KR20110019773A - Apparatus and method for measuring bio-impedance - Google Patents

Abstract

PURPOSE: A bio-impedance measuring apparatus and a method for the same are provided to improve the accuracy and the reliability of measurement by increasing the number of frequency used for the measurement. CONSTITUTION: A bio-impedance measuring unit includes a plurality of electrodes(900), an input signal generating part(100), an impedance measuring part(300), a displaying part(530). The configuration of the impedance measuring part and the input signal generating part is based on a program code which is operated by a microprocessor. The input electric signal outputted from the input signal generating part includes a signal which is synthesized electric signals with different frequencies.

Description

Apparatus and method for measuring bio-Impedance

The present invention relates to a bioimpedance measuring device.

Bioimpedance measuring devices are widely used to measure body fat. The muscles in your body are high in water, while the fat is low in water. Accordingly, the bioimpedance value decreases with more muscle and increases with more fat. By measuring the impedance of the body, the body water, muscle mass, and fat mass of the subject can be obtained with a simple and high reproducibility.

These devices attach electrodes to body parts such as both hands and feet, select a pair according to the measurement site, apply a current signal for measurement, and then select an appropriate electrode pair according to the measurement site. The bioimpedance is measured by selecting and measuring the voltage at both ends thereof. For example, by applying a current from the left arm to the right arm, and measuring the voltage drop from the left arm to the left leg, the biological impedance of the left arm, which is an overlapping section, can be measured.

However, in order to measure impedance for each part, a process of sequentially applying and measuring signals for each part needs to be repeated. In addition, there are intracellular and extracellular moisture in the body water, and cell membranes divide them. Because of the cell membrane, cells act as capacitors in electrical circuits, so they cannot measure intracellular moisture at low frequencies. In healthy people, there is a balance between intracellular and extracellular moisture. Therefore, in order to measure both intracellular and extracellular moisture, bioimpedance should be measured for a plurality of frequencies. Accordingly, the bioimpedance measuring device measures the impedance of the plurality of frequency components and calculates the bioimpedance value based on the impedance.

Since it is repeated for each part and repeated for a plurality of frequencies, the measurement takes a very long time. If the subject moves or speaks during this measurement time, the bioimpedance value becomes unstable.

As described above, the conventional bioimpedance measurement technology has a problem in that the measurement takes a long time because the signal application and the measurement process must be repeated for several frequency components. In addition, when the subject moves or speaks during a long measurement time, there is a problem in that the measurement conditions are changed for each frequency component and the measurement error is increased accordingly.

The present invention has been made to solve such a problem, and an object thereof is to reduce the time required for measuring the bioimpedance.

Furthermore, an object of the present invention is to reduce the measurement error of the bioimpedance measurement.

Furthermore, an object of the present invention is to simplify the circuit configuration while reducing the time required for measuring the bioimpedance.

In accordance with an aspect of the present invention, a bioimpedance measuring apparatus includes a plurality of electrodes in contact with a body part of a subject, and an input electrical signal for measuring a bioimpedance, to a part of the plurality of electrodes. An input signal generator for supplying, an impedance measuring unit for measuring the bio-impedance from an output electrical signal output from a portion of the plurality of electrodes, and a display unit for displaying the measurement status and results. According to one of the characteristic aspects of the present invention, an input electrical signal is respectively supplied to some of the plurality of electrodes and includes a plurality of electrical signals having different frequencies. The electrodes to which the input electrical signal is supplied and the electrodes to which the output electrical signal is output may be the same electrodes, different electrodes, or only some of them may be the same electrodes.

According to this aspect of the invention, the site-specific measurements can be made simultaneously using signals of different frequency components.

In accordance with another aspect of the present invention, a bioimpedance measuring apparatus includes a plurality of electrodes in contact with a body part of a subject, and an input signal generator configured to generate an input electrical signal for measuring a bioimpedance and supply it to some of the plurality of electrodes. And an impedance measuring unit for measuring bioimpedance from an output electrical signal output through another part of the plurality of electrodes, and a display unit for displaying a measurement state and a result. The electrodes to which the input electrical signal is supplied and the electrodes to which the output electrical signal is output may be the same electrodes, different electrodes, or only some of them may be the same electrodes.

According to this aspect of the invention, the measurement for a plurality of frequencies can be performed at once by a composite signal including all of the plurality of frequency components.

According to one of the aspects of the present invention, the input electrical signal comprises a signal synthesized from electrical signals of different frequencies. In the present invention, the living body may be viewed as a linear circuit in which the superposition principle is schematically applied to the circuit. If the living body does not change in time, the sequential measurement results for the plurality of frequencies to be obtained can be obtained from the results for the signal combining these frequencies.

According to another characteristic aspect of the present invention, the impedance measuring unit measures the bioimpedance by separating the output electrical signal for each frequency component.

According to this aspect of the present invention, the impedance measurement for a plurality of frequencies is made only once, so that the measurement time can be reduced by the ratio of the number of measurement frequencies. This also avoids measurement errors caused by the subject during the measurement time.

In the bioimpedance measuring apparatus according to the present invention, the impedance measurement for a plurality of frequencies can be performed as a single measurement, and thus the measurement time can be reduced by a ratio of the number of measurement frequencies. Furthermore, as the measurement time becomes longer, measurement errors caused by the subject can be avoided.

In addition, conventionally, the number of frequencies that can be used to avoid excessively long measurement time is limited. However, according to the present invention, the number of frequencies used for the measurement may be significantly increased. As a result, more accurate, accurate and rich biometric information can be obtained.

1 is a view schematically illustrating the overall configuration and use of the bioimpedance measuring apparatus according to an embodiment of the present invention.
2 illustrates one more specific embodiment of the present invention.
3 illustrates another embodiment of the present invention.
4A illustrates an example of an input signal generator 100 according to another embodiment of the present invention.
4B illustrates another example of the input signal generator 100 according to another embodiment of the present invention.
5A shows an example of an impedance measuring unit 330 according to another embodiment of the present invention.
5B illustrates another example of the impedance measuring unit 330 according to another embodiment of the present invention.
5C illustrates another example of the impedance measuring unit 330 according to another embodiment of the present invention.

The foregoing and further aspects of the present invention will become more apparent through the following embodiments. DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described to be understood and reproduced by those skilled in the art through preferred embodiments described with reference to the accompanying drawings.

1 is a view schematically illustrating the overall configuration and use of the bioimpedance measuring apparatus according to an embodiment of the present invention. As shown, the bioimpedance measuring apparatus according to an embodiment generates a plurality of electrodes 900 in contact with the body part of the subject, and generates an input electrical signal for measuring the bioimpedance and supplies them to some of the plurality of electrodes. An input signal generation unit 100, an impedance measurement unit 300 for measuring bioimpedance from an output electrical signal output from some of the electrodes, and a display unit 530 for displaying a measurement state and a result. . The input electrical signal is respectively supplied to some of the plurality of electrodes and includes a plurality of electrical signals having different frequencies. In a preferred embodiment, the plurality of electrical signals constituting the input electrical signals are each simultaneously supplied to some of the plurality of electrodes.

In the present invention, the electrodes to which the input electrical signal is applied and the electrodes to which the output electrical signal are output may be the same electrodes, different electrodes, or only some of the same electrodes in another embodiment according to an embodiment. . In the illustrated embodiment, two electrodes 900 are allocated to both hands and both feet. When an input electrical signal is applied to one of these two, the output electrical signal is measured on the other. For example, when measuring the impedance of the right hand, an input electrical signal, for example, a current signal is applied to the driving electrodes of the left and right hands. In addition, the voltage drop between the sensing electrode of the right hand and the sensing electrode of the right foot is measured. Then, the impedance of the right hand, which is the portion where the input signal section and the output signal section overlap, is measured. However, the present invention is not limited thereto, and covers various electrode methods such as a method that is not measured for each part.

According to an aspect of the present invention, the input signal generation unit 100 outputs a plurality of electrical signals. These plurality of electrical signals differ in frequency from each other. In one preferred embodiment, the plurality of electrical signals are sinusoidal signals of different frequencies. Each signal is supplied to a corresponding drive electrode. The impedance measuring unit 300 separates the output electrical signal for each frequency component to measure the bioimpedance.

The display unit 530 displays the measurement state information to help the electrode 900 is in sufficient contact with the measurement site and maintain the correct measurement posture. In addition, the display unit 530 displays the intermediate and final measurement results. The operation unit 510 may be a data input means using a keypad or a touch pad or an acceleration sensor for inputting personal information such as gender, key, age, etc. which are basic data of measurement. The controller 500 collectively controls the entire apparatus and includes a microprocessor and a memory in which program codes are stored. As will be apparent to those skilled in the art, some components of the impedance measuring unit 300 or the input signal generator 100 may be implemented by program code executed in a microprocessor.

2 illustrates one more specific embodiment of the present invention. As shown, the input signal generator 100 includes a plurality of sinusoidal oscillators 110-1, 110-2, 110-3, and 110-4 that oscillate at different frequencies. The outputs of the sine wave oscillators 110-1, 110-2, 110-3, and 110-4 are connected to the plurality of driving electrodes 910-1, 910-2, 910-3, and 910-4, respectively. The outputs of the plurality of sinusoidal oscillators are applied simultaneously to the plurality of drive electrodes, respectively. Output signals of the plurality of sensing electrodes 930-1, 930-2, 930-3, and 930-4 are connected to the plurality of output filters 310-1, 310-2, 310-3, and 310-4, respectively. . The plurality of output filters are band pass filters passing only the sine wave of the band required for measurement of each part under the control of the controller 500.

In measuring the bioimpedance, the sinusoidal signals of each frequency in steady state are approximated to satisfy the circuit law independently. This is the basic assumption of the superposition principle in linear circuits. For example, a sinusoidal current of f1 frequency is applied to the right arm driving electrode and the left arm driving electrode. In this case, if the voltage signal of the frequency f1 between the right arm sensing electrode and the right foot sensing electrode is measured, the bioimpedance of the right arm region may be measured. For example, by applying a sinusoidal current having an f2 frequency to the right arm driving electrode and the right foot driving electrode, and measuring the voltage signal of the f2 component of the left arm sensing electrode and the left foot sensing electrode, the bioimpedance of the trunk portion may be measured. Output signals of the respective output filters 310-1, 310-2, 310-3, and 310-4 are temporarily stored in a register in the impedance calculator 330. The impedance calculator 330 calculates a bioimpedance value from these values. The controller 500 may control the input signal generator 100 and the impedance calculator 330 to calculate more accurate values by averaging the impedance values calculated by repeating the measurement several times in a short time.

According to this aspect of the present invention, the bioimpedance may apply a plurality of frequency components to all parts of the living body at the same time and measure the plurality of frequency components at the same time to measure the impedance of the whole body part at once.

In the illustrated embodiment, output filters 310-1, 310-2, 310-3, 310-4 are described as bandpass filters. However, the present invention is not limited thereto, and various techniques for separating each frequency component, for example, a digital bandpass filter, an analog Fourier transform, a digital Fourier transform, or the like can be used. These modifications will be understood through the embodiments described below.

Figure 3 is a block diagram schematically showing the overall configuration of another embodiment of the present invention. As shown, the input signal generator 100 includes a plurality of sinusoidal oscillators 110-1, 110-2, 110-3, and 110-4 that oscillate at different frequencies. The outputs of the plurality of sinusoidal oscillators 110-1, 110-2, 110-3, and 110-4 pass through the driving switching unit 150, respectively, and the plurality of driving electrodes 910-1, 910-2, 910-3, 910-4). The driving switching unit 150 outputs the outputs of the plurality of sinusoidal oscillators 110-1, 110-2, 110-3, and 110-4 to the plurality of driving electrodes 910-1, 910-2, 910-3, and 910-. 4) Connect sequentially according to the measurement site.

Meanwhile, the output signals of the plurality of sensing electrodes 930-1, 930-2, 930-3, and 930-4 pass through the sensing switching unit 350 to output the plurality of output filters 310-1, 310-2, and 310, respectively. -3, 310-4). The plurality of output filters are band pass filters passing only the sine wave of the band required for measurement of each part under the control of the controller 500. The sensing switching unit 3500 outputs the output signals of the plurality of sensing electrodes 930-1, 930-2, 930-3, and 930-4 to the plurality of output filters 310-1, 310-2, 310-3, and 310-. 4) Connect sequentially according to the measurement site.

Table 1 below is for explaining the operation of the driving switching unit 150 and the sensing switching unit 350. At time T = t1, a current signal of frequency f1 is applied to the drive electrode for measuring the right arm, and a voltage of frequency f1 is measured on the corresponding sensing electrode. At the same time, a frequency f2 is used for the left arm, a frequency f3 for the body, a frequency f4 for the right leg, and a frequency f5 for the left leg. At time T = t2, frequency f5 is used for the right arm, frequency f1 for the left arm, frequency f2 for the torso, frequency f3 for the right leg, and frequency f4 for the left leg. At time T = t3, frequency f4 is used for the right arm, frequency f5 for the left arm, frequency f1 for the torso, frequency f2 for the right leg, and frequency f3 for the left leg.

Measuring area T = t1 T = t2 T = t3 T = t4 T = t5 Right arm f1 f5 f4 f3 f2 Left arm f2 f1 f5 f4 f3 body f3 f2 f1 f5 f4 Right leg f4 f3 f2 f1 f5 Left leg f5 f4 f3 f2 f1

It can be seen that the above switching operation proceeds in a rotary manner.

In this embodiment, the measurement for the plurality of frequencies is performed sequentially by the switch, but the bioimpedance values at different frequencies for each part at a moment can be calculated. Since the number of measurement frequencies is greater than the number of measurement sites, the overall measurement time can be much shorter than before.

In the illustrated embodiment, output filters 310-1, 310-2, 310-3, 310-4 are described as bandpass filters. However, the present invention is not limited thereto, and various techniques for separating each frequency component, for example, a digital bandpass filter, an analog Fourier transform, a digital Fourier transform, or the like can be used. These modifications will be understood through the embodiments described below.

Another embodiment of the present invention will be described with reference to FIG. 1. The bioimpedance measuring apparatus according to an embodiment may include a plurality of electrodes 900 contacting a body part of a subject, and an input signal generator configured to generate an input electrical signal for measuring a bioimpedance and supply them to some of the plurality of electrodes. 100, an impedance measuring unit 300 measuring a bioimpedance from an output electrical signal output through another portion of the plurality of electrodes, and a display unit 530 displaying a measurement state and a result.

According to one aspect of the present invention, the input electrical signal output by the input signal generator 100 includes a signal obtained by synthesizing electrical signals of different frequencies. In addition, according to another aspect of the invention, the impedance measuring unit 300 separates the output electrical signal for each frequency component to measure the bioimpedance.

The display unit 530 displays the measurement state information to help the electrode 900 is in sufficient contact with the measurement site and maintain the correct measurement posture. In addition, the display unit 530 displays the intermediate and final measurement results. The operation unit 510 may be a data input means using a keypad or a touch pad or an acceleration sensor for inputting personal information such as gender, key, age, etc. which are basic data of measurement. The controller 500 collectively controls the entire apparatus and includes a microprocessor and a memory in which program codes are stored. As will be apparent to those skilled in the art, some components of the impedance measuring unit 300 or the input signal generator 100 may be implemented by program code executed in a microprocessor.

FIG. 4A illustrates an embodiment of the input signal generator 100 in the bioimpedance measuring apparatus shown in FIG. 1 and described above. As shown, the input signal generator 100 according to an embodiment includes a plurality of oscillators 110 each oscillating at a different frequency, and a mixing unit 130 for synthesizing the output signals of the plurality of oscillators. do. The output switching unit 150 switches and supplies the input electrical signal synthesized by the mixing unit 130 according to the measurement site. The plurality of oscillators 110 may each be independent oscillation circuits. However, it will be apparent to those skilled in the art that, for example, the plurality of oscillators 110 may be modified in various forms, including one oscillation circuit, a circuit for dividing the same to generate a multiplication frequency, and a circuit for modulating the sine wave. Do.

4B illustrates another embodiment of the input signal generator 100 in the bioimpedance measuring apparatus shown in FIG. 1 and described above. As shown, the input signal generator 100 according to another embodiment may include an input signal memory 120 that stores sample values of a single digital signal corresponding to a signal in which a plurality of signal components having different frequencies are synthesized. And a signal synthesizing unit 140 for reading a sample value stored in the memory 120 and converting the sample value into an analog signal. The synthesized signal of sinusoids each having a different frequency is a single periodic signal having a period corresponding to the period of the sinusoid with the largest period. According to an aspect of the present invention, the input signal memory 120 stores sample values for one period of the digital signal, and the signal synthesizing unit synthesizes signals while periodically accessing the memory. In the case of a signal symmetric about the half cycle, such as a sine wave, only half a sample value is stored, and the other half period may be generated by taking a negative value of the stored sample value.

The signal synthesizing unit 140 generates a memory controller 144 for generating and supplying an address for accessing the input signal memory 120, and outputs from the history signal memory 120 as the memory controller 144 supplies an address value. And a digital to analog converter 142 for converting the sample values into analog signals.

5A illustrates an embodiment of the impedance measuring unit 330 in the bioimpedance measuring apparatus shown in FIG. 1 and described above. As shown, the impedance measuring unit 330 analyzes the output filter 310 for separating the output electrical signal for each frequency component, and a plurality of signal components output from the output filter 310 to calculate the impedance impedance The calculation unit 330 is included.

In the illustrated embodiment, the input switching unit 350 selects a pair of the plurality of electrodes according to the measurement portion. In a preferred embodiment, the output filter 310 comprises a plurality of bandpass filters 310-1, 310-2, ..., 310- each having passband frequencies corresponding to the frequency components of the input electrical signal. n). These bandpass filters may be composed of analog filters or digital filters.

FIG. 5B illustrates another embodiment of the impedance measuring unit 330 in the bioimpedance measuring apparatus shown in FIG. 1 and described above. As shown, the impedance measuring unit 330 is a Fourier transform unit for Fourier transform the output electrical signal, and the impedance calculation for calculating the impedance from the Fourier coefficient for each frequency component output from the Fourier transform unit 320 The unit 340 is included. Since the input electrical signal supplied from the input signal generator 100 is a composite signal of a sine wave signal of a plurality of frequencies, ideally, only the sine wave component included in the input electrical signal is also output. Therefore, the Fourier transform unit 320 only obtains coefficients corresponding to frequency components included in the input electrical signal. Analog circuits for Fourier transforms are known to combine multipliers and integrators. The impedance calculator 340 obtains a bioimpedance value from the coefficient values obtained by the Fourier transform unit 320. The input switching unit 350 is the same as that of FIG. 3A.

5C illustrates another embodiment of the impedance measuring unit 330 in the bioimpedance measuring apparatus shown in FIG. 1 and described above. As shown, the impedance measuring unit 330 includes an analog-to-digital converter 321 for converting an output electrical signal to digital, a digital Fourier transforming unit 323 for digital Fourier transforming the digitally converted signal, and the digital An impedance calculator 340 is configured to calculate a bioimpedance value from coefficient values of corresponding frequency components of the Fourier transform unit 323. FIG. 3C is the same as that of FIG. 3B except that digital Fourier transforms such as FFT and DFT are used. The input switching unit 350 is also the same as that of FIG. 3A. The input switching unit 350 or the output switching unit 150 is not an essential configuration. If circuits are configured independently for each measurement site, they may be omitted.

Hereinafter, a method of measuring bioimpedance according to the present invention will be described.

In the bioimpedance measuring method according to an embodiment of the present invention, a signal applying step of applying electrical signals having different frequencies to drive electrodes contacting a body part of a subject and a sensing electrode contacting the body part of the subject Impedance measurement step of calculating the bio-impedance value by analyzing the signal component output by the frequency component.

In one embodiment, the impedance measuring step includes filtering only signal components of a specific frequency with respect to signal components output to each sensing electrode, and impedance calculating step of calculating bioimpedance from the values of the filtered signal components. do.

According to another aspect of the present invention, there is provided a bioimpedance measuring method, comprising: applying a signal including a signal obtained by synthesizing a plurality of electrical signals of different frequencies to a driving electrode contacting a body part of a subject; Impedance measurement step of measuring the bio-impedance by analyzing the signal component output to the measurement electrode in contact with the body part of the subject for each frequency component.

In one embodiment, the step of applying a signal comprises oscillating a plurality of electrical signals, each having a different frequency, and synthesizing the plurality of oscillated electrical signals. In another embodiment, the signal applying step includes a memory access step of reading sample values of a single digital signal corresponding to a signal in which a plurality of signal components each having a different frequency are synthesized, and the read data. A signal conversion step of converting the analog electric signal. According to an additional aspect, the signal applying step may be a step of repeating the memory access step and the signal conversion step of reading at least a portion of a period of the sample value stored in the memory.

In an exemplary embodiment, the impedance measuring may include filtering the signal output to the measuring electrode contacting the body part of the subject for each frequency component, and calculating the impedance from the values of the separated signals. Include. In yet another exemplary embodiment, the impedance measuring step includes a Fourier transform step of Fourier transforming a signal output to a measuring electrode in contact with a body part of a subject, and an impedance to calculate a bioimpedance from the Fourier coefficient value obtained in the Fourier transform step. It includes the calculation step.

The present invention has been described above with reference to the preferred embodiments described with reference to the accompanying drawings, but is not limited thereto. Accordingly, the invention should be construed by the appended claims, which are intended to cover modifications apparently derived from the described embodiments.

Claims (18)

A plurality of electrodes in contact with the body part of the subject;
An input signal generator configured to generate an input electrical signal for measuring a bioimpedance and supply it to some of the plurality of electrodes;
An impedance measuring unit measuring a bioimpedance from an output electrical signal output from a portion of the plurality of electrodes;
A display unit which displays a measurement state and a result;
In the bioimpedance measuring apparatus comprising:
And a plurality of input electrical signals having different frequencies, each being simultaneously supplied to a portion of the plurality of electrodes. The apparatus of claim 1, wherein the impedance measuring unit calculates a bioimpedance value from a signal obtained by separating an output electrical signal for each frequency component. The method of claim 2, wherein the input signal generation unit:
A plurality of sinusoidal oscillators for generating sinusoids of different frequencies;
And a driving switching unit configured to connect the outputs of the plurality of sinusoidal oscillators to the plurality of driving electrodes, respectively, according to a measurement part.
The impedance measuring unit:
A plurality of filters each extracting signal values of different frequency components corresponding to the sine wave generators from an input signal;
A sensing switching unit connecting the outputs of the plurality of sensing electrodes to the plurality of filters according to the measurement part;
Biometric impedance measurement apparatus comprising a. The apparatus of claim 3, wherein the input signal generator comprises:
The driving switching unit simultaneously connects the outputs of the plurality of sinusoidal oscillators to the plurality of driving electrodes according to the measurement site, and the sensing switching unit simultaneously connects the outputs of the plurality of sensing electrodes to the plurality of filters, respectively, according to the measurement site. Impedance measuring device. A plurality of electrodes in contact with the body part of the subject;
An input signal generator configured to generate an input electrical signal for measuring a bioimpedance and supply it to some of the plurality of electrodes;
An impedance measuring unit measuring a bioimpedance from an output electrical signal output through some of the plurality of electrodes;
A display unit which displays a measurement state and a result;
In the bioimpedance measuring apparatus comprising:
And the input electrical signal comprises a signal obtained by synthesizing electrical signals of different frequencies. The apparatus of claim 5, wherein the impedance measuring unit calculates a bioimpedance value from a signal obtained by separating an output electrical signal for each frequency component. The method of claim 5, wherein the input signal generation unit:
A plurality of oscillators each oscillating at a different frequency;
A mixing unit for synthesizing output signals of the plurality of oscillators;
Biometric impedance measurement apparatus comprising a. The method of claim 5, wherein the input signal generation unit:
An input signal memory for storing sample values of a single digital signal corresponding to a signal synthesized with a plurality of signal components each having a different frequency;
A signal synthesizer for reading a sample value stored in the memory and converting the sample value into an analog signal;
Biometric impedance measurement apparatus comprising a. The apparatus of claim 8, wherein the input signal memory stores at least a portion of sample values of one period of a digital signal, and the signal synthesizing unit synthesizes signals while periodically accessing the memory. The method of claim 6, wherein the impedance measuring unit:
An output filter for separating the output electrical signal by frequency components;
An impedance calculator configured to calculate a bioimpedance by analyzing a plurality of signal components output from the output filter;
Biometric impedance measurement apparatus comprising a. 11. The method of claim 10, wherein the output filter is:
And a plurality of bandpass filters each having a passband frequency corresponding to a frequency component of the input electrical signal. A signal applying step of simultaneously applying electrical signals having different frequencies to the driving electrodes contacting the body part of the subject;
An impedance measurement step of analyzing a signal component output to a sensing electrode contacting a body part of a subject for each frequency component to calculate a bioimpedance value;
Biometric impedance measurement method comprising a. 13. The method of claim 12 wherein the impedance measuring step is:
Filtering only signal components of a specific frequency for signal components output to each sensing electrode;
An impedance calculation step of calculating a bioimpedance from the values of the filtered signal components;
Biometric impedance measurement method comprising a. A signal applying step of applying an electrical signal including a signal obtained by synthesizing a plurality of electrical signals of different frequencies to a driving electrode contacting the body part of the subject;
An impedance measurement step of measuring a bioimpedance by analyzing signal components output to a measurement electrode in contact with a body part of a subject for each frequency component;
Biometric impedance measurement method comprising a. 15. The method of claim 14 wherein the impedance measuring step is:
Filtering the signal output to the measurement electrode in contact with the body part of the subject for each frequency component;
An impedance calculation step of calculating a bioimpedance from the values of the separated signals;
Biometric impedance measurement method comprising a. The method according to any one of claims 14 to 15, wherein the signal applying step is:
Oscillating a plurality of electrical signals, each having a different frequency;
Synthesizing the plurality of oscillated electrical signals;
Biometric impedance measurement method comprising a. The method according to any one of claims 14 to 15, wherein the signal applying step is:
A memory access step of reading sample values of a single digital signal corresponding to a synthesized signal of a plurality of signal components each having a different frequency from the memory;
A signal conversion step of converting the read data into an analog electric signal;
Biometric impedance measurement method comprising a. 18. The method of claim 17, wherein the signal applying step repeats a memory access step and a signal conversion step of reading at least a portion of a period of sample values stored in a memory.

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