Biosignal measurement system

Abstract

This biosignal measurement system is provided with two first electrode device (100a) and second electrode device (100b), a right foot drive device (120), and a biosignal generation device (130). The biosignal generation device (130) is provided with a midpoint potential calculation circuit (134) that uses biopotential information that has been transmitted respectively from the two first electrode device (100a) and second electrode device (100b) and received by a first wireless receiver (131) to determine a midpoint potential and a second wireless transmitter (135) that wirelessly transmits the midpoint potential to the right foot drive device (120), wherein the right foot drive device (120) includes: a second wireless receiver (121) that receives the midpoint potential transmitted from the second wireless transmitter (135); an amplification circuit (122) that amplifies the midpoint potential received by the second wireless receiver (121); and a second electrode (123) that applies to a human body the midpoint potential amplified by the amplification circuit (122).

Description

Biosignal Measurement System

[0001] The present invention relates to a biological signal measurement system.

[0002] In measuring an electrocardiogram, which is one type of bioelectric potential measurement, the potential difference between electrodes placed on the left and right sides of the human body is measured. For example, as shown in Fig. 5, a measurement system has been proposed in which a device 301 is worn around the center of the torso, and electrodes 304 are attached to the left and right waist areas by wiring 303 that run through compression wear 302 (Non-Patent Document 1).

[0003] Furthermore, in bioelectric potential measurement, the removal of common-mode noise is an important factor for stable operation, and as shown in Figure 6, a Right Leg Drive (RLD) circuit is often implemented, which feeds back the midpoint potential 401 of the differential voltage and controls it to an arbitrary voltage (Non-Patent Document 2).

[0004] Naoko Kasai et al., "Development and Practical Application of Hitoe, a Functional Material that Enables Biometric Measurement Simply by Wearing It," Institute of Electronics, Information and Communication Engineers, Communications Society Magazine, Vol. 11, No. 1, pp. 17-23, 2017. Analog Devices, Inc., Technical Article MS-2385, "Predict and Confirm Your Limits!" [Retrieved August 19, 2022] (https: / / www.analog.com / media / jp / technical-documentation / tech-articles / ms-2385_jp.pdf).

[0005] However, attaching the device to the torso can cause discomfort due to pressure and the laborious process of attachment, leading to aversion. Attaching the device to other parts of the body, such as the limbs, is also possible. However, in this case, the wiring connecting the left and right electrodes forms a loop like handcuffs, which strongly restricts body movement. While these issues could be resolved by cutting the wiring between the left and right electrodes and dividing the device into two, this separation makes it difficult to establish a standard for measuring potential, making biopotential measurement difficult. Furthermore, right-leg-driven devices, as the name suggests, are often attached to the right leg, which further increases the amount of wiring that must be routed around the body, causing discomfort.

[0006] The present invention has been made to solve the above problems, and aims to make it possible to easily measure bioelectric potentials even if the wiring between the two electrodes and the right foot drive device is cut and the device is divided into three devices.

[0007] The biosignal measurement system according to the present invention comprises two electrode devices, a right foot drive device, and a biosignal generating device, each of the two electrode devices comprising a first electrode for measuring a biopotential in a human body of interest, a non-inverting amplifier circuit for inputting the measured biopotential to a non-inverting amplifier terminal, amplifying the amplified signal, and outputting it from an output terminal, a quantization circuit for converting the amplified signal output from the output terminal of the non-inverting amplifier circuit into digital data to generate biopotential information, a first wireless transmitter for transmitting the biopotential information to the biosignal generating device, an FM transmitter for converting the voltage signal output from the output terminal of the non-inverting amplifier circuit into an FM signal and transmitting it to the other electrode device, an FM receiver for receiving the FM signal transmitted from the other electrode device to the own electrode device, converting it into a voltage signal, and outputting it, an adjustment circuit for adjusting the voltage signal output from the FM receiver under set conditions and outputting it to the inverting input terminal of the non-inverting amplifier circuit, and The device comprises a power supply that supplies power to the transfer amplifier circuit, quantization circuit, first wireless transmitter, FM transmitter, FM receiver, and adjustment circuit, and the FM signal transmitted from one of the two electrode devices to the other and the FM signal transmitted from the other to the one have different frequencies.The biosignal generating device comprises a first wireless receiver that receives biopotential information transmitted from each of the two electrode devices, an arithmetic circuit that generates a biosignal waveform using the biopotential information received by the first wireless receiver, a midpoint potential calculation circuit that calculates the midpoint potential from the biopotential information transmitted from each of the two electrode devices and received by the first wireless receiver, and a second wireless transmitter that wirelessly transmits the midpoint potential to the right foot driving device.The right foot driving device has a second wireless receiver that receives the midpoint potential transmitted from the second wireless transmitter, an amplifier circuit that amplifies the midpoint potential received by the second wireless receiver, and a second electrode that applies the midpoint potential amplified by the amplifier circuit to the human body.

[0008] As described above, according to the present invention, the two electrode devices are connected to the biosignal generating device via wireless communication, the two electrode devices are connected to each other via FM communication, and the right foot driving device and the biosignal generating device are connected to each other via wireless communication. Therefore, even if the wiring between the two electrodes and the right foot driving device is cut and divided into three devices, the bioelectric potential can be easily measured.

[0009] FIG. 1A is a configuration diagram showing the configuration of a biosignal measurement system according to a first embodiment of the present invention. FIG. 1B is a configuration diagram showing a partial configuration of a biosignal measurement system according to the first embodiment of the present invention. FIG. 2 is an explanatory diagram showing the concept of a biosignal measurement system according to the first embodiment of the present invention. FIG. 3 is a configuration diagram showing the configuration of another biosignal measurement system according to the first embodiment of the present invention. FIG. 4 is a configuration diagram showing the configuration of a biosignal measurement system according to a second embodiment of the present invention. FIG. 5 is a configuration diagram showing the configuration of a conventional biosignal measurement system. FIG. 6 is a configuration diagram showing the configuration of a conventional biosignal measurement system using a right-foot driven device.

[0010] A biological signal measurement system according to an embodiment of the present invention will be described below.

[0011] First, a biosignal measurement system according to a first embodiment of the present invention will be described with reference to Figures 1A and 1B. This system includes two first electrode devices 100a, a second electrode device 100b, a right foot drive device 120, and a biosignal generation device 130.

[0012] The first electrode device 100a comprises an electrode 101a for measuring the biopotential of a target human body, a non-inverting amplifier circuit 102a for inputting the measured biopotential to a non-inverting amplifier terminal, amplifying the measured biopotential, and outputting it from an output terminal, a quantization circuit 103a for converting the amplified signal output from the output terminal of the non-inverting amplifier circuit 102a into digital data to generate biopotential information, and a first wireless transmitter 104a for transmitting the biopotential information to the biosignal generating device 130.

[0013] The first electrode device 100a also includes an FM transmitter 105a, an FM receiver 106a, and an adjustment circuit 107a. The FM transmitter 105a converts a voltage signal output from the output terminal of the non-inverting amplifier circuit 102a into an FM signal and transmits the converted FM signal to the second electrode device 100b via a transmitting antenna 109a. The FM receiver 106a converts an FM signal transmitted from the second electrode device 100b to the first electrode device 100a and received by a receiving antenna 110a into a voltage signal and outputs the voltage signal. The adjustment circuit 107a adjusts the voltage signal output from the FM receiver 106a according to preset conditions and outputs the adjusted signal to the inverting input terminal of the non-inverting amplifier circuit 102a.

[0014] The output of the non-inverting amplifier circuit 102a is also input to the inverting input terminal. For example, as shown in FIG. 1B, if the signal input to the inverting input terminal of the non-inverting amplifier circuit 102a from the adjustment circuit 107a is Vdev2 at the negative terminal input Vin- of the operational amplifier of the non-inverting amplifier circuit 102a and the output of the non-inverting amplifier circuit 102a is Vout1, the signals are mixed in a ratio of "Vin- = (R + RG) / (2R + RG) Vout + (R) / (2R + RG) Vdev2" and input to the inverting input terminal of the non-inverting amplifier circuit 102a. The same applies to the non-inverting amplifier circuit 102b described below.

[0015] The first electrode device 100a also includes a power supply 108a that supplies power to the non-inverting amplifier circuit 102a, the quantizer circuit 103a, the first radio transmitter 104a, the FM transmitter 105a, the FM receiver 106a, and the adjustment circuit 107a.

[0016] The second electrode device 100b first comprises an electrode 101b for measuring the biopotential of the target human body, a non-inverting amplifier circuit 102b for inputting the measured biopotential to a non-inverting amplifier terminal, amplifying it, and outputting it from an output terminal, a quantization circuit 103b for converting the amplified signal output from the output terminal of the non-inverting amplifier circuit 102b into digital data to generate biopotential information, and a first wireless transmitter 104b for transmitting the biopotential information to the biosignal generating device 130.

[0017] The second electrode device 100b also includes an FM transmitter 105b, an FM receiver 106b, and an adjustment circuit 107b. The FM transmitter 105b converts a voltage signal output from the output terminal of the non-inverting amplifier circuit 102b into an FM signal and transmits the converted FM signal to the first electrode device 100a via a transmitting antenna 109b. The FM receiver 106b converts an FM signal transmitted from the first electrode device 100a to the second electrode device 100b and received by a receiving antenna 110b into a voltage signal and outputs the voltage signal. The adjustment circuit 107b adjusts the voltage signal output from the FM receiver 106b according to preset conditions and outputs the adjusted signal to the inverting input terminal of the non-inverting amplifier circuit 102b.

[0018] The second electrode device 100b also includes a power supply 108b that supplies power to the non-inverting amplifier circuit 102b, the quantizer circuit 103b, the first radio transmitter 104b, the FM transmitter 105b, the FM receiver 106b, and the adjustment circuit 107b.

[0019] Here, the FM signal transmitted from the first electrode device 100a to the second electrode device 100b and the FM signal transmitted from the second electrode device 100b to the first electrode device 100a have different frequencies.

[0020] The biosignal generating device 130 includes a first wireless receiver 131 that receives biopotential information transmitted from the first electrode device 100a and the second electrode device 100b, and an arithmetic circuit 132 that generates a biosignal waveform using the biopotential information received by the first wireless receiver 131. The arithmetic circuit 132 can generate an electrocardiogram signal waveform using two pieces of biopotential information transmitted from the first electrode device 100a and the second electrode device 100b that are attached to any two of the limbs of the human body. The biosignal generating device 130 also includes a memory 133 that stores the biosignal waveform generated by the arithmetic circuit 132.

[0021] Furthermore, the biosignal generating device 130 includes a midpoint potential calculation circuit 134 that calculates the midpoint potential from the biopotential information received by the first wireless receiver 131 and transmitted from each of the two first electrode devices 100a and the second electrode device 100b, and a second wireless transmitter 135 that wirelessly transmits the midpoint potential to the right foot driving device 120.

[0022] The right foot drive device 120 includes a second wireless receiver 121 that receives the midpoint potential transmitted from the second wireless transmitter 135, an amplifier circuit 122 that amplifies the midpoint potential received by the second wireless receiver 121, and a second electrode 123 that applies the midpoint potential amplified by the amplifier circuit 122 to the human body.

[0023] The concept of the biosignal measurement system according to the first embodiment is shown in Figure 2. The biosignal generating device 130 calculates the midpoint potential from biopotential information measured by the first electrode device 100a and the second electrode device 100b attached to the human body 140. The calculated midpoint potential is fed back by wirelessly transmitting it to the right foot driving device 120 attached to the human body 140. As a result, it is possible to perform stable biopotential measurement while preventing discomfort caused by increased wiring. This configuration makes it possible to suppress common-mode noise, thereby enabling stable biopotential measurement.

[0024] In this example, the non-inverting amplifier circuit 102a of the first electrode device 100a and the non-inverting amplifier circuit 102b of the second electrode device 100b are mutually coupled. Since this configuration is similar to that of an oscillator circuit, oscillation occurs when the phase rotation and amplification caused by delays in the mutually coupled signals reach 180 degrees and 1 or greater.

[0025] For example, when constructing a non-inverting amplifier circuit with a bandwidth of DC to 1 kHz, which is typical for biosignals, a 0.1 ms delay results in a 36-degree phase rotation for a 1 kHz signal. In other words, a 0.5 ms delay results in a 180-degree phase rotation, making oscillation undeniable. Therefore, when mutually coupling the non-inverting amplifier circuit 102a and the non-inverting amplifier circuit 102b described above, it is necessary to minimize the delay in the portion where the voltage signals are coupled.

[0026] Next, electrodes 101a and 101b will be described. Various electrodes can be used for these electrodes, including Ag / AgCl electrodes, which are also used in medical applications, conductive cloth electrodes, metal electrodes, and other electrodes. In particular, usability can be further enhanced by using a non-contact electrode configuration in which the sensor device is worn over clothing using cloth or metal electrodes that do not need to be attached to the human body. In particular, non-contact electrode configurations based on capacitive coupling are preferable because they allow high-frequency communication to pass through more easily.

[0027] Next, adjustment circuits 107a and 107b will be described. These circuits adjust the received FM signal by a constant factor, and can therefore be configured with operational amplifiers. Although it is possible to configure them by connecting operational amplifiers in multiple stages, the more stages connected, the greater the accumulation of delay, making them more susceptible to instability. For this reason, it is preferable that each of adjustment circuits 107a and 107b be configured with a minimum of one stage of operational amplifier.

[0028] Next, the non-inverting amplifier circuit 102a and the non-inverting amplifier circuit 102b will be described. Because bioelectric potentials are very weak signals, signal amplification is required by the non-inverting amplifier circuit 102a and the non-inverting amplifier circuit 102b, which are configured with a filter circuit and an amplifier circuit using an operational amplifier. In particular, by using a non-inverting amplifier circuit, it is possible to realize a system configuration equivalent to that of an instrumentation amplifier with high common-mode suppression capabilities.

[0029] Furthermore, the amplification stages of the non-inverting amplifier circuits 102a and 102b require high input impedance to reduce bioelectric potential loss, but the non-inverting amplifier circuits 102a and 102b are less likely to increase noise even when configured with a high input impedance. On the other hand, in an inverting amplifier circuit, the resistor that determines the input impedance also affects the gain setting and contributes directly to thermal noise, lowering the S / N ratio. For this reason, a non-inverting amplifier circuit is effective.

[0030] In biopotential measurement, the potential difference between two electrodes is detected, so the non-inverting amplifier circuit 102a and the non-inverting amplifier circuit 102b require the same reference potential. Therefore, by using the potentials generated by the adjustment circuits 107a and 107b, balanced signal amplification between the first electrode device 100a and the second electrode device 100b is possible, and good biosignal information can ultimately be obtained.

[0031] Furthermore, the FM communication frequencies used when mutually coupling the non-inverting amplifier circuit 102a and the non-inverting amplifier circuit 102b must be different. This is because using the same frequency will cause mutual interference and the desired coupling will not be achieved. This is equivalent to dividing the band in communication, and by increasing the frequency used, the present invention can be used not only in configurations where electrode devices are paired, but also between a larger number of electrode devices.

[0032] Next, the first wireless transmitter 104 a and the first wireless transmitter 104 b will be described. For example, the first wireless transmitter 104 a can be configured as one communication module, and it is sufficient if the first wireless transmitter 104 a can be connected so as to receive the measured potential output from the quantization circuit 103 a and transmit it to the biological signal generating device 130.

[0033] Any standard such as carrier communication, Wi-Fi (registered trademark), or Bluetooth (registered trademark) can be applied to the wireless communication network between the first wireless transmitter 104a, the first wireless transmitter 104b, and the first wireless receiver 131. It is necessary to select a transmitter and a receiver that match the communication standard. In the case of a short-range communication standard such as Bluetooth, a smartphone or other device close to the user (the human body being measured) can be used as the biosignal generating device 130. Furthermore, if Wi-Fi or other standards are used, a server or other device can be used as the biosignal generating device 130.

[0034] Furthermore, the functions required of the biosignal generating device 130 are to receive signals from multiple electrode devices and calculate the target biopotential. These functions can be implemented (built-in) in one of the electrode devices without using the biosignal generating device 130. In this case, for example, the second electrode device 100b is an additional biosignal generating device equipped with an arithmetic circuit, memory, midpoint potential calculation circuit, and second wireless transmitter.

[0035] In this case, the second electrode device 100b is configured to include a first wireless receiver instead of the first wireless transmitter, and receives biopotential information transmitted from the first electrode device 100a and calculates the biopotential by combining it with the biopotential information of the second electrode device 100b. The midpoint potential is calculated using a midpoint potential calculation circuit, and the calculated midpoint potential is wirelessly transmitted to the right foot drive device 120 by the second wireless transmitter. The calculated biopotential is stored in the memory 133 of the second electrode device 100b, achieving the same functions and effects as described above. Additionally, this configuration eliminates the need for a separate biosignal generating device 130, eliminating the need to carry a smartphone or other device, allowing for more flexible measurement.

[0036] The second wireless transmitter can also transmit the midpoint potential to the second wireless receiver via FM communication. This configuration will be described with reference to Fig. 3. As shown in Fig. 3, the midpoint potential calculated by the midpoint potential calculation circuit 134 of the biosignal generating device 130' is transmitted by the FM transmitter 135a to the right foot driving device 120', and the transmitted midpoint potential is received by the FM receiver 121a of the right foot driving device 120'. The other configurations are the same as those described above.

[0037] Furthermore, the human body can be used as a communication channel for at least one of the communication between the two electrode devices and the communication between the biosignal generating device and the right leg drive device, in which case, for example, a transmitting electrode can be used instead of a transmitting antenna and a receiving electrode can be used instead of a receiving antenna in the electrode device.

[0038] FM communication via the human body has the advantages of reducing delay and power consumption, and since the human body functions as a waveguide, it is possible to confine radio waves, making them resistant to external interference and reducing the risk of causing external interference. Even when transmitting through the human body, the FM signal transmitted from the first electrode device 100a to the second electrode device 100b and the FM signal transmitted from the second electrode device 100b to the first electrode device 100a each have a different frequency. By using a frequency band ranging from several MHz to 100 MHz, loss can be reduced due to the electrical properties of the human body.

[0039] Furthermore, when the human body is used as a communication channel, the electrode device uses three electrodes: a first electrode, a transmitting electrode, and a receiving electrode. However, since each electrode has a different frequency, it is possible to configure it with a single electrode by providing a bandpass filter, which has the effect of improving user comfort by reducing the number of parts that come into contact with the human body.

[0040] Furthermore, when the human body is used as a communication channel, the impedance of the human body changes, and the degree of contact between the electrodes and the human body also changes. For this reason, methods such as AM and PM modulation cannot avoid noise generation due to amplitude fluctuations. In contrast, with FM communication, noise related to amplitude does not affect the output. In other words, FM communication is suitable for use as a communication channel using the human body.

[0041] [Embodiment 2] Next, a biosignal measurement system according to embodiment 2 of the present invention will be described with reference to Fig. 4. This system includes two first electrode devices 100a', a second electrode device 100b', a right foot drive device 120'', and a biosignal generation device 130.

[0042] In the second embodiment, the FM transmitter is configured with voltage-controlled oscillators (VCO 105a', VCO 105b', VCO 135b), and the FM receiver is configured with phase-locked loops (PLL 106a', PLL 106b', PLL 121b). The other components are the same as those in the case where the human body is used as the channel, and in the second embodiment, transmitting electrodes 109a', 109b', receiving electrodes 110a', and 110b' are used.

[0043] In the configuration described in the first embodiment, where FM communication is performed using the human body as a communication channel, delay-related parameters may fluctuate significantly. Therefore, it is necessary to use a device that minimizes delays during transmission and reception, especially in FM communication. As an example, the FM transmitter is configured with a voltage-controlled oscillator, and the output frequency is directly modulated by voltage. The FM receiver is configured with a phase-locked loop circuit, and employs a direct detection method.

[0044] When using the human body as a communication channel, a high signal-to-noise ratio can be expected due to the radio wave confinement effect. Therefore, when using the human body as a channel, a configuration with low delay is more effective than high-precision demodulation. Delay can be effectively reduced by configuring the FM transmitter with a voltage-controlled oscillator and the FM receiver with a phase-locked loop.

[0045] By configuring an FM transmitter from a voltage-controlled oscillator and an FM receiver from a phase-locked loop, delay can be reduced. However, when using direct detection and direct modulation, matching the voltage-to-frequency conversion characteristics between the voltage-controlled oscillator in the FM transmitter and the voltage-controlled oscillator in the phase-locked loop in the FM receiver is essential for error-free communication. However, voltage-controlled oscillators generally use LC resonance with variable capacitance diodes called varactors, or oscillation by ring oscillators. Due to manufacturing variations in these elements, there are cases where the voltage-to-frequency conversion characteristics do not match between the voltage-controlled oscillator in the FM transmitter and the voltage-controlled oscillator in the phase-locked loop in the FM receiver.

[0046] As an example of a case where the voltage-to-frequency conversion characteristics do not match, such as when the center frequencies do not match, adjustment can be made by adding an offset to the operational amplifier in the adjustment circuit so that the voltage-frequency characteristics of the voltage-controlled oscillator constituting the FM transmitter of the other electrode device and the voltage-controlled oscillator of the phase-locked loop circuit of the own electrode device match. For example, the offset can be determined by the input voltage to the operational amplifier. In this way, when FM communication is employed, adjustment is possible without increasing delay.

[0047] In addition, as an example of a case where the voltage-frequency conversion characteristics do not match, if the slopes of the voltage-frequency characteristics do not match, the respective oscillation frequency characteristics can be monitored, and the amplification conditions of the operational amplifier in the adjustment circuit can be adjusted so that the voltage-frequency characteristics of the voltage-controlled oscillator constituting the FM transmitter of the other electrode device and the voltage-controlled oscillator of the phase-locked loop circuit of the own electrode device match, thereby making it possible to adjust the voltage-frequency characteristics without increasing the delay. For example, the amplification conditions of the operational amplifier can be adjusted by making the resistance value of the operational amplifier variable.

[0048] As described above, by appropriately adjusting the conditions of the operational amplifier in the adjustment circuit, it is possible to cover the weaknesses of FM communication using a voltage-controlled oscillator and a phase-locked loop, and the above-mentioned configuration is particularly preferable when using the human body as a communication channel.

[0049] As described above, according to the present invention, the two electrode devices are connected to the biosignal generating device via wireless communication, the two electrode devices are connected to each other via FM communication, and the right foot driving device and the biosignal generating device are connected to each other via wireless communication. Therefore, even if the wiring between the two electrodes and the right foot driving device is cut and divided into three devices, the bioelectric potential can be easily measured.

[0050] It should be noted that the present invention is not limited to the embodiments described above, and it is clear that many modifications and combinations can be made by a person having ordinary knowledge in the art within the technical concept of the present invention.

[0051] 100a...first electrode device, 100b...second electrode device, 101a, 101b...electrodes, 102a, 102b...non-inverting amplifier circuit, 103a, 103b...quantization circuit, 104a, 104b...first wireless transmitter, 105a, 105b...FM transmitter, 106a, 106b...FM receiver, 107a, 107b...adjustment circuit, 108a, 108b...power supply, 109a, 109b...transmitting antenna, 110a, 110b...receiving antenna, 120...right foot drive device, 121...second wireless receiver, 123...second electrode, 130...biological signal generating device, 131...first wireless receiver, 132...arithmetic circuit, 133...memory, 134...midpoint potential calculation circuit, 135...second wireless transmitter.

Claims

1. Comprising two electrode devices, a right foot drive device, and a biological signal generation device, Each of the two electrode devices A first electrode for measuring the bioelectric potential in the target human body, A first amplification circuit comprising a non-inverting input terminal, an inverting input terminal, and an output terminal, which amplifies the bioelectric potential input to the non-inverting input terminal via the first electrode and outputs an amplified signal from the output terminal, A quantization circuit that converts the amplified signal output from the output terminal of the first amplification circuit into digital data to generate bioelectric potential information, A first wireless transmitter that transmits the bioelectric potential information to the biological signal generation device, An FM transmitter that converts the amplified signal output from the output terminal of the first amplification circuit into an FM signal and transmits it to the other electrode device, An FM receiver that receives the other FM signal transmitted from the other electrode device and converts the received other FM signal into a voltage signal and outputs it, An adjustment circuit that adjusts the voltage signal output from the FM receiver under set conditions and outputs the voltage signal adjusted under the set conditions as an adjustment signal to the inverting input terminal of the first amplification circuit, A power supply that supplies power to the first amplification circuit, the quantization circuit, the first wireless transmitter, the FM transmitter, the FM receiver, and the adjustment circuit And comprising, The FM signals transmitted from one of the two electrode devices to the other and the FM signals transmitted from the other to one have different frequencies respectively, The biological signal generation device A first wireless receiver that receives the bioelectric potential information transmitted from each of the two electrode devices, An arithmetic circuit that generates a biological signal waveform using the bioelectric potential information received by the first wireless receiver, A midpoint potential calculation circuit that obtains a midpoint potential from the bioelectric potential information transmitted from each of the two electrode devices received by the first wireless receiver, A second wireless transmitter that wirelessly transmits the midpoint potential to the right foot drive device And comprising, The right foot drive device includes a second wireless receiver that receives the midpoint potential transmitted from the second wireless transmitter, A second amplification circuit that amplifies the midpoint potential received by the second wireless receiver, A second electrode that applies the midpoint potential amplified by the second amplification circuit to the human body A biological signal measurement system characterized by having.

2. In the biological signal measurement system according to Claim 1, The biological signal measurement system, wherein the second wireless transmitter transmits the midpoint potential to the second wireless receiver by FM communication.

3. In the biological signal measurement system according to Claim 1, one of the two electrode devices incorporates the biological signal generation device which is a feature of the biological signal measurement system.

4. In the biological signal measurement system according to Claim 1, at least one of the communication between the two electrode devices and the communication between the biological signal generation device and the right foot drive device uses the human body as a communication channel, which is a feature of the biological signal measurement system.

5. In the biological signal measurement system according to Claim 1, at least one of the FM transmitter and the second wireless transmitter is composed of a voltage-controlled oscillator, and at least one of the FM receiver and the second wireless receiver is composed of a phase-locked loop circuit which is a feature of the biological signal measurement system.

6. In the biological signal measurement system according to Claim 5, the adjustment circuit has an operational amplifier, and performs at least one of changing the amplification condition of the operational amplifier and adding an offset so that the voltage-frequency characteristics of the voltage-controlled oscillator of the other electrode device match the voltage-frequency characteristics of the voltage-controlled oscillation unit of the phase-locked loop circuit of its own electrode device. which is a feature of the biological signal measurement system.

7. In the biological signal measurement system according to any one of Claims 1 to 6, the arithmetic circuit generates an electrocardiogram signal waveform using the two pieces of biological potential information transmitted from each of the two electrode devices attached to any two locations of the limbs of the human body. which is a feature of the biological signal measurement system.