JP2024145708A - Body composition measuring device, control method, and control program - Google Patents

Abstract

[Problem] To provide a body composition measuring device, control method, and control program that can minimize averaging of the results of synchronous addition processing while maintaining measurement accuracy. [Solution] A body composition measuring device 1 measures electrical impedance based on voltage signals and current signals when a plurality of probe currents with different frequencies are applied to the body of a subject, and calculates an impedance locus based on the measured electrical impedance. Furthermore, the body composition measuring device 1 has a first measurement mode in which the total number of times the voltage signals are averaged is a predetermined number, and a second measurement mode in which the total number of times averaging is less than that of the first measurement mode. When the impedance locus of the second measurement mode is determined to be abnormal when measurement is performed using the second measurement mode, the total number of times averaging is increased from that of the second measurement mode and measurement is performed again. [Selected Figure] Figure 1

Description

The present invention relates to a body composition measuring device, a control method, and a control program.

Conventionally, devices that measure a subject's body composition, such as body fat weight and body water content, based on the bioelectrical impedance method have been known (see, for example, Patent Documents 1 to 4 below). This device measures the bioelectrical impedance of a subject's body based on the voltage generated in the subject's body and the current flowing through the subject's body when weak alternating currents of multiple frequencies are passed through the subject's body, and calculates the body composition from the measured bioelectrical impedance.

JP 2000-316829 A Japanese Patent Application Publication No. 9-154829 JP 2003-116805 A Patent No. 3984332

Conventionally, in bioelectrical impedance measurement, a noise signal is added to the signal waveform at a period not synchronized with the signal waveform, and an averaging process, such as a synchronous addition process, is performed to remove, for example, noise and quantization errors when converting voltage and current signals from analog values to digital values. In this synchronous addition process, the synchronous addition process is repeated a predetermined number of times. However, depending on the measurement target and measurement conditions, the synchronous addition process may be repeated more than necessary as a result of an increase in the signal-to-noise ratio of the signal. As a result, the time required to measure body composition may be longer than necessary for the measurement accuracy.

The present invention has been made in consideration of the above circumstances, and its main objective is to provide a body composition measuring device, control method, and control program that can minimize the number of repetitions of averaging processing, such as synchronous addition, while maintaining measurement accuracy.

The above object of the present invention is achieved by the following means:

In order to achieve the above object, the body composition measuring device of the present invention measures the body composition of a subject according to measurement conditions. The body composition measuring device includes a current input unit, a voltage detection unit, a current detection unit, a voltage signal amplification unit, a current-voltage conversion unit, an electrical impedance calculation unit, an impedance locus calculation unit, a body composition information calculation unit, an abnormality determination unit, and a mode control unit. The current input unit inputs a plurality of probe currents of different frequencies into the body of the subject. The voltage detection unit detects a voltage signal related to a voltage generated between predetermined parts of the body of the subject when the plurality of probe currents are input into the body of the subject by the current input unit. The current detection unit detects a current signal related to a current flowing through the body of the subject when the plurality of probe currents are input into the body of the subject by the current input unit. The voltage signal amplification unit amplifies the voltage signal detected by the voltage detection unit to a magnitude used for electrical impedance measurement. The current-voltage conversion unit converts the current signal detected by the current detection unit into a voltage signal used for electrical impedance measurement. An electrical impedance calculation unit calculates information on electrical impedance for each frequency based on the voltage signal amplified by the voltage signal amplifier and the voltage signal converted by the current-voltage conversion unit. An impedance locus calculation unit calculates an impedance locus based on information on the electrical impedance for each frequency measured by the electrical impedance measurement unit. A body composition information calculation unit calculates information on the body composition of the subject based on the impedance locus calculated by the impedance locus calculation unit. An abnormality determination unit determines whether the impedance locus calculated by the impedance locus calculation unit is abnormal. A mode control unit controls whether to perform measurement in one of a first measurement mode in which the total number of times the voltage signal amplified by the voltage signal amplifier and the voltage signal converted by the current-voltage conversion unit are averaged by the electrical impedance calculation unit is a predetermined number, and a second measurement mode in which the total number of times averaging is smaller than that in the first measurement mode. Furthermore, when the measurement is performed in the second measurement mode, if the abnormality determination unit determines that the impedance locus in the second measurement mode is abnormal, the mode control unit increases the total number of times that averaging is performed compared to the second measurement mode and performs the measurement again.

In order to achieve the above object, the control method of the body composition measuring device of the present invention measures the composition of a subject's body. The control method includes the steps of: injecting a plurality of probe currents having different frequencies into the subject's body, detecting a voltage signal related to a voltage generated between predetermined parts of the subject's body when the plurality of probe currents are injected into the subject's body, and a current signal related to a current flowing through the subject's body; amplifying the voltage signal related to the voltage detected in the step (a) to a magnitude used for electrical impedance measurement; converting the current signal related to the current detected by the step (a) into a voltage signal related to a current used for electrical impedance measurement (b2); averaging the voltage signal amplified in the step (b) and the voltage signal related to the current converted in the step (b2); and converting the voltage signal averaged in the step (c). , using the voltage signal and the voltage signal related to the current, step (d) of calculating information about the electrical impedance for each frequency, step (e) of calculating an impedance locus based on the information about the electrical impedance for each frequency calculated in step (d), step (f) of calculating information about the body composition of the subject based on the impedance locus calculated in step (e), and step (g) of determining whether the impedance locus calculated in step (e) is abnormal. If it is determined in step (g) that the impedance locus is abnormal, the total number of averaging times in step (c) is increased, and control is performed to re-perform the processes from step (a) to step (g).

In order to achieve the above object, the body measurement device of the present invention is a body composition measurement device that measures the body composition of a subject according to measurement conditions, and includes a current input unit that inputs a plurality of probe currents having different frequencies into the body of the subject, a voltage detection unit that detects a voltage signal related to a voltage generated between predetermined parts of the body of the subject when the plurality of probe currents are input into the body of the subject by the current input unit, a current measurement unit that detects a current signal related to a current flowing through the body of the subject when the plurality of probe currents are input into the body of the subject by the current input unit, a voltage signal amplification unit that amplifies the voltage signal detected by the voltage detection unit to a magnitude used for electrical impedance measurement, a current-voltage conversion unit that converts the current signal detected by the current detection unit into a voltage signal having a magnitude used for electrical impedance measurement, and an electrical impedance converter that calculates information related to the electrical impedance for each frequency based on the voltage signal amplified by the voltage signal amplification unit and the voltage signal converted by the current-voltage conversion unit. an impedance calculation unit, an impedance locus calculation unit that calculates an impedance locus based on information about the electrical impedance for each frequency calculated by the electrical impedance calculation unit, a body composition information calculation unit that calculates information about the body composition of the subject based on the impedance locus calculated by the impedance locus calculation unit, an abnormality determination unit that determines whether the impedance locus calculated by the impedance locus calculation unit is abnormal, and a mode control unit that controls whether to perform measurement in one of a first measurement mode in which the voltage signal amplified by the voltage signal amplifier and the voltage signal converted by the current-to-voltage conversion unit are averaged a predetermined number of times by the electrical impedance calculation unit, and a second measurement mode in which the number of averaging is smaller than that in the first measurement mode. When the measurement is performed in the second measurement mode, the mode control unit notifies the abnormality determination unit that the impedance locus in the second measurement mode is abnormal.

The body composition measuring device of the present invention performs electrical impedance measurement by gradually increasing the number of averagings within a range that does not exceed the maximum number of averagings. This makes it possible to keep the variation in the impedance measurement values within a specified range while minimizing the time required for synchronous addition processing.

1 is a block diagram illustrating a schematic configuration of a body composition measuring device according to a first embodiment of the present invention. FIG. 2 is a conceptual diagram showing a state in which the body composition measuring device shown in FIG. 1 is used. 2 is a schematic block diagram illustrating a hardware configuration of a control unit illustrated in FIG. 1 . 1 is a graph showing an example of an impedance locus. 4 is a flowchart illustrating a main process of a control method of a body composition measuring device. 6 is a subroutine flowchart illustrating details of a preliminary measurement (S102) process in the flowchart shown in FIG. 5. 6 is a subroutine flowchart illustrating details of the main measurement (S103) process in the flowchart shown in FIG. 5. 7B is a subroutine flowchart following FIG. 7A. 7C is a subroutine flowchart illustrating a process (S321) for determining whether or not there is an abnormality in the electrical impedance measurement shown in FIG. 7B. 1 is a schematic diagram illustrating a flow of current (current signal) in cells in a living organism according to the frequency. FIG. FIG. 10 is a schematic electrical equivalent circuit diagram of the living body shown in FIG. 9. 10 is a subroutine flowchart illustrating details of a main measurement (S103) process in the second embodiment. FIG. 11B is a subroutine flowchart following FIG. 13 is a subroutine flowchart illustrating details of a main measurement (S103) process in the third embodiment. FIG. 1 is a conceptual diagram showing the use of a body composition measuring device in a verification experiment of measurement accuracy using pigs. 11 is a graph illustrating the results of confirming V-POWER in a verification experiment of measurement time. 11 is a graph illustrating the results of confirming I-POWER in a verification experiment of measurement time. 13 is a graph illustrating the results of confirming the fluctuation error (%) of R0 in a verification experiment of the measurement time. 13 is a graph illustrating the results of confirming the fluctuation error (%) of R∞ in a verification experiment of measurement time. 13 is a graph illustrating the results of confirming an average value of an abnormality index in a verification experiment of measurement time.

Hereinafter, an embodiment of the present invention will be described with reference to the attached drawings. Note that in the description of the drawings, the same elements are given the same reference numerals, and duplicate descriptions will be omitted. Also, the dimensional ratios in the drawings have been exaggerated for the convenience of explanation, and may differ from the actual ratios.

(First embodiment)
Fig. 1 is a block diagram illustrating a schematic configuration of a body composition measurement device according to a first embodiment, Fig. 2 is a conceptual diagram illustrating a state in which the body composition measurement device is used, and Fig. 3 is a schematic block diagram illustrating a hardware configuration of a control unit shown in Fig. 1.

<Configuration of body composition measuring device 1>
The body composition measuring device 1 is a device for measuring the body composition of a body E of a subject (such as a patient or a care recipient). The body composition measuring device 1 may be a portable body composition measuring device powered by a battery. The portable body composition measuring device can measure the body composition of a subject in any location, such as at the bedside, in an outpatient clinic, or during a home visit.

As shown in FIG. 1, the body composition measuring device 1 includes a control unit 10, a current measuring unit 20, a signal output unit 30, a voltage measuring unit 40, a recording unit 62, an input unit 63, a speaker 64, a display unit 65, and a memory 66. The electrical impedance calculation unit 120, the current measuring unit 20, the signal output unit 30, and the voltage measuring unit 40 constitute an electrical impedance measuring unit 50.

The recording unit 62 can be composed of, for example, a RAM (Random Access Memory), an SSD (Solid State Drive), or an HDD (Hard Disk Drive).

The input unit 63 has, for example, a touch panel, various keys, switches, etc., and accepts instructions from an operator such as a medical professional, various settings, information about the subject, etc. Instructions from the operator include, for example, instructions to start/end measurement, and various settings include, for example, settings about the method of outputting and displaying the measurement results. Information about the subject also includes the subject's gender, age, height, weight, medical history, etc.

The display unit 65 has a display arranged on one side of the housing of the body composition measuring device 1. The display unit 65 can also be equipped with a light-emitting element (LED: Light-Emitting Diode) for visually notifying abnormalities, etc.

<Surface electrodes Lc, Hc, Lp, Hp>
As shown in FIG. 2, surface electrodes Lc and Hc and surface electrodes Lp and Hp are attached (attached with an adhesive sheet or the like) to predetermined locations on the subject's body E. These surface electrodes are connected The surface electrodes Lc and Hc are connected to the body composition measuring device 1 via cables 2A to 2D. More specifically, the surface electrode Lc is attached to the right instep of the body E of the subject during measurement. The electrode Hc is attached to the back of the right hand of the subject's body E. The surface electrode Lc is connected to the current measuring unit 20, and the surface electrode Hc is connected to the signal output unit 30. The surface electrode Hc is paired with the surface electrode Lc. The surface electrode Lp is attached to the right instep of the body E of the subject during measurement, and the surface electrode Hp is attached to the right instep of the body E of the subject during measurement. It is paired with Lp.

<Configuration of control unit 10>
3, the control unit 10 includes a CPU (Central Processing Unit) 11, a ROM 12, a RAM 13, an auxiliary storage unit 14, and an input/output I/F 15. The auxiliary storage unit 14 includes, for example, an SSD or an HDD. The CPU 11, the ROM 12, the RAM 13, and the auxiliary storage unit 14 constitute a computer.

The CPU 11 loads a control program stored in advance in the ROM 12 or the auxiliary storage unit 14 into the RAM 13 and executes it to realize various functions. The ROM 12 is a non-volatile memory. The ROM 12 stores various parameters necessary for the calculation processing of the CPU 11. The RAM 13 is a volatile memory, and temporarily stores the results of the calculation processing by the CPU 11 and various data. The auxiliary storage unit 14 stores programs such as the OS (Operating System) and control programs, and the results of the calculation processing by the CPU 11. The input/output I/F 15 is an input/output interface that transmits and receives data to and from a system unit (not shown).

When the CPU 11 executes the control program, the control unit 10 functions as an impedance trajectory calculation unit 110, an electrical impedance calculation unit 120, a judgment unit 130, a notification unit 140, a body composition measurement unit 150, an abnormality determination unit 160, an effective value calculation unit 170, a measurement condition determination unit 180, and a mode control unit 190 (see FIG. 1 again).

<Electrical impedance measuring unit 50>
The electrical impedance measuring section 50 generates a plurality of probe currents with different frequencies, applies the probe currents with each frequency to the subject's body E, and measures the electrical impedance of the subject's body E from the relationship between the probe current and the voltage between the electrodes when the probe currents with each frequency are flowing through the subject's body E. Note that, although the following mainly describes the case where electrical impedance is measured, the electrical impedance measuring section 50 may be configured to measure electrical admittance, which is the reciprocal of electrical impedance, and/or electrical impedance.

<Signal Output Unit 30>
The signal output unit 30 functions as a current input unit, and flows a multi-frequency probe current (hereinafter referred to as "multi-frequency current") Ib into the subject's body E in accordance with instructions from the control unit 10. The multi-frequency current is a plurality of probe currents with different frequencies. The multi-frequency probe current is, for example, a superposition of AC currents whose frequencies increase by 2.5 kHz from 2.5 kHz to 350 kHz. The signal output unit 30 has a measurement signal generator 31 and an output buffer 32.

The measurement signal generator 31 outputs a measurement signal (current) Ia to the output buffer 32 at a predetermined cycle in accordance with instructions from the CPU 11. The cycle at which the measurement signal generator 31 outputs the measurement signal Ia can be, for example, about 800 nsec. The measurement signal Ia is a signal that changes at predetermined frequency intervals within the predetermined cycle. The measurement signal Ia may change at frequency intervals of 15 kHz in the range of 1 kHz to 400 kHz, for example. Alternatively, it may be a measurement signal that includes many frequency components, such as the M-sequence signal shown in JP-A-10-14898.

More specifically, the measurement signal generator 31 has an M-sequence signal generator, a square wave generator, and a time divider (not shown), and generates, in a time-division manner, an M-sequence signal with a period of T*(2 ⁿ -1) bits (n is a positive integer) and a signal with a period of T*N=2*W (N is an integer of 2 or more) in which the first W period is 1 and the remaining W periods are 0, in accordance with instructions from the CPU 11. For example, the M-sequence signal generator generates an M-sequence signal with a period of 511 (=2 ⁿ -1) that operates at 1.25 MHz, and the square wave generator generates a square wave with a period (32/1.25 MHz) and a duty of 50%. The time divider divides 0.8 μsec=1/1.25 MHz into four equal parts, and provides a control signal that switches the signal so that the M-sequence signal is output for the first three periods (0.6 μsec) and the square wave is output for the remaining 0.2 μsec.

The output buffer 32 outputs the input measurement signal Ia to the surface electrode Hc as a multi-frequency current Ib while keeping it in a constant current state. This causes the multi-frequency current Ib to flow through the subject's body E. The current value of the multi-frequency current Ib is not particularly limited. The current value of the multi-frequency current Ib can be, for example, about 100 to 800 μA. The output buffer 32 applies the measurement signal Ia through a limiting resistor that is sufficiently larger than the electrical resistance of the human body so that the measurement signal Ia is basically constant even if the subject changes. The output buffer 32 may be configured to have an analog filter, and the measurement signal Ia from which high-frequency noise has been removed by the analog filter may be applied.

<Current measuring unit 20>
The current measuring unit 20 converts the multi-frequency current Ib into a voltage and outputs the resulting voltage signal Vb. The current measuring unit 20 has a current detecting unit 24, an I/V converter 23, a BPF (band pass filter) 22, and an A/D converter 21.

The I/V converter 23 is a current/voltage converter that functions as a current-voltage converter. The current detection unit 24 converts the multi-frequency current Ib flowing through the subject's body E when the multi-frequency current is applied to the subject's body E by the signal output unit 30 into a current signal related to the current and detects it. The I/V converter 23 converts the multi-frequency current Ib flowing between the surface electrode Hc and the surface electrode Lc detected by the current detection unit 24 into a voltage Vb of a magnitude used for electrical impedance measurement by a gain Gi. The I/V converter 23 is configured to be able to change the gain Gi in response to an instruction from the control unit 10. The I/V converter 23 outputs the obtained voltage Vb to the BPF 22.

The BPF 22 is a bandpass filter. The BPF 22 cuts out unnecessary band signals from the voltage signal Vb and outputs the signal to the A/D converter 21. The passband of the BPF 22 can be appropriately selected according to the specifications of the body composition measuring device 1. The passband of the BPF 22 can be set to, for example, approximately 1 kHz to 800 kHz.

The A/D converter 21 converts the analog voltage Vb into a digital voltage signal Vb in accordance with a digital conversion instruction from the control unit 10. The digital voltage signal Vb is stored in time series in the memory 66 as voltage data, synchronously added with the synchronously added data up to one period before the M-sequence signal.

The memory 66 transmits and receives the stored data to and from the control unit 10 in response to a request from the control unit 10. Specifically, the data is transmitted and received to and from the effective value calculation unit 70 and the electrical impedance calculation unit 120. The memory 66 can be configured, for example, from an SRAM.

The control unit 10 functions as a synchronous addition unit, and performs synchronous addition on the data of the voltage signal Vb sent from the current measurement unit 20 in order to remove, for example, quantum errors of A/D conversion by the A/D converter 21. More specifically, the synchronous addition unit synchronously adds the synchronously added data of the M-sequence signal up to one cycle before and the current A/D converted data, and stores the result in the memory 66. That is, the memory 66 stores one cycle of the M-sequence signal after the synchronous addition. Thereafter, the next A/D converted data is similarly synchronously added to the one cycle of the M-sequence signal stored in the memory 66, and the data is overwritten in the memory 66. This type of synchronous addition process is repeated a fixed number of times (N times).

Alternatively, the A/D converted data may be stored directly in memory 66, and the synchronous addition process may be performed later. In this case, however, it may take time to perform the synchronous addition process on the huge amount of stored data, and a sufficient number of synchronous additions may not be possible due to limitations on the memory capacity of the memory that stores the data.

If the i-th data in memory 66 is d(i) and the synchronous addition value is D(n) (n = 0 to 1021), then D(n) = Σdv(2*511*m+n). Here, the sum symbol Σ is used to sum up m = 0 to 31.

The number of repetitions of the synchronous addition is stored in advance in the auxiliary storage unit 14. The number of repetitions of the synchronous addition may also be configured so that the operator sets the number of repetitions of the synchronous addition through the input unit 63.

In this way, the digital voltage signal Vb corresponding to the current Ib is input to the electrical impedance calculation unit 120 by the signal output unit 30 and the current measurement unit 20. On the other hand, the digital voltage signal Vp is input to the electrical impedance calculation unit 120 from the voltage measurement unit 40.

<Voltage measuring unit 40>
The voltage measurement unit 40 measures a voltage generated between predetermined parts of the subject's body E when a multi-frequency current is applied to the subject's body E by the signal output unit 30. The voltage measurement unit 40 has a voltage detection unit 44, a differential amplifier 43, a BPF 42, and an A/D converter 41.

The voltage detection unit 44 detects a voltage signal related to the voltage between the surface electrode Hp and the surface electrode Lp. The differential amplifier 43 functions as a voltage signal amplifier, and amplifies the voltage signal detected by the voltage detection unit 44 by a gain Gd to a voltage Vp of a magnitude used for electrical impedance measurement, and outputs the amplified voltage signal. The differential amplifier 43 is configured to be able to change the gain Gd in response to an instruction from the control unit 10. The differential amplifier 43 outputs the voltage Vp to the BPF 42.

The BPF 42 cuts a signal of a predetermined band from the input voltage signal Vp and outputs it to the A/D converter 41. The pass band of the BPF 42 can be appropriately selected according to the specifications of the body composition measuring device 1. The pass band of the BPF 42 can be set to, for example, approximately 1 kHz to 800 kHz.

The A/D converter 41 converts the analog voltage Vp into a digital voltage signal Vp according to a digital conversion command from the control unit 10. The digital voltage signal Vp is stored in the memory 66 as voltage data, synchronously added with the synchronous addition data up to one period before the M-sequence signal. Note that the synchronous addition of the voltage data is the same as that for the voltage signal Vb obtained by conversion from the current, so a detailed explanation is omitted.

The electrical impedance calculation unit 120 calculates the electrical impedance of the subject's body E based on the input digital voltage signals Vb and Vp based on the electrical impedance method. More specifically, the electrical impedance calculation unit 120 calculates the electrical impedance of the subject's body E using data based on the voltage signals Vb and Vp after the synchronous addition process has been repeated a specified number of times and stored in the memory 66. At this time, if the measurement signal contains many frequency components such as an M-series signal, the electrical impedance calculation unit 120 first performs a Fourier transform process on the voltages Vb and Vp, which are functions of time. This results in Vp(f) and Vb(f), which are functions of frequency. Note that if the measurement signal is a signal whose frequency changes from time to time, this process is not necessary because Vp(f) and Vb(f) are directly measured as functions of frequency. Next, the voltages Vp(f) and Vb(f) are averaged, and then the electrical impedance Z(f) for each frequency is calculated.

The electrical impedance calculation unit 120 stores the input digital voltage signals Vb, Vp and the calculated electrical impedance in the RAM 13, and outputs them to the impedance trajectory calculation unit 110, the judgment unit 130, and the body composition measurement unit 150. Hereinafter, the voltage signals Vb, Vp are also referred to as measurement data. The principle of the electrical impedance method will be described later.

The impedance locus calculation unit 110 calculates the center coordinates and radius of the impedance locus from the electrical impedance at each frequency input from the electrical impedance calculation unit 120. The impedance locus calculation unit 110 also calculates the resistance R∞ when the frequency of the probe current is ∞, the resistance R0 when the frequency of the probe current is 0, R∞/R0, and the critical frequency fc. The impedance locus calculation unit 110 outputs the impedance locus, R∞, R0, R∞/R0, and the critical frequency fc to the judgment unit 130, the body composition measurement unit 150, and the abnormality judgment unit 160.

The impedance locus calculation unit 110 calculates the impedance locus using the least squares method. The resistances R∞ and R0 can be calculated by determining the intersection of the calculated impedance locus and the reactance X=0. The critical frequency fc can be calculated from the frequency corresponding to the electrical impedance measurement values located on both the left and right sides of the point on the impedance locus where the reactance is smallest.

Figure 4 is a graph showing an example of an impedance locus. The horizontal axis of the graph shown in Figure 4 is resistance R, and the vertical axis is reactance X. In addition, black circles ("●") or white circles ("◯") are measurement points (measurement values) of electrical impedance measurement at each frequency. In the figure, black circles are measurement points of frequencies higher than the critical frequency fc (also called "high frequency"), and white circles are measurement points of frequencies lower than the critical frequency fc (also called "low frequency"). In the example shown in Figure 4, the dots at 350 KHz are measurement values measured when the highest frequency current was applied, and the dots at 2.5 KHz are measurement values measured when the lowest frequency current was applied.

The impedance locus is a curve calculated to fit the electrical impedance measurements at each frequency. Typically, the impedance locus is approximately a Cole-Cole arc.

When the frequency is very low and very high, the reactance X is essentially 0, and the electrical impedance Z is essentially equal to the resistance R. Therefore, among the intersections of the impedance locus and X=0, the one with the greater resistance is the resistance R0 when the frequency is 0, and the one with the smaller resistance is the resistance R∞ when the frequency is ∞. R0 is said to reflect the extracellular fluid volume, and R∞ is said to reflect the amount of water in the body.

The judgment unit 130 judges whether or not there is an abnormality in the electrical impedance measurement based on at least one of the distribution of the electrical impedance measurements at each frequency on the impedance locus and the size of the radius of the impedance locus.

When the judgment unit 130 judges that there is no abnormality in the electrical impedance measurement, it outputs an OK signal indicating "no abnormality" to the body composition measurement unit 150 and the notification unit 140. On the other hand, when the judgment unit 130 judges that there is an abnormality in the electrical impedance measurement, it outputs an NG signal indicating "abnormality" to the body composition measurement unit 150 and the notification unit 140.

The notification unit 140 does not issue a notification when an OK signal is input, and notifies the subject or the operator of the body composition measuring device 1 of an abnormality when an NG signal is input. The method of notifying the abnormality is not particularly limited. For example, the abnormality may be notified by a method of outputting an abnormality notification sound from the speaker 64, a method of displaying on the display unit 65 that an abnormality has occurred in the electrical impedance measurement, or a combination of these methods.

The body composition measurement unit 150 calculates and measures the body composition based on the electrical impedance calculation value, the impedance trajectory, and information about the subject input from the input unit 63. The body composition measurement unit 150 measures the body composition at least when an OK signal is input. Alternatively, the body composition measurement unit 150 may measure the body composition only when an OK signal is input, or may measure the body composition both when an OK signal is input and when an NG signal is input. Note that in this embodiment, an example will be described in which the body composition is measured only when an OK signal is input.

The body composition measurement unit 150 functions as a body composition information calculation unit and outputs the measured body composition to the display unit 65. The display unit 65 displays the measured body composition. If the judgment unit 130 outputs an NG signal to the notification unit 140, it is determined that there is an abnormality in the electrical impedance measurement, and a message is displayed on the display of the display unit 65 indicating that the body composition measurement has been stopped.

The body composition measurement unit 150 also outputs the measured body composition to the recording unit 62. The recording unit 62 records the measured body composition.

The method for measuring the body composition is not particularly limited, and any known method can be used. For example, the total body water content can be measured by regression analysis. Specifically, the conductor part of the human body, i.e., the water part of the body, is assumed to be a cylinder with a length L and a cross-sectional area S. In this case, the resistance of the conductor part of the human body is proportional to the length L and inversely proportional to the cross-sectional area S. Therefore, R=ρL/S, and when deformed, S=ρL/R. Substituting this into the volume V=LS, the volume V of the conductor part of the human body is measured as ρL ² /R. Therefore, the total body water content (TBW) can be measured by TBW=α+βL ² /R. Here, α and β are statistically determined constants. In addition, the accuracy of the measured total body water content can be improved by adding the human body characteristic data such as height to the above formula. Specifically, the total body water content (TBW) can be measured by TBW=α+βL ² /R+γW+δAGE, which allows more accurate measurement of the total body water content. Here, W is body weight and AGE is age. Note that fat-free mass (FFM) can also be measured using a similar method.

The abnormality determination unit 160 calculates an abnormality index, which is an index of abnormality of the impedance trajectory calculated by the impedance trajectory calculation unit 110. A specific method for calculating the abnormality index will be described later. If the abnormality index exceeds a predetermined specified value (first threshold value), the abnormality determination unit 160 determines that the impedance trajectory is abnormal, whereas if the abnormality index is equal to or less than the specified value, the abnormality determination unit 160 determines that the impedance trajectory is not abnormal. The specified value may be, for example, 0.004.

The effective value calculation unit 170 calculates a value related to the magnitude of the voltage signal Vp (hereinafter referred to as "V-POWER") and/or a value related to the magnitude of the voltage signal Vb corresponding to the current Ib (i.e., the magnitude of the current signal) (hereinafter referred to as "I-POWER"). V-POWER and I-POWER can be, for example, the effective value Vpa of the voltage signal Vp and the effective value Vba of the voltage signal Vb, respectively.

For example, the effective value calculation unit 170 uses data of the voltage signal Vp input from the voltage measurement unit after synchronous addition processing has been repeated a specified number of times, and calculates the V-POWER of the voltage signal Vp by performing digital signal processing on the data. The effective value calculation unit 170 also uses data of the voltage signal Vb input from the current measurement unit after synchronous addition processing has been repeated a specified number of times, and performs digital signal processing on the data to calculate the I-POWER of the voltage signal Vb. More specifically, the effective value calculation unit 170 calculates V-POWER and I-POWER by finding the root mean square (RMS) of all sampled data based on the definition of the effective value of an AC signal.

In contrast, in this embodiment, a current Ib consisting of only AC components is applied to the subject's body E via the capacitor of the output buffer 32. The effective value is equal to the standard deviation σ for AC signal data with no DC component and an average value of 0. Therefore, the effective value calculation unit 170 calculates V-POWER and I-POWER, respectively, by calculating the standard deviation σ of the data of the digital voltage signals Vp and Vb.

Here, it is desirable that V-POWER be as large as possible within the range that the circuit can process. For example, an upper threshold value for V-POWER can be set within a range in which almost all data falls within the range of ±3σ. If the resolution of the A/D converter 41 is 8 bits, V-POWER can be preferably set to a value between 20 and 40, and more preferably between 30 and 40.

The output buffer 32 has a limiting resistor that is sufficiently larger than the electrical resistance of the human body, and is configured to apply the measurement signal Ia through the limiting resistor so that the measurement signal Ia is essentially constant even if the subject being measured is changed to another subject. When the resolution of the A/D converter 21 is 8 bits, I-POWER is preferably set to a value between 20 and 40, and more preferably between 30 and 40.

On the other hand, I-POWER can change depending on the contact state of the surface electrodes attached to the subject's body E. Therefore, based on the measured I-POWER, the control unit 10 can detect abnormalities, such as one of the surface electrodes being measured becoming detached from the subject's body E.

The measurement condition determination unit 180 determines changeable measurement conditions of the body composition measuring device 1 based on at least one of V-POWER, I-POWER, and the abnormality index. Changeable measurement conditions in the body composition measuring device 1 can be, for example, the gain Gd of the differential amplifier 43, the Gi of the I/V converter 23, the frequency band Bw (or upper limit frequency) of the electrical impedance measurement, and the number of data points Np for creating the electrical impedance locus. However, the number of data points Np is determined according to the frequency band Bw. Also, the upper limit frequency is the upper limit frequency of the frequency band Bw. A method for determining the measurement conditions and specific examples will be described later.

In this embodiment, the body composition measuring device 1 is configured to be operable in any one of a first measurement mode, a second measurement mode, and a third measurement mode. The mode control unit 190 controls whether the measurement is performed in any one of the first measurement mode, the second measurement mode, and the third measurement mode.

The first measurement mode is a measurement mode in which the number of repetitions of the synchronous addition process performed by the electrical impedance measurement unit 50 on the voltage signal Vb obtained by converting the multi-frequency current Ib input from the current measurement unit 20 into a voltage and the data of the voltage signal Vp input from the voltage measurement unit 40 is a predetermined number (for example, the synchronous addition process of the synchronous addition data of the M-series signal one cycle before and the M-series signal for one cycle after is repeated a total of 128 times x 40 times. The 128 times of the process are performed to cancel the pseudo noise caused by the square wave, and the process of repeating it 40 times is performed because the more times it is repeated, the higher the removal rate of the asynchronous noise becomes). Hereinafter, the first measurement mode may also be called the normal mode. The second measurement mode is a measurement mode in which the number of repetitions is smaller than that of the first measurement mode, and the third measurement mode is a measurement mode in which the number of repetitions is greater than that of the first measurement mode. For example, the predetermined number of repetitions of the second measurement mode may be 128 times x 30 times, and the total number of repetitions of the third measurement mode may be 128 times x 50 times. The number of repetitions of the second measurement mode may be set as a multiple of the number of repetitions of the first measurement mode, and may be 2/3 times or 1/2 times. Similarly, the number of repetitions of the third measurement mode may be set as a multiple of the number of repetitions of the first measurement mode, and may be 3/2 times or 2 times. With respect to the number of repetitions of 128 times x 40 times, the number of 128 times may be increased or decreased, or the number of 40 times may be increased or decreased.

For example, the mode control unit 190 starts the measurement of the subject's body composition in the second measurement mode. When the abnormality determination unit 160 determines that the impedance trajectory in the second measurement mode is abnormal when the measurement is performed in the second measurement mode, i.e., when the abnormality index exceeds a specified value, the mode control unit 190 increases the number of repetitions of the synchronous addition process compared to the second measurement mode and performs the measurement again. The increment Δn in the number of repetitions is not particularly limited (for example, +1 time, +5 times, etc.).

Furthermore, when the abnormality determination unit 160 determines that the impedance locus in the first measurement mode is abnormal when the measurement is performed in the first measurement mode, the mode control unit 190 may perform measurement again in the third measurement mode. More specifically, the mode control unit 190 first performs measurement in the second measurement mode, and if the abnormality determination unit 160 determines that the impedance locus in the second measurement mode is abnormal, the mode control unit 190 transitions to measurement in the first measurement mode, and if the abnormality determination unit 160 determines that the impedance locus in the first measurement mode is abnormal, the mode control unit 190 transitions to measurement in the third measurement mode.

(Control method of body composition measuring device 1)
A method for controlling the body composition measuring device according to the present embodiment will be described below with reference to Figures 5 to 7B. Figure 5 is a flow chart illustrating the processing procedure of the main processing. The processing of the flow chart shown in the figure is realized by the CPU 11 executing a control program.

[Main processing]
As described above, the electrical impedance may vary depending on factors such as the subject's physique, body movement, and whether or not the arm is in contact with the armpit. Therefore, if the measurement conditions set are not suitable for measuring the subject's electrical impedance, the accuracy of the body composition measurement may not be sufficient. For example, if the subject moves a lot during measurement, if the subject is extremely swollen, or if the subject is extremely thin, the measurement of the electrical impedance may not be stable, and there is a high possibility that jumps in the measurement results may occur in the impedance trajectory. This is because if the subject is extremely swollen, the internal resistance may be significantly low, and if the subject is extremely thin, the surface resistance may be high.

Therefore, in this embodiment, a preliminary measurement (hereinafter referred to as a "preliminary measurement") is performed to determine the measurement conditions for the main measurement prior to the main measurement of the subject's body composition. In this specification, a preliminary measurement refers to a measurement that is performed to determine the measurement conditions for the main measurement that is performed after the preliminary measurement, and does not directly aim to calculate information about the body composition. Furthermore, a main measurement refers to a measurement that is performed according to the measurement conditions determined by the preliminary measurement, and calculates information about the body composition.

First, the control unit 10 sets the measurement conditions for the preliminary measurement (step S101). The control unit 10 sets each measurement condition to an initial value for the preliminary measurement. For example, the initial value of the gain Gd of the differential amplifier 43 can be set so that V-POWER is about 40 (approximately the maximum value). The initial value of the gain Gd of the differential amplifier 43 may start from the maximum value. The initial value of Gi of the I/V converter 23 can be set so that I-POWER is about 40 (approximately the maximum value). The initial value of the frequency band Bw for the electrical impedance measurement can be set, for example, to 2.5 kHz to 350 kHz. For example, the number of data points Np is set so that the frequency band Bw is measured every 2.5 kHz. When the frequency band Bw is, for example, 2.5 kHz to 350 kHz, the control unit 10 sets the number of data points Np to 350 kHz/2.5 kHz = 140 points.

Next, the control unit 10 performs a preliminary measurement to determine the measurement conditions for the main measurement (step S102). In this embodiment, the control unit 10 performs the preliminary measurement under conditions that involve fewer repetitions of synchronous addition than the main measurement. This reduces the time required for the preliminary measurement. In addition, in the preliminary measurement, the steps up to the calculation of I-POWER and V-POWER are performed, and the measurement conditions are determined without calculating the electrical impedance for each frequency, calculating the impedance locus, or calculating the body composition, thereby further reducing the time required for the preliminary measurement. Note that FIG. 6 shows a case where the preliminary measurement is completed with the steps up to the calculation of I-POWER and V-POWER.

In the preliminary measurement, when the abnormality index is below a specified value (preferably lower), the measurement conditions are selected such that V-POWER is maximized without exceeding a specified value (upper limit). Also, if any of the abnormality index, V-POWER, or I-POWER is inappropriate, the measurement conditions are reviewed. The specific processing procedure will be described later.

Next, the control unit 10 performs the main measurement (step S103). At this time, the control unit 10 sets the measurement conditions to the measurement conditions determined in the preliminary measurement, fixes the measurement conditions, and then performs the main body composition measurement.

[Preliminary measurement process]
Fig. 6 is a subroutine flowchart illustrating the details of the preliminary measurement (S102) process in the flowchart of Fig. 5. The process of the subroutine flowchart shown in Fig. 6 is realized by the CPU 11 executing a control program.

First, the signal output unit 30, which functions as a current input unit, applies a probe current using an M sequence to the subject (S201), and then the current detection unit and voltage detection unit detect the voltage between specific parts of the subject's body E and the current flowing (steps S202 and S203). The specific parts can be, for example, the hands and feet.

Next, the voltage signal amplifier (differential amplifier 43) amplifies the detected voltage (step S205). The voltage signal amplifier amplifies the voltage signal detected in step S203 to a voltage Vp that is suitable for measuring electrical impedance.

In parallel, the current-voltage converter (I/V converter 23) converts the detected current into a voltage (step S204). The current-voltage converter converts the current signal detected in step S202 into a voltage Vb used for measuring electrical impedance. The obtained voltage signal Vp and voltage signal Vb are filtered by the BPFs 42 and 22, respectively, to cut signals in a predetermined band including noise (steps S207 and S206). Furthermore, A/D conversion is performed on these data (steps S209 and S208), and synchronous addition is performed on the synchronously added data up to one period before the M-sequence signal and the A/D converted data, thereby averaging the voltage signal and the current signal (steps S211 and S210), thereby improving the S/N ratio. Thereafter, the effective value calculator 170 calculates V-POWER using the averaged voltage signal Vp and I-POWER using the averaged voltage signal Vb (steps S213 and S212).
In reality, the current input unit, voltage signal amplifier, current-voltage converter, and effective value calculator are implemented by hardware (electronic circuits), so the above steps S201 to S213 are performed simultaneously. That is, signal processing related to current and signal processing related to voltage are performed in parallel.

Next, the measurement condition determination unit 180 determines whether the measured voltage and current are appropriate (step S214). The measurement condition determination unit 180 determines whether the measured voltage Vp and current Ib are appropriate based on V-POWER and I-POWER. If the measured voltage Vp and current Ib are appropriate (step S214: YES), the measurement condition determination unit 180 determines the measurement conditions for this measurement (step S215) and ends the process (return). For example, if V-POWER and I-POWER are each in the range of 20 to 40 and the abnormality index is below a specified value, the measurement condition determination unit 180 determines that the measured voltage Vp and current Ib are appropriate. On the other hand, if at least one of V-POWER and I-POWER is outside the range of 20 to 40 and/or the abnormality index exceeds a specified value, the measurement condition determination unit 180 determines that the measured voltage Vp and current Ib are inappropriate.

On the other hand, if the measured voltage Vp and current Ib are not appropriate (step S214: NO), the measurement condition determination unit 180 changes the measurement conditions (step S216). The control unit 10 changes at least one of the measurement conditions and returns to the processing of step S201. As a change in the measurement conditions, the control unit 10 sets, for example, the gain Gd and/or the gain Gi to a value that is one step lower.

[Main measurement process]
Fig. 7A is a subroutine flowchart illustrating the details of the process of main measurement (S103) in the flowchart of Fig. 5, and Fig. 7B is a subroutine flowchart subsequent to Fig. 7A. The processes of the subroutine flowcharts shown in Fig. 7A and Fig. 7B are realized by the CPU 11 executing a control program.

First, the control unit 10 sets the measurement conditions set by the preliminary measurement (step S301). The mode control unit 190 also starts the measurement of the subject's body composition in the second measurement mode.

Next, in steps S302 to S310, the electrical impedance measuring unit 50 processes the current signal and voltage signal used to measure the electrical impedance of the subject's body. The control unit 10 performs steps S302 to S310. These processes are the same as the processes (steps S201 to S209) of the current signal and voltage signal used to measure the electrical impedance of the subject's body in the preliminary measurement process, so detailed explanations will be omitted. Next, for each of the voltage signal Vp and the voltage signal Vb, synchronous addition is performed between the synchronous addition data up to one cycle before the M-series signal and the A/D conversion data (steps S312 and S311). At this time, the number of repetitions of the synchronous addition (averaging number; N times) is the number set in the second measurement mode (for example, the synchronous addition process between the synchronous addition data of the M-series signal one cycle before and the M-series signal for the next cycle is performed 128 times x 30 times. At this time, the averaging number; N = 30 is considered in this specification). Then, I-POWER and V-POWER are calculated in the same manner as in the preliminary measurement process (steps S313 and S314).

Next, the electrical impedance measuring unit 50 calculates the electrical impedance of the subject's body E (step S317). More specifically, the electrical impedance measuring unit 50 performs Fourier transform processing on the voltage signals Vp and Vb, which are functions of time in steps S316 and S315, respectively, to convert them into functions of frequency. Then, based on Vp and Vb, which are functions of frequency, the electrical impedance measuring unit 50 calculates information about the electrical impedance for each frequency (step S317), and performs curve fitting using a least squares calculation means to calculate the impedance locus (step S318).

Next, the abnormality determination unit 160 calculates the abnormality index (step S319). The abnormality determination unit 160 calculates the abnormality index based on the impedance locus calculated in step S318. In this embodiment, the abnormality index is calculated as the variation in the impedance measurement value at each frequency for the impedance locus. In other words, the larger the abnormality index, the greater the variation and the lower the fitting accuracy of the measurement data, and the smaller the abnormality index, the less the variation and the higher the fitting accuracy of the measurement data.

More specifically, the anomaly determination unit 160 calculates the distance e(f) in a predetermined direction between the electrical impedance Z(f) measured at a frequency (f) and the impedance locus. The distance e(f) may be, for example, the distance in the radial direction of the impedance locus between the electrical impedance and the impedance locus, or the distance in the horizontal or vertical direction. For example, in the case of the radial direction, the distance e0(f) between the measured electrical impedance Z(f) and the impedance locus can be expressed as the following formula (1) using the distance d(f) between the electrical impedance Z(f) and the center of the impedance locus and the radius r.

e0(f)=d(f)−r…(1)
The abnormality determination unit 160 calculates the sum of squares of the calculated distances e0(f), Σe0(f) ² , as an abnormality index.

In addition, as shown in the following formula (2), taking into account the size of the subject's body E, the sum of ^squares of e0(f)/r, which is e0(f) divided by r, can be calculated as the abnormality index.

Σe1(f) ² =Σ{e0(f)/r} ² ...(2)
The radius r of the impedance locus varies greatly depending on the body type of the subject, that is, the size (length and cross-sectional area) of the body E. Therefore, the magnitude of e0(f) varies greatly depending on the height of the subject. By dividing e0(f) by the radius r, the dependency of the abnormality index on the size of the subject's body E can be suppressed. In other words, by using the above formula (1), the dependence of the abnormality index on the size of the subject's body E can be suppressed. In either case, the abnormality index can be calculated accurately.

Furthermore, as shown in the following formula (3), instead of dividing e0(f) by the radius r, the sum of squares of e0(f)/h, which is obtained by dividing e0(f) by the subject's height h, can be calculated as the abnormality index. ^Σe2 (f)

Σe2(f) ² =Σ{e0(f)/h} ² ...(3)
In this manner, the abnormality determining unit 160 calculates, for example, Σe0(f) ² , Σe1(f) ² , or Σe2(f) ² as the abnormality index.

Next, the abnormality determination unit 160 determines whether the calculated abnormality index is equal to or less than a specified value (step S320). If the abnormality index is equal to or less than a specified value (step S320: YES), the control unit 10 determines whether there is an abnormality in the electrical impedance measurement (step S321). Details of the determination method for determining whether there is an abnormality in the electrical impedance measurement will be described later. If there is no abnormality in the electrical impedance measurement (step S321: YES), the body composition measurement unit 150 calculates and displays the body composition of the subject (step S322). The body composition measurement unit 150 calculates information about the body composition based on information about the electrical impedance calculated in step S317, the resistance R∞ when the frequency of the probe current is ∞ and the resistance R0 when the frequency of the probe current is 0, which are obtained from the impedance locus calculated in step S318, and information about the subject (particularly, gender, age, height, and weight). The body composition measurement unit 150 transmits the measurement results to the display unit 65, and the display unit 65 displays the measurement results on the display. Additionally, the recording unit 62 stores the measurement results.

On the other hand, if there is an abnormality in the electrical impedance measurement (step S321: NO), the control unit 10 stops the measurement of body composition, notifies the abnormality (step S323), and ends the process (return). For example, the control unit 10 sends a warning message to the display unit 65 indicating that there is an abnormality in the electrical impedance measurement, and the display unit 65 displays the warning message on the display. This prevents an operator such as a medical professional from misinterpreting the body composition of the subject's body E.

On the other hand, when the abnormality index exceeds the specified value (step S320: NO), the control unit 10 increases the number of averagings (the number of repetitions in synchronous addition) in steps S311 and S312 (step S324). For example, the control unit 10 increases the total number of averagings from 128 times × N times to 128 times × (N + Δn) times. Alternatively, the mode control unit 190 switches the measurement mode from the second measurement mode to the first measurement mode. As a result, when the increment Δn is 10 times, the total number of averagings increases from 128 times × N times to 128 times × (N + 10) times. Also, when the abnormality index exceeds the specified value in the first measurement mode, the mode control unit 190 switches the measurement mode from the first measurement mode to the third measurement mode. As a result, the total number of averagings increases by another 128 times × 10 times. If the abnormality index exceeds a specified value, instead of or in addition to increasing the total number of averaging attempts, the user may be notified that there is an abnormality in the measurement by displaying a message on the display unit or by sound or voice.

Next, the control unit 10 determines whether the total number of averaging times is equal to or greater than the maximum number (step S325). The maximum number may be, for example, 128 times x 80 times, or may be 128 times x 120 times. If the total number of averaging times is equal to or greater than the maximum number (step S325: YES), the control unit 10 stops the body composition measurement, notifies the user of an abnormality (step S326), and ends the process (return). The control unit 10 determines that the accuracy of the measurement data is insufficient, and stops the body composition measurement. The control unit 10 also notifies the operator that measurement data of sufficient accuracy cannot be obtained. Alternatively, the control unit 10 may control the display unit 65 to display the measurement results as reference values without stopping the body composition measurement.

On the other hand, if the total number of averaging times is less than the maximum number (step S325: NO), the control unit 10 transitions to the electrical impedance measurement process (steps S302 to S319) again. In this way, the control unit 10 performs electrical impedance measurement by gradually increasing the total number of averaging times within a range in which the total number of averaging times does not exceed the maximum number, thereby minimizing the total number of averaging times while keeping the variation in the impedance measurement values within a specified range.

[Process for determining the presence or absence of an abnormality in electrical impedance measurement (step S321)]
8 is a subroutine flowchart illustrating a process for determining whether or not there is an abnormality in the electrical impedance measurement. The process of the subroutine flowchart shown in the figure is realized by the CPU 11 executing a control program.

In the following step S401, the critical frequency fc is used as an index to evaluate the bias in the distribution of impedance measurement values at each frequency relative to the impedance locus to determine whether there is an abnormality in the electrical impedance measurement. In step S402, R∞/R0 is used as an index to determine whether there is an abnormality in the electrical impedance measurement based on whether the magnitude of the impedance locus is within the normal range. Note that steps S401 and S402 may be determined in any order. The following describes an example in which steps S401 and S402 are performed in that order.

The judgment unit 130 judges whether or not there is an abnormality in the critical frequency fc (step S401). In this step, the critical frequency fc is used as an index to evaluate the bias in the distribution of impedance measurement values at each frequency on the impedance locus to judge whether or not there is an abnormality in the critical frequency fc.

The judgment unit 130 judges whether the critical frequency fc calculated by the impedance locus calculation unit 110 is within a predetermined range. If the critical frequency fc is within the predetermined range, the judgment unit 130 judges that there is no abnormality in the critical frequency fc (step S401: YES) and proceeds to step S402. On the other hand, if the critical frequency fc is outside the predetermined range, the judgment unit 130 judges that there is an abnormality in the critical frequency fc (step S401: NO). Therefore, the judgment unit 130 judges that there is an abnormality in the electrical impedance measurement (step S404) and ends the process (return).

Normally, for a healthy person, the critical frequency fc is around 50 kHz. However, there are individual differences in the critical frequency fc. For this reason, it is preferable that the lower limit of the critical frequency fc is about 5 to 20 kHz, and the upper limit is 90 to 150 kHz. In other words, in step S401, the allowable range of the critical frequency fc is set to about 5 to 150 kHz, and more preferably to about 10 to 100 kHz.

When it is determined that there is no abnormality in the critical frequency fc (step S401: YES), the determination unit 130 determines whether there is an abnormality in R∞/R0 (step S402). In this step, using R∞/R0 as an index, it is determined whether there is an abnormality in the electrical impedance measurement based on whether the magnitude of the impedance locus is within a normal range. The determination unit 130 determines whether R∞/R0 is within a predetermined range. When R∞/R0 is within the predetermined range, the determination unit 130 determines that there is no abnormality in the value R∞/R0 (step S402: YES) and proceeds to step S403, where it determines that there is no abnormality in the electrical impedance measurement.

On the other hand, when the value R∞/R0 is outside the predetermined range, the judgment unit 130 judges that there is an abnormality in R∞/R0 (step S402: NO). Therefore, the judgment unit 130 judges that there is an abnormality in the electrical impedance measurement (step S404) and ends the process (return).

Normally, for a healthy individual, the value of R∞/R0 is approximately 0.6 to 0.8 (60% to 80%). For this reason, in step S403, the allowable range of R∞/R0 can be set to approximately 0.85 to 0.9 or less (approximately 0% to 90%).

In this embodiment, only the example of determining only the value of R∞/R0 in step S402 has been described, but it may be configured to determine whether or not each of the values of R∞ and R0 is within an appropriate range, in addition to the value of R∞/R0. In other words, it may be configured to determine that there is an abnormality in the measurement of electrical impedance when R∞ or R0 becomes abnormally large or abnormally small. For example, the determination index may be that R∞ and R0 are both >0Ω. Also, the determination index may be that R∞ and R0 are each within the range of 100 to 1000Ω.

In this embodiment and in FIG. 6 and FIG. 7A, the measurement conditions are determined using I-POWER and V-POWER as indices in the preliminary measurement, and the measurement results are displayed or abnormalities during measurement are notified based on the abnormality index and the judgment of the presence or absence of an abnormality in the electrical impedance measurement in the main measurement, but this is not limited to the configuration. That is, in the preliminary measurement, in addition to I-POWER and V-POWER, the measurement conditions may be determined by adding the abnormality index and the judgment of the presence or absence of an abnormality in the electrical impedance measurement, as in the main measurement. Also, in the main measurement, I-POWER and V-POWER may be added to the judgment index, or the judgment may be made based on any one or more combinations of I-POWER, V-POWER, the abnormality index, and the judgment of the presence or absence of an abnormality in the electrical impedance measurement. Furthermore, the judgment of the presence or absence of an abnormality in the electrical impedance measurement may also be made based on any one or more combinations of the critical frequency fc, R∞/R0, and the respective values of R∞ and R0.

[Measurement principle using electrical impedance method]
FIG. 9 is a schematic diagram illustrating the flow of current (current signal) in cells in a living organism according to the frequency, and FIG. 10 is a schematic electrical equivalent circuit diagram of the living organism shown in FIG.

Bioelectrical impedance analysis is a method for measuring (or estimating) a subject's body composition, such as the distribution of body water, body fat percentage, and body fat mass, from bioelectrical impedance. Bioelectrical impedance is composed of the resistance of the body to the electric current carried by ions in the body, and reactances associated with various types of polarization processes produced by cell membranes, tissue interfaces, and non-ionized tissues.

Capacitance, which is the inverse of reactance, mainly causes a time delay in the current, creating a phase shift. This phase shift can be geometrically quantified as the electrical phase angle, which is the arc tangent of the ratio of reactance to resistance. The magnitude of bioelectrical impedance Z is defined as ^Z2 = ^R2 + ^X2 , where R is resistance and X is reactance.

Bioelectrical impedance Z, resistance R, reactance X, and electrical phase angle Φ are frequency dependent. As shown in FIG. 9, when the frequency of the current is very low, the bioelectrical impedance Z at the cell membrane and tissue interface becomes very high. Therefore, the current does not flow through the cell membrane or tissue interface, but only through the extracellular fluid. Therefore, the measured bioelectrical impedance Z is substantially equal to the resistance R.

As the frequency of the current increases, the current (low frequency components) flows through cell membranes and tissue interfaces. This causes the reactance X to increase and the phase angle Φ to widen. However, when the frequency of the current exceeds the critical frequency fc, the capacitive performance of the cell membranes and tissue interfaces is lost. Therefore, when the frequency of the current (high frequency components) exceeds the critical frequency fc and becomes even higher, the reactance X decreases. When the frequency of the current becomes very high, the bioelectrical impedance Z becomes substantially equal to the resistance R again. Note that the "critical frequency" refers to the frequency at which the reactance is maximum.

As shown in Figure 10, the equivalent circuit of the human body is composed of a circuit in which the cell membrane capacitance Cmk and intracellular fluid resistance Rik are connected in series, and a parallel circuit with the extracellular fluid resistance Re.

When the current frequency is low, the current flows mainly through the extracellular space. Therefore, impedance Z is substantially equal to the extracellular fluid resistance Re. On the other hand, when the current frequency is high, the current essentially passes through the cell membrane. Therefore, the cell membrane capacitance Cm is considered to be essentially short-circuited. Therefore, when the current frequency is high, impedance Z is substantially equal to the combined resistance Ri·Re/(Ri+Re). Here, Cm and Ri refer to the combined capacitance and combined resistance of Cmk and Rik for the entire tissue.

Therefore, the extracellular fluid resistance Re can be obtained by applying a low-frequency current and measuring the electrical impedance of the subject's body. Intracellular fluid resistance Ri can be obtained based on Z = Ri·Re/(Ri+Re) from the obtained extracellular fluid resistance Re and the electrical impedance of the subject's body when a high-frequency current is applied. The subject's body composition value can then be estimated based on the obtained intracellular fluid resistance Ri and extracellular fluid resistance Re. The method for measuring the subject's body composition is not particularly limited, and any conventionally known method can be used.

In this specification, "body composition" refers to data related to the composition of body E in general. For example, "body composition" includes the amount of body composition, the ratio of a specific composition to body E, and the distribution of a specific composition to body E. "Composition" refers to what constitutes body E, and specific examples of the composition include body water, intracellular fluid, extracellular fluid, protein, fat, and calcium. Specific examples of body composition include body fat percentage, body fat weight contained in the subject's body E, lean mass (muscle mass), phase angle (muscle quality), body water distribution, bone density, skeletal muscle mass, fat-free index, skeletal muscle mass index, and edema rate. Specific examples of body water distribution include intracellular fluid volume, extracellular fluid volume, and body water volume. In the above, body water volume is the sum of intracellular fluid volume and extracellular fluid volume.

<Effects of the First Embodiment>
The body composition measuring device 1 of the first embodiment described above provides the following advantageous effects.

The body composition measuring device 1 performs electrical impedance measurement by gradually increasing the number of averagings (number of repetitions of synchronous addition) within a range in which the number of averagings does not exceed the maximum number. This makes it possible to minimize the number of repetitions of the synchronous addition process while keeping the variation in the impedance measurement values within a specified range. This makes it possible to prevent or suppress the time required for averaging the current (converted into a voltage signal for use during impedance measurement) and the voltage signal from being longer than necessary for the measurement accuracy. This makes it possible to minimize the measurement time of the body composition measuring device 1. As a result, when the body composition measuring device 1 is a portable battery-powered device, battery power consumption can be reduced.

The body composition measuring device 1 also determines measurement conditions suitable for the subject in a preliminary measurement, and measures the subject's body composition in the main measurement according to the determined measurement conditions. This makes it possible to reduce variation in the measurement results of the subject's body composition due to factors such as the subject's physique, body movement, whether or not there is contact between the arms and armpits, and whether or not there is contact between the thighs of both legs. Furthermore, because the body composition measuring device 1 is configured to minimize the measurement time, it is possible to reduce the possibility of the subject's body movement or contact between the arms and armpits during measurement.

Second Embodiment
In the second embodiment, a case will be described in which a preliminary measurement is performed prior to the main measurement, and in addition, if the voltage and current measured in the main measurement are not appropriate, the measurement conditions are changed. In order to avoid duplication, detailed descriptions of the same configuration as in the first embodiment will be omitted.

FIG. 11A is a subroutine flowchart illustrating the details of the main measurement (S103) process in the second embodiment, and FIG. 11B is a subroutine flowchart following FIG. 11A. The process of the subroutine flowcharts shown in FIG. 11A and FIG. 11B is realized by the CPU 11 executing a control program.

The processes in steps S501 to S523 are the same as steps S301 to S317 in FIG. 7A and steps S318 to S320 and S324 to S326 in FIG. 7B in the first embodiment, so detailed descriptions are omitted. In addition, the processes in steps S528 to S530 are the same as steps S321 to S323 in FIG. 7B, so detailed descriptions are omitted.

In this embodiment, in step S524, the magnitude of the voltage signal Vp and the voltage signal Vb corresponding to the current Ib are calculated. Step S524 is the same as the processing in steps S212 and S213 in FIG. 6 of the first embodiment, so a detailed description is omitted.

In step S525, the measurement condition determination unit 180 determines whether the measured voltage and current are appropriate. Based on V-POWER, I-POWER, and the abnormality index, the measurement condition determination unit 180 determines whether the measured voltage Vp and current Ib are appropriate. If the measured voltage Vp and current Ib are appropriate (step S525: YES), the measurement condition determination unit 180 maintains the measurement conditions for this measurement (step S526) and proceeds to the processing of step S528. For example, the measurement condition determination unit 180 determines that the measured voltage Vp and current Ib are appropriate when V-POWER and I-POWER are each in the range of 20 to 40 and the abnormality index is equal to or less than a specified value. The specified value of the abnormality index may be, for example, 0.004.

In this way, the control unit 10 can perform the main measurement multiple times in succession during one measurement of the subject's body composition. In this case, the measurement condition determination unit 180 maintains the measurement conditions so that the measurement conditions during one main measurement are the same as the measurement conditions for the next main measurement.

On the other hand, if the measured voltage Vp and current Ib are not appropriate (step S525: NO), the measurement condition determination unit 180 changes the measurement conditions (step S527). The control unit 10 changes at least one of the measurement conditions and returns to the processing of step S502. As a change in the measurement conditions, the control unit 10 sets, for example, the gain Gd and/or the gain Gi to a value that is one step lower.

In the above example, a case where a preliminary measurement is performed is described, but the present invention is not limited to such a case. It is also possible to configure the device to change the measurement conditions if the voltage and current measured in the main measurement are not appropriate, without performing a preliminary measurement.

<Effects of the Second Embodiment>
The body composition measuring device 1 of the second embodiment described above provides the following effects in addition to the effects of the first embodiment.

The body composition measuring device 1 changes the measurement conditions depending on whether the voltage Vp and current Ib measured in this measurement are appropriate, so it is possible to reduce variation in the measurement results of the subject's body composition due to factors such as the subject's physique, body movement, whether there is contact between the arms and armpits, and whether there is contact between the thighs of both legs.

Third Embodiment
In the third embodiment, during the main measurement, the control unit 10 performs the main measurement operation multiple times, and the control unit 10 also functions as a measurement result excluding unit, and a case will be described in which the resistance R∞ when the frequency of the probe current is ∞ and the resistance R0 when the frequency of the probe current is 0, which are calculated by the impedance locus calculation unit 110 in each of the multiple main measurements, are excluded from the inappropriate ones (hereinafter also referred to as "outliers"). The reason for excluding inappropriate measurement results is as follows. For example, since a subject with edema has low resistance throughout the body, it is difficult to determine optimal measurement conditions, and the resistance is prone to fluctuations due to body movement, etc. Therefore, it is useful to perform body composition measurement multiple times, exclude inappropriate measurement results, and average the remaining appropriate measurement results. In order to avoid duplication of explanation, detailed explanation of the same configuration as in the first embodiment will be omitted.

Figure 12 is a subroutine flowchart illustrating the details of the main measurement (S103) process in the third embodiment. The process of the subroutine flowchart shown in Figure 12 is realized by the CPU 11 executing a control program.

The control unit 10 can remove outliers, for example, using any of the following methods (a) to (c).

(a) Method for Removing Outliers Using V-POWER, I-POWER, and Anomaly Indicators
First, in step S601, the control unit 10 sets the measurement conditions set by the preliminary measurement. Next, in step S602, the main measurement is performed. This main measurement is repeated a preset number of times (L times). There is no limit to the number of times, but it may be set to, for example, 3 to 5 times. Each main measurement of the main measurement performed multiple times is the same as the processing of steps S301 to S326 in FIG. 7 of the first embodiment, so detailed explanations are omitted. Note that steps S603 and S604 in FIG. 12 are the same as steps S313 and S314 in FIG. 7A. Steps S605 and S608 in FIG. 12 are the same as steps S318 and S319 in FIG. 7B. In addition, in steps S606 and S607 in FIG. 12, the resistance R∞ when the frequency of the probe current is ∞ and the resistance R0 when the frequency of the probe current is 0 are calculated, but these are also obtained from the calculated impedance locus in the same manner as step S318 in FIG. 7B.

Next, in step S609, the measurement result exclusion unit excludes, as outliers, R∞ and R0 obtained from main measurements that are determined to be inappropriate among the L main measurements. Then, in step S610, the remaining R∞ and R0 are used to calculate the average values of R∞ and R0. The body composition measurement unit 150 then calculates the body composition using the average values of R∞ and R0. The measurement result exclusion unit excludes inappropriate main measurements from the multiple main measurements performed based on at least one of V-POWER, I-POWER, and the abnormality index. For example, the measurement result exclusion unit excludes, as outliers, R∞ and R0 obtained from main measurements in which the abnormality index exceeds a specified value (e.g., 0.004) among the L measurement results stored in RAM 13.

Next, in step S611, the control unit 10 displays the body composition measurement results obtained in step S610, the presence or absence of outliers, and the fluctuation error between R0 and R∞. The presence or absence of outliers may be indicated by the number of main measurements that did not include outliers relative to the set number of loops of the main measurement. That is, if two measurements determined to be outliers were included in a measurement set with L=5, it may be displayed as 3/5. The fluctuation error between R0 and R∞ may also be calculated using the fluctuation error of R∞ and R0 used in the body composition measurement.
(b) Method of Removing Outliers Using Mean Value μ and Standard Deviation σ of Measurement Results
The control unit 10 calculates the average value μ and the standard deviation σ for each of the measurement results of R0 and R∞ obtained for the number of measurements.

(b-1) The control unit 10 excludes the Kth measurement result from the multiple measurements of R0 and R∞, and calculates the average value μ and standard deviation σ from the remaining measurement results.

(b-2) The control unit 10 compares the Kth measurement result for each of R0 and R∞ with the average value μ calculated in (b-1) above, and if the measurement data is more than three times the standard deviation σ (i.e., 3σ) away from the average value μ, it is determined to be an outlier.

(b-3) The control unit 10 executes the above processes (b-1) and (b-2) in sequence for K=1 to the number of measurements.
<(c) Removing outliers using the quartiles of the measurement results (c-1) The control unit 10 arranges the measurement results of R0 and R∞ in order from largest to smallest, and determines the measurement results that correspond to one-quarter (upper quartile) and three-quarters (lower quartile) of the total.

(c-2) Add 1.5 times the difference between these two quartiles to the upper quartile, and any measurement greater than this is considered an outlier.

(c-3) Similarly, subtract 1.5 times the difference from the lower quartile and determine any measurement results smaller than that as outliers.

In this manner, in this embodiment, the main measurement is performed multiple times consecutively in one measurement of the subject's body composition, and the body composition measurement unit 150 calculates the final measurement result of the subject's body composition using one or more measurement results related to the remaining body composition after inappropriate calculation results are excluded by the measurement result exclusion unit.

Although the above describes a case where the control unit 10 removes outliers using any one of the above methods (a) to (c), the present invention is not limited to such a case. The control unit 10 may be configured to remove outliers using a combination of two or more of the above methods (a) to (c). The control unit 10 may also be configured to remove outliers using a method other than the above methods (a) to (c).

Furthermore, although the above describes a case where calculations are performed to determine whether or not each of R0 and R∞ is an outlier, multiple calculation results of body composition may be calculated the same number of times (L times) that the main measurement is repeated, and the mean value μ and standard deviation σ may be used to remove any body composition results that are outliers, and the remaining body composition results may be used to calculate the final measurement result of the subject's body composition. Similarly, multiple calculation results of body composition may be calculated, outliers may be removed using quartiles, and the remaining body composition results may be used to calculate the final measurement result of the subject's body composition. Furthermore, these methods may be combined.

<Verification experiment of measurement accuracy>
FIG. 13 is a conceptual diagram showing the state of use of the body composition measuring device 1 in a verification experiment of measurement accuracy using a pig.

The inventors conducted a verification experiment on the measurement accuracy using pigs, which have low resistance values throughout the body, as an evaluation system simulating subjects with extreme swelling.

In the verification experiment, surface electrodes Hp, Hc and surface electrodes Lp, Lc were attached to the right front leg and buttocks of the pig, respectively, and the body composition measuring device 1 was connected to the surface electrodes Hp, Hc, Lp, Lc by cables, and the pig's electrical impedance was measured. In the measurement using a conventional body composition measuring device that does not have the function of setting measurement conditions by preliminary measurement, the gain Gd was 8 times, but in the body composition measuring device of this embodiment that has the function of optimizing measurement conditions by preliminary measurement, the gain Gd during measurement was 12 times.

In this verification experiment, the measurement was repeated five times in both the conventional body composition measuring device and the body composition measuring device of this embodiment, and the results were compared. In the body composition measuring device of this embodiment, the measurement was repeated five times using a function for repeatedly performing the measurement. In the conventional body composition measuring device, which does not have the function for repeating the measurement, this was substituted by fixing the measurement conditions and performing body composition measurement five times in a row.

Table 1 below shows the results of a comparison of the average values, deviations, and error rates of R0, R∞, and abnormality index for a conventional body composition measuring device and the body composition measuring device 1 of this embodiment. In Table 1, the averages of R0, R∞, and abnormality index are the results of averaging five measurements taken under the same measurement conditions. In addition, the body composition measuring device 1 of this embodiment was evaluated three times under the same conditions.

For the body composition measuring device 1 of this embodiment, good results were obtained for the error rate of R0, the error rate of R∞, and the average abnormality index.

On the other hand, with conventional body composition measuring devices, the error rates of R0 and R∞ are low, but the average abnormality index exceeds 1.0, so fitting of the measurement data on the impedance locus is insufficient.

As such, the results of the above verification experiments confirmed that the body composition measuring device 1 of this embodiment has higher measurement accuracy than conventional body composition measuring devices.

<Verification experiment of measurement time>
Fig. 14A is a graph illustrating the results of confirming V-POWER in a verification experiment of the measurement time, and Fig. 14B is a graph illustrating the results of confirming I-POWER in a verification experiment of the measurement time. Fig. 15A is a graph illustrating the results of confirming the fluctuation error (%) of R0 in a verification experiment of the measurement time, and Fig. 15B is a graph illustrating the results of confirming the fluctuation error (%) of R∞ in a verification experiment of the measurement time. Fig. 15C is a graph illustrating the results of confirming the average value of the abnormality index in a verification experiment of the measurement time.

The inventors conducted a verification experiment on the measurement time using a pig with low resistance throughout the body as an evaluation system simulating a subject with extreme swelling. The attachment positions of the surface electrodes Hp, Hc, Lp, and Lc were the same as those in the verification experiment on the measurement accuracy (Figure 13).

The measurement time was 59.71 ± 0.08 seconds in normal mode (i.e., a mode in which synchronous addition is repeated 128 times x 40 times, and the number of repetitions that increases or decreases between measurement modes (the number of repetitions of the averaging process that is performed because the more the number, the higher the rate of removal of asynchronous noise) is 40 times). On the other hand, the measurement time in 2/3 mode (a measurement mode in which the number of averaging times is 27 times, which is roughly 2/3 of the normal mode (equivalent to 67% when the number of averaging times in the normal mode is 100%)) was 39.00 ± 0.07 seconds (65.3%). Similarly, the measurement time in 1/2 mode (a measurement mode in which the number of averaging times is 20 times, which is 1/2 of the normal mode (equivalent to 50% when the number of averaging times in the normal mode is 100%)) was 28.67 ± 0.05 seconds (48.0%).

In addition, the results of checking V-POWER in the verification experiment of the measurement time confirmed that there was no abnormality in the measured voltage signal Vp. Specifically, as shown in FIG. 14A, measurements were performed five times for each of the normal mode, 2/3 mode (2/3 hours), and 1/2 mode (1/2 hour), and the results of measuring V-POWER were all within the range of 30 to 40. Note that the same evaluation was performed again for the 1/2 mode (1/2 hour) for which there was concern that the accuracy would be adversely affected due to the reduced number of averaging (1/2 hour circle 2 in FIG. 14A), but the same results were obtained as the first time (1/2 hour circle 1 in FIG. 14A). From this result, it became clear that there was no problem with V-POWER in either the 2/3 mode (2/3 hours) or the 1/2 mode (1/2 hour).

In addition, the I-POWER was checked in the measurement time verification experiment, and it was confirmed that there was no abnormality in the measured current signal Ib. As shown in Figure 14B, measurements were performed five times for each of the normal mode, 2/3 mode (2/3 hours), and 1/2 mode (1/2 hour), and the I-POWER measurements were all within the range of 30 to 40. In addition, the same evaluation was performed again for the 1/2 mode (1/2 hour) for which there was concern that the accuracy would be adversely affected due to the reduced number of averaging times (1/2 hour circle 2 in Figure 14B), but the same results were obtained as in the first evaluation (1/2 hour circle 1 in Figure 14B). From this result, it was clear that there was no problem with I-POWER in either the 2/3 mode (2/3 hours) or the 1/2 mode (1/2 hour).

In addition, the R0 fluctuation error (%) was checked in a verification experiment of the measurement time, and it was confirmed that there was no abnormality in the calculated R0 fluctuation error. Specifically, as shown in FIG. 15A, five measurements were performed twice each in normal mode (indicated as "none" in FIG. 15A), 2/3 mode (indicated as "2/3 times" in FIG. 15A), and 1/2 mode (indicated as "1/2 times" in FIG. 15A), and the R0 fluctuation error (error rate) was calculated, and all were below the 2% set as the standard value. From this result, it was clear that there was no problem with the measurement accuracy of R0 in either 2/3 mode (2/3 hours) or 1/2 mode (1/2 hours).

In addition, the R∞ fluctuation error (%) was checked in a verification experiment of the measurement time, and it was confirmed that there was no abnormality in the calculated R∞ fluctuation error. Specifically, as shown in FIG. 15B, five measurements were performed twice each in normal mode (indicated as "none" in FIG. 15B), 2/3 mode (indicated as "2/3 times" in FIG. 15B), and 1/2 mode (indicated as "1/2 times" in FIG. 15B), and the R∞ fluctuation error (error rate) was calculated, and all were below the 2% set as the standard value. From this result, it was clear that there was no problem with the R∞ measurement accuracy in either 2/3 mode (2/3 hours) or 1/2 mode (1/2 hours).

In addition, the average value of the abnormality index was checked in the measurement time verification experiment, and it was confirmed that there was no abnormality in the calculated average value of the abnormality index. Specifically, as shown in FIG. 15C, five measurements were performed twice for each of the normal mode (indicated as "none" in FIG. 15C), 2/3 mode (indicated as "2/3 times" in FIG. 15C), and 1/2 mode (indicated as "1/2 times" in FIG. 15C), and the average value of the abnormality index was calculated. All of the results were below the standard value of 0.004. This result made it clear that there was no problem with the calculation accuracy of the impedance locus in either the 2/3 mode (2/3 hours) or the 1/2 mode (1/2 hours).

As such, the results of the above verification experiments confirmed that the body composition measuring device 1 of this embodiment can significantly reduce the measurement time while maintaining the same measurement accuracy as conventional body composition measuring devices.

<Effects of the Third Embodiment>
The body composition measuring device 1 of the third embodiment described above provides the following effects in addition to the effects of the first and second embodiments.

The body composition measuring device 1 calculates the final measurement result by eliminating outliers from the measurement results, thereby improving the measurement accuracy of the subject's body composition.

As described above, the body composition measuring device, control method, and control program of the present invention have been described in the embodiments. However, it goes without saying that a person skilled in the art can make additions, modifications, and omissions to the present invention as appropriate within the scope of its technical concept.

For example, the system may be configured to calculate electrical admittance and admittance locus instead of or in addition to electrical impedance and impedance locus. Furthermore, the attachment locations of surface electrodes are not limited to hands and feet.

The control program may be provided by a computer-readable recording medium such as a USB memory, flexible disk, or CD-ROM, or may be provided online via a network such as the Internet. In this case, the program recorded on the computer-readable recording medium is usually transferred to and stored in memory or storage. The control program may be provided, for example, as a standalone application software, or may be incorporated into the software of each device as a function of the server.

In addition, in the embodiment, some or all of the processing executed by the control program may be replaced with hardware such as a circuit.

In addition, as for the number of repetitions of the synchronous addition, in the normal mode, the synchronous addition process of the synchronous addition data of the M-sequence signal of one cycle before and the M-sequence signal of one cycle after the next is performed 128 times x 40 times, but this is not limited to this. The number of 128 processes performed to cancel the pseudo-noise due to the square wave can also be freely set. In addition, the number of processes performed to cancel the pseudo-noise due to the square wave may be set according to the M-sequence generator or square wave generator of the signal output unit, and in this embodiment, it may be set to 32 times or a number that is a multiple of 32 times. Furthermore, the number of repetitions of the synchronous addition process performed to cancel the pseudo-noise due to the square wave may be increased or decreased between measurement modes.

1. Body composition measuring device,
10 control unit,
20 current measuring unit,
21 A/D converter,
22 BPF,
23 I/V converter,
24 current detection unit,
30 signal output unit,
31 measurement signal generator,
32 output buffer,
40 voltage measuring unit,
41 A/D converter,
42 BPF,
43 differential amplifier,
44 voltage detection unit,
50 Electrical impedance measuring unit,
62 recording unit,
63 input unit,
64 speakers,
65 display unit,
66 memory,
110 impedance locus calculation unit,
120 Electrical impedance calculation unit,
130 Judgment section,
140 Notification unit,
150 Body composition measurement section,
160 Abnormality determination unit,
170 voltage/current calculation unit,
180 Measurement condition determination unit,
190 Mode control unit.

Claims (9)

A body composition measurement device that measures a body composition of a subject according to measurement conditions, comprising:
a current applying unit that applies a plurality of probe currents having different frequencies to the body of the subject;
a voltage detection unit that detects a voltage signal related to a voltage generated between predetermined parts of the body of the subject when the plurality of probe currents are applied to the body of the subject by the current application unit;
a current detection unit that detects a current signal related to a current flowing through the body of the subject when the plurality of probe currents are applied to the body of the subject by the current application unit;
a voltage signal amplifier that amplifies the voltage signal detected by the voltage detector to a level used for measuring electrical impedance;
a current-voltage converter that converts the current signal detected by the current detector into a voltage signal having a magnitude used for electrical impedance measurement; and an electrical impedance calculator that calculates information regarding electrical impedance for each frequency based on the voltage signal amplified by the voltage signal amplifier and the voltage signal converted by the current-voltage converter.
an impedance locus calculation unit that calculates an impedance locus based on information about the electrical impedance for each frequency calculated by the electrical impedance calculation unit;
a body composition information calculation unit that calculates information regarding a body composition of the subject based on the impedance locus calculated by the impedance locus calculation unit;
an abnormality determination unit that determines whether the impedance locus calculated by the impedance locus calculation unit is abnormal;
a mode control unit that controls whether to use a first measurement mode in which the total number of times that the voltage signal amplified by the voltage signal amplifier and the voltage signal converted by the current-to-voltage converter are averaged by the electrical impedance calculation unit is a predetermined number, or a second measurement mode in which the total number of times that the voltage signal is averaged is smaller than that of the first measurement mode,
A body composition measuring device in which, when measurement is performed using the second measurement mode, if the abnormality determination unit determines that the impedance trajectory of the second measurement mode is abnormal, the mode control unit increases the total number of averaging times compared to the second measurement mode and performs measurement again. The body composition measuring device of claim 1, wherein the mode control unit starts measuring the subject's body composition from the second measurement mode. The body composition measuring device according to claim 1 or 2, wherein the abnormality determination unit calculates an abnormality index that is an index of abnormality of the impedance trajectory, and determines that the impedance trajectory is abnormal if the abnormality index exceeds a predetermined first threshold, and determines that the impedance trajectory is not abnormal if the abnormality index is equal to or less than the predetermined first threshold. The body composition measuring device according to claim 1 or 2, wherein the mode control unit has a third measurement mode in which the total number of times the voltage signal is averaged by the electrical impedance calculation unit is greater than the first measurement mode, and the mode control unit performs measurement again in the third measurement mode if the abnormality determination unit determines that the impedance trajectory of the first measurement mode is abnormal when measurement is performed in the first measurement mode. The body composition measuring device according to claim 4, wherein the mode control unit first performs measurement in the second measurement mode, and if the abnormality determination unit determines that the impedance trajectory in the second measurement mode is abnormal, transitions to measurement in the first measurement mode, and if the abnormality determination unit determines that the impedance trajectory in the first measurement mode is abnormal, transitions to measurement in the third measurement mode. The body composition measuring device according to claim 3, wherein the abnormality determination unit calculates the abnormality index based on the distance between the impedance locus calculated by the impedance locus calculation unit and the electrical impedance for each frequency calculated by the electrical impedance calculation unit. A method for controlling a body composition measuring device that measures a body composition of a subject, comprising:
(a) injecting a plurality of probe currents having different frequencies into the body of the subject, and detecting a voltage signal related to a voltage generated between predetermined parts of the body of the subject when the plurality of probe currents are injected into the body of the subject, and a current signal related to a current flowing through the body of the subject;
(b) amplifying a voltage signal related to the voltage detected in step (a) to a magnitude for use in electrical impedance measurement;
a step (b2) of converting a current signal related to the current detected by the step (a) into a voltage signal related to the current used for electrical impedance measurement;
A step (c) of averaging the voltage signal amplified in the step (b) and the voltage signal related to the current converted in the step (b2);
(d) calculating information about electrical impedance for each frequency using the voltage signal and the voltage signal related to the current averaged in the step (c);
A step (e) of calculating an impedance locus based on the information about the electrical impedance for each frequency calculated in the step (d);
(f) calculating information about the subject's body composition based on the impedance locus calculated in (e);
and (g) determining whether the impedance locus calculated in the step (e) is abnormal,
and when it is determined in step (g) that the impedance locus is abnormal, the total number of times of averaging in step (c) is increased, and control is performed so as to re-perform the processing from step (a) to step (g). A control program for causing a computer to execute the control method described in claim 7. A body composition measurement device that measures a body composition of a subject according to measurement conditions, comprising:
a current applying unit that applies a plurality of probe currents having different frequencies to the body of the subject;
a voltage detection unit that detects a voltage signal related to a voltage generated between predetermined parts of the body of the subject when the plurality of probe currents are applied to the body of the subject by the current application unit;
a current measuring unit that detects a current signal related to a current flowing through the body of the subject when the plurality of probe currents are applied to the body of the subject by the current applying unit;
a voltage signal amplifier that amplifies the voltage signal detected by the voltage detector to a level used for measuring electrical impedance;
a current-voltage converter that converts the current signal detected by the current measuring unit into a voltage signal having a magnitude used for electrical impedance measurement; and an electrical impedance calculator that calculates information regarding electrical impedance for each frequency based on the voltage signal amplified by the voltage signal amplifier and the voltage signal converted by the current-voltage converter.
an impedance locus calculation unit that calculates an impedance locus based on information about the electrical impedance for each frequency calculated by the electrical impedance calculation unit;
a body composition information calculation unit that calculates information regarding a body composition of the subject based on the impedance locus calculated by the impedance locus calculation unit;
an abnormality determination unit that determines whether the impedance locus calculated by the impedance locus calculation unit is abnormal;
a mode control unit that controls whether to use a first measurement mode in which the total number of times that the voltage signal amplified by the voltage signal amplifier and the voltage signal converted by the current-to-voltage converter are averaged by the electrical impedance calculation unit is a predetermined number, or a second measurement mode in which the total number of times that the voltage signal is averaged is smaller than that of the first measurement mode,
A body composition measuring device in which, when measurement is performed using the second measurement mode, the mode control unit notifies the user if the abnormality determination unit determines that the impedance trajectory of the second measurement mode is abnormal.