Sensor configuration for sensing the fill state of an absorbent article - Patent Application 20070122997

Abstract

A sensor configuration for sensing the filling state of an absorbent article with a liquid-absorbing layer comprises a substrate, a plurality of planar capacitors each comprising a set of at least two corresponding capacitor electrodes arranged next to each other on or within the substrate, and a plurality of conductor paths on or within the substrate connecting the capacitor electrodes to terminals of a readout circuit, at least two of the planar capacitors being connected in parallel.

Description

[Technical Field]

[0001] The present invention relates to a sensor arrangement for sensing the fill state of an absorbent article. The present invention particularly relates to improving the manner in which a urination event is identified in which bodily fluid is released toward a liquid-absorbent layer of the absorbent article. The present invention further relates to absorbent articles such as diapers. [Background technology]

[0002] Absorbent articles are used to address conditions such as leakage problems or incontinence. Such absorbent articles, mostly in the form of diapers, are similarly used by individuals, but in the context of nursing home, hospital, and home care settings, they are applied and managed by caregivers. In each of these settings, the fill status and need for replacement of a full absorbent article is of considerable interest, as well as an assessment of the individual's specific urination behavior. In particular, assessment of urination behavior is important information for making absorbent article use predictable, planning replacement schedules, and managing an adequate supply, not only in individual settings but also in larger settings such as the aforementioned nursing homes.

[0003] Among other technologies, there are those for detecting the fill state of absorbent articles such as diapers that consider the use of conductive wires incorporated into the liquid-absorbing layer of the diaper. Because the sensor configuration is incorporated into and wired to the absorbent article, it must be discarded when the absorbent article is full or requires replacement. At the same time, measuring urination behavior and related data such as urination volume and timing is usually important over an extended period of time. While an initial assessment of possible urination patterns requires at least several days or weeks of monitoring, long-term application in care facilities under a regime of change alerts requires sensors on a daily basis.

[0004] Therefore, there is a desire to separate the sensor configuration from the absorbent article itself so that the sensor configuration can be reused several times and the absorbent article can be disposed of whenever needed, thereby keeping the costs associated with them low. However, the application of external sensor configurations has reliability issues as close or direct contact solutions are not feasible, and other alternatives offer little sensitivity and / or reliability while being susceptible to external conditions such as patient movement and the immediate surroundings of the bed or patient station. Summary of the Invention [Problem to be solved by the invention]

[0005] Thus, there is a need for improved sensor configurations for use in the context of absorbent articles that offer not only ease of operation but also reliability, as well as correspondingly improved absorbent articles, such as diapers. [Means for solving the problem]

[0006] The aforementioned problems and disadvantages are addressed by the subject matter of the independent claims. Further preferred embodiments are defined in the dependent claims. Clearly, embodiments of the present invention can provide substantial benefits, some of which are described herein.

[0007] According to one aspect of the present invention, there is provided a sensor arrangement for sensing the filling state of an absorbent article with a liquid-absorbing layer, comprising a substrate, a plurality of planar capacitors each comprising a set of at least two corresponding capacitor electrodes arranged next to each other on or in the substrate, and a plurality of conductor paths on or in the substrate connecting the capacitor electrodes to terminals of a readout circuit, wherein at least two of the planar capacitors are connected in parallel.

[0008] According to another aspect of the present invention, there is provided an absorbent article comprising a sensor arrangement for sensing the filling state of an absorbent article with a liquid-absorbing layer, the absorbent article comprising a substrate, a plurality of planar capacitors each comprising a set of at least two corresponding capacitor electrodes arranged next to each other on or in the substrate, and a plurality of conductor paths on or in the substrate connecting the capacitor electrodes to terminals of a readout circuit, wherein at least two of the planar capacitors are connected in parallel.

[0009] Embodiments of the present invention will now be described with reference to the figures, which are provided for a better understanding of the inventive concept, but are not to be taken as limiting the invention. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of a sensor configuration for sensing the fill state of an absorbent article according to an embodiment of the present invention. [Figure 2A] FIG. 1 is a schematic diagram of a sensor configuration in a strip configuration according to an embodiment of the present invention. [Figure 2B] FIG. 1 is a schematic diagram of a sensor configuration in a strip configuration according to an embodiment of the present invention. [Figure 3] FIG. 1 is a schematic diagram of the impedance behavior of a sensor configuration according to an embodiment of the present invention. [Figure 4A] 10 is a schematic diagram of a parallel connection of capacitors in a sensor configuration in accordance with a corresponding embodiment of the present invention. [Figure 4B] 10 is a schematic diagram of a parallel connection of capacitors in a sensor configuration in accordance with a corresponding embodiment of the present invention. [Figure 4C] 10 is a schematic diagram of a parallel connection of capacitors in a sensor configuration in accordance with a corresponding embodiment of the present invention. [Figure 5A] 3A and 3B are schematic diagrams of electrode arrangements of capacitors in a sensor configuration according to corresponding embodiments of the present invention. [Figure 5B] 3A and 3B are schematic diagrams of electrode arrangements of capacitors in a sensor configuration according to corresponding embodiments of the present invention. [Figure 5C]3A and 3B are schematic diagrams of electrode arrangements of capacitors in a sensor configuration according to corresponding embodiments of the present invention. [Figure 6A] 3A and 3B are schematic diagrams of electrode and capacitor configurations in a strip-shaped sensor configuration according to corresponding embodiments of the present invention. [Figure 6B] 3A and 3B are schematic diagrams of electrode and capacitor configurations in a strip-shaped sensor configuration according to corresponding embodiments of the present invention. [Figure 6C] 3A and 3B are schematic diagrams of electrode and capacitor configurations in a strip-shaped sensor configuration according to corresponding embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] FIG. 1 shows a schematic diagram of a sensor configuration for sensing the fill state of an absorbent article according to an embodiment of the present invention. Specifically, the absorbent article includes a liquid-absorbing layer, such as the diaper 9 shown. However, generally, the absorbent article can be any of a baby diaper, an adult diaper, a pad, a protective device, and the like. The liquid-absorbing layer is a layer comprising or consisting of an absorbent material capable of absorbing liquid in a specific context, including bodily fluids such as urine, blood, face fluids, and the like. The absorbent material can be configured to absorb such liquid up to a given capacity and to retain the liquid for a given period of time. Furthermore, the absorbent material can be configured to transport liquid to adjacent regions so that nearby absorbent material can absorb liquid not absorbed by upstream absorbent material toward the liquid source.

[0012] A sensor arrangement 1 is provided for use with such absorbent articles, and for that purpose may be arranged so as to be attachable to, for example, the outer surface 91 of the exemplary diaper 9. The sensor arrangement 1 may take the form of a strip and generally comprises a substrate and a plurality of planar capacitors 11, 12, each comprising a set of at least two corresponding capacitor electrodes arranged next to each other on or in the substrate. The capacitor electrodes are arranged next to each other in the sense that their main surfaces do not face each other. In other words, the larger surfaces of the electrodes do not face each other and may be arranged in one potentially flexible plane of the sensor arrangement and / or substrate, while the much smaller sides of the conductive material forming the capacitors may be oriented facing each other.

[0013] Because the capacitor is positioned near the liquid-absorbing layer, absorbed liquid interacts with the capacitor to change the effective measurable capacitance, at least when the sensor arrangement is attached to the absorbent article. The sensor arrangement 1 is configured to sense the fill state of the absorbent article, which in this manner may include use to detect urination events themselves, assess the amount absorbed, and potentially determine the degree of saturation in relation to a maximum or target absorption capacity. In this manner, potential applications of embodiments of the present invention may include urination behavior assessment, urination monitoring, capacity monitoring, and monitoring the need to change the absorbent article. To assess the capacitors 11 and 12, the absorbent article 9 further comprises a plurality of conductor paths on or within the substrate that connect the capacitor electrodes to terminals of a readout circuit.

[0014] According to an embodiment of the present invention, at least two of the planar capacitors are connected in parallel. When each of the two capacitors is connected in series, it can be referred to as a capacitor pair. However, in general, embodiments of the present invention interpret a pair in the sense of a set including at least two of the planar capacitors connected in parallel, and a set can also include three or more planar capacitors connected in parallel.

[0015] 2A and 2B show schematic diagrams of a sensor arrangement in a strip-like configuration according to an embodiment of the present invention. Specifically, the sensor arrangement for sensing the filling state of an absorbent article 9 is shown as comprising a substrate 102 with a plurality of planar capacitors 11, 12, .... The capacitors are spaced apart in the longitudinal direction or a longer extension of the strip-like sensor arrangement 1. Specifically, in this embodiment, the substrate has an elongated strip-like shape with a longitudinal direction along the elongated length, and the planar capacitors are arranged along said longitudinal direction. The term "elongated" is understood as meaning that the strip-like sensor arrangement is longer in the longitudinal direction compared to its width in the transverse direction. Typically, the length / width ratio is greater than 3. Furthermore, the longitudinal direction of the sensor arrangement is preferably intended to be aligned with the longitudinal (front / back) extension of the absorbent article, or at least with the extension of the liquid-absorbing layer in the absorbent article. Typical lengths are therefore, for example, 490 mm, 500 mm, 690 mm, or 700 mm, and may range from 150 mm to 1000 mm, 200 mm to 800 mm, or 300 mm to 700 mm. Generally, the length of the sensor arrangement should be adapted to the length of the absorbent core of the absorbent article, or, in other words, to the area of ​​interest. Typical widths are in the range of 10 mm to 40 mm, or 15 mm to 30 mm, for example, about 25 mm.

[0016] Generally, the substrate can be flexible and can be configured as a flexible printed circuit board (PCB) with a corresponding base material known per se, which has conductive paths or conductive areas formed, for example, from a copper or metal layer by etching or other types of applicable lithographic techniques. As an alternative to etching, all conductive paths or conductive areas may also be formed by printing, inkjet printing, silkscreen printing, etc.

[0017] In this method, the substrate 102 has a first surface 1201 and a second surface 1202, and the capacitor electrodes are arranged together on one of the first and second surfaces. Preferably, the capacitor electrodes are arranged together on the first surface 1201, which is the surface that is closer to the liquid-absorbing layer of the absorbent article when attached to the absorbent article. In this way, the distance between the capacitor electrodes and the liquid-absorbing layer, from which any absorbed liquid is measured, can be minimized, optimizing the sensitivity of the sensor arrangement as a whole.

[0018] Generally, the sensor arrangement according to embodiments of the present invention may be configured to accompany the liquid-absorbing layer of an absorbent article. To this end, the sensor arrangement 1 may comprise an adhesive layer 103 facing the absorbent article (e.g., diaper 9). For example, the adhesive layer 103 may be formed from or comprise a portion of an adhesive or hook-and-loop fastener that can sufficiently secure the sensor arrangement to the absorbent article. However, generally, other methods of fastening or accompaniment are contemplated, including, for example, that the sensor arrangement could be incorporated into outer pants, or could be positioned in some kind of pocket inside the absorbent article, or on the outside of the absorbent article.

[0019] However, if an adhesive layer is used, the material and / or components of the adhesive layer 103 can be adapted to the specific properties of the surface 91 of the absorbent article 9. For example, an absorbent article in the exemplary form of a diaper 9 can feature a fibrous or fibrous surface 91 to which the hook portions of a hook-and-loop fastener can adhere well. Such an adhesive layer can provide the additional benefit of being removable from the absorbent article when it needs to be replaced. As such, the sensor arrangement can be easily reused by attaching it to a new absorbent article (e.g., a diaper) without compromising the integrity of the used and absorbent article, i.e., without destroying or damaging the surface 91 during attachment, attachment, and / or detachment. As such, the sensor arrangement can be positioned to adhere to the outer surface of the absorbent article, while still being galvanically insulated from the liquid-absorbing layer, and is equally well adapted to sense the fill state of the absorbent article.

[0020] Absorbent articles generally may include additional components, seals, and / or layers. As also shown in FIG. 2B , the sensor configuration 1 includes an outer layer 101 that may include or consist of a sealant, such as rubber, lacquer, silicone, or thermoplastic. Similarly, the entire sensor configuration, i.e., the substrate strip in this embodiment, may be completely embedded in silicone. Considering the context of sensing the fill state of an absorbent article, and especially in the specific context of absorbing body fluids, sealing and / or protection from a moist environment may be desirable. Furthermore, since the sensor configuration may be used several times, cleaning the configuration for hygienic purposes may also be desirable, which may involve, for example, treatment with detergents and / or disinfectants, heat treatment, radiation treatment, etc. As a further additional layer, a ground plane may be provided to protect the electrical measurement circuitry from external electromagnetic interference (EMI). For example, such a ground plane may be implemented by a mesh-like pattern of conductive material on the second surface 1202 of the substrate 102.

[0021] FIG. 3 shows a schematic diagram of the impedance behavior of a sensor configuration according to an embodiment of the present invention. As described, an embodiment of the present invention provides a sensor configuration for sensing the fill state of an absorbent article with multiple planar capacitors, at least two of which are connected in parallel. Specifically, an embodiment of the present invention contemplates sensing the fill state of a liquid-absorbing layer using the interaction of absorbed liquid with the effective dielectric properties of the capacitors. Furthermore, the normal behavior of body fluid discharge is considered to be that the discharge and corresponding absorption are not a continuous process but rather occur in events. That is, body fluid is discharged in so-called urination events, during which a specific amount of body fluid is discharged in a relatively short period of time, with no or little fluid discharge during intermittent, relatively long periods of time (urination pauses).

[0022] Assuming a single planar capacitor is placed in parallel with a liquid-absorbing layer, the absorbed liquid will alter the dielectric properties of the capacitor. The effective capacitance, C, generally determines the impedance of the capacitor circuit, which is the opposition of an alternating current represented by the combined effects of resistance and reactance in the circuit.

[0023] Specifically, an AC voltage source can be applied to the capacitor electrodes and the strength of the AC signal reflected by the capacitor in the sense of an AC resistor can be measured. This technique is known per se and is usually referred to as network analysis (e.g., a corresponding so-called network analyzer is a readout circuit that applies an AC signal to an AC impedance such as a capacitor and measures the reflected AC power to determine the impedance value). The readout circuit can therefore generally comprise a radio / AC (radio frequency, AC current) source, a directional coupler, an impedance measurement test set, and a so-called "S-parameter" test set or part thereof, which includes connectors and conductor paths in the sense of impedance-matched or well-defined impedance striplines, and generally takes into account the impedance changes of the entire circuit due to capacitance changes that predominate in the capacitor as a result of liquid absorption in the immediate vicinity of the capacitor electrodes.

[0024] Under the above assumption, the capacitance, and therefore the impedance, changes over time as one or more urination events occur, and the liquid-absorbent article increasingly contains liquid, which acts as a changing capacitor dielectric. The measured impedance will, in principle, vary over time along a first impedance curve Z1 as shown in FIG. 3 . During the time period T1 before the first urination event, the impedance Z1 remains approximately constant, i.e., assumes an impedance value that remains within some predetermined limit setting for characterizing constant behavior. However, after the first urination event during T2, the impedance changes, e.g., decreases to a first level Z11. After remaining at an approximately constant level again, a further urination event during T4 will again result in a change in impedance, e.g., assuming a further level Z12. As can be seen from the schematic diagram of FIG. 3, the difference in impedance between the first level Z11 and the second level Z12 is relatively small and can pose considerable difficulties in reading out the sensor configuration and evaluating the measured readings, particularly in situations where individual urination events are to be identified and / or counted.

[0025] Since embodiments of the present invention contemplate multiple planar capacitors, at least two of said planar capacitors being connected in parallel, the capacitors are again positioned along the liquid-absorbing layer as in the scenario described above, although the readout is different. More specifically, the capacitors are planar and thereby also coplanar with the liquid-absorbing layer, but the "planarity" of the sensor configuration also encompasses the fact that they are flexible to assume a curved form that roughly follows the outer surface of the absorbent article (see schematic curvature in Figures 1 and 2B).

[0026] As a result, the first urination event will result in the accumulation of fluid in a first zone or region. Therefore, the capacitor facing this zone or region will change its capacitance and affect the measured impedance. That is, impedance Z2 will take on value Z21 at time T3 after the first urination event after time T1 and during time T2. A second urination event during time T4 will result in the accumulation of fluid in a different zone than the first, and thus an additional, different capacitor will be affected. If this additional capacitor is connected in parallel with the capacitor affected by the first urination event, the impedance Z2 of the parallel combination of both capacitors will reach value Z22, with the "plateaus" Z21 and Z22 having additional characteristics that are substantially more different from each other than the plateaus Z11 and Z12 of a single, larger capacitor. Thus, embodiments of the present invention can much more reliably identify individual urination events by taking advantage of the much more clearly different behavior of the measured impedance (Z1 relative to Z2).

[0027] 4A-4C show schematic diagrams of parallel connections of capacitors in a sensor configuration according to corresponding embodiments of the present invention. Specifically, in principle, FIG. 4A reflects the situation of at least two of the capacitors connected in parallel as described in conjunction with FIG. 3 for the second impedance Z2. The impedance can be measured by connecting a network analyzer to the terminals or junctions T1 and T2 of the two branches of the parallel connection of capacitors C1 and C2.

[0028] 4B further shows a schematic diagram of a parallel connection in which there are at least two pairs of parallel-connected planar capacitors. That is, a first pair of parallel capacitors C1 and C2 and a second pair of parallel capacitors C3 and C4 are provided. The first pair is accessible through terminals T1 and T2, and the second pair is accessible through terminals T2 and T3. In this embodiment, a primarily longitudinal extension of the liquid-absorbent layer and its associated absorption sequence are again assumed, such that a urination event, for example, affects C1, then C1 and C2, then C1, C2, and C3, and so on. By forming several pairs of individually parallel-connected capacitors, the readout can be even more improved, for example, because the second pair C3 / C4 is not affected at all by the first two urination events.

[0029] FIG. 4C further illustrates a schematic diagram of a parallel connection in which at least two pairs of parallel-connected planar capacitors are provided. That is, the individual planar capacitors of the parallel-connected planar capacitor pairs are arranged in alternating order. That is, a first pair of parallel capacitors C1 and C3 and a second pair of parallel capacitors C2 and C4 are again provided. The first pair is accessible through terminals T1 and T2, and the second pair is accessible through terminals T2 and T3. However, capacitor C2 is located between the parallel-connected capacitors C1 and C3, and capacitor C3 is located between the parallel-connected capacitors C2 and C4. In other words, the individual planar capacitors of the parallel-connected planar capacitor pairs are arranged in alternating order such that the individual planar capacitors of a pair are not located next to each other. Clearly, such an arrangement can be used to maximize the distance between the individual planar capacitors of a pair.

[0030] In this embodiment, again, a primarily longitudinal extension of the liquid-absorbent layer and its associated absorption sequence is assumed, whereby a urination event, for example, affects C1, then C1 and C2, then C1, C2, and C3, etc. Forming several pairs of individually parallel-connected capacitors and an interleaved arrangement can be used to improve the readout, for example, since an early urination event can be identified not only by a separate capacitor, but also by a separate capacitor of a separate pair with a corresponding separate readout line. Considering such an embodiment can be particularly advantageous when the focus is on identifying early urination events versus later urination events, or when focusing on a first group of capacitors versus a second group of capacitors that are generally associated with less significance and / or importance.

[0031] 5A-5C show schematic diagrams of capacitor electrode arrangements in sensor configurations according to corresponding embodiments of the present invention. In principle, all of these embodiments are considered to have coplanar capacitor electrodes, in the sense that the electrode area follows the shape of the substrate, allowing for bending and curvature. Generally, the 0 volt or ground terminal of the network analysis function is connected to the outer electrode, and the signal is connected to the inner circle, or vice versa. Typical dimensions, in terms of diameter, width, or diagonal extension, range from approximately 15 to 25 mm in the transverse direction and approximately 15 to 70 mm in the longitudinal direction, preferably 30 to 60 mm. Having oval electrodes, as in FIG. 5B, is preferred, primarily to achieve good coverage in the strip, with small "dead zones" between adjacent electrodes, while keeping the number of electrodes reasonable.

[0032] In some embodiments, such as that shown in FIG. 5A, the capacitor electrodes take the form of pads 21 and 22, forming a planar capacitor using a simple and reliable shape with easy contact that can avoid, at least to some extent, crossover of conductive paths. FIGS. 5B and 5C show schematic diagrams of electrode arrangements in which the capacitor electrodes take the form of concentric electrodes (FIG. 5B: pads 31 and 32, such as ellipses; FIG. 5C: circles 31′ and 32′). Such an arrangement can contribute to focusing the electric field distribution within the dielectric, i.e., within the liquid-absorbent article. Thus, the response can be focused on the liquid, localized in a specific and predeterminable manner, because the locus of the electric field lines is concentrated in the volume defined by the footprints of the outermost of the concentric electrodes, i.e., the electrodes 32 and 32′, respectively.

[0033] 6A-6C show schematic diagrams of electrode and capacitor configurations in a strip-shaped sensor configuration according to a corresponding embodiment of the present invention. FIG. 6A focuses on a broader aspect of the strip-shaped sensor configuration 1, which exemplarily comprises circular, concentric electrode pads for a plurality of capacitors C1, C2, ..., C8. Also shown are a plurality of conductor paths 40, 41, ..., 44 on or within the substrate 1, connecting the capacitor electrodes to terminals of a readout circuit. Specifically, an embodiment is shown in which the sensor configuration 1 also comprises a connector 50 toward the readout circuit. The connector 50 may be formed by a compact, encapsulated electronic device that can be interchangeably secured and connected to the sensor configuration 1, for example, by an interference fit into the connector 50. The mentioned readout circuit can provide appropriate applicable functionality, such as power supply, network analysis, data processing, communication, operation, etc. Other related embodiments of the present invention include such readout circuitry in the sensor configuration, which may omit the connector and allow the readout circuitry to be implemented on the same substrate on which the capacitor electrodes and / or conductive paths are configured. In either method, the readout circuitry may also include the transmitter component, so that only the transmitter component may be removable.

[0034] In this embodiment, the parallel connection of the planar capacitors C1, C2, ..., C8 is realized before the connector 50. That is, all first electrodes of all planar capacitors C1, C2, ..., C8 are connected to a first common terminal line, which is implemented by a conductive path 40. The second electrodes of each of the parallel-connected capacitors C1 and C5 are connected to a corresponding second common terminal line, which is implemented by a conductive path 41. A similar scheme is applied to further pairs of capacitors C2 and C6, C3 and C7, and C4 and C8. In this manner, the planar capacitors are connected in parallel using the plurality of conductor paths 40, 41, ..., 44 on the substrate 1. The conductor paths 40, 41, ..., 44 as well as the electrode pads of the capacitors C1, C2, ..., C8 may be implemented as conductive paths and conductive areas of a flexible printed circuit board, including the usual multiple layers and vias between them.

[0035] In application, this embodiment can be considered under the assumption that the middle capacitor C4 is intended to represent the primary point of urination, with a relatively high probability of being the first capacitor to detect wetness. Following this, in subsequent detection of impedance changes in the pair comprising capacitors C1 and C5, since none of C2, C3, C6, C7, or C8 detect "wetness," it can be assumed that capacitor C5 adjacent to the middle capacitor C4 detects liquid absorption, while capacitor C1 at the far end (but connected in parallel) does not. Similarly, if the pair of capacitors C3 and C7 experiences an impedance change after capacitor C4, it can be assumed that liquid absorption occurred near C3 but not near C7. In this manner, the direction of subsequent liquid absorption can also be considered and / or determined.

[0036] FIG. 6B shows a schematic diagram of an electrode and capacitor configuration in a strip-shaped sensor configuration according to an embodiment of the present invention, focusing on the mutual distance between adjacent capacitors. Specifically, the sensor configuration 1′ comprises a plurality of capacitors C1, C2, ..., in which the mutual distance between two adjacent planar capacitors increases toward at least one edge of the substrate 102. In the illustrated configuration, the distance between capacitors C1 and C2 and the distance between capacitors C5 and C6 are greater than the distance between capacitors C3 and C4. Capacitors C1, C2, C5, and C6 are positioned closer to the edges of the strip-shaped sensor configuration 1′ compared to the somewhat “central” capacitors C3 and C4. This embodiment takes into account specific locations that may be assumed to be sources of bodily fluid. Specifically, when the strip-shaped sensor configuration 1′ is attached to a diaper 9, for example, as shown in FIG. 1, the center of the strip may coincide with, or at least be close to, the urinary outlet. Thus, this embodiment may be preferred when the first urination event is of particular interest and one or more subsequent urination events do not need to be distinguished.

[0037] 6C shows a schematic diagram of an arrangement of electrodes and capacitors in a strip-shaped sensor configuration according to an embodiment of the present invention, focusing again on the mutual distance between adjacent capacitors. Specifically, the sensor configuration 1″ comprises a plurality of capacitors C1, C2, ... in which the mutual distance between two adjacent planar capacitors decreases towards at least one edge of the substrate 102. In the configuration shown, the distance between capacitors C1 and C2 and the distance between capacitors C7 and C8 are smaller than the distance between capacitors C4 and C5. Capacitors C1, C2, C7, and C8 are positioned closer to the edges of the strip-shaped sensor configuration 1″ compared to the somewhat “central” capacitors C4 and C5. This embodiment again takes into account specific locations that may be assumed as sources of bodily fluids. However, this embodiment may be preferred when the first urination event is of less importance and it is later urination events that are of particular interest. Specifically, applications that consider the need for replacement of a full absorbent article and the corresponding time points may want to clearly distinguish between urination events that occur towards the full capacity of the absorbent article.

[0038] Although detailed embodiments have been described, these are merely to provide a better understanding of the invention as defined by the independent claims and should not be understood as limiting. [Explanation of symbols]

[0039] 1, 1', 1" sensor configuration, absorbent article 9 Diapers and absorbent articles 11, 12 Planar capacitor 21, 22 Pad-like shape 31, 32 Oval pad shape 31', 32' circular pad shape 40, 41, 42, 43, 44 Conductor path, conductive path, conductive path 50 connectors 91 Surface 101 Outer layer 102 Circuit Board 103 Adhesive layer 1201 First Surface 1202 Second Surface C1, C2, C3, C4, C5, C6, C7, C8 capacitors T1, T2, T3 terminals, connection points Z1 First impedance curve T1 Time period before the first micturition event T2 During the first micturition event T4 During the second micturition event Z1 Impedance curve of a single capacitor Z2 Impedance curve of parallel connected capacitors Z11, Z12 Impedance of a single capacitor Z21, Z22 Impedance of parallel connected capacitors

Claims

1. 1. A sensor arrangement for sensing the fill state of an absorbent article with a liquid-absorbing layer, comprising: A substrate; a plurality of planar capacitors each comprising at least two corresponding sets of capacitor electrodes disposed next to each other on or within the substrate; a plurality of conductor paths on or within the substrate, connecting the capacitor electrodes towards terminals of a readout circuit; Equipped with A sensor configuration wherein at least two of the planar capacitors are connected in parallel.

2. The sensor configuration of claim 1 , wherein the substrate has an elongated strip shape with a longitudinal direction along the elongated dimension, and the planar capacitor is disposed along the longitudinal direction.

3. The sensor configuration of claim 2 , wherein the mutual distance between two adjacent planar capacitors increases towards at least one edge of the substrate.

4. The sensor configuration of claim 2 , wherein the mutual distance between two adjacent planar capacitors decreases towards at least one edge of the substrate.

5. 5. A sensor arrangement according to claim 1, comprising at least two pairs of planar capacitors connected in parallel.

6. The sensor configuration of claim 5 , wherein the individual planar capacitors of the pairs of parallel-connected planar capacitors are arranged in alternating order.

7. The sensor arrangement of claim 1 , further comprising a connector towards the readout circuitry.

8. The sensor configuration of claim 7 , wherein the parallel connection of the planar capacitors is realized before the connector.

9. The sensor configuration of claim 8 , wherein the planar capacitors are connected in parallel using the plurality of conductor paths on the substrate.

10. A sensor arrangement according to any one of claims 1 to 9, wherein the capacitor electrodes are in the form of pads.

11. A sensor arrangement according to any one of claims 1 to 9, wherein the capacitor electrodes are concentric.

12. 12. The sensor configuration of claim 1, wherein the substrate comprises a first surface and a second surface, and the capacitor electrodes are disposed together on one of the first surface and the second surface.

13. The sensor configuration of claim 12 , wherein the capacitor electrodes are coplanar.

14. The sensor arrangement of claim 1 , wherein the substrate is flexible.

15. The sensor arrangement according to any one of claims 1 to 14, configured to be associated with the liquid-absorbing layer of the absorbent article.

16. The sensor arrangement of claim 1 , further comprising the readout circuit.

17. An absorbent article comprising a sensor arrangement according to any one of claims 1 to 15.

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