JP2002153437A - Body impedance measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To respectively independently extract and provide a value for which the impedance of a body end tissue peripheral part is included in the contact impedance of an electrode and a body end tissue skin surface together with the value of a conventional intra-body impedance. SOLUTION: A current path having finite electric conductivity is formed by connecting a resistor r1 between at least two electrodes E2 and E3 among a plurality of the electrodes E1-E4 in direct or indirect contact with the body skin surface at the two parts of the body skin surface. A measuring circuit is constituted so as to make both electrodes apply a current at least once in a measuring process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for arranging a plurality of electrodes in direct or indirect contact with a body skin surface at two places on the body skin surface, and to provide an internal body existing between the two body skin surfaces. The present invention relates to a body impedance measuring device for measuring impedance.

[0002]

2. Description of the Related Art Conventionally, as a body fat mass measuring device for measuring a fat mass in a human body, a plurality of electrodes which are in direct contact with a plurality of places on a body skin surface are installed, and an alternating current or a voltage is applied between these electrodes. There is known a method in which the impedance of a body tissue sandwiched between the plurality of electrodes is measured by applying the voltage, and the amount of fat in the body tissue is obtained from the impedance. The method (two-electrode method) and the four-terminal method (four-electrode method) are known.

FIG. 13 (a) shows a principle of measuring body impedance in a conventional body fat measuring apparatus using a two-terminal method. In this two-terminal method, two electrodes E1 and E2 are mounted on two skins of the body such as both hands, respectively, and a known constant current I flows between the electrodes E1 and E2. The voltage V1 generated between E2 is measured by a voltage measuring circuit composed of AMP1, and the impedance R between the two electrodes E1 and E2 is measured by calculating the equation V1 / I = R. .

However, in the case of the two-terminal method, there are impedance components irrelevant to the physical characteristics of the individual to be measured, such as dirt and moisture, on the electrode surface, and the contact impedance between the electrode and the skin is caused by these factors. Is formed, the impedance R that can be actually measured is the sum of the impedance r0 in the body and the contact impedances r1 and r2 between the electrodes E1 and E2 and the skin (R = r0
+ R1 + r2), and these contact impedances r
1, 1 and r2 cannot be measured separately from the body impedance r0, and only the body impedance cannot be measured. By the way, the contact impedance varies from several tens of ohms to several hundreds of ohms depending on the state of the electrode surface as described above, and in some cases can reach several kilohms. This value cannot be ignored. For this reason, the measurement method for obtaining the body fat content from the impedance value in the body obtained by the two-terminal method is hardly used.

On the other hand, FIG. 13 (b) shows the principle of measuring body impedance in a body fat measuring device using a conventional four-terminal method. This four-terminal method is a method of measuring the impedance in the body used to overcome the above-mentioned deficiencies of the two-terminal method. In this four-terminal method, for example, electrodes E that come into contact with two skins at the tip of both hands are used.
11, E12; E21 and E22 are provided, and electrodes E12 and E12 are provided.
22 is used as a power supply electrode, and a constant current I is applied.
11 and E21 as electrodes for voltage measurement, these electrodes E1
A voltage V11 generated between E1 and E21 is measured by a voltage measurement circuit including AMP11. Now, the total value of the contact impedance of the contact portions between the electrodes E11, E12, E21, E22 and the skin and the body terminal tissue impedance around the contact portions is represented by r11, r12, r21, r2.
2, the input impedance of the voltage measurement circuit is selected to be a sufficiently large value compared to the impedances r11 and r21, and when a constant current flows between the power supply electrodes E12 and E22, the impedances r11 and r21 and the electrode E1
A current that affects the measurement accuracy is prevented from flowing to the E1 and E21. Thus, the impedance r
Since the voltage drop at 11, r21 can be ignored, the voltage measurement circuit can measure the voltage V11 generated between the points P and Q in the body of the measurer. Thus, the in-body impedance r0 can be obtained by the equation V11 / I = r0.

[0006] As described above, the measuring device based on the four-terminal method has a power supply electrode for applying a constant current (or a constant voltage) to apply a voltage drop to the tissue in the body, and an error in the measured value at the contact portion between the electrode and the body. And an electrode configured to measure only the voltage generated in the body (generally called a measurement electrode). The function of the electrode is It is classified.

[0007]

However, in the conventional impedance measuring apparatus based on the four-terminal method, the contact impedance of the contact portion between the skin and the electrode of the subject and the body around the contact portion are compared with the impedance in the body. Since it is not configured to obtain the total value with the impedance of the terminal tissue independently, there are the following problems.

As shown in FIG. 14, for example, in a body fat meter of the type in which two fingers of both hands are put in contact with an electrode so as to sandwich the electrode, not only the contact impedance but also a relatively high value is obtained. (Several hundred ohms) In order to avoid mixing of the body tissue impedance value around the contact part (impedance value of the finger part) into the measurement value, the finger on the measurement electrode side is used instead of the measurement terminal, and the current application electrode , Voltage measurement points P and Q are created in the middle of a current path flowing into the body, and the impedance M of the tissue existing between these measurement points P and Q is measured as the impedance inside the body.

However, when such a body fat meter is used, it is common in everyday life that the hands become wet or wet, and if measurement is performed in such a state, the distance between the electrode and the skin may be increased. Although the contact impedance is small, the current flows on the finger surface, so that the voltage measurement points P and Q move toward the fingertip as compared with the case of a normal dry state. Therefore, the tissue distance in the body between the measurement points P and Q becomes longer, and the body impedance M between the increased P and Q is measured.

By the way, the tip of the hand has less muscle mass,
Since the impedance measurement value per unit length is made of a relatively high tissue and its cross-sectional area is small, when the voltage measurement points P and Q move toward the fingertip, the degree of increase in the measured impedance in the body is reduced. This increases the body fat amount calculated from the impedance value in the body. In other words, there is a possibility that even the same measurer may have a disadvantage that the measured value of the impedance in the body differs depending on the wetness of the hand.

[0011] Further, when it is intended to accurately detect mental stress or sway with high sensitivity by knowing the state of sweating on the skin surface by a change in the contact impedance value,
The conventional four-terminal method has a problem that the contact impedance is not measured.
In the terminal method, since the contact impedance is measured as a total value including the impedance in the body in which the impedance value tends to fluctuate, there is a problem that a fluctuation value of only the contact impedance cannot be accurately extracted from the total value.

Further, in the conventional measuring method, when the contact resistance is too large depending on the condition of the skin surface of the measurer or when the contact condition of the measurer is incorrect, the impedance obtained by looking at the signal source from the input of the voltage measurement circuit is measured. When the voltage rises, the voltage measurement circuit receives an induction noise, causing a malfunction or a measurement error. Here, if the impedance of the contact portion between the two current applying electrodes connected to the constant current circuit becomes too large, the output of the operational amplifier of the constant current control circuit is saturated. Defects can be determined by checking the size, but if the contact impedance of the voltage measurement circuit electrode section becomes too large, a correct measurement value cannot be obtained. Therefore, it is difficult to reliably determine whether the contact state is appropriate.

As a solution to such a problem,
There is one disclosed in JP-A-8-154910. The technology disclosed in this publication includes a high-frequency application electrode for applying a high-frequency power to two measurement points on the body,
The present invention relates to an apparatus configured to provide a set including a measurement electrode for measuring a voltage generated in a body. More specifically, a pair of two types of electrodes having different functions are provided at two measurement points on the body, and a pair of high-frequency electrodes is generated in the body by applying a power source such as a constant current between the electrodes. In a device using the conventional four-terminal measurement principle of measuring the voltage to be applied between the measurement electrodes where no current flows and no potential drop occurs at the contact portion, a resistance between the high-frequency application electrode and the measurement electrode is measured. Is connected to prevent erroneous measurement due to induced noise.

However, the technique disclosed in this publication also basically avoids the potential drop due to the contact impedance between the high-frequency application electrode and the body surface and avoids the potential generated in the body impedance by the measurement electrode. Although only the drop is measured and a resistor is connected between the electrodes, the measurement by the same four-terminal method as that of the related art is performed after the connection of the resistor. Therefore, in this prior art, although the effect of preventing erroneous measurement due to induction noise is obtained, it is not possible to simultaneously extract and measure the contact impedance of the high-frequency application electrode portion and the measurement electrode portion. You can't get the various effects it brings.

The present invention has been made in view of the above problems, and the contact impedance between an electrode or a conductive object on the electrode and the skin surface of the body end tissue includes the impedance of the periphery of the body end tissue. The values obtained are independently extracted together with the values of the conventional impedance in the body, and the values obtained include the contact impedance and the impedance around the peripheral tissues of the body so that the values can be accurately evaluated. It is intended for.

More specifically, it is evaluated whether or not the condition of the skin surface around the tissue at the end of the body of the measurer is suitable for accurately measuring body fat. Knowing, detecting mental sweating, accurately detecting stress and mental sway, and ensuring that the measurer is in direct contact with the electrodes or the measurement surface made of conductive objects on the electrodes It is an object of the present invention to ensure that an alarm can be issued when there is no alarm.

[0017]

Means for Solving the Problems and Action / Effect To achieve the above object, a body impedance measuring apparatus according to a first aspect of the present invention comprises a plurality of body impedance measuring devices which directly or indirectly contact the body skin surface at two places on the body skin surface. In the body impedance measuring device for arranging the electrodes, and measuring the impedance in the body existing between the two body skin surfaces, a finite electrical conductivity between at least two of the plurality of electrodes While forming a current path having
The measurement circuit is configured so that each electrode becomes a current application electrode at least once in the measurement process, and for all electrodes, the contact impedance of the contact portion between the electrode or a conductive object on the electrode and the body skin surface And the impedance in the body independently of the total value of the impedance of the body and the tissue around the contact part.

Further, in the first invention, in order to further simplify the device configuration, the body impedance measuring device according to the second invention comprises a plurality of body impedance measuring devices which directly or indirectly contact the body skin surface at two places on the body skin surface. In the body impedance measuring device for arranging the electrodes, and measuring the impedance in the body existing between the two body skin surfaces, a finite electrical conductivity between at least two of the plurality of electrodes While forming a current path having
A measurement circuit is configured to use at least two electrodes as current application electrodes, and for the current application electrodes, a contact impedance of a contact portion between the electrode or a conductive object on the electrode and a body skin surface and the contact portion thereof The present invention is characterized in that the total value of the peripheral body terminal tissue impedance and the in-body impedance are obtained independently.

According to the first and second aspects of the present invention, the value of the contact impedance between the electrode and the skin surface of the body end tissue such as a finger, which includes the impedance of the periphery of the body end tissue,
Since it can be obtained independently together with the value of the body impedance, it is possible to evaluate a value including the contact impedance and the impedance of the peripheral part of the body terminal tissue based on the obtained value. Specifically, it is possible to determine whether or not the condition of the skin surface around the body end tissue of the measurer is suitable for measuring body fat with high accuracy. In addition, in all body contact parts, the total value of the contact impedance of the contact part between the electrode and the body skin surface and the body terminal tissue impedance around the contact part is obtained. The amount of change can be evaluated with high sensitivity. In addition, in the range of minute values, the impedance in the body, which constantly fluctuates every moment, is not added. By doing so, it is possible to know a minute change in only the contact impedance, to detect the degree of mental sweating, and to accurately detect stress and mental sway. Further, when the contact state of the measurer with the electrodes is incorrect, it is possible to reliably warn whether the contact states of all the electrode contact portions are appropriate.

In the first invention and the second invention, the current path having the finite electric conductivity is preferably formed by connecting a resistor between two electrodes (third invention). In another aspect, the current path having a finite electric conductivity may be formed of a conductive material (a fourth invention). In this case, it is preferable that the conductive material is formed including a contact portion with the body skin surface (fifth invention). At this time, the body contact surface and the electrode come into indirect contact with each other via the conductive material.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a specific embodiment of the body impedance measuring device according to the present invention will be described with reference to the drawings.

FIG. 1 shows a body measurement equivalent impedance circuit in a body impedance measurement device according to one embodiment of the present invention. FIG. 2 shows an application example in which the impedance measurement device is applied to a finger-measurement type body fat meter. FIGS. Application examples when applied to a total are shown.

In the present embodiment, four electrodes E1, E2, E3, and E4 are arranged at two places on the skin surface of the measurer at contact portions with the skin surface. Also, between the two electrodes E2-E3,
The resistor r1 is connected so as to form a current path having non-zero finite electrical conductivity. Here, each of the electrodes E1 to E1
The total value of the contact impedance of the contact portion between E4 and the skin surface in contact with the electrode and the body end tissue impedance around the contact portion is X, Y, Z, U, and the impedance in the body is M. .

Each of the electrodes E1 to E4 has a terminal p
1, p2, p3, and p4, and as shown in FIG. 4, can be connected to the output terminal o1 and the input terminal o2 of the constant current circuit 1 via these terminals p1 to p4.
Further, it can be connected to the terminals s1 and s2 of the voltage measuring circuit 2. Here, the constant current circuit 1 includes an operational amplifier AMP1 receiving a voltage signal V0 (known) from a non-inverting input terminal and outputting a constant current I, and an operational amplifier AMP1.
And a reference resistor Rs (known) that controls a circuit so that a constant current I is output from the device, and is configured to flow a constant current of I = V0 / Rs into the body and the attached resistor. The voltage measurement circuit 2 includes an operational amplifier AMP2 that outputs a voltage generated between the terminals s1 and s2, and input resistors R1 and R2 of the operational amplifier AMP2. Note that the input resistors R1 and R2 are selected to have values sufficiently larger than the impedance.

In such a configuration, at the time of measurement, first, as shown in FIG. 4A, the output terminal o1 and the terminal p1 are connected to the input terminal o2 and the terminal p4 of the constant current circuit 1 in a connected state. Is connected with an analog switch. Then, the current I becomes the impedance M in the body forming a body equivalent circuit, the impedance X forming the sum of the tissue impedance of the body end and the contact impedance, respectively.
The shunt flows to Y, Z, U and the attached resistor r1. That is, by connecting the resistor r1, all the electrodes E
A current flows through 1 to E4.

In this state, terminals p2 and p3, terminals p1 and p1,
p4, terminals p1 and p2 and the input terminal s of the voltage measurement circuit 2
The voltages V1, V2, and V3 generated at the respective terminals of the equivalent circuit are measured by sequentially switching the respective connections to S1 and S2. The voltage V2 may be obtained by reading the output voltage of the operational amplifier AMP1 without passing through the operational amplifier AMP2, and subtracting a known value V0 = Rs · I from the value.

Subsequently, as shown in FIG. 4B, the output terminal o1 of the constant current circuit 1 is switched to the terminal p2, and in this state, the terminals p2, p3, the terminals p2, p4, the terminal p1,
The connection between p2 and the input terminals s1 and s2 of the voltage measurement circuit 2 is sequentially switched to measure the voltages V4, V5 and V6 generated at the terminals of the equivalent circuit. As for the voltage V5, the output voltage of the operational amplifier AMP1 is
Reading without passing through MP2, a known value V0 =
It may be obtained by subtracting Rs · I.

In the connection state shown in FIG.
When the connections of the terminals p1 and p4, the terminals p1 and p2, the terminals p2 and p3, and the input terminals s1 and s2 of the voltage measurement circuit 2 are sequentially switched, the following equations are established for each impedance unit. X ・ I + M ・ (Ii) + UIＵV2 X ・ I + Y ・ i = V3 Z ・ i + UI ・ = V2-V1-V3 (1)

The following equation is established between the measured voltage value and i and I. r1 · I = V1 I = V0 / Rs (2)

When V1, V2 and V3 are measured in this way, if r1 having a known resistance value is connected,
From the equation (2), all the coefficients of the equation (1) are known. Prior to the measurement, the resistances r1 were measured at terminals p2 and p3 in a state where the measurer did not touch the electrodes.
A current I during this time, and at the same time V0 is subtracted by the operational amplifier AMP2 or by connecting the terminals p2 and p3 to the input terminals s1 and s2 of the voltage measuring circuit 2 or directly from the output of the operational amplifier AMP1. Thus, the voltage between both ends of r1 may be measured and divided by a known value I to obtain the voltage.

Next, in the connection state shown in FIG. 4B, the terminals p2 and p3, the terminals p2 and p4, the terminals p2 and p
1 and the input terminals s1 and s2 of the voltage measuring circuit 2 are sequentially switched, and the following equation is established for each impedance section. Y · (I−j) = V6 Z · j + UI = V5−V4 (3)

The following equation holds between the measured voltage value and the current j. r1 · j = V4 (4)

Similarly, when V4, V5, and V6 are measured in the same manner, all the coefficients of the equation (3) are known from the equations (4).

Therefore, the simultaneous equations represented by the following equations can be solved, and the values of the impedances X, Y, Z, U, and M can be obtained. In other words, all the impedances can be obtained by substituting the measured V1 to V6 voltage values.

As described above, according to the present embodiment, the total value of the contact impedance and the body end tissue impedance can be obtained as X, Y, Z, and U. For example, in FIG. The impedances X + Y and Z + U around the two fingers can be obtained as the impedance around the body measurement end.

By the way, if the hand is wet, the impedance X + Y, Z + U around the body measurement end becomes smaller than a certain value, so that the value of the impedance M in the body fluctuates by moving the points P and Q in FIG. Assuming that the boundary value when the variation becomes small enough to affect the measured body fat value is E, if the following formula X + Y <E or U + Z <E is satisfied, or if it is determined by the total value, the following formula X + Y + Z + U When <E 2 is satisfied, it is preferable that a warning is given to the measurer by display, voice, or the like as measurement inappropriate.

The following method is used to perform the above-described determination of the suitability of the measurement state for each individual. That is, a storage switch is provided in the impedance measuring device or the body fat meter using the impedance measuring device, and the impedance X, Y, Z, around the body measurement end is measured for each individual when the skin is in a normal dry state.
U or an added value thereof or an average value of N times of the added value can be registered as a standard value of the impedance value around the body measurement end in a correct measurement state. Then, with respect to the standard value registered for each individual, a value set to k% is provided as a boundary value at which correct measurement cannot be performed, and this is used as a boundary value E for individual determination, whereby strict measurement for each individual is performed. Perform state appropriateness determination. The registration of the standard value may be manually performed by the measurer, or the moving average of N times of X, Y, Z, U or the sum thereof may be automatically calculated for each individual. May be calculated and stored in the memory.

According to this embodiment, X, Y, Z,
Since U does not include the value of the impedance in the body that changes every moment, in the case of a finger-measuring type body fat meter, the amount of change in the total value of the tissue impedance around the body end including the contact portion impedance is determined by the fingertip and the electrode. And the amount of mental sweating can be obtained from the amount of change in the total value. Moreover,
If the amount of change in impedance at each contact is small, the sensitivity is low at one measured value, but by obtaining the amount of change at all contacts, a good measurement of sensitivity can be made by adding these values. Is possible.

In the conventional method for detecting the inadequacy of the contact state of the measurer with the electrode, if a contact failure occurs in the constant current application electrode, the output of the operational amplifier for constant current control is used. Although an alarm can be accurately issued by detecting saturation, there is a drawback that accurate detection cannot be performed when a contact failure occurs at an electrode of an input terminal of a voltage measurement circuit.

On the other hand, according to the impedance measuring apparatus of the present embodiment, as is clear from the circuit shown in FIG. 4A, in the connection state shown in FIG. When a contact failure occurs in any one of the electrodes E1 to E4, a current equal to or more than a predetermined value does not flow through the resistor r1. Therefore, when the current i at the time of measuring the voltage between the terminals p2 and p3 is smaller than the fixed value _imin, it can be determined that the measurement is defective. This can be determined by determining whether the value of the voltage V1 is smaller than a predetermined value because the resistance r1 is known.

Even if the contact between the electrode and the skin surface to be measured completely disappears, the input terminals of the voltage measuring circuit are coupled by the resistor r1 having a resistance value sufficiently smaller than the impedance of the inductive noise signal source. Therefore, the voltage measurement circuit does not produce unstable output. Therefore, regardless of the contact state of the measurer to the electrodes, if the determination of the suitability of the measurement is performed based on the result of the measurement at both ends of the resistance, the correct determination or measurement is always performed without being affected by noise. be able to.

Next, a specific circuit example based on the measurement principle of this embodiment will be described with reference to FIG.

As shown, in this circuit, an analog switch AS1 for switching between a terminal p1 and a terminal p2 is provided.
And an analog switch AS2 for switching between the terminals p1 and p2, and an analog switch AS3 for switching between the terminals p1, p2, p3 and p4. On the output side of the operational amplifier AMP2 of the voltage measuring circuit 2, a rectifier circuit 3 for rectifying an output voltage of the operational amplifier AMP2, a filter 4 for smoothing a voltage signal output from the rectifier circuit 3, and An A / D converter 5 for digitizing an analog signal output from the A / D converter 4;
I / O circuit 6 for reading output data from D converter 5
And a CPU 7 for executing various calculations based on data from the I / O circuit 6 and a memory 8 for storing the calculation results of the CPU 7 and various programs and the like. Display 9 for data display
And an operation switch 10 for data input.

With this configuration, first, in the first step of the measurement, as shown in FIG. 4A, the analog switch AS1 is switched and selected, and the output terminals o1 and o2 of the power supply circuit are connected to the terminal p1. , P4 to supply a current (or voltage) I from a power supply circuit (constant current circuit) 1. Then, as described in the aforementioned measurement principle, the terminal p2 and the terminal p3 (both ends of the resistor r1), the terminal p
1 and p4, and voltages V1 and V2 between terminals p1 and p2, respectively.
2 and V3 are generated, and these values are sequentially converted into analog switches AS2 and A3 connected to the input terminal of the voltage measurement circuit 2.
The contacts of S3 are p2-p3, p1-p4, p1-
Measurement is performed while switching to p2, and the measurement result is temporarily stored in the memory 8. In addition, regarding the voltage V2, AM
The output Va of P1 may be measured and calculated as V2 = Va−Rs · I.

Next, in the second step, FIG.
As shown in (b), the analog switch AS1 is switched and selected, and the output terminals o1 and o2 of the power supply circuit are connected to the terminal p.
Power supply circuit (constant current circuit) 1
More current (or voltage) I is given. Then, the terminal p
Since the voltages V4, V5, and V6 are generated between the terminals p2 and p3 (both ends of the resistor r1), between the terminals p2 and p4, and between the terminals p2 and p1, these values are sequentially connected to the input terminal of the voltage measurement circuit 2. The measurement is performed while switching the contacts of the analog switches AS2 and AS3 to p2-p3, p2-p4, and p2-p1, respectively, and the measurement result is temporarily stored in the memory 8. In addition, regarding the voltage V5, the output Va of the AMP1 is used.
And V5 = Va−Rs · I.

Subsequently, in a third step, the memory 8
The values of V1 to V6 stored in are stored in the above (1) to (4).
By substituting into the equations, the desired impedance values X, Y, Z, U, and M can be obtained.

Here, the total impedance A = X at the end of the body at the time of normal measurement for each individual of the measurer.
+ Y + Z + U, the average value Aave thereof is obtained, and a constant k (<1) is set to set the abnormal boundary value to k.
・ Aave. Then, the determination is made possible after the number of measurements exceeds N, and the following equation A is used as the determination logic.
When <k · Aave is satisfied, an alarm is issued assuming that the impedance of the measured skin surface is abnormally low, and a measurer is alerted to the state of the measured skin surface.

Further, when measuring the degree of stress due to mental sweating, the subject is placed in the above-mentioned A in a normal state.
After obtaining = A1, the subject is given a mental stress prepared in advance, and A = A2 is measured again. In this case, A
Since the value of 1-A2 represents the amount of change in contact impedance due to mental stress, the rank boundary value A
r1 and Ar2 (Ar1 <Ar2) are set, and A
If 1-A2 <Ar1, the influence is evaluated to be small, and if A1-A2> Ar2, the effect is evaluated to be large, and a message is sent to the measurer.

It should be noted that it is possible to accurately determine whether or not the contact state of the measurer with the electrode is appropriate based on the magnitude of the current i flowing through the resistor r1, and that the measurer can perform an abnormal alarm using the resistor r1 and the method thereof. Is as described above.

Next, another embodiment of the present invention will be described with reference to FIGS.

In the embodiment shown in FIG. 6, a current I flows between the terminals p1 and p4 in the first measurement step shown in FIG. 6A, and the current I flows between the terminals p2 and p3 in the second measurement step shown in FIG. And a voltage generated between the respective terminals is measured in the same manner as shown in FIG. 5, so that the impedances X, Y, Z,
U and M are obtained. Here, in FIG.
All of the two electrodes are used as current electrodes, and in FIG. 6B, two electrodes (E2, E3) are used as current electrodes. In FIG. 6, instead of the current I, in the second measurement step, a current J that satisfies I ≠ J flows as shown in FIG. 6A, and the impedances X and Y are set in a state where all electrodes are current electrodes. , Z, U, M can also be determined.

In the embodiment shown in FIG.
E3 is connected by a resistor r1, and electrodes E1, E4
Are connected by a resistor r2. In this embodiment, in the first measurement step shown in FIG.
The current I flows between the terminals p1 and p4, and the current I flows between the terminals p2 and p3 in the second measurement step shown in FIG. In this example, every measurement step uses all electrodes as current electrodes.

In the embodiment shown in FIG. 8, the electrodes E1,
E2 is connected by a resistor r1, and the electrodes E3, E4
Are connected by a resistor r2. In this embodiment, in the first measurement step shown in FIG.
The current I is caused to flow between the terminals p1 and p3, and the current I is caused to flow between the terminals p2 and p4 in the second measurement step shown in FIG. Also in this example, all the electrodes are used as current electrodes in each measurement step.

In the embodiment shown in FIG.
E3 is connected by a resistor r1, and electrodes E3, E4
Are connected by a resistor r2. In this embodiment, in the first measurement step shown in FIG.
The current I is caused to flow between the terminals p1 and p4, and the current I is caused to flow between the terminals p2 and p4 in the second measurement step shown in FIG. In this example, in the first measurement step (a), all electrodes are used as current electrodes, and in the second measurement step (b), three electrodes are used as current electrodes.

In the embodiment shown in FIG.
3 and E4 are connected by a resistor r1. In this embodiment, the current I is caused to flow between the terminals p1 and p4 in the first measurement step shown in (a), and the current I is made to flow between the terminals p2 and p3 in the second measurement step shown in (b). I do. In this example, three electrodes are used as current electrodes in each measurement step.

In the embodiment shown in FIG. 11, only the two electrodes E2 and E3 are used as current electrodes, and
A resistor r1 is connected so that a current i flows between E2 and E3. In this embodiment, when a current I flows between the electrodes E2 and E3, the electrodes E2 and E3
And the voltage generated between the electrodes E3 and E4 is V1,
Assuming that V2 and V3, if these voltage values are measured, the current i can be obtained by the following equation: i = V2 / r1, so if a constant current I is given, Ii becomes known.

Therefore, the impedance in the body can be obtained by the following equation M = (V2-V1-V3) / (Ii), and the following equations Y = V1 / (Ii) and Z = V3 / ( According to I-i), the amount of change in the contact impedance of at least two electrode portions serving as current electrodes can be obtained.

In each of the above embodiments, the following effects are obtained because the measuring method of connecting a resistor between the electrodes is adopted regardless of the number of current electrodes. That is, the connection resistance value at one location is a stable and known value, and when the measurer is not touching the electrodes, a constant current I flows between the electrodes E2 and E3 in FIG. The generated voltage Vc is measured. At this time, the value of the voltage Vc is always expressed as Vc = r1 / I and should always show a constant value. Therefore, if this value changes, the measurement surface may be moist or dirty. If the measurement has changed with respect to conductivity so as to cause an error in the measured value, or if the measurement surface is properly maintained, it is easy to indicate that the measurement circuit has malfunctioned or has either a problem. It turns out. Therefore, this reference value Vc
If a boundary value is provided for the measurement and the failure determination measurement is performed before the measurement, it is possible to diagnose the use state of the measuring device and perform a function diagnosis.

As described above, according to each of the above-described embodiments, by forming a current path between the electrodes, a large number of electrode portions for passing a current from the electrodes to the body are formed, and the potential drop of the electrode portions is measured. Since it is configured to determine the contact impedance and the body end tissue impedance with respect to the electrode unit, it becomes possible to measure mental sweating,
Further, there is an advantage that it is possible to determine that the use state of the measuring device is correct and to determine that the measurement state of the measurer is correct.

In each of the above embodiments, the case where a resistor is connected between the electrodes to form a current path between the electrodes has been described. However, as shown in FIG. 12A, the current path is formed. The space between the electrodes Ea and Eb may be made of a conductive material 20 having appropriate electric conductivity. In FIG. 12A, reference numerals 21 and 22 indicate wiring of a measurement circuit.

As shown in FIG. 12 (b), the measurement surface that comes into contact with the body is made of a single conductive material 23, and the electrode is provided on the back side of the measurement surface made of the conductive material 23. A modification is also possible in which electric signal extraction terminals (measurement terminals) 24 and 25 are arranged and wirings 21 and 22 of the measurement circuit are connected to these terminals 24 and 25, respectively. In this case, the measurer makes indirect contact with the measurement terminals (electrodes) 24 and 25 via the conductive material 23, but the measurer places the foot or finger 26 in a fixed place near the electric signal extraction terminals 24 and 25 as much as possible. So that the measurement contact surface
It is preferable to provide a picture or the like for designating a measurement location on the surface of the conductive material 23 on the measurement surface. The slight electrical resistance caused by the conductive material between the measurement terminals (electrodes) 24 and 25 and the body skin surface is processed by being included in the contact resistance.

[Brief description of the drawings]

FIG. 1 is a body measurement equivalent impedance circuit diagram in an impedance measuring device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an application example in which the impedance measurement device according to the present embodiment is applied to a finger measurement type body fat meter.

FIGS. 3A and 3B are diagrams showing an application example in which the impedance measuring device of the present embodiment is applied to a foot-measuring body fat meter.

FIGS. 4A and 4B are measurement principle diagrams of the impedance measuring device of the present embodiment.

FIG. 5 is a diagram showing a specific circuit example based on the measurement principle of the present embodiment.

FIGS. 6A and 6B are measurement principle diagrams of an impedance measuring device according to another embodiment.

FIGS. 7A and 7B are measurement principle diagrams of an impedance measuring device according to still another embodiment.

FIGS. 8A and 8B are measurement principle diagrams of an impedance measuring device according to still another embodiment.

FIGS. 9A and 9B are measurement principle diagrams of an impedance measuring device according to still another embodiment.

FIGS. 10A and 10B are measurement principle diagrams of an impedance measuring device according to still another embodiment.

FIG. 11 is a measurement principle diagram of an impedance measuring device according to still another embodiment.

FIGS. 12A and 12B are diagrams showing a measurement surface shape of an impedance measuring device according to a modification of the present embodiment.

FIG. 13A is a diagram showing a measurement principle of an impedance measuring apparatus using a conventional two-terminal method, and FIG.
It is a measurement principle figure of the impedance measuring device using the conventional four terminal method.

FIG. 14 is a diagram for explaining a problem of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Constant current circuit 2 Voltage measurement circuit 3 Rectifier circuit 4 Filter 5 A / D converter 6 I / O circuit 7 CPU 8 Memory 9 Display 10 Operation switch 20, 23 Conductive material 24, 25 Electrical signal extraction terminal AMP1, APM2 Operational amplifier AS1 to AS3 Analog switch E1 to E4 Electrode M, X, Y, Z, U Impedance o1, o2 terminal p1 to p4 terminal s1, s2 terminal r1 Resistance

Claims (5)

[Claims] A body impedance for measuring a body impedance existing between two body skin surfaces by arranging a plurality of electrodes in direct or indirect contact with the body skin surface at two places on the body skin surface. In the measurement device, a current path having finite electrical conductivity is formed between at least two of the plurality of electrodes, and at least one of the electrodes becomes a current application electrode in a measurement process. A measurement circuit is configured, and for all electrodes, the total value of the contact impedance of the contact portion between the electrode or a conductive object on the electrode and the body skin surface and the body end tissue impedance around the contact portion, A body impedance measuring device characterized in that impedance is obtained independently. 2. A body impedance for measuring a body impedance existing between two body skin surfaces by arranging a plurality of electrodes in direct or indirect contact with the body skin surface at two places on the body skin surface. In the measurement device, a current path having a finite electrical conductivity is formed between at least two of the plurality of electrodes, and a measurement circuit is configured to use at least two electrodes as current application electrodes. The total value of the contact impedance of a direct contact portion or an indirect contact portion between the electrode or a conductive object on the electrode and the body skin surface and the body terminal tissue impedance around the contact portion, A body impedance measurement device characterized by independently determining an internal impedance. 3. The body impedance measuring device according to claim 1, wherein the current path having a finite electric conductivity is formed by connecting a resistor between two electrodes. 4. The body impedance measuring device according to claim 1, wherein the current path having a finite electric conductivity is formed of a conductive material. 5. The body impedance measuring device according to claim 4, wherein the conductive material is formed including a contact portion with the body skin surface.