of electrodes, the driving signal wiring, the sensing wiring, and a plurality of connection wirings grouping the first and second groups are the same layer. , and intersecting regions among the driving signal wire, the sensing wire, and the plurality of connection wires may be electrically connected.

In addition, the sensing unit may further include a guard unit including first and second guard electrodes arranged in the horizontal direction adjacent to a first electrode among the plurality of electrodes.

Also, the capacitance changed by the sensing unit may be any one of mutual capacitance and cross capacitance.

In addition, the first guard electrode may be connected to the shield through a via.

In addition, the guard unit may be connected to the shield through a plurality of barrier ribs.

In addition, the guard unit may be connected to ground, and the ground connected to the guard unit may be insulated from the driving signal wire and the sensing wire.

In addition, the guard part may have a shape that protrudes more upward than the electrode part.

Further, the main circuit unit includes: a driving circuit unit supplying the driving signal; a sensing circuit unit receiving the sensing signal; and a controller configured to determine the amount of change in cross capacitance from the sensing signal and determine the moisture content in the soil.

In addition, an input terminal is connected to the driving circuit unit and the sensing circuit unit, and an output terminal is connected to the plurality of electrodes, respectively, according to a command of the control unit to the driving circuit unit and at least a first electrode among the plurality of electrodes and the sensing circuit unit. It may further include a switching unit configured to connect at least a second electrode among the plurality of electrodes.

In addition, the control unit may include a first moisture content determined by a sensing signal received from the second group electrode when the drive signal is applied to the first group electrode among the first and second group electrodes that alternate with each other among the plurality of electrodes; a second moisture content determined by a sensing signal received from at least one electrode adjacent to the one electrode when the driving signal is applied to any one of the plurality of electrodes; and a sensing signal received from second neighboring group electrodes of neighboring electrodes having the same number of electrodes as the first neighboring group electrodes when the drive signal is applied to the first neighboring group electrodes among the plurality of electrodes. 3 Based on the moisture content, the final moisture content can be determined.

The soil moisture content sensor according to the present invention measures the change in permittivity according to the amount of moisture contained in the soil, and has an optimal electrode arrangement, a guard electrode arrangement between electrodes, and a shield to minimize external influences. As a sensor structure, it can accurately measure the moisture content of the soil.

1 shows a soil moisture content sensor according to the present invention.
2 to 4 show a vertical cross-sectional view, a horizontal cross-sectional view, and a wiring diagram of a sensing unit according to an embodiment of the present invention.
5 and 6 show vertical and horizontal cross-sectional views of a sensing unit according to another embodiment of the present invention.
7 to 9 show vertical and horizontal cross-sectional views and wiring diagrams of a sensing unit according to another embodiment of the present invention.
10 and 11 show a block diagram of the main circuit of the present soil moisture content sensor.
12 shows a plurality of capacitances C1 to C5 that may occur between the first and second electrodes.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention. The terms and/or include any combination of a plurality of related recited items or any of a plurality of related recited items. 'Or' can be interpreted as a logical exclusive sum in context, but generally means the same as 'and/or', that is, a logical sum unless there is a direct description of 'otherwise' or 'logical exclusive sum'. do.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle. In addition, that the first component and the second component on the network are connected or connected means that data can be exchanged between the first component and the second component in a wired or wireless manner.

In addition, the suffixes "module" and "unit" for the components used in the following description are simply given in consideration of ease of preparation of this specification, and do not themselves give a particularly important meaning or role. Accordingly, the “module” and “unit” may be used interchangeably.

When these components are implemented in actual applications, two or more components may be combined into one component, or one component may be subdivided into two or more components as needed. The same reference numerals have been assigned to the same or similar components throughout the drawings, and detailed descriptions of components having the same reference numerals may be omitted as they are replaced with descriptions of the components described above.

Further, the present invention covers all possible combinations of the embodiments presented herein. The various embodiments of the present invention are different but not mutually exclusive. Specific shapes, structures, functions, and characteristics described in one embodiment may be implemented in another embodiment. For example, components mentioned in the first and second embodiments may perform all functions of the first and second embodiments.

1 shows a soil moisture content sensor according to the present invention. 2 to 4 show a vertical cross-sectional view, a horizontal cross-sectional view, and a wiring diagram of a sensing unit according to an embodiment of the present invention. 5 and 6 show vertical and horizontal cross-sectional views of a sensing unit according to another embodiment of the present invention. 7 to 9 show vertical and horizontal cross-sectional views and wiring diagrams of a sensing unit according to another embodiment of the present invention. 10 and 11 show a block diagram of the main circuit of the present soil moisture content sensor. 12 shows a plurality of capacitances C1 to C5 that may occur between the first and second electrodes.

Referring to FIG. 1 , the soil moisture content sensor includes a body portion 10, a sensing portion 30, and a wiring portion 40, and may measure moisture content of soil and medium.

For reference, FIGS. 1 (a) to (c) are a plan view, a horizontal cross-sectional view, and a bottom view of the soil moisture content sensor in turn.

Referring to FIG. 1 , the soil moisture content sensor may further include a main circuit unit 20 connected to the sensing unit 30 through a wiring unit 40 .

The main circuit unit 20 may include only a connection unit (not shown) connected to the wiring unit 40 and an external signal line by wire to exchange only the driving signal S_d and the sensing signal S_s with the outside. The soil moisture content sensor according to the present invention will be described as an embodiment capable of measuring the moisture content by itself.

The body portion 10 may have a plate shape extending in the longitudinal direction. The body part 10 may be manufactured in various lengths.

One side of the body portion 10 may have a shape in which the width becomes narrower in the longitudinal direction so as to be easily inserted into the soil. For example, one side of the body portion 10 may have a pointed shape. One end of the body portion 10 may further include a protective cap (not shown) for protecting the body portion 10 from friction with soil during insertion.

The sensing unit 30 may be disposed on one side of the body unit 10 . The electrodes of the sensing unit 30 may be arranged to measure mutual capacitance or cross capacitance between the electrodes according to the moisture content in the soil.

2 to 9, the sensing unit 30 includes an electrode unit 120 having a plurality of electrodes disposed on a substrate 60, a shield 70 disposed under the substrate 60, and a plurality of electrodes. An upper coating layer 83 to protect the electrode of the and a shield coating layer 81 to protect the shield 70 may be provided.

The electrode unit 120 may include an even number of electrodes 121 to 124 as shown in FIGS. 2 to 6 or an odd number of electrodes 121 to 125 as shown in FIGS. 7 to 9 .

A plurality of electrodes of the electrode unit 120 may be arranged in a horizontal direction. The plurality of electrodes are coplanar electrodes and may be disposed on the same plane.

Among the plurality of electrodes, a guard electrode may be inserted and installed between neighboring first and second electrodes to function as an electrode of a cross capacitor based on the Thompson-Lampard theorem. When the first electrode is a high electrode and the second electrode is a low electrode, cross capacitance between the first and second electrodes may be measured according to the moisture content of the soil. That is, in the present invention, the capacitance of the electrode unit 120 may vary depending on the moisture content of the soil, and this is because the higher the moisture content, the higher the dielectric constant. Therefore, the moisture content of the soil can be measured by the capacitance change of the electrode unit 120 . However, if the guard electrode between the first and second electrodes is removed, the water content measurement according to the capacitance change can use the mutual capacitance change instead of the cross capacitance change, or both can be used. This is because the structure of the electrode or the change in capacitance between the first and second electrodes is related to the change in permittivity between the first and second electrodes.

The substrate 60 , the upper coating layer 83 , and the shield coating layer 81 may extend throughout the body portion 10 .

The substrate 60 is made of a dielectric material such as epoxy, and is preferably made of a hard insulating material.

The shield 70 is made of a metallic material and can electrically shield one surface of a plurality of electrodes.

The shield 70 preferably has a smaller width than the substrate 60 . The shield 70 is preferably wider than the area occupied by the electrode unit 120 .

The shield coating layer 81 is for protecting the substrate 60 or upper and lower components (electrode unit 120, shield 70, wiring unit 40, etc.) of the substrate 60, and is preferably an insulating material. do.

The shield coating layer 81 may seal the entire shield 70 so that any part of the shield 70 is not exposed to the outside.

Referring to FIGS. 5(a) and 7(a) , the sensing unit 30 may further include a guard unit 130 that is a plurality of guard electrodes 131 to 135 and 131 to 136 . The plurality of guard electrodes 131 to 135 and 131 to 136 may be arranged in a horizontal direction. The plurality of guard electrodes 131 to 135 and 131 to 136 may be arranged adjacent to each other in a horizontal direction with respect to each of the plurality of electrodes. For example, the first and second guard electrodes 131 and 132 of the plurality of guard electrodes may be disposed adjacent to the first electrode 121 of the plurality of electrodes in the left and right directions.

The guard unit 130 may minimize unnecessary capacitance generated between side surfaces of the plurality of electrodes 121 to 124 and 121 to 125 that are the main electrodes. In addition, the shield 70 can remove the influence of the dielectric state (dielectric constant) change on the lower surface of the sensing unit 30 .

12 illustrates a plurality of capacitances C1 to C5 that may occur between the first and second electrodes e1 and e2.

Referring to FIG. 12 , the first capacitance C1 is the capacitance of the upper portions of the first and second electrodes and may change according to the moisture content of the soil. This first capacitance C1 is the main measurement target of the soil moisture content sensor according to the present invention.

The second capacitance C2 is the capacitance inside the upper coating layer 83 on the upper surfaces of the first and second electrodes.

The third capacitance C3 is the capacitance between the side surfaces of the first and second electrodes, and the fourth capacitance C4 is the capacitance along the substrate 60 on the lower surfaces of the first and second electrodes.

The second to fourth capacitances C2 to C4 are capacitances having fixed values determined according to the size and arrangement of the electrode structure, and become one of sensor characteristics.

The fifth capacitance C5 is the capacitance generated between the rear surfaces of the first and second electrodes and may vary as the permittivity of the soil on the rear surface of the sensor changes. Accordingly, the moisture content of the soil may be measured by the change in the first and fifth capacitances C1 and C5.

When the moisture content of the soil is measured by the changes in the first and fifth capacitances C1 and C5, the material of the wall of the pot into which the soil moisture content sensor is inserted may be affected. In this case, it is advantageous to keep the fifth capacitance C5 unchanged. To this end, the rear surface of the soil moisture content sensor may be shielded so that the fifth capacitance C5 does not vary according to the soil moisture content.

Since the first to fifth capacitances C1 to C5 are connected in parallel, the total capacitance Ct between the first and second electrodes in FIG. 12 is the sum of the first to fifth capacitances C1 to C5. Same as Since it is advantageous to react sensitively to the amount of capacitance change with respect to the water content, the larger the ratio of capacitance to variable capacitance to the total capacitance (Ct), the more advantageous it is. That is, the smaller the ratio of the remaining capacitance excluding the variable capacitance, the more advantageous it is. For example, when the water content is measured with the first and fifth capacitances C1 and C5, it is preferable that the second to fourth capacitances C2 to C4 are zero or smaller. As another example, when the water content is measured with the first capacitance C1, it is preferable that the second to fifth capacitances C2 to C5 are zero or smaller.

A shield 70 is applied to the rear surface of the sensor to remove the fifth capacitance C5. In addition, the guard electrode 130 is applied to reduce or eliminate the effect of the third capacitance C3.

The guard part 130 and the shield 70 are floated on the electrode part 120 and connected to the ground of the main circuit part 20 to protect all parts except the electrode part 120 from external noise. have.

The ground connected to the guard unit 130 and the shield 70 may be the same ground as that of the driving signal S_d and the sensing signal S_s, or may be an independent separate ground. In order not to affect the total capacitance (Ct), it is preferable that the grounds connected to the guard part 130 and the shield 70 are independent grounds.

The guard part 130 and the shield 70 are preferably connected to each other through a conductive material passing through the substrate 60 . This is because it is not necessary to do double wiring for connection to the external ground, or if the shield 70 is formed to extend throughout the body 10, the shield 70 itself can function as a separate ground. .

Referring to FIG. 5( b ) , the guard part 130 and the shield 70 may be connected to each other through the via 140 . A plurality of vias 140 may be formed in any one guard electrode.

Referring to FIG. 7 ( b ) , the guard part 130 and the shield 70 may be connected to each other through the partition wall 150 . The barrier rib 150 may remove the fourth capacitance C4 of FIG. 12 from among the total capacitance Ct of the first and second electrodes or minimize its effect.

The guard part 130 , the partition wall 150 , and the shield 70 may be formed as an integral guard shield 160 . It may be manufactured by forming an opening in the substrate 60 through which the plurality of guard electrodes 131 to 136 pass, and then combining the integrally formed guard shield 160 . The step of coating the electrode unit 120 on the substrate 60 is preferably performed before bonding the guard shield 160 .

Referring to FIGS. 5(c) and 7(c) , the guard part 130 may have a shape that protrudes more upward than the electrode part 120. An upper portion of the guard part 130 may be substantially the same height as the upper coating layer 83 . The protruding guard part 130 may remove or minimize the second capacitance C2 of the arbitrary first and second electrodes according to FIG. 12 .

Each capacitance between the first electrode and the shield 70, the first electrode and the first guard electrode, and the first electrode and the barrier rib 150 always becomes a constant having a fixed value, and thus can be ignored. Since only the amount of capacitance change between arbitrary first and second electrodes of the electrode unit 120 needs to be sensed, the moisture content can be accurately measured.

Referring to FIG. 1 , the soil moisture content sensor may further include a wiring unit 40 connected to the sensing unit 30 . The wiring unit 40 may be connected to the sensing unit 30 . The wiring unit 40 may include a driving signal wire 41 for supplying a driving signal to the sensing unit 30 and a sensing wire 42 for receiving a sensing signal from the sensing unit 30 .

Referring to FIG. 4, the first group of electrodes 121 and 123, which are some of the plurality of electrodes, are alternately arranged with the rest of the second group of electrodes 122 and 124, and the first group is a driving signal wire ( 41), and the second group may be connected to the sensing wires 42. The plurality of electrodes 121 to 124, the driving signal wiring 41, the sensing wiring 42, and the plurality of connection wirings 51 to 54 grouped in the first and second groups are disposed on the same layer, and the driving signal wiring ( 51), the sensing wire 52, and the plurality of connection wires 51 to 54 are preferably electrically connected to each other.

Referring to FIG. 10 , the main circuit unit 20 of FIG. 1 may include a driving circuit unit 210, a sensing circuit unit 220, a storage unit 250, and a control unit 200.

The driving circuit unit 210 may generate a driving signal S_d. The generated driving signal S_d may be supplied to the sensing unit 30 through the wiring unit 40 . The driving circuit unit 210 may include an oscillator for generating the driving signal S_d. The driving signal S_d may be a voltage signal of various waveforms.

The sensing circuit unit 220 may receive the sensing signal S_s. The sensing signal S_s may be supplied from the sensing unit 30 through the wiring unit 40 .

The storage unit 250 transmits the driving signal S_d to the sensing unit 30 inserted into the soil having a known moisture content, and then functions according to the relationship between the magnitude change of the waveform or amplitude of the received sensing signal S_s. I can have a related table.

The control unit 200 may determine the amount of change in capacitance compared to the reference capacitance from the sensing signal S_s to determine the moisture content in the soil. The changed capacitance may be any one of cross capacitance and mutual capacitance.

The reference capacitance may be a preset value or a value determined upon initialization of the soil moisture content sensor. The initialization decision may be based on whether the soil in which the soil moisture content sensor is to be inserted is very dry or very wet. For example, after sufficiently supplying water to the soil to be inserted, a soil moisture content sensor may be inserted and the measured sensing signal S_s may be initialized as a reference capacitance when the moisture content is maximum. Alternatively, the capacitance of the sensing unit 30 in the air may be set as the reference capacitance. The control unit 200 may quantify the moisture content of the soil based on the capacitance value of the sensing unit 30 or the capacitance change in the soil into which the sensing unit 30 is inserted, compared to the reference capacitance. When quantifying, a function or table stored in the storage unit 250 may be used.

The control unit 200 may supply a driving signal S_d to a plurality of electrodes of the sensing unit 30 in various ways and allow the sensing signal S_s to be received. For example, when wiring is set as shown in FIG. 4 , the total capacitance of the electrode unit 120 is increased, and measurement sensitivity can be improved. The total capacitance of the electrode unit 120 of FIG. 4 is the capacitance of the first electrode 121 and the second electrode 122, the capacitance of the second electrode 122 and the third electrode 123, and the capacitance of the third electrode 122 and the third electrode 123. As the total capacitance of the electrode 123 and the fourth electrode 124, the total capacitance may be increased.

Referring to FIGS. 9 to 11 , the soil moisture content sensor may further include a switching unit 230 . Through the switching unit 230, the control unit 200 may connect the driving signal wire 41 and the sensing wire 42 to the electrode unit 120 in various ways to receive various sensing signals.

To this end, the switching unit 230 is connected to the driving circuit unit 210 and the sensing circuit unit 220 at an input terminal, and is connected to a plurality of electrodes 121 to 125 at an output terminal, respectively, and is driven according to the command of the control unit 200. At least a first electrode of the circuit unit 210 and a plurality of electrodes and at least a second electrode of the sensing circuit unit 220 and a plurality of electrodes may be connected.

The control unit 200 may determine the first moisture content determined by the sensing signal received from the second group electrode when a drive signal is applied to the first group electrode among the plurality of electrodes of the first and second groups that alternate with each other. For example, the controller 200 controls the switching unit 230 to supply the driving signal S_d to the first, third, and fifth electrodes 121, 123, and 125 to the second and fourth electrodes. The 1-1st moisture content may be determined by receiving the sensing signal S_s from (122, 124), or conversely, the 1-2nd moisture content may be determined. The first water content may be any one of the 1-1 and 1-2 water contents, or an average thereof.

When a drive signal is applied to any one of the plurality of electrodes, the controller 200 may determine the second moisture content based on a sensing signal received from at least one electrode adjacent to the one electrode. For example, after supplying the driving signal S_d to the first electrode 121, the controller 200 controls the second electrode 122 to receive the sensing signal S_s, and then drives the second electrode 122. After the supply of the signal S_d, control is sequentially performed on the plurality of electrodes to receive the sensing signal S_s from the first and third electrodes 121 and 123, and then the second moisture content is determined from these sensing signals S_s. can

When a driving signal is applied to the first neighboring group electrodes among the plurality of electrodes, the control unit 200 uses the sensing signal received from the second neighboring group electrodes of the neighboring electrodes having the same number of electrodes as the first neighboring group electrodes. 3 Moisture content can be determined. For example, the controller 200 supplies the driving signal S_d to the first and second electrodes 121 and 122 and receives the sensing signal S_s from the third and fourth electrodes 123 and 124. control, and based on this, the third moisture content can be determined.

The controller 200 may provide the final moisture content to the user. The controller 200 may determine any one of the first to third moisture contents as the final moisture content or determine the final moisture content based on the first to third moisture contents. In the former case, the controller 200 may measure only one of the first to third moisture contents and provide it as the final moisture content, or may determine a highly accurate one among the first to third moisture contents as the final moisture content. In the latter case, the control unit 200 determines the average value of the calculated first to third moisture contents as the final moisture content, or multiplies the first to third moisture contents by the first to third weights, respectively, and calculates the average value as the final moisture content. It can be determined by the moisture content. The magnitudes of the first to third weights may be proportional to the accuracy of the multiplied first to third moisture contents.

When the guard unit 130 does not exist, the control unit 200 can sense any one of cross capacitance and mutual capacitance for capacitance change by variously combining driving signals and sensing signals to a plurality of electrodes. have. For example, the control unit 200 may apply a driving signal to a first electrode among a plurality of electrodes and then receive a sensing signal from a second electrode adjacent to the first electrode to measure a mutual capacitance change amount. . In addition, the control unit 200 applies a driving signal to a first electrode of a plurality of electrodes, grounds a second electrode adjacent to the first electrode, receives a sensing signal from a third electrode adjacent to the second electrode, With the fourth electrode grounded, the amount of change in cross capacitance can be measured.

Referring to FIG. 10 , the soil moisture content sensor may further include a communication unit 240 and a power supply unit 260.

The communication unit 240 may transmit the measured moisture content to an external device such as an external terminal or server. As mentioned above, the communication unit 240 may receive the driving signal S_d and transmit the detected sensing signal S_s to an external device. The external device is a device that obtains soil information and uses it, and may be, for example, a control device and/or a monitoring device of a smart farm.

The power supply unit 260 may receive internal and/or external power under the control of the control unit 200 and supply power necessary for the operation of each component.

Such a soil moisture content sensor can measure soil moisture content in a wide range of environments without or being less affected by temperature, acidity (pH), electrical conductivity, etc. of a medium (soil, etc.). Of course, it may be necessary to separately determine a proportional relationship according to the reference capacitance and capacitance change according to the temperature section or the acidity section, or to correct the temperature or acidity value. In addition, the present soil moisture content sensor can have high durability because there is no mechanical operation.

The present invention may be implemented in hardware or software. In implementation, the present invention can also be implemented as computer readable codes on a computer readable recording medium. That is, it may be implemented in the form of a recording medium including instructions executable by a computer. Computer readable media includes all types of media in which data that can be read by a computer system is stored. Computer readable media may include computer storage media and communication storage media. Computer storage media includes all storable media implemented in any method or technology for storing information, such as computer readable instructions, data structures, program modules, and other data, and includes volatile/nonvolatile/hybrid memory. It is not limited to whether or not, separable/non-separable. Communication storage media includes modulated data signals or transmission mechanisms such as carrier waves, any information delivery media, and the like. In addition, functional programs, codes, and code segments for implementing the present invention can be easily inferred by programmers in the art to which the present invention belongs.

In addition, although the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific embodiments described above, and the technical field to which the present invention belongs without departing from the gist of the present invention claimed in the claims. Of course, various modifications are possible by those skilled in the art, and these modifications should not be individually understood from the technical spirit or perspective of the present invention.

10: body part 20: main circuit part
30: sensing unit 40: wiring unit
41: driving signal wiring 42: sensing wiring
60: substrate 70: shield
81: shield coating layer 83: upper coating layer
120: electrode unit 130: guard unit
140: via 150: bulkhead
200: control unit 210: driving circuit unit
220: sensing circuit unit 230: switching unit

Claims (10)

A plate-shaped body portion extending in the longitudinal direction;
a sensing unit that is disposed on one side of the body and changes capacitance according to moisture content in the soil;
a driving signal wire connected to the sensing unit and supplying a driving signal to the sensing unit;
a sensing wire receiving a sensing signal from the sensing unit; and
A main circuit unit connected to the sensing unit through a wiring unit; includes,
The sensing unit,
an electrode unit having a plurality of electrodes of 4 or more disposed on a substrate;
a metallic shield disposed under the substrate;
an upper coating layer protecting the plurality of electrodes; and
A shield coating layer protecting the shield,
The plurality of electrodes are arranged in a horizontal direction,
The electrodes of the first group, which are some of the plurality of electrodes, are alternately arranged with the electrodes of the second group, which are the rest,
One of the first group and the second group is connected to the driving signal wire, and the other group is connected to the sensing wire;
The sensing unit further includes a guard unit including first and second guard electrodes arranged in the horizontal direction adjacent to a first electrode among the plurality of electrodes,
The guard unit is connected to the shield through a plurality of barrier ribs,
The guard part, the plurality of partition walls, and the shield are integrally formed,
The substrate is formed with an opening through which the first and second guard electrodes pass,
The guard part has a shape that protrudes more upwardly than the electrode part,
The main circuit part,
a driving circuit unit supplying the driving signal;
a sensing circuit unit receiving the sensing signal; and
A control unit for determining the amount of change in cross capacitance from the sensing signal and determining the moisture content in the soil;
An input terminal is connected to the driving circuit unit and the sensing circuit unit, and an output terminal is connected to the plurality of electrodes, respectively, according to a command of the control unit, at least a first electrode among the driving circuit unit and the plurality of electrodes and the sensing circuit unit and the plurality of electrodes. A switching unit for connecting at least a second electrode of the electrodes; further comprising,
The control unit,
a first moisture content determined by a sensing signal received from the second group electrode when the driving signal is applied to the first group electrode among the plurality of electrodes of the alternating first and second group electrodes;
a second moisture content determined by a sensing signal received from at least one electrode adjacent to the one electrode when the driving signal is applied to any one of the plurality of electrodes; and
When the driving signal is applied to the first neighboring group electrodes among the plurality of electrodes, a third sensing signal received from second neighboring group electrodes of neighboring electrodes having the same number of electrodes as the first neighboring group electrodes A soil moisture content sensor that determines, based on the moisture content, a final moisture content. According to claim 1,
The plurality of electrodes, the driving signal wire, the sensing wire, and the plurality of connection wires grouping the first and second groups are disposed on the same layer, and among the drive signal wire, the sensing wire, and the plurality of connection wires, A soil moisture content sensor, wherein the intersecting areas are electrically connected. delete delete delete According to claim 1,
The guard unit is connected to ground,
The ground connected to the guard unit is insulated from the drive signal wire and the sensing wire, the soil moisture content sensor. delete delete delete delete

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