JP4711718B2 - ECG and electrode pads - Google Patents

Description

  The present invention relates to an electrocardiograph and an electrode pad for an electrocardiograph that can be used in the electrocardiograph, and in particular, removes polarization noise and myoelectric noise generated by body movement of a subject to generate a clear electrocardiogram signal. The present invention relates to an electrocardiograph and an electrode pad that can be measured.

As a conventional electrocardiograph, for example, one disclosed in Patent Document 1 is known, and this electrocardiograph exposes two electrodes that are identical to each other on the case, and the subject touches the electrodes with both hands while touching the electrodes. When operated with the case, the ECG signals detected through the electrodes from both hands were amplified by the amplifier, the difference between those signals was obtained by the differential amplifier, and the output signal was amplified. After that, it is converted into a digital signal, which is processed by a microcomputer into electrocardiogram data, which is displayed on the display on the surface of the case. Even when an electrocardiogram signal is detected from an electrical signal detected by a plurality of electrode pads mounted near the heart of a subject such as a patient, the conventional electrocardiograph performs the same signal processing.
JP-A-9-117420

  However, as shown in the cross-sectional views of FIGS. 5A and 5B, the perspective view showing the back surface excluding the electrode gel, and the perspective view showing the back surface of only the electrode in FIG. Covers a single disk-like electrode 11b with a projecting connection terminal 11a on the back surface with a cover sheet 11c, and the electrode 11b is brought into contact with the skin of the subject via an electrode gel 11d. Since the electrocardiograph only uses a plurality of electrode pads 11 each having the one electrode 11b and obtains a difference between signals from those electrodes 11b, the electrode pad 11 is shaken by the body movement of the subject. As a result, body motion noise or myoelectric noise is mixed, and there is a problem that a clear electrocardiogram signal cannot be measured.

  That is, the electrolyte solution and the electrode gel 11d are usually interposed between the skin of the subject and the electrode 11b of the electrode pad 11 in contact therewith in order to improve the current between them. When viewed microscopically, a polarization potential is generated between the skin and the electrolyte solution or electrode gel 11d and between the electrolyte solution or electrode gel 11d and electrode 11b, and this polarization potential is applied to the electrode 11b to the skin. Fluctuates due to changes in contact pressure. Therefore, when the electrode pad 11 is shaken and the contact pressure is changed, the polarization potential is changed and body motion noise is generated.

  Further, when the electrode pad 11 is shaken and the contact pressure is changed, the electric capacity is changed between the skin and the electrolytic solution or the electrode gel 11d and between the electrolytic solution, the electrode gel 11d and the electrode 11b, and the impedance is also changed. This impedance variation also causes body movement noise.

  Furthermore, the body movement of the subject is accompanied by generation of an electromyographic signal for moving the muscle, and this myoelectric signal becomes myoelectric noise.

  The object of the present invention is to advantageously solve the above-mentioned problems of the conventional electrocardiograph, and the electrocardiograph according to claim 1 comprises a plurality of electrodes comprising electrodes in contact with a subject. An electrocardiograph for measuring an electrocardiogram signal by processing an electric signal detected using an electrode pad, wherein the electrocardiograph includes a plurality of electrodes each having a different area in contact with a subject. A first difference circuit for obtaining an original electrocardiogram signal by taking a difference between signals from any one of the two electrode pads of the plurality of electrode pads, and the two electrode pads. A second difference circuit for obtaining a body motion noise signal by taking a difference between signals from a relatively smaller area electrode and a larger area electrode, and each of the two electrode pads. Low frequency generation of body motion noise signal Is characterized by comprising comprises a body motion noise removing circuit for removing from the original electrocardiogram signal.

  The electrocardiograph according to claim 2 is an electrocardiograph for measuring an electrocardiogram signal by processing an electric signal detected using a plurality of electrode pads including an electrode in contact with a subject. Each of the plurality of electrode pads includes a plurality of electrodes having different areas in contact with the subject, and the electrocardiograph is configured to start from any one of the two electrode pads of the plurality of electrode pads. The first difference circuit for obtaining the original electrocardiogram signal by taking the difference between the two signals and the signal from the electrode having the smaller area and the electrode having the larger area for each of the two electrode pads A second difference circuit that obtains a body movement noise signal by taking a difference between them, and a near-electrode electromyogram waveform removal circuit that removes a high frequency component of each body movement noise signal of the two electrode pads from the original electrocardiogram signal And this It is characterized in.

Further, an electrode pad of the present invention according to claim 3 is the electrode pad for an electrocardiograph according to claim 1 or 2 , wherein the electrode includes an electrode that contacts the subject, A plurality of electrodes having different areas in contact with the specimen are characterized.

  In the electrocardiograph according to the first and second aspects of the present invention, each of the plurality of electrode pads includes a plurality of electrodes having different areas in contact with the subject, and the plurality of electrodes of one electrode pad These signals are basically of the same waveform but have a potential (magnitude) corresponding to the area of the electrode. Therefore, if the signal difference between the electrode with the relatively small area and the electrode with the larger area of one electrode pad is taken, the electrocardiogram signal is removed and the contact pressure of the electrode due to body movement is reduced. Body motion noise having a relatively low frequency due to the fluctuation of the electrode due to fluctuations in polarization potential and impedance due to the change and generally myoelectric noise having a relatively high frequency remain.

  Thus, in the electrocardiograph according to the first aspect of the present invention, the first differential circuit includes a difference between signals from any one of the two electrode pads of the plurality of electrode pads. And the second differential circuit calculates a difference between signals from the relatively smaller area electrode and the larger area electrode for each of the two electrode pads. And the body motion noise signal is obtained as described above. Then, the body motion noise removing circuit removes the low frequency component of the body motion noise signal of each of the two electrode pads from the original electrocardiogram signal.

  Therefore, according to the electrocardiograph of the present invention, a body motion noise signal having a relatively low frequency can be effectively removed from the original electrocardiogram signal, and a clear electrocardiogram signal can be obtained.

  In the electrocardiograph of the present invention according to claim 2, the first differential circuit takes a difference between signals from any one of the two electrode pads of the plurality of electrode pads. The second electrocardiogram signal is obtained, and the second differential circuit takes the difference between the signals from the relatively smaller area electrode and the larger area electrode for each of the two electrode pads. The body motion noise signal is obtained as described above. Then, the body movement noise removing circuit removes the high frequency components of the body movement noise signals of the two electrode pads from the original electrocardiogram signal.

  Therefore, according to the electrocardiograph of the present invention, a myoelectric noise signal having a relatively high frequency can be effectively removed from the original electrocardiogram signal, and a clear electrocardiogram signal can be obtained. In addition, you may combine the electromyograph of Claim 1 and the electromyograph of Claim 2. In this way, the body motion noise signal and the myoelectric noise signal can be effectively removed from the original ECG signal, and a clearer ECG signal can be obtained.

  On the other hand, in the electrode pad according to the third aspect of the present invention, in the electrode pad having an electrode that contacts the subject, the electrodes of one electrode pad have a plurality of areas that are different from each other in contact with the subject. Because it is an electrode, the electrocardiogram signal is removed by taking the difference in signal between the electrode with the relatively small area and the electrode with the larger area of the one electrode pad, and due to body movement Body motion noise with a relatively low frequency due to fluctuations in the electrode due to fluctuations in the polarization potential and impedance due to changes in the contact pressure of the electrodes and generally myoelectric noise with a relatively high frequency remain.

  Therefore, according to the electrode pad of the present invention as set forth in claim 3, the body movement having a relatively low frequency is caused by the fluctuation of the electrode due to the polarization potential fluctuation and the impedance fluctuation caused by the change of the contact pressure of the electrode due to the body movement. An electrical signal that includes noise and generally myoelectric noise having a relatively high frequency but does not include an electrocardiogram signal can be extracted. Moreover, by taking a signal from the electrode having the relatively small area and the smaller electric capacity of each of the two electrode pads, the fluctuation in impedance due to body movement can be reduced, and the noise due to the fluctuation in impedance is reduced. An electrocardiogram signal can be obtained.

  In the electrode pad of the present invention, as described in claim 4, at least one of the plurality of electrodes has an annular shape, and at least one other of the plurality of electrodes. Preferably, an electrode is located inside the annular electrode (ie, at least one electrode surrounds at least one other electrode). In this way, an electrode with a small variation in impedance due to a change in contact pressure can be arranged at a position closer to the center where the change in contact pressure is small with respect to the fluctuation of the electrode tip, for example, because the area is relatively small. An electrocardiogram signal with less body movement noise can be obtained with a small electrode pad.

  In the electrode pad of the present invention, it is preferable that the annular electrode and the electrode located on the inner side are located concentrically as described in claim 5. In this way, since the plurality of electrodes are concentrically positioned, an electrocardiographic signal with less body motion noise can be obtained with a smaller electrode pad.

  Furthermore, in the electrode pad of this invention, as described in claim 6, the annular electrode and the electrode located on the inside extend radially from the center of the annular electrode. It is preferable to have In this way, the change in contact pressure due to body movement is approximately the same between the annular electrode and the electrode located inside thereof, so the electrode with the relatively smaller area and the electrode with the larger area When the body motion noise signal is obtained by taking the difference between the signals from the above, it is possible to prevent a difference in the body motion noise signal due to a difference in the contact pressure due to the position of the electrode on the pad. .

  Furthermore, in the electrode pad according to the present invention, as described in claim 7, it is preferable that the plurality of electrodes are arranged in the circumferential direction at intervals from each other to form an annular shape as a whole. In this way, since the distance from the center of the ring is substantially the same for a plurality of electrodes with different areas in contact with the subject, the change in contact pressure due to body movement is almost the same, so the area is relatively When the body motion noise signal is obtained by taking the difference between the signals from the smaller electrode and the electrode with the larger area, the change in contact pressure varies depending on the position of the electrode on the pad, and the body motion noise It is possible to prevent a difference from occurring in the signal.

  Furthermore, in the electrode pad according to the present invention, as described in claim 8, the plurality of electrodes are dispersed in the circumferential direction and are electrically connected to each other so as to be a plurality of electrodes having different areas in contact with the subject. It is preferable that they are connected to each other. In this way, a plurality of electrodes having different areas in contact with the subject are dispersed in the circumferential direction, and the changes in contact pressure due to body movement are substantially the same among the plurality of electrodes having different areas in contact with the subject. Therefore, when calculating the body movement noise signal by taking the difference between the signals from the electrode with the smaller area and the electrode with the larger area, the contact pressure depends on the position of the electrode on the pad. It is possible to prevent the body movement noise signal from being different due to the difference in the change of the.

  Furthermore, in the electrode pad of this invention, as described in claim 9, it is preferable that the plurality of electrodes are located on the inner side separated from the outer peripheral edge of the insulating substrate. In this way, the variation in contact pressure due to the electrode pad fluctuation is the greatest in the vicinity of the outer peripheral edge of the insulating substrate of the electrode pad, whereas the fluctuation of the contact pressure is increased on the inner side away from the outer peripheral edge of the insulating substrate. Since it becomes smaller than the vicinity, an electric signal with less body movement noise can be obtained from the electrode.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram functionally showing the configuration of one embodiment of the electrocardiograph of the present invention using one embodiment of the electrode pad of the present invention, and FIGS. , A cross-sectional view showing a specific configuration of the electrode pad of the embodiment, and a perspective view showing a back surface excluding the electrode gel, FIGS. 7C and 7D are only the electrode and the insulating substrate of the electrode pad of the embodiment. The perspective view which shows the back surface of this, the perspective view which shows the surface, FIG. 3 (a), (b) is explanatory drawing which each shows the distribution state of the contact pressure when pushing and pulling the electrode pad of the said Example, 4 (a), (b) and (c) are circuit diagrams showing the connection state between the electrode pad of the above embodiment and the second differential amplifier of the electrocardiograph of the above embodiment. A characteristic diagram showing the difference between the output signals of the two electrodes, and the second amplified by taking the difference between the output signals. It is a characteristic diagram showing a differential amplifier output signal.

  As shown in FIG. 1, the electrocardiographs of the above-described embodiments each have an electrode 1b whose area in contact with the subject is relatively small between the electrodes and an area in contact with the subject which is relatively large between the electrodes. The two electrode pads 1 of the above-described embodiment including the electrode 1d are used, and the difference between signals from the electrode 1b having the relatively small area of each of the two electrode pads 1 is obtained. The first differential amplifier 2 as the first differential circuit that amplifies and outputs it as an original electrocardiographic signal to the output circuit 2a, and each of the two electrode pads 1 has a relatively small area. The second differential circuit is a second differential circuit that takes a difference between signals from the electrode 1b and the electrode 1d having a larger area and amplifies the signal and outputs it as a body movement noise signal to the output circuit 3a. Differential amplifier 3 and the second of them Two low-pass filters (for example, having a cut-off frequency of 40 Hz) 4 for extracting low-frequency components of body motion noise signals of the two electrode pads 1 output to the output circuit 3a of the differential amplifier 3 and their bodies A body motion noise elimination circuit comprising two differential amplifiers 5 for amplifying the signals obtained by removing the low frequency components of the motion noise signals from the original electrocardiogram signals and outputting them to the output circuit 5a is provided.

  Further, as shown in FIG. 1, the electrocardiograph of the above embodiment has a high frequency of each body motion noise signal of the two electrode pads 1 output to the output circuit 3a of the two second differential amplifiers 3. Two high-pass filters (for example, having a cut-off frequency of 40 Hz) 6 for extracting components, and high-frequency components of the body motion noise signals are removed from the original electrocardiogram signal from which the low-frequency components of the body motion noise signals are removed. And a myoelectric noise removing circuit comprising two differential amplifiers 7 which finally output from the output circuit 7a to the output terminal 8 as an electrocardiogram signal. In addition, the electrocardiograph of the said Example also uses the indifferent electrode which is not shown in figure connected to a ground circuit like a normal electrocardiograph.

  Specifically, the electrode pad 1 of the above-described embodiment used in the electrocardiograph of the above-described embodiment is, as shown in FIGS. 2 (a) to 2 (d), a disk having a connection terminal 1a protruding on the back surface. One electrode 1b having a relatively smaller shape, and a cylindrical connection terminal 1c surrounding the connection terminal 1a via an insulator are protruded from the back via a plurality of lead pieces, rather than the electrode 1b. A relatively large one electrode 1d that surrounds the electrode 1b in a large annular shape is fixed to a disk-shaped insulating substrate 1e larger than the electrode 1d, and the surface side of the insulating substrate 1e is connected to the connection terminal 1a. , 1c is also covered with a disc-shaped cover sheet 1f, and the electrodes 1b, 1d are also covered with a disc-shaped electrode gel 1g, and adhere to the skin of the subject via the electrode gel 1g. It is to be contacted.

  In the electrode pad 1 of this embodiment, as shown in FIG. 2, the electrodes 1b and 1d are located on the inner side away from the outer peripheral edge of the insulating substrate 1e. 3 (a) and 3 (b), the fluctuation of the maximum is near the outer peripheral edge of the insulating substrate 1e of the electrode pad 1 as shown by the distribution of the contact pressure of the electrode pad 1 against the skin S by pushing and pulling in FIG. On the other hand, the inner side of the insulating substrate 1e that is separated from the outer peripheral edge is smaller than the vicinity of the outer peripheral edge. A signal can be obtained.

  Further, as shown in FIG. 2, the electrode pad 1 of this embodiment is provided with two electrodes 1b and 1d having different areas in contact with the skin of the subject on one electrode pad 1. One electrode pad 1 is brought into contact with the skin near the heart of the subject, and an electric signal obtained from the electrode 1b having a relatively small area of the one electrode pad 1 as shown in FIG. By taking the difference between B and the electric signal A obtained from the electrode 1d having the larger area by the differential amplifier 3, the signals A and B are caused by the fluctuation of the electrode pad 1 as shown in FIG. Since the waveforms are the same and the levels are different, the output circuit 3a of the differential amplifier 3 removes the electrocardiogram signal from those electric signals, and the skin of the electrodes 1b and 1d due to body movement as shown in FIG. Polarization potential fluctuations due to changes in contact pressure Due to impedance variations, electrode 1b, a relatively low frequency body motion noise because due to the shaking of 1d, although not shown so that the generally relatively high frequency myoelectric noise remains.

  Therefore, according to the electrode pad 1 of this embodiment, the frequency of the electrodes 1b and 1d due to fluctuations in the polarization potential and impedance due to changes in the contact pressure of the electrodes 1b and 1d due to body movement is relatively high. An electrical signal that includes low body motion noise and generally myoelectric noise having a relatively high frequency but does not include an electrocardiogram signal can be extracted. In addition, by detecting an electric signal from the electrode 1b having a relatively small area and a smaller electric capacity of each of the two electrode pads 1, the fluctuation in impedance due to body movement can be reduced, and the body An electrocardiographic signal with less dynamic noise can be obtained.

  Furthermore, according to the electrode pad 1 of this embodiment, the electrode 1d having a relatively large area out of the two electrodes has a ring shape, and the electrode 1b having a relatively small area has a ring shape. Is located inside the electrode 1d having a relatively large area (that is, the electrode 1d having a relatively large area surrounds the electrode 1b having a relatively small area). The electrode 1b can be arranged at a position closer to the center where the change in the contact pressure is smaller than the fluctuation of the electrode chip 1 because the area is relatively small and the impedance fluctuation due to the change in the contact pressure is small. 1, an electrocardiogram signal with less body motion noise can be obtained.

  Furthermore, according to the electrode pad 1 of this embodiment, since the electrode 1b having a relatively small area and the electrode 1d having a relatively large area are positioned concentrically, the smaller electrode An electrocardiogram signal with less body movement noise can be obtained with the pad 1.

  Thus, in the electrocardiograph of the above embodiment, the first differential amplifier 2 receives the signal from the electrode 1b having the relatively small area of each of the two electrode pads 1 of the above embodiment. The difference between each other is obtained to obtain an original electrocardiogram signal, and the second differential amplifier 3 has a larger area than the electrode 1b having a relatively smaller area for each of the two electrode pads 1 of the above embodiment. The body movement noise signal is obtained as described above by taking the difference between the signals from the other electrode 1d. Then, the body motion noise elimination circuit comprising the two low-pass filters 4 and the two differential amplifiers 5 removes the low frequency components of the body motion noise signals of the two electrode pads 1 of the above embodiment from the original electrocardiogram signal. At the same time, the myoelectric noise removing circuit including the two high-pass filters 6 and the two differential amplifiers 7 removes the high frequency components of the body motion noise signals of the two electrode pads 1 of the above-described embodiment from the original ECG signal. .

  Therefore, according to the electrocardiograph of this embodiment, both the body motion noise signal having a relatively low frequency and the myoelectric noise signal having a relatively high frequency can be effectively removed from the original electrocardiogram signal. An electrocardiographic signal can be obtained.

  FIG. 5 is a bottom view showing the arrangement of electrodes on the back surface (bottom surface) of another embodiment of the electrode pad according to the present invention, excluding the electrode gel, and the electrode pad 1 of this embodiment is composed of an insulating substrate 1e, One electrode 1b on the back surface that contacts the skin near the heart of the subject and one electrode having a relatively larger area than the electrode 1b that is positioned on the inner side away from the outer peripheral edge of the insulating substrate 1e and surrounds the electrode 1b An annular electrode 1d is fixed, and the electrodes 1b and 1d are spaced apart from each other with a slit-like gap, and each has a portion extending radially with respect to the center of the annular electrode 1d. In this respect, it is different from the previous embodiment, and is otherwise configured in the same manner as the previous embodiment.

  According to the electrode pad 1 of this embodiment, the change in contact pressure due to body movement is almost the same between the annular electrode 1d and the electrode 1b located inside thereof, so that the electrode with a relatively small area is used. When the body motion noise signal is obtained by taking the difference between the signals from 1b and the electrode 1d having the larger area, the change in the contact pressure differs depending on the position of the electrode on the pad 1, and the body motion noise signal is generated. Differences can be prevented from occurring.

  FIG. 6 is a bottom view showing the arrangement of electrodes on the back surface (bottom surface) of another embodiment of the electrode pad according to the present invention, excluding the electrode gel, and the electrode pad 1 of this embodiment is formed of the insulating substrate 1e. A plurality of large and small fan-shaped electrodes 1b and 1d are arranged around the center of the back surface of the subject in contact with the skin in the vicinity of the heart. It is arranged and fixed so that two kinds of large and small electrodes are alternately positioned so as to form an annular shape on the inner side separated from the outer peripheral edge of the insulating substrate 1e. Also, in the figure, the six larger electrodes 1d are electrically connected to each other by lead wires provided on the back side of the insulating substrate 1e, respectively. The configuration is the same as that of the embodiment.

  According to the electrode pad 1 of this embodiment, two types of electrodes 1b and 1d having different areas in contact with the subject are dispersed in the circumferential direction, and two types of electrodes having different areas in contact with the subject are provided. Since the changes in contact pressure due to body movement are almost the same between 1b and 1d, the body movement noise signal is obtained by taking the difference between the signals from the electrode 1b having the smaller area and the electrode 1d having the larger area. Can be prevented when the contact pressure changes due to the position of the electrode on the pad and the body motion noise signal differs.

  Although the present invention has been described based on the illustrated examples, the present invention is not limited to the above-described examples. For example, the electrocardiograph of the present invention receives electric signals from three or more electrode pads and receives the two signals. It may be one that processes each electrical signal. In addition to the electrocardiograph, the configuration of the present invention can be used for, for example, a myoelectric sensor. In that case, body motion noise can be effectively removed and a clear myoelectric signal can be obtained. it can.

  On the other hand, the number of electrodes of one electrode pad of the present invention may be three or more. Further, the plurality of electrodes of the electrode pad may be arranged not concentrically with each other. Further, when the electrode with the larger area of the electrode pad surrounds the electrode with the smaller area, these electrodes may be not in an annular shape but in a rectangle or the like. Furthermore, the electrode pad of the present invention may be one that is fixed to the skin of the subject's limbs or the like by a clamp or the like instead of the electrode gel, and the electrode is brought into contact with the skin through the electrolytic solution. In addition to the electrocardiograph, the electrode pad of the present invention can be used for, for example, a myoelectric sensor, in which case body motion noise can be effectively removed and a clear myoelectric signal can be obtained. .

  Thus, according to the electrocardiograph of the present invention, a body motion noise signal having a relatively low frequency can be effectively removed from the original electrocardiogram signal, and a clear electrocardiogram signal can be obtained. In addition, a myoelectric noise signal having a relatively high frequency can be effectively removed from the original electrocardiogram signal, and a clear electrocardiogram signal can be obtained.

  According to the electrode pad of the present invention, an electrical signal that includes body motion noise due to polarization potential fluctuation and impedance fluctuation due to changes in electrode contact pressure due to body movement, and myoelectric noise, but does not include an electrocardiogram signal. Can be taken out. Moreover, an electrocardiogram signal with less body motion noise can be obtained by taking a signal from an electrode having a relatively small area of each of the two electrode pads.

It is a block diagram which shows functionally the structure of one Example of the electrocardiograph of this invention using one Example of the electrode pad of this invention. (A), (b) is sectional drawing which shows the specific structure of the electrode pad of the said Example, and the perspective view which shows the back surface except electrode gel, (c), (d) is the electrode pad of the Example It is the perspective view which shows the back surface of only the electrode of this, and an insulated substrate, and the perspective view which shows the surface. (A), (b) is explanatory drawing which each shows the distribution state of the contact pressure when the electrode pad of the said Example is pushed and pulled. (A), (b) and (c) are circuit diagrams showing the connection state between the electrode pad of the above embodiment and the second differential amplifier of the electrocardiograph of the above embodiment, and two electrodes of the electrode pad. FIG. 6 is a characteristic diagram showing a difference between the output signals of the first and second differential amplifier output signals amplified by taking the difference between the output signals. It is a bottom view which shows arrangement | positioning of the electrode of the back surface (bottom surface) of other one Example of the electrode pad of this invention except an electrode gel. It is a bottom view which shows arrangement | positioning of the electrode of the back surface (bottom surface) of another one Example of the electrode pad of this invention except an electrode gel. (A), (b) is a perspective view which shows the back surface except the sectional view and electrode gel of the conventional electrode pad, (c) is the perspective view which shows only the back surface of the electrode of the conventional electrode pad.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrode pad 1a, 1c Connection terminal 1b Electrode with a relatively small area 1d Electrode with a relatively large area 1e Insulating substrate 1f Cover sheet 1g Electrode gel 2 1st differential amplifier 2a, 3a, 5a, 7a Output circuit 3 Second differential amplifier 4 Low-pass filter 5, 7 Differential amplifier 6 High-pass filter 8 Output terminal S Skin

Claims (9)

In an electrocardiograph that measures an electrocardiogram signal by processing an electric signal detected by using a plurality of electrode pads including an electrode in contact with a subject,
Each of the plurality of electrode pads comprises a plurality of electrodes having different areas in contact with the subject,
The electrocardiograph is
A first difference circuit for obtaining an original electrocardiogram signal by taking a difference between signals from any one of the two electrode pads of the plurality of electrode pads;
For each of the two electrode pads, a second differential circuit that obtains a body movement noise signal by taking a difference between signals from a relatively smaller area electrode and a larger area electrode;
A body motion noise removing circuit for removing low frequency components of body motion noise signals of the two electrode pads from the original electrocardiogram signal;
An electrocardiograph comprising In an electrocardiograph that measures an electrocardiogram signal by processing an electric signal detected by using a plurality of electrode pads including an electrode in contact with a subject,
Each of the plurality of electrode pads comprises a plurality of electrodes having different areas in contact with the subject,
The electrocardiograph is
A first difference circuit for obtaining an original electrocardiogram signal by taking a difference between signals from any one of the two electrode pads of the plurality of electrode pads;
For each of the two electrode pads, a second differential circuit that obtains a body movement noise signal by taking a difference between signals from a relatively smaller area electrode and a larger area electrode;
A near-electrode myoelectric waveform removing circuit for removing a high-frequency component of a body movement noise signal of each of the two electrode pads from the original electrocardiogram signal;
An electrocardiograph comprising In an electrode pad comprising an electrode in contact with the subject,
The electrode pad for an electrocardiograph according to claim 1 or 2 , wherein the electrodes of one electrode pad are a plurality of electrodes having different areas in contact with the subject. At least one of the plurality of electrodes has an annular shape,
The electrode pad according to claim 3, wherein at least one other electrode of the plurality of electrodes is located inside the annular electrode.   The electrode pad according to claim 4, wherein the annular electrode and the electrode located on the inner side are located concentrically.   5. The electrode pad according to claim 4, wherein the annular electrode and the electrode located on the inner side have a portion extending radially with respect to a center of the annular electrode.   4. The electrode pad according to claim 3, wherein the plurality of electrodes are arranged in the circumferential direction at intervals from each other to form an annular shape as a whole. 5.   8. The electrode pad according to claim 7, wherein the plurality of electrodes are dispersed in the circumferential direction and electrically connected to each other so as to be a plurality of electrodes having different areas in contact with the subject. .   The electrode pad according to any one of claims 3 to 8, wherein the plurality of electrodes are located on an inner side separated from an outer peripheral edge of the insulating substrate.

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