JP7412694B2 - Salinity measuring device, head-mounted device, and salinity measuring method - Google Patents

Description

The present invention relates to a salinity measuring device, a head-mounted device, and a salinity measuring method.

2. Description of the Related Art In order to prevent heatstroke, devices are known that measure the amount of sweat. For example, Patent Document 1 describes an example of a head-mounted device that can measure the amount of perspiration. In order to improve the accuracy of estimating the possibility of heat stroke, it is desirable to measure the salt concentration of sweat in addition to the amount of sweat. For example, Patent Document 2 describes a salt sensor that can measure the salt concentration of urine. The salt sensor disclosed in Patent Document 2 calculates the salt concentration of urine based on the conductivity between a pair of electrodes.

International Publication No. 2019/078308 Japanese Patent Application Publication No. 2004-226273

By the way, sweat is secreted from a large number of sweat glands over a wide area. In order to improve the accuracy of measuring the salt concentration of sweat, which is necessary for estimating the possibility of heatstroke, it is desirable to measure the average salt concentration of sweat secreted from a large number of sweat glands. When using the salt sensor of Patent Document 2, it is difficult to measure the average salt concentration of sweat secreted from a large number of sweat glands. For this reason, when using the salt sensor of Patent Document 2, there is a limit to improving the accuracy of measuring the salt concentration of sweat.

The present disclosure has been made in view of the above-mentioned problems, and aims to provide a salt concentration measuring device, a head-mounted device, and a salt concentration measuring method that can improve the accuracy of measuring the salt concentration of sweat. purpose.

In order to achieve the above object, a salinity concentration measuring device according to one aspect of the present disclosure includes a salinity sensor including a substrate and a pair of comb-shaped electrodes arranged on the substrate, and an electric current between the pair of electrodes. The device includes an electrical conductivity measurement unit that measures conductivity, and a calculation unit that calculates the salt concentration of sweat between the pair of electrodes based on the electrical conductivity.

A desirable embodiment of the salinity measuring device includes a storage unit that stores cell constants related to the pair of electrodes determined in advance through experiments using standard solutions, and the calculation unit stores Calculate the salt concentration of sweat.

In a desirable aspect of the salt concentration measuring device, the electrical conductivity measurement section measures electrical conductivity based on an AC resistance between the pair of electrodes when an AC voltage is applied to the pair of electrodes, and The frequency of the voltage is 0.5 kHz or more and 15 kHz or less.

A desirable embodiment of the salt concentration measuring device includes a temperature sensor that measures the temperature of the sweat.

In a desirable embodiment of the salt concentration measuring device, the electrode includes a film containing gold or platinum on the surface opposite to the substrate.

In a desirable embodiment of the salinity measuring device, the salinity sensor includes a spacer that is thicker than the height of the electrode.

In a desirable embodiment of the salt concentration measuring device, the electrode includes a plurality of teeth arranged at intervals in one direction, and a base that connects the plurality of teeth, and the spacer connects one of the electrodes. The spacer is arranged closer to the base of the other electrode than the tip of the tooth, and is longer than the base in the direction in which the plurality of teeth are lined up.

To achieve the above object, a head-mounted device according to one aspect of the present disclosure includes an outer shell, an inner shell arranged inside the outer shell and facing the wearer's skin, and a salt concentration measuring device. The salinity concentration measuring device includes a substrate and a pair of comb-like electrodes disposed on the substrate, and measures electrical conductivity between a salinity sensor disposed on the inner shell and the pair of electrodes. The device includes an electrical conductivity measurement unit that measures electrical conductivity, and a calculation unit that calculates the salt concentration of sweat between the pair of electrodes based on the electrical conductivity.

In a desirable embodiment of the head-mounted device, the salinity sensor is placed in the inner shell at a position facing the wearer's forehead.

In a desirable embodiment of the head-mounted device, the electrode includes a plurality of teeth arranged at intervals in one direction, and a base that connects the plurality of teeth, and the pair of electrodes includes a plurality of teeth arranged at intervals in one direction, and a base that connects the plurality of teeth. The tooth portions are arranged so that the direction in which the teeth are lined up is along the direction from the edge of the outer shell toward the top.

In order to achieve the above object, a salt concentration measuring method according to one aspect of the present disclosure includes an electrical conductivity measuring step of measuring electrical conductivity between a pair of comb-shaped electrodes, and based on the electrical conductivity, and a salt concentration calculation step of calculating the salt concentration of sweat between the pair of electrodes.

According to the salt concentration measuring device, the head-mounted device, and the salt concentration measuring method of the present disclosure, it is possible to improve the measurement accuracy of the salt concentration of sweat.

FIG. 1 is a bottom view of a head-mounted device including a salt concentration measuring device according to an embodiment. FIG. 2 is a sectional view taken along line AA in FIG. FIG. 3 is a schematic diagram showing a salt concentration measuring device according to an embodiment. FIG. 4 is a front view of the salinity sensor of the embodiment. FIG. 5 is a sectional view taken along line BB in FIG. FIG. 6 is a sectional view taken along line CC in FIG. FIG. 7 is a graph comparing the conductivity of the standard solution measured by the salinity sensor of the embodiment and the actual conductivity of the standard solution. FIG. 8 is a flowchart illustrating the salt concentration measuring method according to the embodiment.

Hereinafter, the present invention will be explained in detail with reference to the drawings. Note that the present invention is not limited to the modes for carrying out the present invention (hereinafter referred to as embodiments). Furthermore, the constituent elements in the embodiments below include those that can be easily imagined by those skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the embodiments below can be combined as appropriate.

(Embodiment)
FIG. 1 is a bottom view of a head-mounted device including a salt concentration measuring device according to an embodiment. FIG. 2 is a sectional view taken along line AA in FIG. FIG. 3 is a schematic diagram showing a salt concentration measuring device according to an embodiment. FIG. 4 is a front view of the salinity sensor of the embodiment. FIG. 5 is a sectional view taken along line BB in FIG. FIG. 6 is a sectional view taken along line CC in FIG.

As shown in FIG. 2, the head-mounted device 10 is a device that is worn on the head of a wearer 90. The head mounted device 10 of this embodiment is a helmet. As shown in FIGS. 1 and 2, the head mounted device 10 includes an outer shell 11, an inner shell 12, and a salt concentration measuring device 100.

As shown in FIG. 2, the outer shell 11 is a hemispherical member. The outer shell 11 is made of, for example, synthetic resin. Inner shell 12 is arranged inside outer shell 11. Inner shell 12 faces skin 91 of wearer 90 . The inner shell 12 includes a band portion 121, a hammock portion 125, and a belt portion 123. Band portion 121 is an annular member that extends along the edge of outer shell 11 . The hammock section 125 is arranged at a position corresponding to the top of the outer shell 11. The belt portion 123 connects the band portion 121 and the hammock portion 125.

As shown in FIG. 3, the salinity measurement device 100 includes a salinity sensor 31, an electrical conductivity measurement section 39, a battery 101, a temperature sensor 33, a photoplethysmographic sensor 35, a sweat amount sensor 37, and a control unit. It includes a device 50 and an output device 70.

The salt sensor 31 is a sensor that detects information necessary to measure the salt concentration of sweat of the wearer 90. The salt sensor 31 is arranged so as to be in contact with the skin 91 of the wearer 90. As shown in FIG. 1, the salinity sensor 31 is arranged on the band portion 121 of the inner shell 12. As shown in FIG. 2, the salinity sensor 31 is placed in the band portion 121 at a position facing the forehead 95 of the wearer 90. Therefore, when the wearer 90 is wearing the head-mounted device 10, the salinity sensor 31 comes into contact with the forehead 95 of the wearer 90.

As shown in FIGS. 4 to 6, the salinity sensor 31 includes a substrate 40, a first electrode 41, a second electrode 42, a first land 43, a second land 44, a first protective film 45, It includes a second protective film 46, a first spacer 47, and a second spacer 48.

The substrate 40 is a plate made of an insulator. Substrate 40 is a flexible substrate. The substrate 40 is made of polyimide (PI), for example. The first electrode 41 and the second electrode 42 are conductors provided on the surface of the substrate 40. The first electrode 41 and the second electrode 42 are made of copper, for example. The first electrode 41 and the second electrode 42 are provided with a film on the surface opposite to the substrate 40 . Desirably, the film contains gold or platinum. The film is formed of, for example, Ni--Au (nickel gold). The first electrode 41 and the second electrode 42 are comb-shaped electrodes.

As shown in FIG. 4, the first electrode 41 includes a plurality of teeth 411 and a base 413. The plurality of teeth 411 are arranged at equal intervals in one direction. The first electrode 41 is arranged so that the direction in which the tooth portions 411 are lined up is along the direction from the edge 111 of the outer shell 11 toward the top portion 113 (vertical direction in the plane of the paper in FIG. 2). The base 413 connects all the teeth 411.

As shown in FIG. 4, the second electrode 42 includes a plurality of teeth 421 and a base 423. The plurality of teeth 421 are arranged at equal intervals in one direction. The second electrode 42 is arranged so that the direction in which the tooth portions 421 are lined up is along the direction from the edge 111 of the outer shell 11 toward the top portion 113 (in the vertical direction of the plane of the paper in FIG. 2). One tooth 421 is arranged between two teeth 411. That is, the tooth portions 411 and the tooth portions 421 are arranged alternately. A gap is provided between the tooth portion 411 and the tooth portion 421. The base 423 connects all the teeth 421.

In the following description, XYZ orthogonal coordinate axes are used. The X-axis is perpendicular to the substrate 40. The Y-axis is parallel to the longitudinal direction of the tooth portion 411. The Z-axis is parallel to the direction in which the plurality of teeth 411 are lined up. A direction parallel to the X axis is simply referred to as an X direction. A direction parallel to the Y axis is simply referred to as a Y direction. A direction parallel to the Z axis is simply referred to as a Z direction. The direction from the back surface of the substrate 40 to the front surface where the first electrode 41 is arranged is defined as the +X direction. The direction from the first electrode 41 to the second electrode 42 is defined as the +Y direction. The left direction when the +X direction is the top and the +Y direction is the front is the +Z direction.

As shown in FIG. 4, the first land 43 is arranged in the −Y direction of the first electrode 41. As shown in FIG. The first land 43 is connected to the base 413. The first land 43 is connected to the electrical conductivity measuring section 39 via a lead wire or the like.

As shown in FIG. 4, the second land 44 is arranged in the +Y direction of the second electrode 42. As shown in FIG. The second land 44 is connected to the base 423. The second land 44 is connected to the electrical conductivity measuring section 39 via a lead wire or the like.

The first protective film 45 is an insulating film overlaid on the first electrode 41 in the +X direction. The first protective film 45 is made of polyimide, for example. The first protective film 45 is provided over the entire length of the substrate 40 in the Z direction. The first protective film 45 covers the entire base portion 413 of the first electrode 41 and a portion of the tooth portion 411 . A portion of the tooth portion 411 that faces the tooth portion 421 in the Z direction is exposed.

The second protective film 46 is an insulating film overlaid on the second electrode 42 in the +X direction. The second protective film 46 is made of polyimide, for example. The second protective film 46 is provided over the entire length of the substrate 40 in the Z direction. The second protective film 46 covers the entire base portion 423 of the second electrode 42 and a portion of the tooth portion 421 . A portion of the tooth portion 421 that faces the tooth portion 411 in the Z direction is exposed.

The first spacer 47 is a member for providing a gap between the skin 91 of the wearer 90 and the first electrode 41 and between the skin 91 and the second electrode 42. The first spacer 47 is made of, for example, synthetic resin. The first spacer 47 is arranged in the +X direction of the first protective film 45. The first spacer 47 is arranged in the −Y direction (on the base 413 side) from the tip of the tooth portion 421. The length of the first spacer 47 in the Z direction is greater than the length of the base portion 413 in the Z direction. The length of the first spacer 47 in the X direction is greater than the lengths of the first electrode 41 and the second electrode 42 in the X direction. That is, the first spacer 47 is thicker than the first electrode 41 and the second electrode 42 in the X direction. The length of the first electrode 41 and the second electrode 42 in the X direction can also be said to be the height of the first electrode 41 and the second electrode 42. The first spacer 47 is thicker than the first electrode 41 and the second electrode 42 . When the wearer 90 is wearing the head-mounted device 10, the first spacer 47 is in contact with the skin 91 of the wearer 90.

The second spacer 48 is a member for providing a gap between the skin 91 of the wearer 90 and the first electrode 41 and between the skin 91 and the second electrode 42. The second spacer 48 is made of, for example, synthetic resin. The second spacer 48 is arranged in the +X direction of the second protective film 46. The second spacer 48 is arranged in the +Y direction (on the base 423 side) from the tip of the tooth portion 411. The length of the second spacer 48 in the Z direction is greater than the length of the base portion 423 in the Z direction. The length of the second spacer 48 in the X direction is greater than the lengths of the first electrode 41 and the second electrode 42 in the X direction. That is, the second spacer 48 is thicker than the first electrode 41 and the second electrode 42 in the X direction. The second spacer 48 is thicker than the first electrode 41 and the second electrode 42 . When the wearer 90 is wearing the head-mounted device 10, the second spacer 48 is in contact with the skin 91 of the wearer 90.

The electrical conductivity measurement unit 39 measures the electrical conductivity of sweat of the wearer 90 using information detected by the salinity sensor 31. The electrical conductivity measurement unit 39 applies an alternating current voltage to the salinity sensor 31 using the battery 101 as a power source. The electrical conductivity measurement unit 39 applies an AC voltage to the first electrode 41 and the second electrode 42 . The frequency of the alternating current voltage is preferably 0.5 kHz or more and 15 kHz or less. The electrical conductivity measurement unit 39 calculates electrical conductivity based on AC resistance (impedance) when an AC voltage is applied to the salinity sensor 31. Electrical conductivity is the reciprocal of alternating current resistance.

The temperature sensor 33 is a sensor that detects the temperature of sweat of the wearer 90. The temperature sensor 33 is arranged so as to be in contact with the skin 91 of the wearer 90. As shown in FIG. 1, the temperature sensor 33 is arranged on the band portion 121 of the inner shell 12. It is known that electrical conductivity changes depending on temperature. For this reason, it is desirable to measure the correction value of electrical conductivity depending on temperature in advance using a standard solution or the like. It is desirable that the electric conductivity correction value is stored in a storage unit 53 of the control device 50, which will be described later. Thereby, the calculation unit 51 of the control device 50, which will be described later, can correct the electrical conductivity based on the stored electrical conductivity correction value.

The photoelectric pulse wave sensor 35 is a sensor that detects the pulse wave of the wearer 90. The photoplethysmographic sensor 35 is arranged so as to be in contact with the skin 91 of the wearer 90. As shown in FIG. 1, the photoplethysmographic sensor 35 is arranged on the band portion 121 of the inner shell 12. As shown in FIG.

The sweat amount sensor 37 is a sensor that detects information necessary to measure the amount of sweat of the wearer 90. Information necessary for measuring sweat amount is not particularly limited. For example, the sweat amount sensor 37 may include two humidity sensors and an air volume sensor. The sweat amount sensor 37 transmits the humidity and air volume detected by the humidity sensor to the control device 50.

The control device 50 is a computer, and includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input interface, and an output interface. The CPU, ROM, RAM, input interface, and output interface are connected by an internal bus. As shown in FIG. 3, the control device 50 includes a calculation section 51 and a storage section 53. Each function of the calculation unit 51 and the storage unit 53 is realized by linking the CPU, ROM, RAM, input interface, and output interface. The control device 50 is electrically connected to the electrical conductivity measuring section 39, the temperature sensor 33, the photoplethysmographic sensor 35, and the sweat amount sensor 37, and receives measured values.

The calculation unit 51 calculates the salt concentration of the sweat of the wearer 90 based on the electrical conductivity received from the electrical conductivity measurement unit 39. The calculation unit 51 calculates the salt concentration based on the following equation (3). Let κ be the conductivity of sweat (S/cm). Let the concentration (mol/L) of each ion (i) contained in sweat be Ci (i=1, 2, 3, . . . ). Let the molar conductivity (S·cm ² /mol) of each ion (i) contained in sweat be λi (i=1, 2, 3, . . . ). Let ΣCiλi be the sum of the products of Ci and λi for all ions contained in sweat. In this case, the following formula (1) holds true. Note that sweat contains sodium ions, chloride ions, potassium ions, calcium ions, lactate ions, and the like.

κ=1000×ΣCi×Σλi...(1)

Let G be the electrical traditionality (S) of sweat. The distance (cm) between the teeth 411 of the first electrode 41 and the teeth 421 of the second electrode 42 is d. Let A be the surface area (cm ² ) of the teeth 411 and 421. Let K be a cell constant (1/cm) regarding the first electrode 41 and the second electrode 42. In this case, the following formula (2) holds true.

κ=G×(d/A)=G×K...(2)

The following equation (3) is derived from equations (1) and (2). ΣCi is the sum of Ci regarding all ions contained in sweat. Σλi is the sum of λi regarding all ions contained in sweat.

ΣCi=K×G/(1000×Σλi) ...(3)

The storage unit 53 stores the sum of λi (Σλi) and a cell constant (K) regarding all ions contained in sweat. The cell constant (K) is determined by an experiment conducted in advance using a standard solution. A standard solution is a liquid with known physical properties. That is, the concentration (Ci) of each ion contained in the standard solution and the molar conductivity (λi) of each ion contained in the standard solution are known. The electrical conductivity (G) of the standard solution is measured using the salt sensor 31. By substituting ΣCi, Σλi, and G of the standard solution into equation (3), the cell constant (K) regarding the first electrode 41 and the second electrode 42 is derived. The cell constant (K) derived in this way is stored in the storage section 53.

FIG. 7 is a graph comparing the conductivity of the standard solution measured by the salinity sensor of the embodiment and the actual conductivity of the standard solution. As shown in FIG. 7, by changing the frequency of the AC voltage that the electrical conductivity measurement section 39 applies to the salinity sensor 31, the electrical conductivity of the standard solution measured by the electrical conductivity measurement section 39 and the standard solution The correlation coefficient (R) with actual conductivity is 0.9999. That is, by changing the frequency of the AC voltage that the electrical conductivity measuring section 39 applies to the salinity sensor 31, the electrical conductivity measuring section 39 can measure the electrical conductivity of the standard solution with high precision. The conductivity of sweat is generally about 10 mS/cm or more and 20 mS/cm or less. Therefore, in order to improve the measurement accuracy of the electrical conductivity (G) of sweat by the electrical conductivity measuring section 39, the frequency of the AC voltage that the electrical conductivity measuring section 39 applies to the salinity sensor 31 should be 0.5 kHz or more. It is desirable that the frequency be 15 kHz or less. If such an optimal measurement frequency (the frequency of the AC voltage that the electrical conductivity measuring section 39 applies to the salinity sensor 31) is determined in advance, even if the measurement frequency of the electrical conductivity measuring section 39 cannot be changed, sweat can be avoided. It is possible to accurately measure the electrical conductivity of Therefore, even if the measurement frequency of the electrical conductivity measuring section 39 cannot be changed, the concentration of each ion contained in sweat (average ion equivalent concentration) can be determined.

The calculation unit 51 corrects G received from the electrical conductivity measurement unit 39 based on the sweat temperature received from the temperature sensor 33. The calculation unit 51 calculates ΣCi by substituting Σλi and K stored in the storage unit 53, and the corrected G into equation (3). The calculation unit 51 regards the calculated ΣCi as the salt concentration of sweat. The calculation unit 51 stores ΣCi in the storage unit 53 as the salinity concentration. Note that the calculation unit 51 may calculate the salt concentration based on ΣCi and a predetermined coefficient.

The calculation unit 51 calculates the sweat amount of the wearer 90 based on the information received from the sweat amount sensor 37. The calculation unit 51 calculates the amount of perspiration based on, for example, the relative humidity of the air flowing into the outer shell 11, the relative humidity of the air flowing out from the outer shell 11, the amount of air flowing into (or flowing out of) the outer shell 11, etc. do. Note that the calculation unit 51 may calculate the sweat amount using other methods.

The calculation unit 51 calculates the amount of salt loss (g) of the wearer 90 based on the following equation (4). For this reason, the salinity concentration measuring device 100 can also be said to be a lost salt amount measuring device. M in equation (4) is the amount of salt loss. P in equation (4) is the sweat amount (L). C in equation (4) is the salt concentration (mol/L). The value of 58.5 in formula (4) is the molar mass (g/mol) of sodium chloride.

M=P×C×58.5 (4)

Sweat is a mixture of ions such as sodium, potassium, magnesium, and chloride. Since sodium chloride is the main component of sweat, formula (4) holds true when the molar mass is represented by sodium chloride. More specifically, if the molar mass is corrected proportionally with the value of other substances (for example, potassium chloride) depending on the sweat mixture ratio, the value of the amount of salt lost can be calculated more accurately.

The calculation unit 51 changes the state of the output device 70 based on the calculated amount of salt loss. The output device 70 is, for example, an alarm device that emits sound or light. For example, when the calculated amount of salt loss exceeds the threshold value stored in the storage unit 53, the calculation unit 51 causes the output device 70 to issue an alarm. Note that the output device 70 may be a display device that displays numerical values, images, or the like. For example, the calculation unit 51 displays the calculated amount of salt loss on the output device 70. Thereby, the head-mounted device 10 can make the wearer aware that he or she may suffer from heatstroke.

Note that the salt concentration measuring device 100 does not necessarily have to be applied to the head-mounted device 10. The salt concentration measuring device 100 may be applied to clothing, for example. The salt concentration measuring device 100 may be applied to a wearable terminal, for example. Further, the head-mounted device 10 is not limited to a helmet, but may be a hat.

The cell constants regarding the first electrode 41 and the second electrode 42 do not necessarily have to be measured by experiment using a standard solution. For example, the calculation unit 51 calculates the cell constant based on the distance (cm) between the teeth 411 of the first electrode 41 and the teeth 421 of the second electrode 42 and the surface areas of the teeth 411 and 421. It may be calculated.

The salinity sensor 31, the temperature sensor 33, the photoplethysmographic sensor 35, and the sweat amount sensor 37 do not necessarily have to be arranged on the band portion 121 of the inner shell 12. The positions where the salinity sensor 31, temperature sensor 33, photoplethysmographic sensor 35, and sweat amount sensor 37 are arranged are not particularly limited.

The arrangement and shape of the first spacer 47 and the second spacer 48 of the salinity sensor 31 are not particularly limited. The first spacer 47 and the second spacer 48 may be arranged, for example, on the surface of the substrate 40 or may be arranged so as to overlap the teeth 411 and the teeth 421. The first spacer 47 and the second spacer 48 do not have to have a shape extending in the Z direction, and may have, for example, a substantially cylindrical shape, a substantially spherical shape, or the like.

FIG. 8 is a flowchart illustrating the salt concentration measuring method according to the embodiment. As shown in FIG. 8, the salt concentration measuring method of the embodiment is a method of measuring the salt concentration of sweat using the above-described salinity sensor 31. The salt concentration measuring method of the embodiment includes steps S1 to S4.

In step S1, cell constants regarding the pair of electrodes (first electrode 41 and second electrode 42) of the salinity sensor 31 are measured. The cell constant is determined, for example, by experiment using a standard solution. Step S1 can also be called a cell constant measurement step.

After step S1, in step S2, the electrical conductivity of the pair of electrodes (first electrode 41 and second electrode 42) is calculated with sweat in contact with the pair of electrodes. Electric conductivity is calculated based on the AC resistance when an AC voltage is applied to the first electrode 41 and the second electrode 42. Step S2 can also be called an electrical conductivity measurement step.

After step S2, in step S3, the salt concentration of sweat is calculated based on the cell constant and electrical conductivity. For example, the salt concentration of sweat is calculated based on the above-mentioned equation (3). Step S3 can also be called a salinity concentration calculation step.

After step S3, in step S4, the amount of salt lost by the subject is calculated based on the salt concentration of the sweat and the amount of sweat of the subject. For example, the amount of salt lost by the subject is calculated based on the above-mentioned equation (4). Step S4 can also be called a lost salt amount calculation step. The salt concentration measurement method of the embodiment can also be called a loss salt amount measurement method.

As explained above, the salinity concentration measuring device 100 of this embodiment includes the salinity sensor 31, the electrical conductivity measurement section 39, and the calculation section 51. The salt sensor 31 includes a substrate 40 and a pair of comb-shaped electrodes (a first electrode 41 and a second electrode 42) arranged on the substrate 40. The electrical conductivity measuring section 39 measures electrical conductivity between a pair of electrodes. The calculation unit 51 calculates the salt concentration of sweat between the pair of electrodes based on the electrical conductivity.

According to the salt concentration measuring device 100, since the electrodes are comb-shaped, it is easy to arrange the pair of electrodes over a wide range. Therefore, sweat secreted from a large number of sweat glands enters between the pair of electrodes in a mixed state. The salt concentration measuring device 100 can measure the average salt concentration of sweat secreted from a large number of sweat glands. Therefore, the salt concentration measuring device 100 can improve the measurement accuracy of the salt concentration of sweat.

The salinity measuring device 100 includes a storage unit 53 that stores cell constants for a pair of electrodes (first electrode 41 and second electrode 42) determined in advance through an experiment using a standard solution. The calculation unit 51 calculates the salt concentration of sweat based on the electrical conductivity and cell constant.

This increases the accuracy of the cell constant compared to the case where the cell constant is calculated from the shape, arrangement, etc. of a pair of electrodes. Therefore, the salt concentration measuring device 100 can further improve the measurement accuracy of the salt concentration of sweat.

Further, in the salt concentration measuring device 100, the electrical conductivity measurement section 39 measures electrical conductivity based on the AC resistance between the pair of electrodes when an AC voltage is applied to the pair of electrodes. The frequency of the alternating current voltage is 0.5 kHz or more and 15 kHz or less.

Thereby, the electrical conductivity measuring section 39 can measure the electrical conductivity of sweat with higher accuracy. Therefore, the salt concentration measuring device 100 can further improve the measurement accuracy of the salt concentration of sweat.

The salt concentration measuring device 100 includes a temperature sensor 33 that measures the temperature of sweat.

The electrical conductivity of sweat changes depending on the temperature of the sweat. By providing the temperature sensor 33, the calculation unit 51 can correct the electrical conductivity of sweat based on the temperature of the sweat. Therefore, the salt concentration measuring device 100 can further improve the measurement accuracy of the salt concentration of sweat.

In the salt concentration measuring device 100, the electrodes (first electrode 41 and second electrode 42) are provided with a film containing gold or platinum on the surface opposite to the substrate 40.

Since the electrode comes into contact with sweat, the surface of the electrode may corrode. By providing a film containing gold or platinum on the surface of the electrode, the salt concentration measuring device 100 can suppress corrosion of the electrode.

In the salinity concentration measuring device 100, the salinity sensor 31 includes a spacer (the first spacer 47 or the second spacer 48) that is thicker than the height of the electrodes (the first electrode 41 and the second electrode 42).

Thereby, when the salt sensor 31 is brought into contact with the skin 91 of the wearer 90, the spacer comes into contact with the skin 91. A gap is created between the electrode and the skin 91. Therefore, sweat easily flows between the pair of electrodes. Sweat retention between the pair of electrodes is suppressed. Therefore, the salt concentration measuring device 100 can further improve the measurement accuracy of the salt concentration of sweat.

In the salt concentration measuring device 100, the electrode (first electrode 41) includes a plurality of teeth 411 arranged at intervals in one direction (Z direction) and a base 413 that connects the plurality of teeth 411. . The spacer (for example, the first spacer 47) is arranged closer to the base 413 of the other electrode (first electrode 41) than the tip of the tooth portion 421 of one electrode (second electrode 42). The spacer is longer than the base 413 in the direction in which the plurality of teeth 411 are lined up.

This makes it easier for the spacer to guide sweat to the area where the teeth of the pair of electrodes face each other. The amount of sweat flowing into the area where the teeth of the pair of electrodes face each other increases. Therefore, the state in which fresh sweat is in contact with the pair of electrodes is easily maintained. Therefore, the salt concentration measuring device 100 can further improve the measurement accuracy of the salt concentration of sweat.

The head mounted device 10 of this embodiment includes an outer shell 11, an inner shell 12, and a salinity measuring device 100. The inner shell 12 is arranged inside the outer shell 11 and faces the skin 91 of the wearer 90. The salinity measurement device 100 includes a salinity sensor 31, an electrical conductivity measurement section 39, and a calculation section 51. The salinity sensor 31 includes a substrate 40 and a pair of comb-shaped electrodes (a first electrode 41 and a second electrode 42) arranged on the substrate 40, and is arranged on the inner shell 12. The electrical conductivity measuring section 39 measures electrical conductivity between a pair of electrodes. The calculation unit 51 calculates the salt concentration of sweat between the pair of electrodes based on the electrical conductivity.

As a result, since the salinity sensor 31 is disposed on the inner shell 12, the salinity sensor 31 is pressed against the skin 91. As a result, a state in which sweat is present between the pair of electrodes is likely to be maintained. Therefore, the salt concentration measuring device 100 can improve the measurement accuracy of the salt concentration of sweat.

In the head-mounted device 10, the salinity sensor 31 is placed in the inner shell 12 at a position facing the forehead 95 of the wearer 90.

As a result, the salinity sensor 31 comes into contact with the forehead 95 when the wearer 90 is wearing the head-mounted device 10 . By disposing the salt sensor 31 on the forehead 95, which is a part where sweat is likely to occur, the amount of sweat flowing into the area where the teeth of the pair of electrodes face each other increases. Therefore, the state in which fresh sweat is in contact with the pair of electrodes is easily maintained. Therefore, the head-mounted device 10 can further improve the measurement accuracy of the salt concentration of sweat.

In the head-mounted device 10, the electrode (first electrode 41) includes a plurality of teeth 411 arranged at intervals in one direction (Z direction) and a base 413 that connects the plurality of teeth 411. . The pair of electrodes are arranged such that the direction in which the plurality of teeth 411 are lined up is along the direction from the edge 111 of the outer shell 11 to the top 113.

If the direction in which the teeth 411 are lined up is the same as the direction along the edge of the outer shell 11, the lead wires connected to the electrodes would be arranged so as to extend above and below the electrodes when viewed from the wearer 90. Ru. Therefore, the lead wire may obstruct the wearer's 90's view. On the other hand, since the direction in which the teeth 411 are lined up is along the direction from the edge to the top of the outer shell 11, the lead wires are arranged so as to extend to the right and left sides of the electrode when viewed from the wearer 90. Therefore, the head-mounted device 10 can prevent the wearer's 90 vision from being obstructed by the lead wire.

The salt concentration measuring method of this embodiment includes an electrical conductivity measuring step (step S2) of measuring electrical conductivity between a pair of comb-shaped electrodes (first electrode 41 and second electrode 42); and a salt concentration calculating step (step S3) of calculating the salt concentration of sweat between the pair of electrodes based on the degree of water.

According to the salt concentration measuring method of this embodiment, since the electrodes are comb-shaped, it is easy to arrange the pair of electrodes over a wide range. Therefore, sweat secreted from a large number of sweat glands enters between the pair of electrodes in a mixed state. The salt concentration measuring method of this embodiment can measure the average salt concentration of sweat secreted from a large number of sweat glands. Therefore, the salt concentration measuring method of this embodiment can improve the accuracy of measuring the salt concentration of sweat.

In this embodiment, the salinity sensor 31 includes a substrate on which electrodes and lands are formed on one side, but it may also have a structure in which the land has a through hole and a lead wire is taken out from the back side of the substrate. good. By doing so, the head-mounted device 10 can further suppress the wearer's 90's view from being obstructed by the lead wire.

10 Head-mounted device 11 Outer shell 12 Inner shell 31 Salinity sensor 33 Temperature sensor 35 Photoplethysmographic sensor 37 Sweat rate sensor 39 Electrical conductivity measuring section 40 Substrate 41 First electrode 42 Second electrode 43 First land 44 Second land 45 First protective film 46 Second protective film 47 First spacer 48 Second spacer 50 Control device 51 Arithmetic unit 53 Storage unit 70 Output device 90 Wearer 91 Skin 95 Forehead 100 Salt concentration measuring device 101 Battery 111 Edge 113 Top 121 Band Part 123 Belt part 125 Hammock part 411 Tooth part 413 Base part 421 Tooth part 423 Base part

Claims (10)

a salt sensor comprising a substrate and a pair of comb-shaped electrodes disposed on the substrate;
an electrical conductivity measurement unit that measures electrical conductivity between the pair of electrodes;
a calculation unit that calculates the salt concentration of sweat between the pair of electrodes based on the electrical conductivity;
A memory for storing cell constants for the pair of electrodes, which are determined in advance by experiments using standard solutions containing sodium ions, chloride ions, potassium ions, calcium ions, and lactate ions, each of which has a known ion concentration and molar conductivity. Department and
Equipped with
In the salt sensor, sweat flows into a region where the teeth of the pair of electrodes face each other,
The cell constant is a value calculated from the electrical conductivity of the standard solution, each ion concentration, and each molar conductivity measured using the salinity sensor,
The calculation unit is a salt concentration measuring device that calculates the salt concentration of sweat based on the electrical conductivity and the cell constant. The electrical conductivity measurement unit measures electrical conductivity based on AC resistance between the pair of electrodes when an AC voltage is applied to the pair of electrodes,
The salt concentration measuring device according to claim 1, wherein the frequency of the alternating current voltage is 0.5 kHz or more and 15 kHz or less. The salt concentration measuring device according to claim 1 or 2, further comprising a temperature sensor that measures the temperature of the sweat. The salt concentration measuring device according to any one of claims 1 to 3, wherein the electrode includes a film containing gold or platinum on a surface opposite to the substrate. The salinity concentration measuring device according to any one of claims 1 to 4, wherein the salinity sensor includes a spacer that is thicker than the height of the electrode. The electrode includes a plurality of teeth arranged at intervals in one direction, and a base that connects the plurality of teeth,
The spacer is arranged closer to the base of the other electrode than the tip of the tooth of one of the electrodes,
The salt concentration measuring device according to claim 5, wherein the spacer is longer than the base in the direction in which the plurality of teeth are lined up. outer shell and
an inner shell disposed inside the outer shell and facing the wearer's skin;
A salinity measuring device,
Equipped with
The salinity measuring device includes:
a salt sensor disposed on the inner shell, comprising a substrate and a pair of comb-shaped electrodes disposed on the substrate;
an electrical conductivity measurement unit that measures electrical conductivity between the pair of electrodes;
a calculation unit that calculates the salt concentration of sweat between the pair of electrodes based on the electrical conductivity;
A memory for storing cell constants for the pair of electrodes that have been determined in advance through experiments using standard solutions containing sodium ions, chloride ions, potassium ions, calcium ions, and lactate ions, each of which has a known ion concentration and molar conductivity. Department and
Equipped with
In the salt sensor, sweat flows into a region where the teeth of the pair of electrodes face each other,
The cell constant is a value calculated from the electrical conductivity of the standard solution, each ion concentration, and each molar conductivity measured using the salinity sensor,
The calculation unit calculates the salt concentration of sweat based on the electrical conductivity and the cell constant. The head-mounted device according to claim 7, wherein the salinity sensor is arranged in the inner shell at a position facing the forehead of the wearer. The electrode includes a plurality of teeth arranged at intervals in one direction, and a base that connects the plurality of teeth,
The head mounted device according to claim 7 or 8, wherein the pair of electrodes are arranged such that the direction in which the plurality of teeth are lined up is along the direction from the edge to the top of the outer shell. an electrical conductivity measurement step of measuring electrical conductivity of sweat flowing into an area where the teeth of a pair of comb-shaped electrodes of the salinity sensor face each other;
a salt concentration calculation step of calculating the salt concentration of sweat between the pair of electrodes based on the electrical conductivity;
Equipped with
The salinity concentration calculation step includes:
storing cell constants for the pair of electrodes that were determined in advance through experiments using standard solutions containing sodium ions, chloride ions, potassium ions, calcium ions, and lactate ions, each of which has a known ion concentration and molar conductivity;
The cell constant is a value calculated from the electrical conductivity of the standard solution, each ion concentration, and each molar conductivity measured using the salinity sensor,
A salt concentration measuring method for calculating the salt concentration of sweat based on the electrical conductivity and the cell constant.

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