JPH09327445A - Sensor for organism measurement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the S/N ratio by reducing the effect of noise. SOLUTION: This sensor 10 for organism measurement is equipped with a grounding cable 82 from the grounding potential GND, a grounding electrode 84 connected to the grounding cable 82 and in contact with a human body B, a detecting electrode 86 in contact with the human body B and to detect an electrical organism signal S, and an impedance converting circuit 12 to input the organism signal S, detected by the detecting electrode 86, in high impedance and to output it in low impedance. The impedance converting circuit 12 is a noninversible amplifying circuit constituted centering on a differential amplifier 881. A negative input terminal 883 is connected to the grounding cable 82 through a resistor 121, a positive input terminal 882 is connected to the detecting electrode 86, and a resistor 122 is connected between the output terminal 884 and the negative input terminal 883. supplied from a gas pressure vessel through a second valve V2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biometric sensor used when measuring an electrical biosignal such as an electroencephalogram and a myoelectric potential. More specifically, the detected biosignal is input with high impedance and low. The present invention relates to a biometric sensor including an impedance conversion circuit that outputs impedance.

[0002]

2. Description of the Related Art FIGS. 6 and 7 show a conventional biometric sensor, FIG. 6 is a circuit diagram, and FIG. 7 is a sectional view. Hereinafter, description will be given with reference to these drawings.

A conventional biometric sensor 80 has a ground wire 82 derived from a ground potential GND, a ground electrode 84 connected to the ground wire 82 and in contact with the human body B, and an electric wire in contact with the human body B. The detection electrode 86 for detecting the biological signal S is provided, and the impedance conversion circuit 88 for inputting the biological signal S detected by the detection electrode 86 with high impedance and output with low impedance.

The impedance conversion circuit 88 is a buffer circuit composed of a differential amplifier 881. The differential amplifier 881 has a + input terminal 882 and a − input terminal 88.
3, output terminal 884, + Vcc input terminal 885 and -Vcc
An input terminal 885 is provided. The + input terminal 882 is connected to the detection electrode 86, and the − input terminal 883 is the output terminal 88.
4, the output terminal 884 is connected to the electroencephalograph 90, and the + Vcc input terminal 885 and the −Vcc input terminal 885 are connected to the power supply 92.

Further, the biometric sensor 80 has an electronic circuit board 96 on which the IC package 94 of the impedance conversion circuit 88 is mounted, an external terminal 98 connected to the electronic circuit board 96, the electronic circuit board 96 and the detection electrode 86. The lead wire 100 for connecting to and is sealed with a resin 102. The lead wire 100 is connected to the electronic circuit board 96 and the detection electrode 86 by, for example, soldering or brazing.

[0006]

However, the conventional biometric sensor 80 has a problem that it is easily affected by noise because the biosignal S is extremely weak.

[0007]

SUMMARY OF THE INVENTION Therefore, a main object of the present invention is to provide a biometric sensor having an improved SN ratio by reducing the influence of noise.

[0008]

The present inventor has obtained the following findings as a result of repeated research on a technique for reducing the influence of noise of the biometric sensor 80.

In the circuit of the biometric sensor 80, the impedance conversion circuit 88 is provided at a position that is considerably distant from the ground potential GND. Therefore, the impedance conversion circuit 88 is in an unstable state and is easily affected by noise. Therefore, if the ground potential GND is provided in the impedance conversion circuit 88 and a part of the impedance conversion circuit 88 is connected to the ground potential GND, the impedance conversion circuit 88 is in a stable state close to the ground potential GND. , The effect of noise is reduced.

In the structure of the biometric sensor 80, the electronic circuit board 96 and the detection electrode 86 are connected by the lead wire 100. Therefore, since the impedance conversion circuit 88 has a high input impedance, the lead wire 1
It is easy to pick up noise at 00. Therefore, if the lead wire 100 is removed and the detection electrode 86 is directly connected to the electronic circuit board 96, the influence of noise is reduced.

The biometric sensor according to the present invention is made based on the above findings. That is, claim 1
The biometric sensor described is a ground wire derived from a ground potential, a ground electrode connected to the ground wire and in contact with a living body, and a detection electrode for contacting the living body and detecting an electrical biosignal. And an impedance conversion circuit for inputting a biomedical signal detected by the detection electrode with high impedance and outputting with low impedance. The impedance conversion circuit includes a first input terminal connected to the ground line and a second input terminal connected to the detection electrode. Here, the living body is, for example, a human body.

According to a second aspect of the present invention, there is provided a biometric sensor according to the first aspect, wherein the impedance conversion circuit is a non-inverting amplifier circuit mainly composed of a differential amplifier. The input terminal is the negative input terminal of the differential amplifier connected to the ground line via a resistor, and the second input terminal is the positive input terminal of the differential amplifier connected to the detection electrode. A resistor is connected between the output terminal and the-input terminal of the differential amplifier. The biometric sensor according to claim 3 is the biometric sensor according to claim 1, wherein the impedance conversion circuit is an inverting amplifier circuit configured around a differential amplifier, and the first input terminal is the The positive input terminal of the differential amplifier connected to the ground line, the second input terminal is the negative input terminal of the differential amplifier connected to the detection electrode via a resistor, A resistor is connected between the output terminal of the amplifier and the negative input terminal.

A biometric sensor according to a fourth aspect is the biometric sensor according to the first aspect, wherein an electronic circuit board on which the impedance conversion circuit is formed is provided, and the impedance conversion circuit is provided on the electronic circuit board. Of the second input terminal, and an engaging projection provided in a state of being engaged with the insertion hole and being electrically connected to the detection electrode.

According to a fifth aspect of the present invention, there is provided the biometric sensor according to the fourth aspect, wherein the insertion hole and the engaging projection are engaged by press fitting. A biometric sensor according to a sixth aspect is the biometric sensor according to the fourth aspect, wherein the insertion hole and the engaging projection are engaged with each other by screwing.

[0015]

1 is a circuit diagram showing a first embodiment of a biometric sensor according to the present invention. Hereinafter, description will be given with reference to this drawing. However, the same parts as those in FIG.

The biometric sensor 10 has a ground potential GND.
From the ground wire 82, a ground electrode 84 connected to the ground wire 82 and in contact with the human body B, a detection electrode 86 in contact with the human body B and for detecting an electrical biological signal S, and a detection electrode 86. The impedance conversion circuit 12 that inputs the biomedical signal S detected in 1. with high impedance and outputs with low impedance is provided.

The impedance conversion circuit 12 is a non-inverting amplifier circuit mainly composed of a differential amplifier 881. −
The input terminal 883 is connected to the ground wire 82 via the resistor 121, the + input terminal 882 is connected to the detection electrode 86,
The resistor 12 is provided between the output terminal 884 and the-input terminal 883.
2 is connected.

In the biometric sensor 10, one end of the resistor 121 in the impedance conversion circuit 12 is connected to the ground potential GN.
It is D. Therefore, the impedance conversion circuit 1
Since 2 is in a stable state close to the ground potential GND, the influence of noise is reduced.

FIG. 2 is a circuit diagram showing a second embodiment of the biometric sensor according to the present invention. Hereinafter, description will be given with reference to this drawing. However, the same parts as those in FIG.

The impedance conversion circuit 22 of the biometric sensor 20 is an inverting amplification circuit mainly composed of a differential amplifier 881. The + input terminal 882 is connected to the ground line 82, and the − input terminal 883 is connected to the detection electrode 86 and the resistor 22.
1 and the output terminal 884 and the-input terminal 88.
The resistor 222 is connected between the resistor 222 and the resistor 3.

In the biometric sensor 20, the + input terminal 882 in the impedance conversion circuit 22 has the ground potential GND.
Due to the virtual ground, the-input terminal 883 is also at the ground potential GND. Therefore, the impedance conversion circuit 22 is in a stable state close to the ground potential GND, and the influence of noise is reduced.

FIG. 3 is a sectional view showing a third embodiment of the biometric sensor according to the present invention. Hereinafter, description will be given with reference to this drawing. However, the same parts as those in FIG. 1 and FIG.

The biometric sensor 30 includes the IC package 32 of the impedance conversion circuit 12 (FIG. 1) in addition to the circuit configuration of the biometric sensor 10 (FIG. 1) of the first embodiment.
In the state in which the electronic circuit board 34 mounted with, the insertion hole 36 provided in the electronic circuit board 34 and electrically connected to the + input terminal 882 of the impedance conversion circuit 12, and the detection electrode 38 are engaged with the insertion hole 36. The engaging projection 40 is provided.

The + input terminal 882 and the insertion hole 36 are electrically connected by the conductor pattern 42. The insertion hole 36 is, for example, a metal cylinder having good conductivity and appropriate elasticity. The engagement protrusion 40 is, for example, a metal rod fixed to the detection electrode 38 and having good conductivity and appropriate elasticity. Since the inner diameter of the insertion hole 36 is slightly smaller than the outer diameter of the engagement protrusion 40, the engagement protrusion 40 is press-fitted into the insertion hole 36, whereby the engagement protrusion 40 is strongly fixed to the insertion hole 36. it can.

According to the biometric sensor 30, since the detection electrode 86 is directly connected to the electronic circuit board 34, the electronic circuit board 34 and the detection electrode 38 can be connected in the shortest distance. Therefore, the electronic circuit board 34 and the detection electrode 38
The influence of noise that enters from between is reduced.

FIG. 4 shows a fourth embodiment of the biometric sensor according to the present invention, and FIG. 4A is a vertical sectional view.
[B] is a cross-sectional view. Hereinafter, description will be given with reference to this drawing. However, the same parts as those in FIG.

The biometric sensor of this embodiment has the same structure as the biometric sensor 30 (FIG. 3) of the third embodiment, except that the engaging projection 50 has a different shape. Engagement protrusion 5
No. 0 is a metal rod provided with a ridge 501 and a valley 502 along the press-fitting direction, for example, having good conductivity and appropriate elasticity. The inner diameter of the insertion hole 36 is D1, and the ridge 501
Let D2 be the outer diameter of the groove and D3 be the outer diameter of the valley 502.
>D1> D3. Therefore, the engaging protrusion 50
When the insert is pressed into the insertion hole 36, the ridges 501 are slightly deformed, so that the engaging protrusion 50 can be firmly fixed to the insertion hole 36. Further, the ridges 501 and the valleys 502 may be provided on the insertion hole 36 side, or may be provided on both the engaging projection 50 and the insertion hole 36.

FIG. 5 shows a fifth embodiment of the biometric sensor according to the present invention, and FIG. 5A is a sectional view.
[B] is a partially enlarged sectional view. Hereinafter, description will be given with reference to this drawing. However, the same parts as those in FIG.

The biometric sensor of this embodiment has the same structure as the biometric sensor 30 (FIG. 3) of the third embodiment except that the shapes of the engaging projection 60 and the insertion hole 62 are different. The engagement protrusion 60 is a male screw, the insertion hole 62 is a female screw, and the engagement protrusion 60 and the insertion hole 62 are screwed together. R of the inner diameter of the mountain portion of the insertion hole 62
1, R2 is the inner diameter of the trough of the insertion hole 62 and R2 is the outer diameter of the crest of the engaging projection 60, and R3 is the outer diameter of the trough of the engaging projection 60, then R2>R1> R3. . Therefore, when the engagement protrusion 60 is screwed into the insertion hole 62, the engagement protrusion 60 can be strongly fixed to the insertion hole 62.

[0030]

According to the biometric sensor of the first to third aspects, the impedance conversion circuit has the first input terminal connected to the ground line and the second input terminal connected to the detection electrode. Since it is provided, the entire impedance conversion circuit can be maintained in a stable state close to the ground potential via the first input terminal. Therefore, since the influence of noise can be reduced and the SN ratio can be improved, even a weak biological signal can be detected more accurately than before.

According to the biometric sensor of any one of claims 4 to 6, in addition to the configuration of the biometric sensor of claim 1, an electronic circuit board on which an impedance conversion circuit is formed, and the electronic circuit board are provided. The following effects can be obtained by providing an insertion hole that is electrically connected to the second input terminal of the impedance conversion circuit and an engagement protrusion that is engaged with the insertion hole and is electrically connected to the detection electrode. Play.

[0032] Since the detection electrodes are directly connected to the electronic circuit board, the electronic circuit board and the detection electrodes can be connected in the shortest distance. Therefore, the influence of noise entering between the electronic circuit board and the detection electrode can be reduced, and the SN ratio can be further improved.

.. Since the electronic circuit board and the detection electrode can be easily connected only by engaging the insertion hole and the engagement protrusion,
Workability can be improved and soldering and brazing can be eliminated. Therefore, it is possible to use metals such as stainless steel and titanium that are difficult to solder or braze, to avoid damage to electronic circuits due to heating, and to avoid adverse effects of corrosive residues such as flux.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a biometric sensor according to the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of a biometric sensor according to the present invention.

FIG. 3 is a sectional view showing a third embodiment of the biometric sensor according to the present invention.

FIG. 4 shows a fourth embodiment of a biometric sensor according to the present invention, FIG. 4A is a vertical sectional view, and FIG. 4B is a horizontal sectional view.

FIG. 5 shows a fifth embodiment of the biometric sensor according to the present invention, FIG. 5 [A] is a sectional view, and FIG. 5 [B] is a partially enlarged sectional view.

FIG. 6 is a circuit diagram showing a conventional biometric sensor.

7 is a cross-sectional view showing the biometric sensor of FIG.

[Explanation of symbols]

10, 20, 30 Biometric sensor 12, 22 Impedance conversion circuit 34 Electronic circuit board 36 Insertion hole 38, 86 Detection electrode 40, 50, 60 Engagement protrusion 82 Ground wire 84 Ground electrode 121, 122, 221, 222 Resistance Device 881 differential amplifier 882 + input terminal of differential amplifier (second or first input terminal) 883-input terminal of differential amplifier (first or second input terminal) B human body (living body) S biological signal GND Ground potential

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Chiei Ishiida 2-1, Sakuranamiki, Tsuzuki-ku, Yokohama-shi, Kanagawa Suzuki Co., Ltd. Technical Research Institute

Claims (6)

[Claims] 1. A ground wire derived from a ground potential, a ground electrode connected to the ground wire and in contact with a living body, a detection electrode for contacting the living body and detecting an electrical biological signal, In a biometric sensor including an impedance conversion circuit that inputs a biosignal detected by a detection electrode with high impedance and outputs with low impedance, the impedance conversion circuit is a first input terminal connected to the ground line. And a second input terminal connected to the detection electrode, a biometric sensor. 2. The impedance conversion circuit is a non-inverting amplification circuit mainly composed of a differential amplifier, and the first input terminal of the differential amplifier is connected to the ground line via a resistor. A − input terminal, the second input terminal is a + input terminal of the differential amplifier connected to the detection electrode, and a resistor is provided between the output terminal of the differential amplifier and the − input terminal. The biometric sensor according to claim 1, which is connected. 3. The impedance conversion circuit is an inverting amplification circuit mainly composed of a differential amplifier, and the first input terminal of the differential amplifier is connected to the ground line.
An input terminal, the second input terminal is a − input terminal of the differential amplifier connected to the detection electrode via a resistor, and between the output terminal of the differential amplifier and the − input terminal The biometric sensor according to claim 1, wherein a resistor is connected to the sensor. 4. An electronic circuit board on which the impedance conversion circuit is formed, an insertion hole provided on the electronic circuit board and electrically connected to a second input terminal of the impedance conversion circuit, and engaged with the insertion hole. The biometric sensor according to claim 1, further comprising: an engagement protrusion provided in a conductive state with the detection electrode. 5. The biometric sensor according to claim 4, wherein the insertion hole and the engagement protrusion are engaged by press fitting. 6. The biometric sensor according to claim 4, wherein the insertion hole and the engagement protrusion are engaged with each other by screwing.