JP2003052658A - Internal fat measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a correct impedance in a body by judging whether a contact state of a person to be measured with electrodes is accurate nor not or whether the person's skin is suitable for its measurement or not. SOLUTION: An internal fat measuring apparatus obtains a body fatty content and a body fatty rate from the impedance in the body by bringing the electrodes into contact with two body ends and measuring the impedance in the body existing between the two body ends. The apparatus comprises a judging means for judging whether a measuring state is suitable or not by judging an amplitude of a contact impedance existing between skin surfaces of the body ends brought into contact with the electrodes and the electrodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal fat measuring device for measuring the amount of internal fat in the body.

[0002]

2. Description of the Related Art Conventionally, in order to determine the amount of fat in a body tissue of a body, a pair of current applying electrodes and a pair of voltage measuring electrodes are installed on two body surfaces sandwiching the body tissue to be measured. An alternating current or voltage having a frequency of several tens of KHz to 100 KHz is applied between them, and the impedance of the internal tissue is measured by the voltage generated between the voltage measuring electrodes at that time, and the obtained impedance value and age, sex, and height It is carried out by calculating personal fat data such as, and deriving the amount of fat in the body based on statistical grounds.

The internal tissues are composed of muscles, bones, fats, etc., but in the tissues composed of muscles and fats having a relatively low impedance, the impedance value differs depending on whether the fat component is large or the muscle component is large. The impedance value increases as the number of components increases. The large amount of fat in the body tissues is considered to be one of the judgment indexes for health management, and is also of great interest to the general public.

[0004] Therefore, recently, household devices for measuring the amount of fat in the body have been developed and marketed, but if it is for home use, the manufacturer aims to be able to make it at a low cost and the buyer The side wants to get it cheaply.

By the way, there are the following two types of simple measuring methods used in the low-cost internal impedance measuring apparatus for obtaining the internal fat amount.

One is a method called a two-terminal method or a two-electrode method, and the measurement principle is shown in FIG. In this measuring device, a pair of electrodes A1 and A2, which come into contact with the left and right feet, are provided on the measurement surface of the measuring instrument, and an alternating current or voltage is applied between the electrodes A1 and A2 to exist between the electrodes A1 and A2. It is a device that seeks the impedance to operate. That is, a circuit for supplying a constant current I is provided so that a current flows between the electrodes A1 and A2. Here, Rs is an operational amplifier AMP
Reference numeral 1 is the value of the reference resistance for controlling the circuit including the internal impedance at a constant current.

The voltage V generated between the electrodes A1 and A2 while the current I is flowing is measured by the operational amplifier AMP2.
Now, measure the body impedance you want to measure, Zi, electrode A1,
If the contact impedance values between A2 and the skin surface of the sole of the foot are RX1 and RY1, respectively, the inter-electrode impedance can be calculated by the following equation. (RX1 + Zi + RY1) · I = V ………… (50) ∴Zi + RX1 + RY1 = V / I ………… (51) where the contact impedance values RX1 and RY1 are Zi.
If it is sufficiently smaller than, then Zi + RX1 + RY1≈
The internal impedance can be obtained as Zi.

However, the condition of human skin is not constant from time to time and may be moist or dry. It also depends on your constitution. Therefore, the values of the contact impedances RX1 and RY1 are 100 even for people with normal skin.
Originally 40
It is said that this two-terminal method is not sufficient for obtaining the in-body impedance Zi having a value of about 0 to 1000 ohms with high accuracy.

As an alternative method to the above-mentioned two-terminal method,
There is a method called a 4-terminal method or a 4-electrode method. Figure 7
The measurement principle is shown in (a). This FIG. 7 (a)
In, the measuring device is for the foot, and the impedance in the body existing between the both feet is to be measured. Also, RX
2 and RY2 represent the contact impedance values between the electrodes B1 and B2 and the skin surface of the sole of the foot, respectively.

As shown in FIG. 7A, in measuring the internal impedance Zi, electrodes A1 and A2 for supplying current and electrodes B1 and B2 for measuring generated voltage are used.
The electrodes A1 and B1 are installed for one foot, and the electrodes A2 and B2 are installed for the other foot. Further, the current I is supplied between the electrodes A1 and A2, and the generated voltage is measured between the electrodes B1 and B2.

Input resistors R1 and R2 of the operational amplifier APM2
Assuming that the contact impedance has a resistance value sufficiently larger than RX2 and RY2, almost no current I flows into the operational amplifier APM2, and even if the contact impedances RX2 and RY2 change, the operational amplifier AMP2.
Does not affect the amplification rate of. Therefore, the operational amplifier A
MP2 is the impedance Zi in the body obtained by removing the voltage generated between the virtual points P and Q in the foot tissue, that is, the contact impedance component and the tissue impedance component at the end of the body.
It means that the voltage V generated at both ends of is measured, and between the voltage V obtained from the measurement and the known constant current value I, the following expression (5
By calculating 2), the in-body impedance Zi can be obtained without being affected by the individual difference or the value of the contact impedance that changes each time the measurement is performed. Zi = V / I (52) For the above reasons, most of the present body fat meters are dominated by the latter four-terminal method.

[0012]

Recently, the body fat meter for measuring the impedance of body tissues existing between both hands or both legs by using the four-terminal method and statistically estimating the amount of body fat from the measured values. Is commercially available. For example, when measuring the impedance between both feet, it is designed to contact the skin on the back of the foot with the electrodes for both feet provided on the weight measuring table of the health meter, but keratinization of the skin on the sole of the foot , The back surface of the foot or the electrode surface is dirty or insufficiently contacted, resulting in a high contact impedance between the skin surface and the electrode,
Induced noise may be induced in the voltage measurement circuit, and the measured value may include this induced noise value.

The influence of the inductive noise voltage on the measurement signal is determined by the ratio of the impedance value to the inductive noise signal source at the input point of the voltage measuring device and the contact impedance value and the magnitude of each original signal. Depending on the magnitude, the induced noise signal may take a magnitude close to the voltage generated in the internal impedance of the body, that is, the measured voltage signal.

Further, even if the value of the contact impedance is not so large as to make the influence of the induced noise a problem, if the load on the constant current loop is larger than the controllable value of the constant current control circuit, the constant current characteristic is maintained. Since this is not possible, a measurement error will occur in the measurement method that assumes that a predetermined constant current flows in the body impedance to be measured.

As a countermeasure against such a problem, in order to check the contact state of the measuring person with the electrode, in Japanese Patent Laid-Open No. 8-154910, as shown in FIG. Method, current applying electrode A
1 and A2 and the voltage measuring electrodes B1 and B2, resistors Ra and Rb having values that do not affect the measurement accuracy, respectively.
When the contact impedance is high, a large clamp voltage is applied from the constant current circuit to the voltage measurement circuit input so that it can be clearly distinguished from the measurement target voltage generated in the body impedance. It has been proposed to avoid.

However, the above-mentioned publication (JP-A-8-15)
The technique described in Japanese Patent No. 4910) has the following problems.

When a normal person touches the electrodes, the contact impedances RX1, RX2, RY1, RY2 are 1
Although the value is about 00 ohms, it may be several 100 ohms for a person whose skin condition is a little dry. Here, the constant current value I = 0.5 mA, the contact impedance 100 ohms, and the body impedance Zi = 1 K ohms.
In FIG. 7B, the current i ₁ on the P point side is expressed by the following equation. i ₁ = (RX1 / (RX1 + RX2 + Ra)) · I ... (53) Further, the voltage e generated across RX2 by i _{1
Since 1} is e ₁ = i ₁ · RX 2 = (RX 1 · RX 2 / (RX 1 + RX 2 + Ra)) · I ············ (54), the value of E ₁ is e ₁ = 2 .27 mV It becomes (55). However, when the contact impedance increases to 200 ohms, e ₁ = 8.3 mV (56), which is about 5 mV.

The side of the point Q _{e 2} is also _added, results in a change of about 10mV of e 1 + _{e 2} affects the measurement, since the voltage is 500mV generated into the body impedance, 1/50 = In-body impedance measurements by 2% are affected by an increase in contact resistance.

Therefore, as long as the measurement is carried out by applying the four-terminal method, if a resistor is connected between the current electrode and the voltage electrode, the contact impedance will be small depending on the connected resistance value, and the change depending on the measuring condition of the measurer. The small amount is imposed on the measurement conditions, which narrows the cases where accurate measurement can be performed. On the other hand, if the value of the resistance to be connected is increased, the effect of fluctuations in contact impedance is reduced, but the damping effect on the induced noise voltage is reduced,
It is more susceptible to the induced noise voltage.

Further, the contact impedance is not so large as to be affected by the induced noise voltage, but if the value becomes larger than the range in which the constant current circuit can control the constant current (for example, about 1 K ohm), the impedance in the body is changed beforehand. Since the current of the magnitude that should flow does not flow, an error occurs in the measured value. However, the technique described in the above publication does not take measures to cope with this situation.

On the other hand, in the technique disclosed in Japanese Patent Laid-Open No. 8-154911, the measured voltage value becomes unstable due to the inductive noise when the contact impedance is greatly changed. Since the internal impedance fluctuates in an unstable manner, it is designed to impose a stability determination calculation that defines a measured value as correct if the measured value continuously enters a predetermined range a plurality of times or more.

However, even if it can be confirmed that the measurement data is stable, the contact state is not appropriate, or the condition of the skin of the measurer is particularly dry, so that the contact impedance value is several K ohms. If so, the constant current circuit output voltage saturates and the circuit current value decreases below a predetermined value, and an accurate measurement value cannot be obtained, but the measurement data itself is stable in this state.

Even if the circuit current I becomes smaller than the specified value, the voltage value generated in the body impedance may obtain a measured voltage value in the same range as in the correct measurement state, so it is simply judged whether the measured value is large or small and a fixed range. It is not possible to completely check that the measured values are correct by using only the stability discriminant logic that is the continuity of the measured values in.

The present invention has been made in view of the above problems, and in measuring the impedance in the body, the state of contact with the electrode of the measurer and the skin of the measurer are more suitable than the conventional methods. You can determine whether or not
It is an object of the present invention to provide an internal fat measurement device capable of measuring the correct internal impedance.

[0025]

Means for Solving the Problems and Actions / Effects In order to achieve the above object, the body fat measuring device according to the first aspect of the present invention uses an impedance in the body existing between two end portions of the body, In the body fat measuring device for measuring the body fat mass and the body fat percentage from the measured in-body impedance, the electrode is brought into contact with the body end part of the body fat part, and the skin surface of the body end part in contact with the electrode and the electrode It is characterized in that it is provided with a judging means for judging the suitability of the measurement state by judging the magnitude of the contact impedance existing between them.

When the contact state of the measurer with the electrode is insufficient, the electrode contact surface is dirty, or the condition of the skin of the measurer is not suitable for the measurement, a constant current is applied during the measurement. Since the value of the contact impedance included in the path and the value of the contact impedance connected in series with the input impedance of the measurement voltage are large and fluctuate in an unstable manner, some measure is required to obtain a correct measurement value. In the measurement method based on the 4-terminal method which is widely used at present, the voltage generated between two points of the body must be measured by a voltage measuring device having a high input impedance in principle of measurement. Therefore, in order to obtain the reliability of the measured value itself, as described in JP-A-8-154910, hardware measures are taken to prevent the influence of inductive noise, and JP-A-8-154911. Software measures are taken as described in the publication. However, these methods include the above-mentioned problems. In the present invention, since it is configured to determine the suitability of the measurement state by determining the magnitude of the contact impedance existing between the electrode and the skin surface of the body end portion that contacts the electrode, the measurer It is possible to accurately determine whether or not the contact state of the electrode with the electrode and whether or not the skin of the measurer is suitable for measurement, and the impedance in the body can be accurately measured based on this determination.

In the present invention, the determination of the magnitude of the contact impedance may be performed in a measuring process different from the measuring process of the in-body impedance (second invention), or in the measuring process of the in-body impedance. You may go in (3rd invention).

Next, the internal fat measuring device according to the fourth aspect of the present invention measures the internal impedance existing between the two body end portions by contacting electrodes with the two body end portions, and measuring this. The internal fat measuring device for obtaining the amount of body fat and the percentage of body fat from the measured internal impedance is characterized by including a common electrode in contact with the two body end portions.

When measuring the in-body impedance existing between two skins, in the conventional method, the electrically insulated electrodes must be in contact with the two skins to be measured, and the skins to be measured are to be measured. Although it was measured as a measurement end, in the present invention, a common electrode is provided on the skin surface of both of the measurement ends, and from this common electrode in each skin, it is between the common electrode and each skin surface. It is designed to set up a current route that flows through the contact impedance. In this way, a constant current is switched and applied to two routes in the installed current route, and the in-body impedance is obtained from the generated voltage obtained by the current flowing in each route, and at the same time, the contact is made in the process of obtaining the in-body impedance. It is designed to evaluate the appropriateness of the condition. By doing so, the effect according to the first aspect of the invention can be more reliably obtained.

In the present invention, it is preferable that the same in-body impedance is measured by a plurality of measurement processes, and the measurement results of each measurement process are mutually used (fifth invention). In this case, the suitability of the measurement state may be determined by comparing the in-body impedances obtained in the plurality of ways with each other (sixth invention). By doing so, the measurement of the impedance in the body can be performed by comparing the values of the impedance in the body obtained in two ways by using the measurement values at different measurement timings and confirming the closeness of the relationship between these values. The appropriateness of the contact state of the measurer can also be confirmed by the value itself.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION Next, specific embodiments of the body fat measuring device according to the present invention will be described with reference to the drawings.

The present embodiment shows an apparatus capable of determining the measurement principle and the appropriateness of the contact state in the present invention.
In addition, in the following description, what was applied to the body fat meter of the system which calculates | requires the amount of body fat by measuring the internal impedance which exists between both legs is demonstrated.

FIG. 1 shows electrodes for both feet in a body fat meter according to one embodiment of the present invention. In the body fat meter 1 of this embodiment, the electrode E for the left foot is provided on the surface of the measuring table 2.
1, E2 are provided and electrodes E3, E for the right foot
4 is provided, and an electrode E5 common to both feet is provided. When the measurement is performed using such a body fat meter 1, the measurement is performed in two steps of mode 1 and mode 2.

FIG. 2 shows a measurement mode in the mode 1. In this mode 1, the constant current I is applied to the electrode E.
Flowed between the 5 and the electrode E4, the voltages V ₁ generated between the electrodes E5 and the electrode E2, measuring the voltage V ₂ generated between the electrodes E5 and the electrode E3, respectively.

Then, in the mode 2 shown in FIG. 3, the current path is switched, the constant current I is caused to flow between the electrodes E5 and E2, and the voltage V ₄ generated between the electrodes E5 and E1 is
The voltage V ₃ generated between the electrode E5 and the electrode E4 is measured.

In the mode 1, the following equation is established in the circuit. X · (I-i ₁ ) / M · (I-i ₁ ) = X / M = V ₁ / (V ₂ −V ₁ ) ≡a. ……………… (1) i ₁ = ((M + X) / (M + X + Y)) ・ I ………… (2) ∴V ₂ = Y ・ i ₁ = Y ・ ((M + X) / (M + X + Y) )) ・ I ………… (3)

In the mode 2, the circuit has the following equation. Let Y · (I−i ₂ ) / M · (I−i ₂ ) = Y / M = V ₃ / (V ₄ −V ₃ ) ≡b. ……………… (4) i ₂ = ((M + Y) / (M + X + Y)) ・ I ……………… (5) ∴V ₄ = X ・ i ₂ = X ・ ((M + Y) / (M + X + Y) )) ・ I ………… (6)

Substituting equations (1) and (4) into equation (3), V ₂ = b · M · ((M + aM) / (M + aM + bM)) · I = M · (b · (1 + a) / ( 1 + a + b)) · I ∴M = ((1 + a + b) / b · (1 + a)) · (V ₂ / I) ≡M1 (7) When equations (1) and (4) are substituted into equation (6), , V ₄ = a · M · ((M + bM) / (M + aM + bM)) · I = M · (a · (1 + b) / (1 + a + b)) · I ∴M = ((1 + a + b) / a · (1 + b)) · (V ₄ / I) ≡M 2 (8)

Since the values of a and b are obtained from the measured voltage value, M can be derived in two ways as described above.
M1 = M2 = M is established when the measurer completely contacts the electrode and maintains a proper contact impedance state. However, when the measurer is not sufficiently in contact with the electrodes, (1) the values of X, Y, r ₁ , r ₂ , r ₃ and r ₄ are in the order of infinity to several tens of K ohms. However, the measurement voltages V ₁ , V ₂ , V ₃ , and V ₄ cannot be accurately measured due to induced noise. (2) The contact impedances X and Y in mode 1 and the contact impedances X and Y in mode 2 are different. (3) The constant current I cannot be controlled when X, Y, r ₁ , r ₂ , r ₃ and r ₄ are larger than the order of 1 K ohm, so the value of the constant current I saturates, and moreover, in the mode 1 and the mode 2. Therefore, the value of the constant current I is likely to be different.

In the conventional method, in order to determine whether or not the measured in-body impedance is a correct value, the measured in-body impedance value is within a predetermined range, or is within a predetermined range for a plurality of consecutive times. However, there is a problem that the saturation of the current cannot be judged only by the size of the impedance value in the body and the continuous stability. On the other hand, the present invention is characterized by adopting a method of directly flowing a current through the contact impedance to determine whether or not the value is sufficiently small not to saturate the constant current circuit. In addition, when the target in-body impedance is obtained, a method of determining whether or not the voltage measurement value used to calculate the in-body impedance was appropriate is determined by comparing the in-body impedance values obtained in two ways. Is characterized by.

Next, the following three methods will be sequentially described as the determination means for determining the contact state. (1) A contact state measuring process for evaluating a contact state is provided before executing the measuring process for obtaining the in-body impedance, and the in-body impedance measuring process is performed after determining that the contact state is good. Method. (2) A method of determining the contact state in the process of measuring the internal impedance, and calculating the internal impedance if the contact state is good. (3) A method of judging by the calculated value of the impedance in the body itself.

First, the method (1) will be described. In this method, the measurement includes a contact state measurement process and a body impedance measurement process. When the measurement start instruction is given by the measurer, the measuring device first executes the contact state measuring process. In the circuit of FIG. 2, the contact impedances r ₁ and r ₃ are evaluated in this process because no current is passed in the process of measuring the in-body impedance.

In the contact state measuring process, a constant current circuit is connected between the electrodes E5 and E1 as mode 1, and the electrodes E5 and E1 are connected.
The voltage V ₀₁ between ₁ is measured. Then, in mode 2, a constant current circuit is connected between the electrodes E5 and E3, and the electrode E
The voltage V ₀₂ between 5 and E3 is measured. Both are shown by dotted lines in FIG. Since these voltages V ₀₁ and V ₀₂ are measured by the output of the constant current circuit on the measuring instrument side, the impedance of the signal source is always low and is not affected by induced noise.

The impedance existing between the electrodes E5 and E1 is r ₁ + X // (X + M + Y) <r ₁ + X≡Rs1 (9) Further, the impedance existing between the electrodes E5 and E3 is r ₃ + Y // (X + M + Y) <r ₃ + Y≡Rs2 ……………… (10). However, // means a parallel resistance value.

In the current path set as described above, it is not necessary to consider the magnitude of impedance in the body, so that only the magnitude of contact impedance can be evaluated and judged. For example, assuming that the contact impedance value is 250 ohms and the minimum possible value is 100 ohms, Rs1 and Rs2 <500 ohms are used in the determination formula. Even if one of the two contact impedances takes 100 ohms, the other one is within 400 ohms, and it can be determined that its magnitude is almost appropriate for measurement.

As a practical method, if the contact state is good, it is assumed that Rs1 = Rs2 = 500 ohms at the maximum, and if the constant current value I = 0.5 mA is set, V _{0 1} , V ₀₂ The value of V ₀₁ = Rs1 · I <500 · I = 250mV ………… (11) V ₀₂ = Rs2 · I <500 · I = 250mV ………… (12) If so, r ₁ , r ₃ , X, and Y are sizes suitable for measurement.

Next, to measure the _{V 5} by flowing a current between the electrodes E5, E4 in FIG. 2, the determination by the equation (9), (10) and (11), (12) similar to equation concept Method is used to confirm the suitability of Y and r ₄ , and then the electrodes E5, E
A current is passed between the two to measure V ₆ to confirm the suitability of X and r ₂ , and when all the impedances involved in the measurement are within the proper range, the process of measuring the in-body impedance is started.

As a method applicable to the conventional 4-terminal method, a mode for applying a constant current I between the electrodes A1 and B2 and between the electrodes A2 and B2 in FIG. The voltages V ₀₁ ′ and V ₀₂ ′ generated between the electrodes are measured. Then, the determination condition of the following equation is set. V ₀₁ '= (RX1 + RX2) · I <500 · I = 250mV …… (13) V ₀₂ ′ = (RY1 + RY2) · I <500 · I = 250mV …… (14) By adding this condition, the conventional 4 Even in the terminal measurement method, it is possible to confirm the appropriateness of the contact state related to the voltage measurement electrode and the current electrode, and to prevent abnormal measurement that is affected by inductive noise and that the output of the constant current circuit is saturated. You can

In both cases, when measuring the in-body impedance, there is a procedure for determining in advance whether the magnitude of the contact impedance is suitable for the measurement by applying a current to the contact impedance. r ₁ , r
If the appropriateness of the contact impedance of ₃ , X, Y and r ₂ , r ₄ can be determined, V ₁ , V ₂ , V ₃ , in the body impedance measurement process using the measurement principle described first.
It can be considered that V ₄ can be measured correctly under a constant current I that is properly controlled.

In this way, the suitability of r ₂ and r ₃ has been determined in mode 1 of the process of measuring the impedance in the body, so by measuring V ₁ and V ₂ , a = X /
The value of M = V ₁ / (V ₂ −V ₁ ) can be obtained.
In addition, since the suitability of r ₁ and r ₄ has been determined in mode 2 of the process of measuring the in-body impedance, V ₃ ,
By measuring V ₄ , b = Y / M = V ₃ / (V
Value of ₄ -V ₃₎ can be obtained. And a, b
When is obtained, the in-body impedances M1 and M2 can be obtained using the equations (7) and (8). This M1, M2
The process after obtaining is described later.

Next, as the method (2) above, a special connection is made.
Measurement process to confirm the touch condition (current switching process)
In the process of measuring the internal impedance,
Impeder in the body while judging that the contact state is correct
The method of measuring the resistance will be described. This method is
Contact impedance r in the method of (1)₁, R _Three
The electrometric determination of the size of is omitted.

Here, it is assumed that the measuring instrument 2A adopts an electrode disposing method other than the example shown in FIG. For example, as shown in FIG. 4, electrodes E1 and E3 are connected to electrode E5 and electrode E5.
2 and E4, respectively, the electrodes E5 and E5
The electrode between the electrodes E2 and E4 is automatically checked by confirming the adequacy of the contact state between the electrodes E2 and E4 without checking the relationship between the shape of the bottom surface of the foot and the position of the electrode by an electrical measurement method. The contact state with E1 and E3 can also be regarded as appropriate.

In this method, the voltage V ₅ between the electrodes E5 and E4 is measured in the mode 1 of the internal impedance measurement process. The impedance between the electrodes E5 and E4 is expressed by the following equation. Y // (M + X) + r ₄ <Y + r ₄ (15) The constant current value is set to I = 0.5 mA, and the contact impedance at the two points is 500 ohms or less. If something is taken as a boundary and V ₅ = (Y + r ₄ ) · I <250 mV (16) is satisfied, then the values of Y and r ₄ are considered to be appropriate for measurement.

Here, considering the positional relationship between the electrode arrangement of the measuring table 2A and the bottom surface of the foot, if the contact state relating to the electrodes E4 and E5 is normal, the contact state of the electrode E3 is necessarily normal. As a result, r ₃ is determined to be appropriate. At this point, the suitability of X and r ₂ has not been confirmed, but V
_{If 5} satisfies the above inequality (16), the values of V ₁ and V ₂ that make the appropriateness of X and r ₂ an essential condition are measured for the time being.

Then, by V ₁ and V ₂ , a = X / M =
Determine the value of _{V 1 / (V 2 -V 1} ). Assuming that the minimum possible value of M is 500 ohms and the maximum value of contact impedance that is determined to be appropriate is 250 ohms, 0 <a <0.5 ............ (17) holds in the proper contact state. There must be. If X is large or r ₂
If inductive noise occurs due to too large, the probability that this inequality relationship holds is small.

If the condition is not satisfied, the mode 1 is executed again. Further, if the conditions are satisfied, V ₁ , V ₂
The measured value of A, that is, the value of a is assumed to be reliable, the value of a is stored in the memory, and the mode 2 is executed after a short time (for example, several tens of milliseconds to 100 msec) from the start of the mode 1. Since the time interval is short, it can be considered that the contact state between the skin and the electrode hardly changes between the adjacent modes 1 and 2.

Mode 2 of impedance measurement process in the body
Then, the voltage V ₆ between the electrodes E5 and E2 is measured. The impedance between the electrodes E5 and E2 is X // (M + X) + r ₂ <X + r ₂ (18), so V ₆ = (X + r ₂ ) · I <250 mV. If (19) is satisfied, it is determined that X and r ₂ are appropriate for measurement.

If the inequality (19) is satisfied, X, r ₂
Is appropriate, and considering the positional relationship between the electrode arrangement of the measuring table and the back surface of the foot, if the contact state related to the electrodes E2 and E5 is normal, then the contact state of the electrode E1 is inevitably normal, and r ₁ Is determined to be appropriate. If X and r ₂ are not proper, return to the start point of mode 1. Since the suitability of Y and r ₄ and r ₃ has been confirmed in mode 1, it can be confirmed at this point that all contact states involved in the measurement are proper.

Here, V ₃ and V ₄ are measured, and b = Y / M = V ₃ / (V ₄ −V ₃ ) is measured by these V ₃ and V ₄ .
At the timing when is obtained, the judgment condition of 0 <b <0.5 (20) is imposed. However, if this condition is not satisfied, the mode 1 is returned to the starting point. If satisfied, b
The value of is judged to be highly reliable. In addition, since the suitability of X and r ₂ was confirmed by the judgment result of mode 2,
Assuming that the value of is also substantially reliable at this point, the values of a and b are used to express M in equations (7) and (8).
The procedure for calculating the in-body impedance for obtaining 1, M2 is entered.

As described above, the contact state measuring process is not specially provided, and the mode 1 and the mode 2 in the body impedance measuring process are switched at a short time interval so that an appropriate condition is maintained between the adjacent modes 1 and 2. Only when all of the above are satisfied, the measured voltage value is regarded as reliable, and the body impedance calculation process is started.

Next, a method of evaluating the appropriateness of the in-body impedance obtained by using a and b, which is applied to both the methods (1) and (2), will be described.

Strictly speaking, although the contact state sufficient for measurement in the measurement process up to now can be confirmed, the reliability of the measurement value itself used for calculating the impedance in the body has not been confirmed yet. M in the equations (7) and (8) is introduced on the condition that the values of X and Y are constant between the mode 1 and the mode 2 executed by switching the measurement current at a time interval. Therefore, X and Y are constant when the measurement of both modes is performed, and the measurement voltage V related to the electrodes E1, E2, E3, E4, and E5 is
The measured values of ₁ , V ₂ , V ₃ , and V ₄ do not include induced noise,
Stableness is a necessary condition for obtaining correct measured values. Therefore, in addition to the expression (20), if M1 = M2 = M (21) holds, X and Y are constant, and V ₂ and V ₃ are correctly measured. Take a look. Actually, if the allowable boundary value R is set in consideration of measurement error and some data fluctuations, and if the relationship of | M1-M2 | <R ………… (22) holds between M1 and M2, In the process of measuring the internal impedance, each measurement voltage measured to calculate the internal impedance was obtained correctly without being affected by the inductive noise signal, and the values of the contact impedances X and Y were almost constant during the measurement. It was judged to be correct.

As described above, the conventional four-terminal method is used in which the electrodes common to both feet are provided and the judgment of the contact state and the judgment of the reliability of the body impedance itself are combined by the method (1) or (2). Even if the contact state measuring process of the present invention is applied to, it can be determined that the measurement conditions of the in-body impedance are satisfied, but the reliability of the in-body impedance measurement value itself cannot be confirmed. However, since the reliability of the measurement value itself can be determined, there is an effect that more reliable measurement can be performed.

In the method (3), the contact state measurement process is not performed, and the relationship between the two is (2) at the time when M1 and M2 are obtained even during the body impedance measurement process.
If the expression (2) is satisfied, M is determined assuming that all the contact states are proper and that the measurement is performed with almost no changes in X and Y during the measurement. This is based on the fact that if the contact state between all electrodes and the skin is not proper, the probability that the formula (22) is satisfied is extremely small. This will be proved below.

In mode 1, the values of X and Y are X respectively.
If it is 1, Y1, then in Mode 1
The following equation holds.     X1 · (I-i₁') / M ・ (I-i₁') = X1 / M = V₁'/ (V_Two'-V ₁ ')                                       Put ≡a1. ………… (1) '     i₁'= ((M + X1) / (M + X1 + Y1)) ・ I ……………… (2)'     ∴V_Two'= Y1 · i₁'= Y1 ・ ((M + X1) / (M + X1 + Y1)) ・ I                                                 ……………… (3) '

In mode 2, the values of X and Y are X respectively.
2 and Y2, the circuit in mode 2
The following equation holds.     Y2 · (I-i_Two') / M ・ (I-i_Two') = Y2 / M = V_Three'/ (V_Four'-V _Three ')                                       Put ≡b2. ………… (4) '     i_Two'= ((M + Y2) / (M + X2 + Y2)) ・ I ……………… (5)'     ∴V_Four'= X2 · i_Two'= X2 ・ ((M + Y2) / (M + X2 + Y2)) ・ I                                                 ……………… (6) '

In mode 1, from the equation (1) ', X1 =
a1 · M. Moreover, if was Y1 = b1 · M, the M = ((1 + a1 + b1) / b1 · (1 + a1)) · (V 2 '/ I) ≡M1' .................. (7) ' mode 2 , (4) ′, Y2 = b2 · M. If X2 = a2 · M, then M = ((1 + a2 + b2) / b2 · (1 + a2)) · (V ₄ '/ I) ≡M2' ……………… (8) ' You can ask. However, a1 ≠ a
2, b1 ≠ b2.

However, in mode 1, the value of Y1 and in mode 2
Therefore, it is not possible to measure the relational value of X2 with M. Therefore, the measured value of mode 1 is stored, and mode 2 is stored.
When the value of M is calculated instead of Y1 when the relation value Y2 = b2 · M of Y2 in M is obtained, M = ((1 + a1 + b2) / b2 · (1 + a1)) · (V ₂ '/ I ) ≡M1 "……………… (9) 'Similarly, after measuring in mode 2 and substituting X1 for X2 and calculating the value of M, M = ((1 + a1 + b2) / a1 · (1 + b2 )) ・ (V ₄ '/ I) ≡M2 "……………… (10)'

However, a1 ≠ a2, b1 ≠ b2, a1>
Under the conditions of 0, a2> 0, b1> 0, b2> 0, M
1 "≠ M1 '= M and M2" ≠ M2' = M. To prove this, a1 ≠ a2, b1 ≠ b2, a1> 0, a
Under the conditions of 2> 0, b1> 0, b2> 0, the formula (7) ′ =
Expression (9) 'does not hold, and expression (8)' = (1
It is possible to show that the expression 0) 'does not hold.

However, the necessary and sufficient condition for the expression (9) '= (10)' to be satisfied under the condition of expression (7) '= expression (8)' is expression (11) '. , B1 and b2 are a1
≠ a2, b1 ≠ b2, a1> 0, a2> 0, b1> 0,
Even if the relationship of b2> 0 is satisfied, it is considered that the expression (11) ′ is satisfied, so the following expression is obtained. a1 ・ a2 ・ (b2-b1) + b1 ・ b2 (a2-a1) + a2 ・ b2-a1 ・ b1 = 0 ............ (11) 'When the formula is satisfied, M1 "= M2" is To establish.

If the contact state is stable and the contact impedance has a low value between mode 1 and mode 2 and is almost unchanged, there is no influence of the induction noise signal and a1≈a2, b1.
≈b2, and M1′≈M1 ”and M2′≈M2”
Is satisfied, | M1 ″ −M2 ″ | <R is satisfied.

On the contrary, even if M1 '≠ M1 "and M2' ≠ M2", there is a condition that satisfies | M1 "-M2" | <R, but a1, a2, b1 and b2 are expressed by the equation (11) '. And the probability of taking a value that satisfies the above inequality is small, and in most cases, it can be determined that the values of X and Y are stable and the value of M has been accurately obtained by the establishment of the above inequality. .

In this embodiment, when the equation (21) is satisfied but M1 and M2 are not equal to each other, for example, M = (M1 + M2) / 2 (23) and the value of M is calculated. It is good to decide.

Further, in the present embodiment, r ₁ , r ₂ , r ₃ , r ₄ , X and Y are dealt with as contact impedances between the electrodes and the measurement skin surface of the body end of the measurer. Actually, the virtual shunt points P and Q in the body tissue in FIG.
Since it represents the impedance up to, the impedance of the body tissue around the contact portion with the electrode is also included. In the case of a measuring instrument that uses the sole of the foot, the body tissue impedance up to the point where P and Q are present in the tissue of the foot is small, but in the case of a measuring instrument that contacts with the fingers, the impedance of the finger joint is high. Therefore, in the case of the finger measuring device, the voltage generated in the contact impedance portion becomes high, and thus the voltage for determining the adequacy of the contact state is set higher than the value in this embodiment.

[0075]

EXAMPLES Next, specific examples of the body fat measuring device according to the present invention will be described.

FIG. 5 shows a circuit configuration diagram of the body fat measuring device according to this embodiment. In the present embodiment, the A side represents the measurer and the B side represents the measuring instrument with the dashed-dotted line as the boundary. The measurer has an impedance M in the body, and electrodes E1, E2, E3, E4, E5 are installed on the measuring table of the measuring instrument, and the contact between each of these electrodes and the skin surface of the measurer in contact with those electrodes. Impedance is r1, r
2, r3, r4, X, Y.

In the measuring instrument of this embodiment, the reference voltage V
A constant current control amplifier AMP1 that receives s and outputs a constant current I, and a reference resistor Rs that controls the circuit so that a constant current is output from the amplifier AMP1 are provided.
The amplifier AMP1 is configured to control the output voltage within the controllable maximum output voltage range so that Vs = Rs · I is always satisfied regardless of the load of the amplifier AMP1.

When the load impedance of the amplifier AMP1 on the side of the measurer is Z, the total load of the amplifier AMP1 is Z + R.
Therefore, when the current I is being output, the amplifier AM
(Z + Rs) · I is required as the output voltage of P1. However, the constant current I can be maintained even if the contact impedance becomes large because the saturated output voltage of the amplifier AMP1 =
The value of Z is up to the value of (Z + Rs) · I, and the value of I decreases as Z increases.

In the figure, AMP2 is a voltage measuring amplifier, and this amplifier AMP2 is provided with input resistors of impedances R1 and R2 which are sufficiently higher than the impedance of the signal source to be measured. Since an alternating current is applied to the measuring current, the measuring signal is also an alternating current. The measured voltage output of the amplifier AMP2 is rectified by the rectifier circuit RE, smoothed by the smoothing circuit F, and converted into a DC signal. The signal output from the smoothing circuit is digitized by the A / D converter and read by the CPU through the I / O circuit. This CPU has a ROM,
A memory MEM such as RAM and an I / O circuit are provided, and CP
Bus-coupled with U.

Measurement data and memory M input to the CPU
A calculation for obtaining the internal impedance is performed with the EM data. Further, a program for giving a calculation procedure to the CPU is also written in the memory MEM. KEY
Represents a key switch for setting personal data such as the age of the measurer to the measuring instrument and giving a command to start measuring to the measuring instrument. The DIS is a display for displaying a value converted into a value such as a body fat percentage based on the in-body impedance calculated by the CPU. AS1 and AS2 are analog switches, and C
A switching control signal for circuit connection is output from the I / O circuit according to the operation procedure corresponding to the measurement process and the measurement mode given by the program of the PU, and the operational amplifier AMP
1. Switch the signal line between AMP2 and the measurement load. Terminals p1, p2, p3, p4 are electrodes E1, E2, E
3 and E4, respectively, and are also connected to analog switches AS1 and AS2 as shown in the figure.

The operation in the case of the contact state measuring process in the above method (1) will be described. When the measurer gives a determination start command from the KEY to the CPU, both the analog switches AS1 and AS2 are selectively connected to the terminal p1, and the load of the constant current circuit becomes r ₁ , X, M, Y, and the voltage V ₀₁ is at a constant time interval. Measured at. The constant current circuit has a constant current value I =
It is assumed that it is set to 0.5 mA. V ₀₁ = X // (Y + M) + r ₁ <(X + r ₁ ) · I <
The measurement is performed any number of times until 250 mV is satisfied, but if the above formula is not satisfied for a certain period of time or more or a certain number of times of measurement, an alarm is output indicating that the measurement is impossible. CPU
If the above inequality is satisfied in the calculation in
Connects the analog switches AS1 and AS2 to the terminal p3 and measures the voltage V ₀₂ at regular time intervals. V ₀₂ = Y // (X + M) + r ₃ <(X + r ₃ ) · I <
The measurement is performed any number of times until 250 mV is satisfied, but if the above formula is not satisfied for a certain period of time or more or a certain number of measurement times or more, an alarm is output and measurement is output. Also, C
If the above inequality is satisfied in the calculation in PU, r
Assuming that the contact state of ₁ , r ₃ , X, and Y is good, the CPU connects the analog switches AS1 and AS2 to the terminal p4 and measures the voltage V ₅ . V ₅ = Y // (X + M) + r ₄ <(X + r ₄ ) · I <2
The measurement is performed any number of times at a constant time interval until 50 mV is satisfied, but if the above formula is not satisfied for a certain time or more or a certain number of measurement times or more, an alarm is output as the measurement is impossible. If the inequality is satisfied in the calculation in the CPU, the contact state of r ₁ , r ₃ , r ₄ , X, and Y is good, and the CPU connects the analog switches AS1 and AS2 to the terminal p2 to set the voltage V ₆ to the voltage V ₆ . taking measurement. V ₆ = X // (Y + M) + r ₂ <(X + r ₂ ) · I <2
The measurement is performed any number of times at a constant time interval until 50 mV is satisfied, but if the above formula is not satisfied for a certain time or more or a certain number of measurement times or more, an alarm is output as the measurement is impossible. Further, if the above inequality is satisfied in the calculation in the CPU, the contact state of r ₁ , r ₂ , r ₃ , r ₄ , X, and Y is considered to be good, and the process of measuring the in-body impedance is entered.

After measuring the voltage V ₆ , the analog switch AS2 is connected to the terminal p1 to measure the voltage V ₄ , and then the analog switch AS2 is connected to the terminal p4 to measure the voltage V ₃ . When the voltages V ₃ and V ₄ are measured, the value of b is determined, so the following inequality is evaluated. 0 <b = Y / M = V ₃ / (V ₄ −V ₃ ) <0.5

If this inequality is not satisfied, the procedure returns to the measurement start point. If satisfied, the voltages V ₄ and b
The value of is stored in the memory MEM, and the analog switch AS
1 is connected to the terminal p4. The voltage _{V 2} is measured by connecting the analog switch AS2 to the terminal p3, followed by measuring the voltages _{V 1} connects the analog switch AS2 to the terminal p2.

When the voltages V ₁ and V ₂ are measured, the value of a can be obtained. Therefore, the following inequality is evaluated. _{0 <a = X / M =} V 1 / (V 2 -V 1) <0.5 If this inequality is returned to the start of measurement to be satisfied.

If this inequality is satisfied, b,
Using the values of V ₄ , a, V ₂ , and I, M1 and M2 are obtained from the equations (7) and (8). Then, it is determined whether or not | M1-M2 | <R holds between M1 and M2. If not, the process returns to the measurement start time.

When returning in the calculation process for judging b or a, or returning when the inequality regarding M1 and M2 is not satisfied, if it is returned a certain number of times or more than a certain time repeatedly, an alarm is output as unmeasurable. .

If the above inequality is satisfied, M = (M1 + M2) / 2 is calculated, the value of M is taken as the in-body impedance value, and this value and personal data such as weight and age are used to calculate the body fat mass,
Estimate and calculate values related to body fat such as body fat percentage and display D
Output to IS.

[Brief description of drawings]

FIG. 1 is a diagram showing electrodes for both feet in a body fat meter according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a measurement mode in measurement mode 1.

FIG. 3 is an explanatory diagram of a measurement mode in measurement mode 2.

FIG. 4 is a diagram showing electrodes for both feet in a body fat meter according to another embodiment of the present invention.

FIG. 5 is a circuit configuration diagram of an internal fat measurement device according to an embodiment.

FIG. 6 is a circuit diagram showing a measurement principle by a conventional two-terminal method.

7A and 7B are circuit diagrams showing a measurement principle by a conventional two-terminal method.

[Explanation of symbols]

1 body fat meter 2,2A measuring stand E1~E5 electrodes _{X, Y, r 1, r} 2, r 3, r 4 contact impedance M bodily impedance

Claims (6)

[Claims] 1. An in-body impedance existing between two body end portions is measured by bringing an electrode into contact with the two body end portions. From the measured in-body impedance, the body fat mass and the body mass are measured. An in-vivo fat measuring device for determining a fat percentage is provided with a judging means for judging the adequacy of the measuring state by judging the magnitude of the contact impedance existing between the electrode and the skin surface of the body end portion in contact with the electrode. A body fat measuring device characterized by: 2. The body fat measurement device according to claim 1, wherein the determination of the magnitude of the contact impedance is performed by a measurement process different from the process of measuring the in-body impedance. 3. The body fat measuring device according to claim 1, wherein the measurement and determination of the magnitude of the contact impedance is performed in the process of measuring the in-body impedance. 4. An in-body impedance existing between two body end portions is measured by bringing an electrode into contact with the two body end portions, and the measured body impedance is used to measure body fat mass and body mass. An in-body fat measuring device for determining a fat percentage, comprising a common electrode in contact with the two body end portions, the in-body fat measuring device. 5. The body fat measuring device according to claim 4, wherein the same in-body impedance is measured by a plurality of measurement processes, and the measurement results of the respective measurement processes are mutually used. 6. The body fat measuring device according to claim 5, wherein the suitability of the measurement state is determined by mutually comparing the in-body impedances obtained in the plurality of ways.