JP2015002779A - Biometric device and biometric method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biometric device and a biometric method which can determine whether or not a human body contacting with an electrode is in a state suitable for the measurement (an adhered state), namely in a state of being wet with water.SOLUTION: A biometric device includes: biological information measuring means which includes a cluster of electrodes used for measurement of biological impedance of a user; contact impedance measurement means which, by using two or more electrodes, measures contact impedance caused between the user and the electrode when the user is contacting with the electrode; and determination means which determines whether or not the contact impedance measured by the contact impedance measurement means is in a first prescribed range.

Description

  The present invention relates to a biometric apparatus and a biometric method for accurately measuring a user's bioimpedance.

  A conventional biometric apparatus such as a body fat scale and a body composition meter has four electrodes including a pair of current supply electrodes and a pair of voltage measurement electrodes, and the bioimpedance of the user is determined using these electrodes. Body composition information such as fat thickness is derived by the BIA (Bioelectrical Impedance Analysis) method to be measured. In such bioimpedance measurement, each electrode is brought into contact with the user's skin, a predetermined weak current is applied from the current application electrode, and the voltage is measured with the voltage measurement electrode to obtain bioimpedance. In order to accurately measure the bioelectrical impedance, it is necessary to consider the influence of contact impedance (contact resistance) caused by contact between the user's body and the electrode. That is, if the contact impedance is large, it is impossible to accurately measure the bioimpedance of the user's human body.

  This contact impedance is known to be inversely proportional to the area of the contact surface between the electrode and the human body. Therefore, in order to reduce the contact impedance, it is only necessary to increase the contact area with the human body using an electrode having a large area. However, using a large electrode is particularly important in a handy-type small biometric device. This is not preferable because it increases the size. As a handy-type biometric device, for example, a biometric device configured to be small in order to easily measure local subcutaneous fat thicknesses such as an arm part and a thigh part, four electrodes having a small area are used. Some measure bioimpedance by the electrode method. As described above, if an electrode with a small area is used as it is, contact impedance becomes large and accurate bioimpedance measurement cannot be performed. Therefore, a larger contact area with the human body can be secured without increasing the electrode. In order to reduce the impedance, measurement is performed in a state where the skin to be brought into contact with the electrode is wet with water.

  Here, as a conventional biometric measurement device, the applicant, in the body composition meter described in Patent Document 1, whether or not all the electrodes are in contact with the human body (as shown in FIG. 11 of Patent Document 1, A configuration has been proposed in which a contact abnormality can be determined (whether or not the measurement circuit is in an open state due to the presence of an electrode that is not in contact with the human body) (Patent Document 1).

JP 2012-17592 A

  However, in the case of detecting contact abnormality as in the body composition meter of Patent Document 1 by the conventional impedance measurement by the four-electrode type, even if the skin in contact with the electrode is dry, the human body and the electrode are in contact with each other. For example, it may be determined that the contact is not abnormal. In that case, since the skin in contact with the electrode is dry, the electrode and the human body are not in close contact with each other, so that the contact impedance becomes large and accurate bioimpedance cannot be measured. (Fat thickness) sometimes showed an abnormal value.

  Therefore, the present invention provides an improved biometric apparatus and biometric measurement that can determine whether the human body that is in contact with the electrode is in a state suitable for measurement (in close contact), that is, whether or not it is wet with water. It aims to provide a method.

  In order to solve the above-described problems, the biometric apparatus of the present invention uses a biometric information measuring unit including an electrode group used for measuring a bioimpedance of a user and two or more electrodes, so that the user can connect to the electrodes. Contact impedance measuring means for measuring contact impedance generated between the user and the electrode when contacted, and discrimination for determining whether or not the contact impedance measured by the contact impedance measuring means is within the first predetermined range Means.

  The biometric apparatus of the present invention is characterized by comprising an instruction means for instructing the user to wet the skin to be brought into contact with the electrode group when the contact impedance is not within the first predetermined range.

  The biometric apparatus of the present invention includes a current supply unit that supplies current from an electrode group to a user, a voltage measurement unit that measures a voltage via the electrode group based on the current supplied by the current supply unit, A first electrode connection for connecting an electrode used for measuring bioimpedance by the information measuring means to the current supply unit or voltage measuring unit, and an electrode used for measuring the contact impedance by the contact impedance measuring unit connected to the current supplying unit or voltage measuring unit. And electrode switching means for switching between the second electrode connection and the second electrode connection.

  In the biometric apparatus of the present invention, the electrode switching means can switch to the third electrode connection for connecting the electrode used when the contact impedance is measured by the contact impedance measuring means to the current supply unit or the voltage measurement unit. There are two or more electrodes connected to the current supply unit and the voltage measurement unit in the electrode connection, and the electrode group is an electrode that is not connected to the current supply unit or the voltage measurement unit in the second electrode connection, and is determined by the determination unit. Determines whether the contact impedance measured by the contact impedance measuring means in the second electrode connection is within the first predetermined range, and the contact impedance measured by the contact impedance measuring means in the third electrode connection is the first predetermined range. It is characterized by including determination of whether or not it is within.

  In the biometric apparatus of the present invention, the electrode switching means can switch to the third electrode connection for connecting the electrode used when the contact impedance is measured by the contact impedance measuring means to the current supply unit or the voltage measurement unit. In the electrode connection, there are three or more electrodes connected to the current supply unit and the voltage measurement unit. Of the electrode group, the electrode not connected to the current supply unit or the voltage measurement unit in the second electrode connection, and the second electrode connection And determining whether or not the contact impedance measured by the contact impedance measuring means in the second electrode connection is within the first predetermined range. Determining whether the contact impedance measured by the contact impedance measuring means in the third electrode connection is within the first predetermined range; It is characterized in that it comprises.

  In the biometric device of the present invention, instead of the contact impedance measuring means, contact resistance measurement is performed for measuring contact resistance generated between a user and an electrode when the user contacts the electrode using two or more electrodes. Means and / or contact reactance measuring means for measuring a contact reactance generated between the user and the electrode when the user contacts the electrode using two or more electrodes, and the discriminating means comprises a contact impedance Instead of determining whether the contact impedance measured by the measuring means is within the first predetermined range, it is determined whether the contact resistance measured by the resistance measuring means is within the second predetermined range; And / or determining whether or not the contact reactance measured by the reactance measuring means is within a third predetermined range.

  The biometric measurement method of the present invention includes a biometric information measurement step for measuring a bioimpedance of a user using an electrode group, and a contact impedance when the user contacts the electrode using two or three electrodes. A contact impedance measuring step, and a determining step for determining whether or not the contact impedance measured by the contact impedance measuring means is within a first predetermined range.

  The biometric measurement method of the present invention is characterized by comprising an instruction step for instructing the user to wet the skin to be brought into contact with the electrode group when the contact impedance is not within the first predetermined range.

  According to the present invention, it is possible to determine whether the human body in contact with the electrode is in a state suitable for measurement (in close contact), that is, whether or not the body is wet with water. This makes it possible to accurately measure the bioimpedance.

It is a figure which shows the external appearance of the biometric apparatus which concerns on 1st Embodiment, Comprising: (a) is a front view, (b) is a side view, (c) is a rear view. It is a block diagram which shows the structure of the biometric apparatus which concerns on 1st Embodiment. It is a figure which shows notionally the connection relation of the electrode and circuit at the time of contact impedance measurement. (A) is a figure which shows the equivalent circuit in the case of 4 electrode method, (b) is a figure which shows the equivalent circuit in the case of 2 electrode method, (c) is a figure which shows the equivalent circuit in the case of 3 electrode method is there. It is a flowchart which shows the flow of the process by the biometric apparatus which concerns on 1st Embodiment. It is a figure which shows the connection relation of the electrode and circuit in the biometric apparatus which concerns on the modification 1 of 1st Embodiment. It is a flowchart which shows the flow of the process by the biometric apparatus which concerns on the modification 2 of 1st Embodiment. (A) is an equivalent circuit in the measurement of contact resistance and / or contact reactance, (b) is a figure which shows the waveform of an input current and an output voltage. It is a figure which shows notionally the connection relation of the electrode at the time of contact impedance measurement in the biometric apparatus which concerns on the modification 6 of 1st Embodiment, and a circuit. It is a figure which shows the external appearance of the biometric apparatus which concerns on 2nd Embodiment of this invention.

  Hereinafter, a biological information measuring device according to an embodiment of the present invention and a biological measuring method using the biological measuring device will be described in detail with reference to the drawings.

<First Embodiment>
The biometric apparatus according to the first embodiment is an application of the biometric apparatus of the present invention to a handy type fat thickness gauge, which measures bioimpedance using four electrodes and uses two electrodes. Use to measure contact impedance.

  With reference to FIG.1 and FIG.2, the structure of the fat thickness meter (biometric measuring apparatus) which concerns on 1st Embodiment is demonstrated. FIG. 1 is a perspective view showing an appearance of a fat thickness meter 10 according to the first embodiment, and FIG. 2 is a block diagram showing a configuration of the fat thickness meter 10 according to the first embodiment.

The fat thickness meter 10 includes four electrodes 12A, 12B, 12C and 12D as current supply electrodes or voltage measurement electrodes, an AC power source 14, a voltage measurement circuit 15, a multiplexer 16 as electrode switching means, an arithmetic control unit 20, and an input device. 21, a display device 22 as an instruction means, a clock device 24, a storage device 25, and a determination circuit 26 as a determination means.
Here, the four electrodes 12A, 12B, 12C, and 12D are arranged with a size of, for example, 5 × 12.5 mm and an interelectrode distance of 15 mm.

An input device 21 and a display device 22 are arranged on the front surface 11 </ b> A of the main body 11 of the fat thickness gauge 10.
The input device 21 is a switch button operated by the user, and can input height, age, sex, and the like.
The display device 22 is, for example, a liquid crystal display, and is a display unit that displays input personal body information and biological information such as fat thickness calculated based on the measured biological impedance, and as an instruction unit. When the contact impedance is not within the first predetermined range, the user is instructed to wet the skin in contact with the electrode.

  Four electrodes 12A, 12B, 12C, and 12D as current supply electrodes or voltage measurement electrodes are provided on the back surface 11B of the main body 11 of the fat thickness meter 10 so that the bioimpedance and contact impedance of the user can be measured. Is provided. These electrodes 12A, 12B, 12C, and 12D are connected to a multiplexer 16, respectively. The multiplexer 16 has an AC power source 14 that outputs a weak AC current, and a voltage drop due to the AC current that the AC power source 14 outputs. Are connected to a voltage measuring circuit 15 for measuring the operation of the multiplexer 16 and an arithmetic control unit 20 for controlling the operation of the multiplexer 16.

The multiplexer 16 is connected to the electrodes 12A, 12B, 12C, and 12D, the AC power supply 14, and the voltage measurement circuit 15 depending on whether the bioelectrical impedance is measured or the contact impedance is measured under the control of the arithmetic control unit 20. Switch.
When measuring bioimpedance, as a first electrode connection, a pair of current supply electrodes 12B and 12C are connected to the AC power source 14, and another pair of voltage measurement electrodes 12A and 12D are connected to the voltage measurement circuit 15, respectively. Thus, the connection of the electrodes is switched by the multiplexer 16. The bioelectrical impedance is calculated based on the potential difference between the voltage measurement electrodes 12A and 12D by supplying current to the user's body from the part in contact with the current supply electrodes 12B and 12C based on the control of the calculation control unit 20. Calculation is performed by the control unit 20. Here, current is supplied to the user's body from the AC power supply 14 via the current supply electrodes 12B and 12C, and the potential difference is measured by the voltage measurement circuit 15 connected to the voltage measurement electrodes 12A and 12D. To do.
In this case, the four electrodes 12A, 12B, 12C, and 12D function as an electrode group used for measuring the bioimpedance of the user. Further, the current supply electrodes 12B and 12C, the voltage measurement electrodes 12A and 12D, the AC power supply 14, the voltage measurement circuit 15, and the multiplexer 16 constitute a biological information measurement unit.

When measuring the contact impedance, the connection of the electrodes is switched by the multiplexer 16 so that the electrodes 12A and 12B are connected to the AC power supply 14 and the voltage measurement circuit 15 as the second electrode connection. The contact impedance is an impedance generated between the contact site and the electrodes 12A and 12B when the user brings the electrodes 12A and 12B into contact with his / her body. Based on the control of the calculation control unit 20, the contact impedance supplies a current to the user's body from the part in contact with the electrodes 12A and 12B, and the calculation control unit 20 determines the contact impedance based on the potential difference between the electrodes 12A and 12B. calculate.
Here, the electrodes 12A and 12B are electrodes used for measuring the contact impedance, and the electrodes 12A and 12B, the AC power supply 14, the voltage measuring circuit 15, and the multiplexer 16 constitute a contact impedance measuring means.
The electrodes used for measuring the contact impedance are not limited to the electrodes 12A and 12D as described above, and any two of the electrodes 12A to 12D may be used.

As shown in FIG. 2, an arithmetic control unit 20, a timepiece device 24, a storage device 25, and a determination circuit 26 are arranged inside the main body 11 of the fat thickness gauge 10.
The calculation control unit 20 is a calculation unit that performs conversion from an analog value to a digital value, calculation of contact impedance and biological impedance, calculation of fat thickness and other biological information, and various controls.
The arithmetic control unit 20 also performs operation control of the AC power supply 14, the voltage measurement circuit 15, the multiplexer 16, the input device 21, the display device 22, the clock device 24, the storage device 25, and the determination circuit 26 connected thereto.

  The clock device 24 is a clock circuit, for example, and is a clock means that clocks the current date and time. The storage device 25 stores, as storage means, user registration information (personal data), measured bioimpedance values, and fat thickness and other biometric information calculated from the bioimpedance values.

  The storage device 25 is composed of, for example, a RAM (Random Access Memory), and stores information set in the initial setting, arithmetic expressions and parameters used for discrimination and other arithmetic operations, numerical values obtained by measurement, and the like. The

The discriminating circuit 26 discriminates whether or not the contact impedance measured by the contact impedance measuring unit is within the first predetermined range as the discriminating unit. When the contact impedance is within the first predetermined range, the determination circuit 26 determines that the measurement target portion of the user is wet enough to accurately measure the bioelectrical impedance. The determination result is stored in the storage device 25.
Here, the first predetermined range is determined according to the area and thickness of the electrode, the AC power supply and voltage measurement circuit described below, and the connection form of the electrode, and the like, and is suitable for the measurement of bioimpedance, particularly the electrode. A range or a threshold value (for example, 1000Ω) indicating a state in which the contacting skin can be said to be wet with water is set.

Here, an example of connection between an electrode and a circuit during contact impedance measurement will be described. 3 is a diagram conceptually showing the connection relationship between electrodes and circuits during contact impedance measurement, FIG. 4 (a) is a diagram showing an equivalent circuit in the case of the four-electrode method, and FIG. 4 (b) is a diagram of the two-electrode method. FIG. 4C is a diagram showing an equivalent circuit in the case of the three-electrode method.
FIG. 3 schematically shows a biological measurement apparatus 50 including four electrodes 52A, 52B, 52C, and 52D as voltage measurement electrodes or current supply electrodes, an AC power supply 54, and a voltage measurement circuit 55.

  In the example of FIG. 3A, the connection relationship between the electrode, the AC power source, and the voltage measurement circuit corresponds to the fat thickness meter 10 of the first embodiment, and two electrodes 52A and 52B are used when measuring the contact impedance. Are connected to an AC power supply 54 and a voltage measurement circuit 55, respectively. On the other hand, in another example shown in FIG. 3B, two electrodes 52B and 52D are connected to the AC power supply 54 and the voltage measurement circuit 55, respectively, at the time of contact impedance measurement. In measuring the contact impedance, the measurement may be performed using any two of the electrodes 52A to 52D as described above.

Figure 4 (a), (b) , (c) , the four electrodes 62A, 62B, 62C, 62D, the AC power supply 64, the voltage measuring circuit 65, the contact impedance _Z 1 to Z _4, and, for bioelectrical impedance _{Z Hum} The equivalent circuit is shown. In this circuit, a current i flows from the AC power supply 64 to the user's body through the electrodes.
In FIG. 4A, an AC power supply 64 is connected to the electrodes 62A and 62D to supply current, and a voltage measurement circuit 65 is connected to the electrodes 62B and 62C to measure a potential difference at the contact portion of the user. In this example, as in the conventional bioimpedance method, all four electrodes are used (four-electrode method).
On the other hand, in FIG. 4B, the AC power supply 64 is connected to the electrodes 62A and 62D to supply current, and the voltage measurement circuit 65 is also connected to the electrodes 62A and 62D to cause a potential difference at the contact portion of the user. Measure. In this example, the connection relationship between the electrode, the AC power source, and the voltage measurement circuit corresponds to the fat thickness meter 10 according to the first embodiment, and only two electrodes 62A and 62D are used (two-electrode method). ).
In FIG. 4C, an AC power supply 64 is connected to the electrodes 62A and 62D to supply current, and a voltage measurement circuit 65 is connected to the electrodes 62B and 62D to measure a potential difference at the contact portion of the user. . In this example, the connection relationship between the electrode, the AC power source, and the voltage measurement circuit corresponds to a modification of the first embodiment described later, and only three electrodes 62A, 62B, and 62D are used (3 Electrode method).

In the 4-electrode method shown in FIG. 4A, in principle, the bioimpedance Z _Hum can be measured without being affected by the contact impedance. However, when passing a current, the contact impedance as compared with the Z _Hum is too large, it can not be correctly measured bioelectrical impedance Z _Hum.

On the other hand, in the two-electrode method shown in FIG. 4B, when measuring the bioimpedance Z _Hum , the contact impedances Z ₁ and Z ₄ through which the current i flows are also measured. Then, Z = Z _Hum + Z ₁ + Z ₄ is obtained. Here, the contact impedances Z ₁ and Z ₄ are very large values (Z ₁ , Z ₄ >> Z _Hum ) when the skin of the measurement site of the user is dry. Become very large. In order to reduce the contact impedances Z ₁ and Z ₄ , the skin at the measurement site needs to be wet.

The three-electrode method shown in FIG. 4 (c), like the 2-electrode method, when measuring the bioelectrical impedance Z _Hum, since thereby also measured contact impedance Z ₄ with the current flow i, a measured by the impedance value If Z, then Z = Z _Hum + Z ₄ Here, since the contact impedance Z ₄ is a very large value (Z ₄ >> Z _Hum ) when the skin of the measurement site of the user is dry, the skin becomes wet to reduce the contact impedance. Need to be.

  Next, the flow of measurement of biological information using the fat thickness meter 10 will be described. FIG. 5 is a flowchart showing the flow of processing by the fat thickness meter 10. In the fat thickness meter 10 according to the first embodiment, measurement of biological information (biological information measurement step) is performed after measurement of contact impedance (contact impedance measurement step).

  When measurement of biological information is started by the user operating the input device 21, the calculation control unit 20 displays a display instructing the user to contact the electrodes 12A to 12D with the measurement target region. The display on the device 22 and the operation of the multiplexer 16 make the connection between the electrodes 12A to 12D, the AC power supply 14, and the voltage measurement circuit 15 the second electrode connection (step S1). That is, the electrodes 12A and 12B are connected to the AC power source 14 and the voltage measurement circuit 15, respectively.

Next, the arithmetic control unit 20 applies current to the user's body from the AC power supply 14 via the electrodes 12A and 12B, and causes the voltage measurement circuit 15 to measure the potential difference via the electrodes 12A and 12B. Based on the measured potential difference, the arithmetic control unit 20 calculates and acquires the contact impedance Z _C (step S2, the contact impedance measurement step). Acquired contact impedance Z _C is stored in the storage device 25.

Subsequently, determination circuit 26, obtained in step S2 contact impedance Z _C is the predetermined threshold value (e.g., 1000 [Omega]) or less than, i.e. whether the contact impedance Z _C is within the range of the first predetermined range It discriminate | determines (step S3, discrimination | determination process).

In step S3, when the contact impedance _{Z C} is not within the first predetermined range (No in step S3), and as the error processing, the arithmetic control unit 20, the skin contacting to the user the electrodes 12A, and 12B Is displayed on the display device 22 so as to get wet (step S8). The measurement ends after displaying the instruction to the user in step S8 for a predetermined time.

In step S3, when the contact impedance _{Z C} was in the range of the first predetermined range (Yes in step S3), and the arithmetic control unit 20, by operating the multiplexer 16, interact with the electrode 12A~12D power 14 The connection with the voltage measurement circuit 15 is switched to the first electrode connection (step S4). That is, a pair of current supply electrodes 12B and 12C are connected to the AC power source 14, and another pair of voltage measurement electrodes 12A and 12D are connected to the voltage measurement circuit 15.

Next, the arithmetic control unit 20 applies a current from the AC power supply 14 to the user's body via the electrodes 12B and 12C, and causes the voltage measurement circuit 15 to measure the potential difference via the electrodes 12A and 12D. Based on the measured potential difference, the arithmetic control unit 20 calculates and acquires bioimpedance (step S5, biometric information measurement step). The acquired bioelectrical impedance is stored in the storage device 25.
Subsequently, the arithmetic control unit 20 calculates biological information such as fat thickness from the acquired biological impedance (step S6), and displays the calculated biological information on the display device 22 (step S7). After displaying the biological information in step S7 for a predetermined time, the measurement ends.

With the configuration described above, the following effects are achieved according to the above embodiment.
(1) By measuring the contact impedance, it is possible to determine whether the skin of the measurement site of the user is wet or not.
(2) Depending on the state of the measurement site, the user can be instructed to wet the skin, which can suppress the contact impedance within an appropriate range.
(3) Since the bioimpedance can be measured after the contact impedance is suppressed to an appropriate value, it is possible to acquire an accurate bioimpedance, thereby calculating more accurate biometric information from the bioimpedance. It becomes possible.
(4) Since the contact impedance can be suppressed by wetting the user's skin, there is no need to increase the size of the electrode, and therefore the entire apparatus can be kept compact.

A modification will be described below.
<Modification 1>
In the first embodiment described above, the measurement of the contact impedance using the two electrodes (the two-electrode method of FIG. 4B) has been described. Instead of this, in the first modification, three electrodes are used. Is used to measure the contact impedance (three-electrode method in FIG. 4C). That is, the first embodiment described above is an embodiment that uses the two-electrode method as the second electrode connection, while the first modification is an embodiment that uses the three-electrode method as the second electrode connection. FIG. 6 is a diagram illustrating a connection relationship between electrodes and circuits in the biometric apparatus according to the first modification of the first embodiment. In addition, as an electrode for measuring the contact impedance, it will be described that two electrodes are used in the first embodiment described above, and that three electrodes are used in the first modification, but the present invention is not limited to these, and two electrodes are used. You may make it measure contact impedance using the above electrode.

FIG. 6 schematically shows a biometric device 70 that includes four electrodes 72A, 72B, 72C, and 72D as voltage measuring electrodes or current supply electrodes, an AC power source 74, and a voltage measuring circuit 75.
In the example of FIG. 6A, at the time of contact impedance measurement, as the second electrode connection, the two electrodes 72B and 72D are connected to the AC power source 74, and the two electrodes 72C and 72D are connected to the voltage measurement circuit 75. Three electrodes 72B, 72C, 72D are used.
In the example of FIG. 6B, at the time of contact impedance measurement, as the second electrode connection, the two electrodes 72C and 72D are connected to the AC power source 74, and the two electrodes 72B and 72D are connected to the voltage measurement circuit 75. Three electrodes 72B, 72C, 72D are used.
In the example of FIG. 6C, at the time of contact impedance measurement, as the second electrode connection, the two electrodes 72B and 72D are connected to the AC power source 74, and the two electrodes 72A and 72D are connected to the voltage measurement circuit 75. Three electrodes 72A, 72B, 72D are used.
In the example of FIG. 6D, at the time of contact impedance measurement, as the second electrode connection, the two electrodes 72A and 72D are connected to the AC power source 74, and the two electrodes 72B and 72D are connected to the voltage measurement circuit 75. Three electrodes 72A, 72B, 72D are used.
In the example of FIG. 6E, at the time of contact impedance measurement, as the second electrode connection, the two electrodes 72A and 72D are connected to the AC power source 74, and the two electrodes 72C and 72D are connected to the voltage measurement circuit 75. Three electrodes 72A, 72C, 72D are used.
In addition, the connection of the electrode and circuit at the time of bioimpedance measurement is the same as in the first embodiment.

<Modification 2>
In the first embodiment, the case where the contact impedance is measured only once using two electrodes has been described. Instead of this, in the second modification, the combination of the AC power source, the voltage measurement circuit and the electrode is changed. The contact impedance is measured for all four electrodes used for measuring the bioimpedance. That is, the second modification is an embodiment in which the contact impedance is measured twice in total by each of the second electrode connection (two-electrode type) and the third electrode connection (two-electrode type). Thereby, since it can be confirmed whether the contact impedance of the four electrodes used for the measurement of bioimpedance is an appropriate value, it becomes possible to measure bioimpedance more accurately. FIG. 7 is a flowchart showing the flow of processing by the biometric apparatus according to the second modification of the first embodiment. In the following description, two electrodes are used for one contact impedance measurement (two-electrode method in FIG. 4B).

  In the second modification, when the measurement of biological information is started by the user operating the input device 21, the arithmetic control unit 20 causes the user to contact the electrodes 12A to 12D with the measurement target region. The display device 22 is displayed on the display device 22 and the multiplexer 16 is operated to connect the electrodes 12A to 12D to the AC power supply 14 and the voltage measurement circuit 15 to the second electrode connection (step S11). That is, the electrodes 12A and 12B are connected to the AC power supply 14 and the voltage measurement circuit 15, respectively.

Next, the arithmetic control unit 20 applies current to the user's body from the AC power supply 14 via the electrodes 12A and 12B, and causes the voltage measurement circuit 15 to measure the potential difference via the electrodes 12A and 12B. Based on the measured potential difference, the arithmetic control unit 20 calculates and acquires the contact impedance Z _a (step S12). Acquired contact impedance Z _a is stored in the storage device 25.

Subsequently, determination circuit 26, the contact impedance Z _a acquired in step S12 whether or less than a predetermined threshold value a, namely, whether or not contact impedance Z _a is within the range of the first predetermined range ( Step S13).

In step S13, if the contact impedance _{Z a} was in the range of the first predetermined range (Yes in step S13), and the arithmetic control unit 20, by operating the multiplexer 16, interact with the electrode 12A~12D power 14 The connection with the voltage measurement circuit 15 is switched from the second electrode connection to the third electrode connection (step S14). In the third electrode connection, the electrodes 12C and 12D that are not connected to the AC power supply 14 and the voltage measurement circuit 15 in the second electrode connection are connected to the AC power supply 14 and the voltage measurement circuit 15, respectively.

Next, the arithmetic control unit 20 applies a current from the AC power supply 14 to the user's body via the electrodes 12C and 12D, and causes the voltage measurement circuit 15 to measure a potential difference via the electrodes 12C and 12D. Based on the measured potential difference, the arithmetic control unit 20 calculates and acquires the contact impedance Z _b (step S15). Acquired contact impedance Z _b is stored in the storage device 25.

Subsequently, determination circuit 26, the contact impedance Z _b obtained in step S15 is whether less than a predetermined threshold value b, i.e., whether or not contact impedance Z _b is within the range of the first predetermined range ( Step S16).

If the contact impedance _{Z a} in the step S13 is not within the first predetermined range (No in step S13), and and, if the contact impedance _{Z b} in the step S16 is not within the first predetermined range (step S16 No), as an error process, the calculation control unit 20 instructs the user to display on the display device 22 so as to wet the skin to be brought into contact with the electrode (step S21). The measurement ends after displaying the instruction to the user in step S21 for a predetermined time.

In step S16, if the contact impedance _{Z b} was in the range of the first predetermined range (Yes in step S16), and the arithmetic control unit 20, by operating the multiplexer 16, interact with the electrode 12A~12D power 14 The connection with the voltage measurement circuit 15 is switched from the third electrode connection to the first electrode connection (step S17). That is, a pair of current supply electrodes 12B and 12C are connected to the AC power source 14, and another pair of voltage measurement electrodes 12A and 12D are connected to the voltage measurement circuit 15.

Next, the arithmetic control unit 20 applies a current from the AC power supply 14 to the user's body via the electrodes 12B and 12C, and causes the voltage measurement circuit 15 to measure the potential difference via the electrodes 12A and 12D. Based on the measured potential difference, the arithmetic control unit 20 calculates and obtains bioimpedance (step S18). The acquired bioelectrical impedance is stored in the storage device 25.
Subsequently, the arithmetic control unit 20 calculates biological information including fat thickness from the acquired biological impedance (step S19), and displays the calculated biological information on the display device 22 (step S20). After displaying the biological information in step S20 for a predetermined time, the measurement ends.

<Modification 3>
In the second modification, two electrodes (two-electrode method shown in FIG. 4B) are used for one contact impedance measurement, but three electrodes may be used instead. Good (three-electrode method in FIG. 4C). That is, the third modification is an embodiment in which the contact impedance is measured twice in total by each of the second electrode connection (3-electrode type) and the third electrode connection (3-electrode type).
Since the processing flow of the third modification is the same as that of the second modification, a description thereof will be omitted. Here, in the third electrode connection of the second modification, the electrodes 12C and 12D that were not connected to the AC power supply 14 and the voltage measurement circuit 15 in the second electrode connection were used, whereas the third electrode connection of the third modification was used. In the three-electrode connection, in addition to the electrodes not connected to the AC power supply 14 and the voltage measurement circuit 15 in the second electrode connection, the electrodes connected to the AC power supply 14 and the voltage measurement circuit 15 in the second electrode connection are also included. Contains. With such electrode connection, contact impedance can be measured for all four electrodes used for bioimpedance measurement.

<Modification 4>
In the first embodiment and the first to third modifications described above, the measurement of contact impedance has been described, but in addition to or instead of this, in the fourth modification, the electrode and the skin of the user are used. The contact resistance and / or the contact reactance occurring between In the fourth modification, the determination circuit 26 determines whether or not the measured contact resistance is within the second predetermined range, and / or determines whether or not the measured contact reactance is within the third predetermined range. Determine. When the contact resistance is in the second predetermined range and / or the contact reactance is in the third predetermined range, the biometric information is obtained and biometric information is calculated and displayed as in the first embodiment. On the other hand, when the contact resistance is not within the second predetermined range and / or the contact reactance is not within the third predetermined range, the user is brought into contact with the electrode as error processing as in the first embodiment. It displays on the display device 22 so as to wet the skin.
Here, the second predetermined range and the third predetermined range are determined according to the area / thickness of the electrode, the connection form between the AC power source and the voltage measurement circuit and the electrode, and the like, and particularly suitable for the measurement of bioimpedance, A range or threshold value (for example, 500Ω for contact resistance and 1000Ω for contact reactance) indicating a state in which the skin in contact with the electrode can be said to be wet with water is set.
For example, the electrodes 12A and 12B in the first embodiment are electrodes used for measurement of contact resistance and / or contact reactance, and the electrodes 12A and 12B, the AC power supply 14, the voltage measurement circuit 15, and the multiplexer 16 are contact resistance measurement means and / or Or what is necessary is just to comprise as a contact reactance measurement means.

The method for measuring contact resistance and / or contact reactance is not particularly limited.
For example, (1) when the electrodes 12A and 12B are in contact with the human body, the phase difference between the two is obtained from the current output from the AC power supply 14 and the voltage measured by the voltage measurement circuit 15, and the contact impedance And the contact resistance (R) that is the real part of the contact impedance and the contact reactance (X) that is the imaginary part of the contact impedance may be obtained from the phase difference and the contact impedance.
(2) When the electrodes 12A and 12B come into contact with the human body, a current of i (t) = sinωt is passed through the human body through the electrodes 12A and 12B of the equivalent circuit shown in FIG. The output voltage V _HUM is sampled and AD converted (circuit processing). Thereafter, by performing waveform processing (DFT processing) using the waveform of the input current i (t) shown in FIG. 8B and the waveform of the AD converted output voltage V _HUM , the input current value (i ( The contact resistance (R) and the contact reactance (X) may be obtained based on t)) and the output voltage value (V _HUM ) (software processing). In addition, a phase difference and a contact impedance can be obtained using the obtained contact resistance (R) and contact reactance (X).

<Modification 5>
In the first embodiment, the contact impedance measurement process is performed before the biological information measurement process. Alternatively, the contact impedance measurement process may be performed after the biological information measurement process. In this case, in the determination step using the determination circuit 26, when it is determined that the contact impedance is not within the first predetermined range, the same error processing as in the first embodiment is performed and the user's skin is wetted again. The biological information measurement process is executed.
Further, the biological information measurement process and the contact impedance measurement process may be executed before the determination process by the determination circuit 26.

<Modification 6>
In the first embodiment, the multiplexer 16 as the electrode switching means is used to switch between the first electrode connection and the second electrode connection. However, the electrode switching means in the present invention is not limited to the multiplexer. As an example, a switch as described below may be provided in place of the multiplexer 16. FIG. 9 is a diagram conceptually showing a connection relationship between electrodes and circuits at the time of contact impedance measurement in the biometric apparatus according to Modification 6 of the first embodiment.

In FIG. 9 (a), a living body measuring apparatus 80a schematically including four electrodes 82A, 82B, 82C, and 82D as voltage measuring electrodes or current supply electrodes, an AC power source 84a, a voltage measuring circuit 85a, and a switch 86a. Is shown.
In the example of FIG. 9A, when measuring bioimpedance, the switch 86a is opened and the first electrode is connected. At this time, the two electrodes 82B and 82C are connected to the AC power source 84a, and the two electrodes 82A and 82D are connected to the voltage measurement circuit 85a. On the other hand, when measuring the contact impedance, the switch 86a is closed to establish the second electrode connection. At this time, since the electrodes 82A and 82B are short-circuited by the switch 86a, the electrodes 82A and 82B and the electrode 82C are connected to the AC power supply 84a, and the electrodes 82A and 82B and the electrode 82D are connected to the voltage measurement circuit 85a. The Accordingly, it is possible to realize measurement substantially similar to the three-electrode method while using the four electrodes 82A, 82B, 82C, and 82D.

In FIG. 9B, a living body measurement schematically including four electrodes 82A, 82B, 82C and 82D as voltage measurement electrodes or current supply electrodes, an AC power supply 84b, a voltage measurement circuit 85b, and switches 86b1 and 86b2. Device 80b is shown.
In the example of FIG. 9B, at the time of bioimpedance measurement, the switches 86b1 and 86b2 are opened to be connected to the first electrode. At this time, the two electrodes 82B and 82C are connected to the AC power supply 84b, and the two electrodes 82A and 82D are connected to the voltage measurement circuit 85b. On the other hand, when measuring the contact impedance, the switches 86b1 and 86b2 are closed to be connected to the second electrode. At this time, the electrode 82A and the electrode 82B are short-circuited by the switch 86b1, and the electrode 82C and the electrode 82D are short-circuited by the switch 86b2, so that the electrodes 82A and 82B and the electrodes 82C and 82d are connected to the AC power supply 84b. 82B and the electrodes 82C and 82D are connected to the voltage measurement circuit 85b. Accordingly, it is possible to realize measurement substantially similar to the two-electrode method while using the four electrodes 82A, 82B, 82C, and 82D.

Furthermore, in the example shown in FIG. 9B, when measuring bioimpedance, both the switches 86b1 and 86b2 are opened for the first electrode connection, and when measuring contact impedance, only the switch 86b1 is closed for the second electrode connection. Alternatively, only the switch 86b2 may be closed to establish the third electrode connection.
When only the switch 86b1 is closed (second electrode connection), the electrode 82A and the electrode 82B are short-circuited by the switch 86b1, so the electrodes 82A and 82B and the electrode 82C are connected to the AC power supply 84b, and the electrodes 82A and 82B The electrode 82C is connected to the voltage measurement circuit 85b. When only the switch 86b2 is closed (third electrode connection), the electrode 82C and the electrode 82D are short-circuited by the switch 86b2, so that the electrode 82B and the electrodes 82C and 82D are connected to the AC power supply 84b, and the electrode 82B The electrodes 82C and 82D are connected to the voltage measurement circuit 85b.
As a result, it is possible to substantially realize the measurement combining the three-electrode method using the four electrodes 82A, 82B, 82C, and 82D, and the contact impedance of all the four electrodes used for the measurement of the bioimpedance is reduced. Measurements can be made.

  In the example shown in FIGS. 9A and 9B, the AC power supply and the voltage measurement circuit can be changed to a different configuration.

  In the first embodiment and the above-described modified example, the wetness of the measurement site of the user can be determined by measuring the contact impedance, but instead of or in addition to this, the following determination is made. May be. That is, a plurality of (for example, two) small electrodes that are close to each other are arranged between electrodes for measuring bioimpedance (for example, electrodes 12B and 12C in FIG. 1), and the electrodes for measuring bioimpedance are placed on the user's skin. When the plurality of small electrodes are brought into contact with each other, the wetness of the user's skin is determined based on whether or not the plurality of small electrodes are electrically short-circuited due to the presence of water droplets on the skin surface. Alternatively, the wetness of the electrode surface may be determined based on whether or not the plurality of small electrodes are electrically short-circuited due to the presence of water droplets when the electrodes are directly wetted by spraying or the like. The presence of water droplets on the electrode surface facilitates close contact with the skin and prevents contact impedance from becoming abnormal.

  In the first embodiment and the above-described modified example, the bioimpedance is measured using an electrode group including four electrodes, and the contact impedance is measured using two or three of the electrode groups. If it is possible to measure the contact impedance of the measurement site of the person or the skin in the vicinity thereof, a dedicated electrode different from the electrode used for measuring the bioimpedance, or a combination of the dedicated electrode and the electrode used for measuring the bioimpedance, Contact impedance may be measured.

Second Embodiment
The biometric apparatus according to the second embodiment is an application of the biometric apparatus of the present invention to a body composition meter. The point that the contact impedance is measured using two electrodes is the same as in the first embodiment. FIG. 10 is a diagram illustrating an appearance of a body composition meter 100 (biological measurement device) according to the second embodiment.
Here, the biological information that can be acquired by the body composition meter 100 includes body weight, fat percentage, visceral fat level, body water content, muscle mass, basal metabolic rate, bone mass, lean mass, somatic cell mass, blood pressure, viscera. Includes fat area, BMI, obesity, intracellular fluid volume, extracellular fluid volume, and the like.

As shown in FIG. 10, the body composition meter 100 has four electrodes 120A, 120B, 120C, 120D as current supply electrodes or voltage measurement electrodes, an input device 210, and an instruction means on the upper surface of the main body 110. A display device 220 is provided. The electrodes 120A, 120B, 120C, 120D, the input device 210, and the display device 220 are respectively connected to the electrodes 12A, 12B, 12C, 12D, the input device 21, and the display device 22 in the fat thickness meter 10 of the first embodiment. Correspond. The body composition meter 100 further includes an AC power source corresponding to the AC power source 14, the voltage measurement circuit 15, the multiplexer 16, the arithmetic control unit 20, the clock device 24, the storage device 25, and the determination circuit 26 in the first embodiment. A power supply, a voltage measurement circuit, a multiplexer, an arithmetic control unit, a clock device, a storage device, and a determination circuit (all not shown) are provided.
Here, of the four electrodes 120A, 120B, 120C, and 120D, the electrodes 120A and 120C having a large area have a size of 7 × 11 cm, for example.

About the process in the body composition meter 100, since it is the same as that of 1st Embodiment or its modification, description is abbreviate | omitted.
Since the body composition meter 100 performs measurement with the left foot placed on the electrodes 120A and 120B and the right foot placed on the electrodes 120C and 120D, the state of the user's foot can be determined by measuring the contact impedance. It becomes possible. For example, when the user wears stockings or the like, the contact impedance increases, and therefore it can be determined whether or not the user is placed on the body composition meter 100 with bare feet. In addition, when the sole of the user's foot is keratinized, the contact impedance is increased, so that the presence or absence and degree of keratinization can be determined. When it is determined that the user is wearing stockings or the like or the sole of the foot is keratinized, an error process (step S8 in FIG. 5) is performed to remove the stocking or to remove the sole of the foot. Instruct to get wet. As a result, accurate biometric impedance can be measured, and thereafter, biometric information with a more correct value can be calculated.
Other configurations, operations, and effects are the same as those in the first embodiment.

  Although the present invention has been described with reference to the above embodiment, the present invention is not limited to the above embodiment, and can be improved or changed within the scope of the purpose of the improvement or the idea of the present invention.

  As described above, the biometric apparatus and the biometric information measuring method according to the present invention are useful in that the accurate impedance is calculated by suppressing the contact impedance of the part in contact with the electrode.

10 Fat thickness meter (biological measuring device)
12A, 12B, 12C, 12D electrodes (biological information measuring means)
14 AC power supply (biological information measuring means, contact impedance measuring means)
15 Voltage measurement circuit (biological information measurement means, contact impedance measurement means)
16 Multiplexer (electrode switching means, biological information measuring means, contact impedance measuring means)
20 arithmetic control unit 22 display device (instruction means)
26 Discrimination circuit (discrimination means)
50 Biological Measuring Device 52A, 52B, 52C, 52D Electrode (Biometric Information Measuring Means)
54 AC power supply (biological information measuring means, contact impedance measuring means)
55 Voltage measurement circuit (biological information measurement means, contact impedance measurement means)
62A, 62B, 62C, 62D Electrode (biological information measuring means)
64 AC power supply (biological information measuring means, contact impedance measuring means)
65 Voltage measurement circuit (biological information measurement means, contact impedance measurement means)
70 Biological Measuring Device 72A, 72B, 72C, 72D Electrode (Biometric Information Measuring Means)
74 AC power supply (biological information measuring means, contact impedance measuring means)
75 Voltage measurement circuit (biological information measurement means, contact impedance measurement means)
80a, 80b Biological measuring device 82A, 82B, 82C, 82D Electrode (biological information measuring means)
84a, 84b AC power supply (biological information measuring means, contact impedance measuring means)
85a, 85b Voltage measurement circuit (biological information measurement means, contact impedance measurement means)
86a, 86b1, 86b2 switch 100 body composition meter (biological measuring device)
120A, 120B, 120C, 120D Electrode (biological information measuring means)
220 Display device (instruction means)

Claims (8)

A biological information measuring means comprising an electrode group used for measuring the bioimpedance of the user;
Contact impedance measuring means for measuring a contact impedance generated between the user and the electrode when the user contacts the electrode using two or more electrodes;
A biometric apparatus comprising: a determination unit configured to determine whether or not the contact impedance measured by the contact impedance measurement unit is within a first predetermined range.   2. The living body according to claim 1, further comprising instruction means for instructing the user to wet the skin to be brought into contact with the electrode group when the contact impedance is not within the first predetermined range. measuring device. The biometric device is
A current supply unit for supplying current from the electrode group to the user;
A voltage measurement unit that measures a voltage through the electrode group based on a current supplied by the current supply unit;
A first electrode connection for connecting an electrode used when measuring the bioimpedance by the biometric information measuring unit to the current supply unit or the voltage measuring unit, and an electrode used when measuring the contact impedance by the contact impedance measuring unit. The biometric apparatus according to claim 1, further comprising: an electrode switching unit that switches between a supply unit and a second electrode connection connected to the voltage measurement unit. The electrode switching means is capable of switching to a third electrode connection for connecting an electrode used when measuring the contact impedance by the contact impedance measuring means to the current supply unit or the voltage measuring unit,
There are two or more electrodes connected to the current supply unit and the voltage measurement unit in the third electrode connection, and of the electrode group, the current supply unit or the voltage measurement unit in the second electrode connection An electrode that is not connected,
The determination by the determination means is performed by determining whether the contact impedance measured by the contact impedance measurement means in the second electrode connection is within the first predetermined range, and measuring the contact impedance in the third electrode connection. The biometric apparatus according to claim 3, further comprising: determining whether or not the contact impedance measured by the means is within the first predetermined range. The electrode switching means is capable of switching to a third electrode connection for connecting an electrode used when measuring the contact impedance by the contact impedance measuring means to the current supply unit or the voltage measuring unit,
There are three or more electrodes connected to the current supply unit and the voltage measurement unit in the third electrode connection, and the current supply unit or the voltage measurement unit in the second electrode connection of the electrode group An electrode that is not connected, and an electrode that is connected to the current supply unit and the voltage measurement unit in the second electrode connection,
The determination by the determination means is performed by determining whether the contact impedance measured by the contact impedance measurement means in the second electrode connection is within the first predetermined range, and measuring the contact impedance in the third electrode connection. The biometric apparatus according to claim 3, further comprising: determining whether or not the contact impedance measured by the means is within the first predetermined range. In place of the contact impedance measuring means, contact resistance measuring means for measuring a contact resistance generated between the user and the electrode when the user contacts the electrode using two or more electrodes. And / or contact reactance measuring means for measuring contact reactance generated between the user and the electrode when the user contacts the electrode using two or more of the electrodes,
Instead of determining whether or not the contact impedance measured by the contact impedance measuring unit is within a first predetermined range, the determining unit determines that the contact resistance measured by the resistance measuring unit is within a second predetermined range. The biometric apparatus according to claim 1, wherein it is determined whether or not the contact reactance measured by the reactance measuring means is within a third predetermined range. . A biological information measuring step of measuring the bioimpedance of the user using the electrode group;
A contact impedance measuring step of measuring contact impedance when the user contacts the electrode using two or three electrodes;
And a determining step of determining whether or not the contact impedance measured by the contact impedance measuring means is within a first predetermined range.   The living body according to claim 7, further comprising: an instruction step for instructing the user to wet the skin to be in contact with the electrode group when the contact impedance is not within the first predetermined range. Measuring method.

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