KR101693809B1 - Low voltage biosignal measurement circuit - Google Patents

Low voltage biosignal measurement circuit Download PDF

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KR101693809B1
KR101693809B1 KR1020150161383A KR20150161383A KR101693809B1 KR 101693809 B1 KR101693809 B1 KR 101693809B1 KR 1020150161383 A KR1020150161383 A KR 1020150161383A KR 20150161383 A KR20150161383 A KR 20150161383A KR 101693809 B1 KR101693809 B1 KR 101693809B1
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amplifier
low
voltage
measurement
electrodes
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KR1020150161383A
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Korean (ko)
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황인덕
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웰빙소프트 주식회사
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    • A61B5/04—
    • A61B5/0408—
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7225—Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7235—Details of waveform analysis
    • A61B5/725—Details of waveform analysis using specific filters therefor, e.g. Kalman or adaptive filters
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
    • A61B2562/02—Details of sensors specially adapted for in-vivo measurements

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  • Measurement And Recording Of Electrical Phenomena And Electrical Characteristics Of The Living Body (AREA)

Abstract

The present invention relates to an electrochemical device comprising two electrodes contacting a subject; An instrumentation amplifier including two input terminals connected correspondingly to the respective electrodes; And a low pass filter (250) connected in correspondence with each of the input terminals to supply a bias current to the measurement amplifier and receiving an input signal from an output terminal of the measurement amplifier, And a resistor connected to one of the two resistors.

Description

[0001] LOW VOLTAGE BIOSIGNAL MEASUREMENT CIRCUIT [0002]

The present invention relates to a low-voltage biomedical signal measuring circuit for measuring a voltage generated in an examinee, and more particularly, to an electrographic (ECG) The present invention relates to a low-voltage biomedical signal measurement circuit for measuring a bio-signal such as a biomedical signal.

The most basic and most important biological signal in medical practice is electrocardiogram, and recently, the need for a portable electrocardiograph using a battery is emerging.

 Although the nominal 3V CR2032 battery is typical for portable devices, the battery voltage can drop to almost 2V during use, so a battery-powered electrocardiograph should be designed to operate at about 2V.

Typically, a circuit using a single supply of battery forms an analog ground to one-half the voltage of the battery voltage. Operational amplifiers (OPA) or instrumentation amplifiers (IA) Lt; / RTI >

Therefore, the voltage range of the signal in the electrocardiograph circuit using the battery should be limited to within about +/- 1V. Otherwise, the op amp or instrumentation amplifier is saturated and can not perform normal operation.

On the other hand, a biological signal such as an electrocardiogram or EMG may include a DC voltage generated between the skin and the electrode. Therefore, [ANSI / AAMI / IEC 60601-2-25: 2011 Medical electrical equipment-Part 2-25: Particular requirements for basic safety and essential performance of electrocardiographs, Association for the Advancement of Medical Instrumentation, www.aami.org] Or [ANSI / AAMI / IEC 60601-2-27: 2011 Medical electrical equipment-Part 2-27: Particular requirements for basic safety and essential performance of electrocardiographic monitoring equipment, www.aami.org ] The ECG International Standard specifies that the electrocardiograph should operate without abnormality even when the differential-mode DC offset voltage is +/- 300 mV.

In order to reduce the power line noise of 60 Hz in the electrocardiograph, an instrumentation amplifier having a common-mode rejection ratio (CMRR) can be used. In order to cancel the differential-mode DC offset voltage when the instrumentation amplifier is used, 1, an inverting integrator can be used as shown in FIG.

Referring to FIG. 1, in a conventional bio-signal measuring circuit, an input terminal of an inverting integrator is connected to an output of a measuring amplifier, and an output terminal of the inverting integrator is connected to a reference terminal of the measuring amplifier.

The conventional bio-signal measurement circuit including the above-described measurement amplifier by the feedback effect of the inverting integrator operates as a high-pass filter to cut off the DC offset voltage, but can increase the gain of the input buffer stage of the measurement amplifier And if the gain of the input buffer stage of the measurement amplifier can not be increased, there is a problem that an additional amplification stage for amplifying the electrocardiogram signal is required. In the conventional technique using Fig. 1 in the non-patent document 1, all voltage levels can be based on analog ground.

For example, in the conventional bio-signal measuring circuit, when -150 mV and 150 mV are input to the two input terminals 101 and 106 according to the test conditions of the international standard, respectively, in order to cancel the DC offset voltage, The output of the integrator may be -1 V at the minimum (maximum amplitude), and the output of the operational amplifier 135 may be 1 V maximum.

That is, in the conventional bio-signal measuring circuit, a differential voltage of 150 mV can be applied between the input terminals 141 and 142 of the measurement amplifier when the four input resistors 102, 103, 107 and 108 have the same value.

Therefore, the gain of the input buffer has to be smaller than about 12, and the conventional bio-signal measuring circuit has a problem that an additional amplification stage is required for amplifying the electrocardiogram signal in the above-described case.

1. [E. M. Spinelli, R. Pallas-Areny, and M. A. Mayosky, AC-Coupled Front-End for Biopotential Measurements, IEEE Transactions on Biomedical Engineering, Vol. 50, No. 3, pp. 391-395, Mar. 2003] 2. [R. Pallas-Areny, and J. G. Webster, Common Mode Rejection Ratio in Differential Amplifiers, IEEE Transaction on Instrumentation and Measurement, Vol. 40, No. 4, pp. 669-676, Aug. 1991.]

The present invention overcomes the problem of reducing the gain of a measurement amplifier in a portable bio-signal measurement circuit using a battery of the prior art, and uses a high-gain measurement amplifier. When a high-gain measurement amplifier is used, And reduces the power line noise of 60 Hz to provide a low-voltage bio-signal measuring circuit for measuring a living body signal such as a good electrocardiogram or electromyogram.

The present invention provides a low-voltage bio-signal measuring circuit that can eliminate a power line noise of 60 Hz by increasing the common mode rejection ratio of the measurement amplifier, increase the gain of the input buffer stage of the measurement amplifier, and reduce power line noise.

A low-voltage biosignal signal measuring circuit for measuring a voltage generated from a subject according to an embodiment of the present invention includes two electrodes to be brought into contact with an examinee; An instrumentation amplifier including two input terminals connected correspondingly to the respective electrodes; And a low pass filter (250) connected in correspondence with each of the input terminals to supply a bias current to the measurement amplifier and receiving an input signal from an output terminal of the measurement amplifier, And one of the two resistors.

Wherein the low-pass filter is an inverting integrator, and the measurement amplifier has a high gain of 10 or more, wherein the measurement amplifier is supplied with a single power supply through one battery.

The analog circuit forming the analog ground in the low-voltage bio-signal measuring circuit may be characterized by being one half of the battery voltage.

One of the two resistors has a value of 1Mohm or more, and the two electrodes are dry electrodes.

The present invention overcomes the problem of requiring a small gain of a measurement amplifier in a portable bio-signal measurement circuit using a battery of the prior art, so that a high gain instrumentation amplifier can be used. By using a high gain instrumentation amplifier, And can reduce the power line noise of 60Hz and can measure biological signals such as good electrocardiogram and electromyogram.

The present invention can eliminate the power line noise of 60 Hz by increasing the common mode rejection ratio of the measurement amplifier, increase the gain of the input buffer stage of the measurement amplifier, and reduce the power line noise.

1 shows a conventional bio-signal measurement circuit.
FIG. 2 illustrates a low-voltage bio-signal measurement circuit according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings and accompanying drawings, but the present invention is not limited to or limited by the embodiments.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

To measure living body signals such as electrocardiogram, a measurement amplifier is usually used. This is because the input impedance of the instrumentation amplifier is high and the common mode rejection ratio of the instrumentation amplifier is high, so that the instrumentation amplifier is effective in eliminating power line noise.

FIG. 2 shows a low-voltage bio-signal measurement circuit according to an embodiment of the present invention. The low-voltage bio-signal measurement circuit includes two electrodes 201 and 206, two input terminals 241 and 242 and an output terminal 243, Two resistors 203 and 208, and a low-pass filter 250. The resistors < RTI ID = 0.0 > 230 < / RTI >

The two electrodes 201 and 206 are in contact with the subject and the measurement amplifiers are correspondingly connected to the respective pointers 201 and 206 and the two resistors 203 and 208 are connected to the respective input terminals 241 and 242 And the low-pass filter 250 receives an input signal from the output terminal 243 of the measurement amplifier 230. The low-

Referring to FIG. 2, the measurement amplifier 230 includes three operational amplifiers. In order to increase the common mode rejection ratio, the gain of the input buffer stage including the operational amplifiers 231 and 235 is increased. The resistors 236, 237, 238, and 239 of the differential amplifier must be well matched to increase the common mode rejection ratio.

The measurement amplifier 230 is characterized by a high gain of 10 or more, and 20 dB when converting a high gain of 10 or more to decibels.

Two or more electrodes 201 and 206 are used to measure a biological signal. The electrode uses a wet electrode to reduce the resistance between the skin and the electrode, but dry electrodes can be used for convenience of use in recent years.

Between the electrodes 201 and 206 and the input terminals 241 and 242 of the measurement amplifiers are connected series resistors 202 and 207 and diodes 204 and 204 biased in the opposite direction to prevent breakdown of the measurement amplifier 230 due to transient voltages, 205, 209 and 210 may be inserted between the battery terminals VDD and VSS. The resistors 203 and 208 are connected to supply the bias current to the measurement amplifier 230. The values of the resistors 203 and 208 can be generally 1 Mohm or more to increase the input impedance of the measuring circuit.

In order to remove the DC offset voltage, the input terminal 252 of the low-pass filter 250 is connected to the output terminal 243 of the measurement amplifier 230. In FIG. 2, an inverting amplifier or an inverting integrator is used as the low-pass filter 250 and the cross-cver frequency of the low-pass filter 250 or the inverting amplifier is set to a desired cut-off frequency of the high- For example, 0.5 Hz). Since the low frequency gain of the inverting amplifier is larger than the low frequency gain of the low pass filter 250, the effect of reducing the error signal may be more excellent

As shown in FIG. 2, the output terminal 251 of the low-pass filter or inverting amplifier 250 is connected to the bias resistor 208. This makes it possible to solve the problems of the conventional technique described above and to obtain the effect of the present invention.

In a biosignal measurement circuit of a single power source using a battery, the circuit common of all the analog circuits can be formed at the middle of the battery voltage, that is, VDD / 2.

201, 206: two electrodes
203, 208: Two resistors
230: Instrumentation amplifier
241, 242: two input terminals
243: Output terminal
250: Low-pass filter

Claims (7)

A low-voltage biomedical signal measurement circuit for measuring a voltage generated from an examinee,
Two electrodes contacting the subject;
An instrumentation amplifier including two input terminals connected correspondingly to the respective electrodes;
Two resistors connected in correspondence with the respective input terminals to supply a bias current to the measurement amplifier,
And a low pass filter (250) receiving an input signal from an output terminal of the instrumentation amplifier,
And the output terminal of the low-pass filter is connected to one of the two resistors. The method according to claim 1,
Wherein the low-pass filter is an inverting integrator. The method according to claim 1,
Wherein the measurement amplifier has a high gain of 10 or more. The method according to claim 1,
Wherein the measurement amplifier is supplied with a single power source through one battery. The method according to claim 1,
Wherein the common voltage of the analog circuit forming the analog ground in the low-voltage biomedical signal measuring circuit is 1/2 of the battery voltage. The method according to claim 1,
Wherein one of the two resistors has a value of 1Mohm or more. The method according to claim 1,
Wherein the two electrodes are dry electrodes. ≪ RTI ID = 0.0 > 21. < / RTI >
KR1020150161383A 2015-11-17 2015-11-17 Low voltage biosignal measurement circuit KR101693809B1 (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111214219A (en) * 2018-11-23 2020-06-02 联发科技股份有限公司 Circuit applied to biopotential acquisition system
KR20210111053A (en) * 2020-03-02 2021-09-10 울산과학기술원 Bio signal processing apparatus

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101048567B1 (en) * 2010-01-30 2011-07-11 황인덕 Apparatus for measurement the voltage which occurs in from subject
KR20110108186A (en) * 2010-03-26 2011-10-05 삼성전자주식회사 Apparatus and method for measuring biological signal
KR20150057388A (en) * 2013-11-19 2015-05-28 삼성전자주식회사 Method and device to measure bio-signal with reduced common mode noise
KR20160023270A (en) * 2014-08-22 2016-03-03 클레어픽셀 주식회사 Offset cancellation device for measuring biological signal

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101048567B1 (en) * 2010-01-30 2011-07-11 황인덕 Apparatus for measurement the voltage which occurs in from subject
KR20110108186A (en) * 2010-03-26 2011-10-05 삼성전자주식회사 Apparatus and method for measuring biological signal
KR20150057388A (en) * 2013-11-19 2015-05-28 삼성전자주식회사 Method and device to measure bio-signal with reduced common mode noise
KR20160023270A (en) * 2014-08-22 2016-03-03 클레어픽셀 주식회사 Offset cancellation device for measuring biological signal

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
1. [E. M. Spinelli, R. Pallas-Areny, and M. A. Mayosky, AC-Coupled Front-End for Biopotential Measurements, IEEE Transactions on Biomedical Engineering, Vol. 50, No. 3, pp. 391-395, Mar. 2003]
2. [R. Pallas-Areny, and J. G. Webster, Common Mode Rejection Ratio in Differential Amplifiers, IEEE Transaction on Instrumentation and Measurement, Vol. 40, No. 4, pp. 669-676, Aug. 1991.]

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111214219A (en) * 2018-11-23 2020-06-02 联发科技股份有限公司 Circuit applied to biopotential acquisition system
US11617531B2 (en) 2018-11-23 2023-04-04 Mediatek Inc. Circuit applied to biopotential acquisition system
KR20210111053A (en) * 2020-03-02 2021-09-10 울산과학기술원 Bio signal processing apparatus
KR102338892B1 (en) 2020-03-02 2021-12-13 울산과학기술원 Bio signal processing apparatus

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