JPH03114438A - Biosignal measuring apparatus - Google Patents

Abstract

PURPOSE:To make it possible to measure accurately a biosignal based on the same phase removal of a low frequency noise and a high frequency noise by providing a CMR adjusting circuit corresponding to the low frequency noise and a CMR adjusting circuit corresponding to the high frequency noise in a biosignal amplifier. CONSTITUTION:A biosignal measuring apparatus A consists of a stimulating apparatus 2 adding a stimulus s to an organism 1, a biosignal amplifier 3 amplifying a biosignal v from the organism 1 caused by the stimulus s and a display apparatue 4 displaying the biosignal v. and in the biosignal amplifier 3, a CMR adjusting circuit 5 corresponding to a low frequency noise and a CMR adjusting circuit 6 corresponding to a high frequency noise are provided. As the CMR adjusting circuit 5 corresponding to a low frequency noise and the CMR adjusting circuit 6 corresponding to a high frequency noise are provided in the biosignal amplifier 3, it is possible to remove a alternating current ham caused by a commercial alternating electric source in the same phase. In addition, an interference wave and a high frequency noise from a stimulating apparatus 2 can be removed in the same phase and it is possible to measure accurately the biosignal v accompanying a stimulus s of the organism 1.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention amplifies minute biological signals (evoked potentials) from a living body due to stimulation of the living body with electricity, light, sound, etc., and generates a waveform or graphic model. The present invention relates to a biological signal measuring device that displays a biological signal.

[Summary of the invention]

The present invention provides a biosignal system comprising a stimulator that applies stimulation to a living body, a biosignal amplifier that amplifies a biosignal from the living body associated with the stimulation, and a monitor display device that displays the biosignal in a waveform or graphic model. In the measuring device,
By configuring the biological single-speech amplifier to include a CMR adjustment circuit that handles low-frequency noise and a CMR adjustment circuit that handles high-frequency noise, it is possible to eliminate low-frequency noise (for example, AC hum from a commercial AC power source) and high-frequency noise. (For example, interference waves at a high frequency level from a stimulation device) can be removed in the same phase, thereby making it possible to accurately measure biological signals.

[Conventional technology]

Generally, when measuring the evoked potential associated with stimulation (electricity, light, sound, etc.) of a subject, AC hum from a commercial AC power source enters the measuring device, causing a major hindrance to the measurement.

Causes of AC hum include leakage current, electrostatic conduction, and electromagnetic induction. Regarding leakage current, alternating current hum is mixed in when the current flowing through indoor wiring or insulators between power lines and the ground, that is, the floor or side surfaces where the test subject is, flows into the test subject. Regarding electrical induction, alternating current hum is mixed in due to electrical electrostatic induction that occurs through the capacitance between indoor wiring or electric light lines and the subject. Furthermore, regarding electromagnetic induction, a magnetic field generated by a current flowing through indoor wiring is electromagnetically coupled to the subject, producing an electromotive force, which results in the introduction of AC hum.

Therefore, the external induced noise voltage is usually minimized by using a shield room to shield electrostatic induction or by insulating the IHA head, which is located throughout the shield room, from the floor using an insulator or the like. Furthermore, since AC hum is applied to the input of the amplifier in the same phase, conventionally, a CMR adjustment circuit for removing the frequency component corresponding to the frequency (50k or 60&) of the commercial AC power supply is built into the amplifier.

[Problem to be solved by the invention]

However, although the common mode rejection (CMR) of the biological signal amplifier in the conventional biological signal measuring device has a high ability at the frequency of the commercial AC power supply (50Hz or 60%), it has a high ability at the frequency of the commercial AC power supply (50Hz or 60%), but it has a high ability at the frequency of the 1lill pulse generated by the stimulator. There are 100
For frequencies near μ5eC1 or 10 KHz, its common mode rejection capability is significantly reduced. Therefore, if the stimulation wave from the stimulation device mixes into the amplifier of the measurement device as an interference wave (artifact), there is a problem that the interference wave cannot be removed in phase, and it is also susceptible to the effects of high frequency noise, making it possible to accurately measure biological signals. The disadvantage was that it was not possible to measure the

The present invention has been made in view of the above points, and its purpose is to eliminate in-phase AC hum from a commercial AC power source, as well as to eliminate interference waves and high-frequency noise from a stimulation device in-phase. The object of the present invention is to provide a biosignal measuring device that can perform the following functions.

[Means to solve the problem]

The biological signal measuring device of the present invention provides a biological signal measuring device for a living body (1).
, (s) Wokaeru stimulation! 2[(2)c! :, above 1
The biological signal (
A biological signal measuring device (A) comprising a biological signal amplifier (3) that amplifies the biological signal (V) and a monitor display device (4) that displays the biological signal (V) in a waveform or graphic model. 3), C for low frequency noise
It is configured to include an MR adjustment circuit (5) and a CMR adjustment circuit (6) for dealing with high frequency noise.

[Effect]

According to the configuration of the present invention described above, since the biosignal amplifier (3) is equipped with the CMR adjustment circuit (5) for dealing with low frequency noise and the CMR adjustment circuit (6) for dealing with high frequency noise, commercial AC AC hum caused by the power source can be removed in-phase, and interference waves and high-frequency noise from the stimulator (2) can be removed in-phase. It becomes possible to accurately measure the electric potential (V).

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to FIGS. 1 to 4.

FIG. 1 is a block diagram showing the configuration of a biological signal measuring device (A) according to this embodiment. In this figure, (1) is the subject, (2) is the electrical stimulation device that applies electrical stimulation (S) to the subject (1), and (3) is the subject who is undergoing electrical stimulation (S). 1) is a biosignal amplifier that amplifies the minute biosignal (evoked potential) (V); and (4) is a monitor display device that displays the amplified biosignal (V) in a waveform or graphic model.

Therefore, in this embodiment, the biological signal amplifier (3)
A CMR adjustment circuit (5) for dealing with low-frequency noise and a CMR adjustment circuit (6) for dealing with high-frequency noise are incorporated inside.

Next, the configuration and operation of the biosignal amplifier (3) will be explained in the second section.
This will be explained based on the diagram.

The biological signal amplifier (3) according to this embodiment basically includes, for example, three OP amplifiers OA, as shown in the figure.

It has a configuration of a so-called differential type DC amplifier consisting of OA2 and OA. In other words, plus human-powered OP amplifier ○A1,
A non-inverting amplifier circuit (7) consisting of a resistor R8 and a negative feedback resistor RI, a non-inverting amplifier circuit (8) consisting of a positive input OP amplifier OA2, a resistor R8 and a negative feedback resistor R2, and the above two non-inverting amplifier circuits. It is composed of an OP amplifier OA3 into which the outputs from (7) and (8) are differentially input via resistors R3 and R4, a differential amplifier circuit (9) consisting of a resistor R6 and a negative feedback resistor R5. Become.

This example further includes a CMR adjustment circuit (5) for dealing with low frequency noise, which is composed of a variable resistor Rt between the resistor R6 and the ground, and a CMR adjustment circuit (5) composed of a variable resistor R and a capacitor C between the contacts a3 and 84. CM that supports high frequency noise
It has an R adjustment circuit (6). Next, we will explain the operation, but before that, we will introduce a CMR between contacts a3 and 81 to prevent high frequency noise.
The operation when the adjustment circuit (6) is not connected will be explained.

First, for example, an evoked potential v is applied to the G1 terminal and the G2 terminal, respectively.
1 and v2 are input, each potential v1 and v2
are amplified by non-inverting amplifier circuits (7) and (8), respectively. Potentials v3 and v4 at contacts a1 and G2 are expressed by the following equations.

At this time, since the AC hum (50Hz or 607) from the commercial AC power source mixes into the G1 and G2 terminals in the same phase, the variable resistor Rr is adjusted to remove the AC hum in the same phase. The CMR adjustment circuit (5) for dealing with this low frequency noise, especially the frequency of the commercial AC power supply, is already installed and adjusted in a normal differential type DC amplifier, so there is no need for new adjustment here.

However, in addition to AC hum from the commercial AC power source, interference waves (artifacts) from the electrical stimulation device (2) are mixed into the G terminal and the G2 terminal. This interference wave has approximately the same frequency as the stimulation wave, and currently has a pulse width of approximately 100 μsec, that is, a frequency of approximately 1QkHz. As mentioned above, the CMR characteristics (CMRR) of a normal differential type DC amplifier are relatively low frequency, for example, 100
It has a characteristic of about 80 dB up to around 1 kHz, but it deteriorates extremely when it exceeds 1 kHz.
It deteriorates to about 4QdB for the frequency (see curve ■ in FIG. 4).

Therefore, in this example, a CMR adjustment circuit (6) for dealing with high frequency noise is incorporated between contacts a3 and G4 to remove the above-mentioned interference waves in the same phase. That is, the interference waves are applied to the G terminal and the G2 terminal in the same phase, but there are variations in the potential between the terminals. In order to eliminate such interference waves in the same mode using the differential amplifier circuit (9), it is necessary to equalize the potentials of the interference waves mixed into each terminal. Therefore, in this example, a variable resistor R is connected between the contacts a3 and 81, and by varying the resistor R, the level of each interference wave is moved and the potentials of each interference wave are made to be the same. The reason why the capacitor C is connected after the variable resistor R is to prevent the direct current component of the biological signal from being cut. Note that the output potential Vout from the output terminal is expressed by the following equation.

5...(3) Here, k = (R6+Rr)(R++r).

For (2) and V, see equations (1) and (2) above.

In addition, as an adjustment method for in-phase removal of interference waves, for example, as shown in Fig. 3, the amplitude IE (1) of the stimulation wave (S) output from the electrical stimulation device (2) is changed from small to large. ,
Among the waveforms displayed on the monitor display device (4) via the biosignal amplifier (3), the CMR adjustment circuit (6) focuses on the amplified noise waveform on the baseline and minimizes it.
) may be adjusted by adjusting the variable resistor R.

As mentioned above, according to this example, an AC hum (50Hz or 60Hz) 1 from a commercial AC power source is installed in the biological signal amplifier (3).
CMR adjustment circuit (5) and electric stimulation device (
Since a CMR adjustment circuit (6) corresponding to interference waves (10kHz) from 2) is provided, in-phase AC hum from the commercial AC power source can be removed, and interference from the electric stimulation device (2) can be removed. Waves can also be removed in phase. In addition, by installing the CMR adjustment circuit (6), the frequency characteristics of CMH in the biological signal amplifier (3) are as shown in the curve ■ in Fig. 4.The CMR of <1 kHz is also about 80 dB as in the vicinity of 1007. Therefore, common-mode removal for high-frequency noise around 10 kHz also works effectively.

Therefore, it becomes possible to accurately measure the biological signal (evoked potential) accompanying stimulation of the subject (1), and the reliability of the biological signal measuring device (A) can be further improved.

〔Effect of the invention〕

In the biological signal measuring device according to the present invention, the biological signal amplifier is equipped with a CMR adjustment circuit for dealing with low-frequency noise and a CMR adjustment circuit for dealing with high-frequency noise. In addition, interference waves and high-frequency noise from the stimulation device can be removed in the same phase, and biological signals accompanying stimulation of the living body can be accurately measured.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a biological signal measuring device according to this embodiment, FIG. 2 is a circuit diagram showing an example of a biological signal amplifier according to this embodiment, and FIG. 3 is a CMR adjustment according to this embodiment. FIG. 4 is a waveform diagram used to explain the method, and is a characteristic diagram showing the frequency characteristics of CMR in the biological signal amplifier according to this embodiment. (A) is a biological signal measuring device, (1) is a subject, (2) is an electrical stimulation device, (3) is a biological signal amplifier, (4) is a monitor display device, and (5) is a low frequency noise countermeasure device. CMR adjustment circuit (6) is a CMR adjustment circuit that deals with high frequency noise. Agent Hidemori Matsukuma

Claims (1)

[Claims] A living body comprising a stimulation device that applies stimulation to a living body, a biological signal amplifier that amplifies a biological signal from the living body accompanying the stimulation, and a monitor device that displays the biological signal in a waveform or a graphic model. A biological signal measuring device, wherein the biological signal amplifier is provided with a CMR adjustment circuit for dealing with low frequency noise and a CMR adjusting circuit for dealing with high frequency noise.