JP2001212099A - Equipment for measuring electric nature - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide equipment for measuring electric nature to calculate bioelectric impedance and to estimate distributions of body fat and body fluid while controlling influences caused by outside noise in a low-frequency region. SOLUTION: The equipment for measuring electric nature 100 makes measuring signals Ia at the same intervals of frequencies in a low-frequency region and at intervals of frequencies that is proportional to the square of the measuring frequencies in a high-frequency region. The equipment is equipped with a generator 72 of measuring signals that input measuring signals Ia to an examinee through superficial electrodes Hc, Lc, an analog-to-digital converter 93 that measures an electric current of measuring signals Ia that are input to an examinee, an analog-to-digital converter 83 that measures voltage generated between surfaces of the examinee's body, and a central processing unit 3 that estimates bioelectric impedance between surfaces of the examinee's body and a physical value depending on the impedance from the measured electric current and voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrical characteristic measuring apparatus useful for estimating a body fat state and a body water distribution of a subject based on a bioelectrical impedance method.

[0002]

2. Description of the Related Art The inventor of the present invention has previously applied for an apparatus using an M-sequence signal as a bioelectrical impedance measuring apparatus (Japanese Patent Laid-Open No. 10-14898). In the invention, by performing a Fourier transform on the four-terminal A / D-converted signal, bioelectric impedance at many frequencies is measured to calculate information on the water content inside and outside the cell. Although not described in the specification, this apparatus outputs an M-sequence signal many times and performs synchronous addition of each signal in order to improve the SN ratio of the signal.

[0003] The prior art will be described below. 2. Description of the Related Art In recent years, research on the electrical characteristics of living organisms has been conducted for the purpose of evaluating the body composition of humans and animals. The electrical properties of living organisms vary significantly depending on the type of tissue or organ, for example,
In the case of humans, the electrical resistivity of blood is around 150 Ω · cm, whereas the electrical resistivity of bone and fat is 1 to 5 kΩ · cm.
cm. The electrical characteristics of the living body are called bioelectric impedance, and are measured by passing a small current between a plurality of electrodes attached to the body surface of the living body. The method of estimating the body water distribution, body fat percentage, and body fat mass of the subject from the bioelectric impedance obtained in this way is called bioelectric impedance method ("Bioelectric impedance method as a method for evaluating body composition", Baumgartner , RN, etc.
Author, "Bioelectric impedance and its clinical application", Medical electronics and biotechnology, Hiroshi Kanai, 20 (3) Jun 1982, "Estimation of body limb water distribution by impedance method and its application", Medical electronics and biotechnology. See, Makoto Haeno et al., 23 (6) 1985, "Long-term measurement of urinary bladder volume by impedance method", Ergonomics, Yasuo Kuchinomachi, 28 (3) 1992, etc.).

[0004] Bioelectric impedance is derived from the resistance of a living body to the current carried by ions in the body (resistance) and the reactance associated with various types of polarization processes created by cell membranes, tissue interfaces, or non-ionized tissue. Be composed. Capacitance, which is the reciprocal of reactance, causes a time delay in current rather than voltage, and creates a phase shift (phase shift). This value is the arctangent of the ratio of reactance to resistance (arctangent). It can be determined geometrically as a phase angle.

The bioelectric impedance Z, the resistance R, the reactance X and the electric phase angle φ depend on the frequency. At very low frequencies f _L , the bioelectrical impedance Z at the cell membrane-tissue interface is too high to conduct electricity. Thus, electricity flows only through the extracellular fluid and the measured bioelectrical impedance Z is purely a resistance R.

Next, as the frequency increases, the current penetrates the cell membrane, the reactance X increases, and the phase angle φ increases. The magnitude of the bioelectrical impedance Z is equal to the value of the vector defined by Z ² = R ² + X ² . The frequency at which both the reactance X and the phase angle φ are maximized is called a critical frequency f _C , which is one electrical characteristic value of a living body that is a conductive conductor. Beyond this critical frequency f _C , the cell membrane-tissue interface loses its capacitive capacity, and the reactance X decreases accordingly. At very high frequencies f _H , the bioelectrical impedance Z is again purely equivalent to the resistance R.

FIG. 4 is an electrical equivalent circuit diagram (equivalent circuit model) of the human body. In this figure, Cm represents the cell membrane capacity, and Ri and Re represent the intracellular fluid resistance and the extracellular fluid resistance, respectively. At low frequencies f _L , the current is mainly flowing in the extracellular space, and the impedance Z is equal to the extracellular fluid resistance Re. At high frequencies f _H , the current passes completely through the cell membrane, and the cell membrane capacitance Cm is substantially equivalent to being short-circuited. Accordingly, the impedance at high frequency f _H Z
Is equal to the combined resistance Ri · Re / (Ri + Re).

According to the method described above, the intracellular fluid resistance R
i and the extracellular fluid resistance Re can be determined, and based on these, the body fat status and body water distribution (intracellular fluid volume, extracellular fluid volume, etc.) of the subject such as body fat percentage, fat weight, lean body mass, etc. Volume and the total body water content).
The change in the body water distribution can be estimated from the change in the resistances Re and Ri. As a bioelectrical impedance measuring device that performs measurement / estimation of each of these parameters by injecting a small sine wave current of a plurality of frequencies arbitrarily selected into a living body and digitally processing the obtained signal, there is a special table. Hei 6
The thing described in 506854 is known.

[0009]

In a conventional bioelectrical impedance measuring apparatus, an impedance locus is obtained from the calculated bioelectrical impedance by using a curve fitting method such as a least square method. Next, from the obtained impedance locus, the bioelectric impedance R0 of the subject's body at the frequency 0 and the bioelectric impedance R∞ at the infinite frequency are calculated, and from the calculation result,
The intracellular fluid resistance and the extracellular fluid resistance of the subject's body are calculated.

FIG. 5 is a diagram showing a display example of an impedance locus measured by a conventional bioelectrical impedance measuring device. This bioelectric impedance measuring apparatus uses an M-sequence signal as a measurement signal to be input to a living body. In this impedance locus, the frequency interval is constant, but in the impedance plot, the density of points on the low frequency side is low and the density of points on the high frequency side is large.
This indicates that the energy on the low frequency side is lower than the energy on the high frequency side.

When the number of plot points, ie, the number of samples, is reduced in order to shorten the measurement time, the measured current value applied to the living body can be reduced, but the density of points on the high frequency side decreases and the density of points on the low frequency side decreases. Will also be lower. This makes it more susceptible to external noise on the low frequency side.

An object of the present invention is to reduce the measurement time while avoiding the influence of external noise on the low frequency side, and to measure the electrical characteristics suitable for the measurement of bioimpedance and the state of body fat and body water distribution. It is to provide a device.

[0013]

The electric characteristic measuring apparatus of the present invention generates measurement signals at frequency intervals equal to each other in a low frequency range and at frequency intervals proportional to the square of the measurement frequency in a high frequency range, and measures the subject's signal. Measurement signal supply means for supplying the measurement signal to the subject via first and second electrodes conductively attached to two predetermined surface portions separated from each other; and the measurement supplied to the subject. A current measuring means for measuring a current value of the signal; a voltage measuring means for measuring a voltage value generated between two predetermined surface portions of the subject which are separated from each other; and a current measuring means and a voltage measuring means, respectively. Based on the current value and the voltage value, the bioelectric impedance between the surface portions of the subject is calculated, and the bioelectric impedance or bioelectric impedance to be obtained is calculated. Calculating means for calculating a brute physical quantity,
It is provided with.

Further, the measurement signal supply means is provided as 1+ (f
By generating a measurement signal having a frequency interval proportional to (/ fo) ² (f is a measurement frequency, fo is a reference frequency), the reference frequency can be set in relation to a critical frequency unique to the subject. That is, the frequency interval is equal to 2 or equal to the measurement frequency.
It is possible to freely change the area having an interval proportional to the power.

The reference frequency is 10 kHz to 3 kHz.
By setting the frequency within the range of 00 kHz, the reference frequency can be set near the critical frequency, and the influence of external noise on the low frequency side can be suppressed more reliably.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. The case where the electrical characteristic measuring device of the present invention is used for a bioelectrical impedance measuring device will be described in detail.

FIG. 1 is a block diagram showing an electrical configuration of the bioelectrical impedance measuring device according to the present embodiment. The bioelectrical impedance measuring device includes a keyboard 1
The probe current Ia is transmitted as a measurement signal to the body B of the subject, and thereby the measurement processing unit 2 for digitally processing the voltage / current information obtained from the body B of the subject, and the respective units of the apparatus are controlled and the measurement process is performed. A CPU (Central Processing Unit) 3 for calculating various physical quantities relating to the bioelectrical impedance, body fat, and body water distribution of the human body based on the processing results of the unit 2, and a living body of the subject B calculated by the CPU 3 A display unit 4 for displaying electrical impedance, body fat content, body water content, etc., a ROM 6 for storing a processing program of the CPU 3, and various data (for example, height, weight, sex, extracellular fluid and intracellular (A liquid amount and the like) and a RAM 5 in which a work area of the CPU 3 is set.

The keyboard 1 is used by a measurer to input a measurement start switch for instructing the start of measurement, a human body characteristic item such as height, weight, gender, and age of the subject, a total measurement time T, a measurement interval t, and a measurement interval to be described later. The key 1 comprises various keys for setting / changing a reference frequency fo or the like according to a measurement purpose. Operation data of each key supplied from the keyboard 1 is converted into a key code by a key code generation circuit (not shown). Then, it is supplied to the CPU 3.

Here, a conventional impedance locus (FIG. 5)
Is formed by plotting bioimpedance for each frequency from bioimpedance R0 at frequency 0 to bioimpedance R イ ン ピ ー ダ ン ス at infinity. The intermediate corresponding to the frequency of the bioelectrical impedance Zf _C bioimpedance locus is called the critical frequency f _C, is a unique frequency to the subject. The human critical frequency f _C is
In the case of an adult, it is generally considered to be around 40 kHz. In the case of children, the critical frequency f _C tends to be higher than in the case of adults. However, by setting a reference frequency fo described below up to 300 kHz, even children can measure without any problem.

The reference frequency fo is a frequency parameter for adjusting the frequency interval of the plot forming the impedance locus, and is set near the critical frequency f _C. In the present embodiment, the frequency interval (plot interval) of the measurement signal is adjusted based on (1+ (f / fo) ² ). Where f is the measurement frequency and the reference frequency f
o is set in the range of 10 kHz to 300 kHz. Thereby, the frequency interval on the low frequency side becomes substantially equal to the reference frequency fo, and the frequency interval on the high frequency side becomes an interval substantially proportional to the square of the measurement frequency f.

The measurement processing unit 2 includes a PIO (parallel interface) 71, a measurement signal generator 72, a low-pass filter (hereinafter, referred to as LPF) 73, a coupling capacitor 74, and a surface electrode Hc attached to a predetermined part of the body. Output processing circuit, surface electrodes Hp, Lp, Lc, which are also affixed to predetermined parts of the body, coupling capacitors 80a, 80b, 90, and a differential amplifier 8
1. I / V converter (current / voltage converter) 91, LPFs 82 and 9 comprising analog anti-aliasing filters
2. An input processing circuit including A / D converters 83 and 93 and sampling memories (ring buffers) 84 and 94.

In the measurement processing section 2, the measurement signal generator 7
2 has an output resistance of 10 kΩ or more over the entire range of the generated signal frequency, and every time a signal generation instruction signal is supplied from the CPU 3 via the PIO 71 at a predetermined cycle t during the entire measurement time T, The probe current Ia is repeatedly generated a predetermined number of times, and the generated probe current Ia is removed as a measurement signal having the above-mentioned frequency interval so that a DC component does not flow through the LPF 73 for removing the high-frequency noise and the body B of the subject. The signal is transmitted to the surface electrode Hc via the coupling capacitor 74.

The probe current Ia is equal to the reference frequency fo.
Is adjusted so that the current output power becomes an allowable value (for example, 100 μA · rms for a human body). The supply period of the signal generation instruction signal matches the measurement interval t set by the measurer using the keyboard 1. In this example, the probe current (measurement signal) I
The number of repetitions of “a” is 1 to 2 per signal generation instruction signal.
56 times. The number of repetitions may be arbitrarily set by the measurer using the keyboard 1. The number of repetitions increases as the number of repetitions increases. However, although it is a minute current, it may adversely affect the human body when continuously applied to the human body for a long time. Therefore, the number of repetitions is preferably 1 to 256.

Further, a D / A converter (not shown) may be used to generate a measurement signal in the measurement signal generator 72. In this case, the D / A converter converts the measurement signal wave, which is a digital signal supplied from the CPU 3, into the probe current Ia, which is an analog signal.

FIG. 2 is a diagram schematically showing a state of use of the bioelectrical impedance measuring device according to the present embodiment. The surface electrode Hc (first electrode) is conductively affixed to the right back part H of the subject by a suction method at the time of measurement,
The surface electrode Lc (second electrode) is conductively attached to the right instep L by an adsorption method. Therefore, the measurement signal (probe current) Ia is transmitted from the right hand of the subject to the body B
to go into.

The surface electrode (high potential output terminal) Hp
Is electrically conductively attached to the right back part H of the subject by suction, and the surface electrode Lp is electrically conductively attached to the right instep L by suction. At this time, the surface electrodes Hc and Lc are attached to portions farther from the center of the human body than the surface electrodes Hp and Lp. Each of the above surface electrodes Hp, L
p, Hc, and Lc are connected to the bioelectrical impedance measuring device 100 by a measuring cable 10.

Next, the measurement signal processing will be described. FIG.
As shown in the figure, the surface electrode (high-potential output terminal) Hp is conductively attached to the right back part H of the subject by a suction method, while the front electrode Lp is sucked to the right foot part L. It is stuck conductively by the method.

The differential amplifier 81 shown in FIG. 1 detects a potential (potential difference) between two surface electrodes Hp and Lp. That is, when the probe current Ia is applied to the body B of the subject, the differential amplifier 81 detects the voltage Vp between the right limbs of the subject and inputs the same to the LPF. This voltage V
p is a voltage drop between the surface electrode Hp and the surface electrode Lp due to the bioelectric impedance of the body B of the subject.

The LPF 82 removes high frequency noise from the voltage Vp and supplies it to the A / D converter 83. LPF
The cutoff frequency 82 is lower than half the sampling frequency of the A / D converter 83. Thereby, aliasing noise generated in the A / D conversion processing by the A / D converter 83 is removed.

The A / D converter 83 converts the noise-free voltage Vp into a digital signal at a predetermined sampling cycle every time the digital conversion signal Sd is supplied from the CPU 3, and converts the digitized voltage Vp Is supplied to the sampling memory 84 every sampling period.

Next, as shown in FIG. 2, the surface electrode Lc is attached to the right instep L of the subject by the suction method. The surface electrode Lc and the coupling capacitor 90 (see FIG. 1) are connected by a coaxial cable (not shown), and the shield of the coaxial cable is grounded.

The I / V converter 91 has two surface electrodes H
The current flowing between c and Lc is detected and converted into a voltage. That is, when the probe current Ia is applied to the body B of the subject, the I / V converter 91 detects the probe current Ia flowing between the right limb of the subject, converts the probe current Ia to the voltage Vc,
Supply to F92.

The LPF 92 removes high-frequency noise from the input voltage Vc and supplies it to the A / D converter 93.
The cutoff frequency of the LPF 92 is lower than half the sampling frequency of the A / D converter 93. In this case, A /
The aliasing noise generated in the A / D conversion processing by the D converter 93 is removed.

The A / D converter 93 converts the noise-free voltage Vc into a digital signal at a predetermined sampling cycle every time the digital conversion signal Sd is supplied from the CPU 3, and converts the digitized voltage Vc Is supplied to the sampling memory 94 every sampling period.

The CPU 3 starts the measurement by the above-described measurement processing unit 2 according to the processing program stored in the ROM 6, and detects the detection voltages Vp and V at a predetermined sampling cycle.
After sampling c for a predetermined number of times, the following processing is performed in addition to the control for stopping the measurement. First, the voltage V as a function of time, stored in the sampling memories 84 and 94,
The voltages Vp (f) and Vc (f), which are functions of frequency, are sequentially read out and subjected to Fourier transform processing.
(F is a frequency), and after averaging, the bioelectrical impedance Z (f) [= Vp (f) / V
c (f)] is calculated. Here, the frequency of the signal after the Fourier transform is the same as the frequency of the measurement signal, that is,
It has the same frequency interval as the measurement signal.

FIG. 3 is a diagram showing a display example of an impedance locus measured by the bioelectrical impedance measuring device according to the present embodiment. Based on the obtained bioelectric impedance Z (f) for each frequency, the CPU 3 obtains an impedance locus D as shown in FIG. 3 by making full use of a least-squares method.

The impedance locus shown in FIG. 3 shows an example in which the reference frequency fo is set equal to the critical frequency f _C. Therefore, on the frequency side higher than the critical frequency f _C , the biological impedance is plotted at a frequency interval substantially proportional to the square of the measurement frequency f, and on the frequency side lower than the critical frequency f _C , the biological impedance is plotted at substantially equal intervals. The impedance is plotted.

As described above, since the power spectrum density on the low frequency side can be relatively increased, the influence of external noise on the low frequency side can be suppressed even when the measurement is performed with a small number of samples. Time can be reduced.

Next, the CPU 3 calculates the bioelectric impedance R0 of the body B of the subject at the frequency 0 and the bioelectric impedance R∞ at the infinite frequency of the subject B from the obtained impedance locus D. Then, the intracellular fluid resistance and the extracellular fluid resistance of the body B of the subject are calculated.

In the section of the prior art, cells in a tissue of a human body are expressed by a simple electrical equivalent circuit (FIG. 4: Re is extracellular fluid resistance, R
ik is the intracellular fluid resistance of each cell, and Cmk is the cell membrane capacity of each cell.) In actual human tissues, cells of various sizes are irregularly arranged. A close electrical equivalent circuit has a time constant τ = Cmk ·
It is represented by a distributed constant circuit in which elements connected in series with a capacitor and a resistor having Rik are distributed. Accordingly, in the present embodiment, since the intracellular fluid resistance and the extracellular fluid resistance are determined by using an electrical equivalent circuit that is close to actual, the impedance locus D of the human body is shown in FIG. 3 (and FIG. 5). As shown in (2), the center is an arc raised from the real axis.

Next, based on the calculated intracellular fluid resistance and extracellular fluid resistance, and the human body characteristic data such as the height, weight, sex, and age of the subject input from the keyboard 1, a processing program is prepared in advance. The body fat percentage, fat weight, lean body mass, intracellular fluid volume, extracellular fluid volume, and the sum of these amounts of body water (body fluid volume) ) Is calculated. Then, the calculated data is displayed on the display unit 4 including a display controller and a display (for example, an LCD).

Next, the operation of the bioelectrical impedance measuring apparatus 100 according to the present embodiment will be described. First, prior to the measurement, as shown in FIG.
c, Hp on the right back part H of the subject, two surface electrodes L
p and Lc are attached to the right instep L of the subject by the suction method. At this time, the surface electrodes Hc and Lc are attached to a portion farther from the center of the human body than the surface electrodes Hp and Lp. Next, the measurer (or the subject himself) uses the keyboard 1 of the bioelectrical impedance measuring device 100 to input the human body characteristic items such as the height, weight, sex, and age of the subject, and from the start of measurement to the end of measurement. The measurement time T, the measurement interval t, the reference frequency fo, and the like are set. The data and setting values input from the keyboard 1 are
Stored in the RAM 5. The reference frequency fo may be fixedly set in the ROM 6 or the like.

Next, when the measurer (or the subject himself) turns on the measurement start switch of the keyboard 1, the CPU 3
Sends a signal generation instruction signal to the measurement signal generator 72 of the measurement processing unit 2 after performing a predetermined initial setting. This initial setting includes a process of calculating the total number of samples in the above-described impedance locus, the sampling period of the A / D converters 83 and 93, the generation timing of the digital conversion signal Sd, and the like.

As a result, the measurement signal generator 72 repeatedly generates the probe current Ia a predetermined number of times, and outputs the measurement signal as the measurement signal via the LPF 73, the coupling capacitor 74, and the measurement cable 10 which is a double shielded wire, to the back of the subject. Since the measurement signal Ia is transmitted to the surface electrode Hc (see FIG. 2) attached to the portion H, a measurement signal Ia of about 100 μA flows from the surface electrode Hc through the body B of the subject, and the first measurement is started.

When the measurement signal Ia is applied to the body B of the subject, the voltage Vp generated between the right limb to which the surface electrodes Hp and Lp are affixed in the differential amplifier 81 of the measurement processing unit 2.
Is supplied to the A / D converter 83 via the LPF 82. On the other hand, in the I / V converter 91, the surface electrode H
After the probe current Ia flowing between the right limb to which c and Lc are attached is detected and converted to the voltage Vc, the LPF 9
The signal is supplied to the A / D converter 93 through the second line. At this time, C
The PU 3 outputs an A / D converter 8 every sampling period.
The digital conversion signal Sd is supplied to 3,93.

The A / D converter 83 converts the voltage Vp into a digital signal every time the digital conversion signal Sd is supplied, and supplies the digital signal to the sampling memory 84. The sampling memory 84 sequentially stores the digitized voltage Vp. On the other hand, the A / D converter 93 converts the voltage Vc into a digital signal each time the digital converted signal Sd is supplied, and supplies the digital signal to the sampling memory 94. The sampling memory 94 sequentially stores the digitized voltage Vc.

The CPU 3 calculates the probe current (measurement signal) I
When the number of repetitions of “a” reaches a preset number, after performing control to stop the measurement, first, the voltages Vp, which are stored in the sampling memories 84 and 94 and are a function of time, as a function of time.
The voltages Vp (f) and Vc (f), which are functions of frequency, are sequentially read out and subjected to Fourier transform processing.
(F is a frequency), and after averaging, bioelectric impedance Z (f) (= Vp (f) /
Vc (f)) is calculated.

Next, the CPU 3 performs curve fitting based on the calculated bioelectrical impedance Z (f) for each frequency by a least-squares method, and obtains an impedance locus D as shown in FIG. From the obtained impedance locus D, the body B of the subject
Bioelectric impedance R0 at frequency 0 and bioelectric impedance R∞ at infinite frequency (corresponding to the X-axis coordinate value of the point where the arc of impedance locus D intersects the X-axis)
Is calculated, and the intracellular fluid resistance and the extracellular fluid resistance of the body B of the subject are calculated from the calculation result.

The CPU 3 executes a processing program in advance based on the calculated intracellular fluid resistance and extracellular fluid resistance, and human body characteristic data such as the height, weight, sex, and age of the subject input from the keyboard 1. The body fat percentage, fat weight, lean body mass, intracellular fluid volume, extracellular fluid volume, and the sum of these body water ( Volume). Then, the calculated data are stored in the RAM 5 and displayed on the display unit 4.

Next, the CPU 3 determines whether or not the total measurement time T has elapsed. If it is determined that the total measurement time T has elapsed, the CPU 3 terminates the subsequent measurement processing. After waiting for the corresponding time t to elapse, the same measurement processing is started again. Then, the above process is repeated until the entire measurement time T has elapsed.

As described above, according to the configuration of this example, the probe current Ia disperses in energy of about 1 msec despite including many frequency components.
Since the amplitude of the frequency spectrum uses a signal that is almost flat over the entire frequency range, it is possible to measure the state of body fat and the distribution of body water without damaging the living body and removing the effects of respiration and pulse. As a result, a good SN ratio measurement can be performed over the entire frequency range. Further, the measurement signal can be generated only from the shift register and the plurality of logic circuits, so that the configuration becomes very simple.

Further, since the bioelectrical impedance at infinite frequency can be obtained by using the curve fitting method by the least squares method, the influence of stray capacitance and extraneous noise can be avoided. The extracellular fluid resistance and the intracellular fluid resistance can be determined.

In particular, the power spectrum density on the low frequency side can be increased by setting a predetermined reference frequency fo with respect to the critical frequency f _C unique to the subject from the impedance locus shown in FIG. , The effect of external noise can be suppressed. Also, the reference frequency f
Since the total number of samples can be suppressed by setting o, the measurement time can be shortened, and the current value of the probe current can be reduced as compared with the conventional case.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and a design within a range not departing from the gist of the present invention. May be changed. For example, in the above-described embodiment, a single-frequency measurement signal is generated. However, a configuration in which a single-frequency sine wave or the like is synthesized to generate a measurement signal, and measurements for a plurality of frequencies are collectively performed. It is good. Thereby, the measurement time can be shortened.

In the above embodiment, the surface electrode Hc
And a current value applied to the subject via the surface electrode Lc, and a voltage value generated between two predetermined surface portions via the surface electrode Hp and the surface electrode Lp. As another embodiment, for example, the current value and the voltage value may be measured by the surface electrode Hc and the surface electrode Lc (so-called two-terminal method), and the number of the surface electrodes limits the present invention. Not something.

The calculated bioelectric parameters are not limited to bioelectric impedance, impedance locus, extracellular fluid resistance and intracellular fluid resistance, but also bioelectric admittance, admittance locus, bioelectric impedance or bioelectric admittance, extracellular The amount of temporal change such as fluid resistance and intracellular fluid resistance and a part thereof may be used. In this case, not only measurement of body fat percentage and the like but also various medical systems (for example, dialysis state measurement) ) Can be expected. Also, the location where the electrode is attached is not limited to the hand or foot.

The Fourier transform processing by the CPU 3 is not limited to the present invention, and may be any method that uses an arithmetic technique that converts a function represented in a time domain into a function represented in a frequency domain.

Furthermore, in the above-described embodiment, the case has been described where the height, weight, sex, and age of the subject are input as the human body characteristic items. However, gender, age, and the like may be omitted as necessary. Alternatively, items such as race may be added. The calculated bioelectric parameters of the human body may be output to a printer. Further, a pulse wave sensor or a sensor capable of detecting a respiratory cycle may be attached to a human body, and the measurement timing may be set based on the output signal of each sensor.

[0059]

As described above, according to the electric characteristic measuring apparatus of the present invention, the effect of external noise can be suppressed and the measuring time can be shortened by increasing the power spectrum density in the low frequency region.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electrical configuration of a bioelectrical impedance measuring device according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing a state of use of the bioelectrical impedance measuring device according to the embodiment of the present invention.

FIG. 3 is a diagram showing a display example of an impedance locus measured by the bioelectrical impedance measuring device according to the embodiment of the present invention.

FIG. 4 is an electrical equivalent circuit diagram showing cells in a tissue of a human body.

FIG. 5 is a diagram showing a display example of an impedance locus measured by a conventional bioelectric impedance measuring device.

FIG. 6 is an electrical equivalent circuit diagram showing cells in a tissue of a human body in detail.

[Explanation of symbols]

Reference Signs List 1 keyboard 2 measurement processing unit 3 CPU (calculation means) 4 display unit 5 RAM 6 ROM 10 measurement cable 72 measurement signal generator (part of measurement signal supply means) 73 LPF (part of measurement signal supply means) 81 difference Dynamic amplifier (part of voltage measuring means) 82 LPF (part of voltage measuring means) 83 A / D converter (part of voltage measuring means) 84,94 Sampling memory 91 I / V converter (of current measuring means) 92 LPF (part of current measuring means) 93 A / D converter (part of current measuring device) 100 Bioelectric impedance measuring device (electric property measuring device) Hc surface electrode (first electrode) Lc surface electrode (Second electrode) Hp surface electrode Lp surface electrode

Claims (3)

[Claims] 1. A measurement signal is generated at equal frequency intervals in a low frequency region and at a frequency interval proportional to the square of a measurement frequency in a high frequency region, and can be conducted to two predetermined surface portions of a subject separated from each other. First and second attached to
A measurement signal supply unit that supplies the measurement signal to the subject via the electrodes; a current measurement unit that measures a current value of the measurement signal that is supplied to the subject; Voltage measuring means for measuring a voltage value generated between the surface portions of the location, and a bioelectric impedance between the surface portions of the subject is calculated based on the current value and the voltage value respectively measured by the current measuring means and the voltage measuring means. And a calculating means for calculating a bioelectric impedance to be obtained or a physical quantity based on the bioelectric impedance. 2. The method according to claim 1, wherein the measuring signal supply means is 1+ (f / f
o) The electrical characteristic measuring apparatus according to claim 1, wherein a measuring signal is generated at a frequency interval proportional to (o) ² (f is a measuring frequency, fo is a reference frequency). 3. The reference frequency is 10 kHz to 300 kHz.
The frequency is set within a range of kHz.
The electrical property measurement device according to the above.