JPH073347Y2 - Electrode contact resistance measuring device - Google Patents

Description

[Detailed Description of the Invention] (Industrial field of application) The present invention relates to an electrode to be attached to a living body at the time of measurement by a bioelectricity measuring device such as an evoked response meter, an electroencephalograph, an electrocardiograph, which measures an electrical phenomenon of the living body The present invention relates to an electrode contact resistance measuring device used for measuring the contact resistance value of the electrode.

(Prior Art) Generally, an electric signal obtained from a living body is very weak,
Therefore, when the contact resistance of the electrode is high, noise is mixed in the electric signal obtained from the living body, which makes it difficult to accurately measure the intended electric phenomenon of the living body. Therefore, an electrode having a resistance value as low as possible is used as an electrode of the bioelectricity measuring device, and it is required that the resistance values of all the electrodes are substantially equal. Therefore, it is necessary to measure the contact resistance value of the electrode.

FIG. 5 is a block diagram showing an outline of a contact resistance measuring device for electrodes of this type which has been generally known in the past. In FIG. 5, (Ea) and (Eb) are a pair of active electrodes,
(Ec) is an inactive electrode serving as a reference electrode, (Ra), (Rb),
(Rc) is the contact resistance of each of the electrodes (Ea), (Eb), (Ec). (B) is a constant current source for resistance value measurement, (A) is a resistance value display device, and (SW) is a constant current source for selectively supplying a constant current to the active electrodes (Ea) and (Eb) that are the electrodes to be measured. It is a switch whose connection can be switched as described above.

In the conventional electrode contact resistance measuring device configured in this manner, the switch (SW) is connected to both active electrodes (Ea), (Eb).
One of the electrodes (Ea), (E) is supplied by supplying a constant current (i) from the constant current source (B) by selectively connecting to one of
The voltage between the terminals in b) is detected, the resistance where the voltage between the terminals is a function is measured, and the value is displayed on the display device (A).

In this case, the voltage between the terminals, that is, the resistance value is (Ra + R
c), (Rb + Rc) and two electrodes (Ea, E
c) and (Eb, Ec) are measured as one set.

(Problems to be Solved by the Invention) Since the conventional electrode contact resistance measuring device is configured as described above, one of the two electrodes forming the measurement set has a poor mounting, a disconnection, When it is in a defective state such as opening, it is not possible to know which electrode is defective. Therefore, when a defective state is found, it is necessary to reattach both electrodes. There was inconvenience. In addition, since the actual measurement is not the contact resistance value of each electrode but the sum of the contact resistance values of two electrodes, the measurement itself is inaccurate.

In addition, the electrode may come off when the examiner moves during measurement,
The mounted state may deteriorate, but in such a case, there is a drawback that the measurement is performed without knowing the detachment of the electrode or the deterioration of the mounted state, which may cause an unexpected measurement error.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an electrode contact resistance measuring device capable of accurately and easily measuring the contact resistance value of each electrode.

(Means for Solving the Problems) In order to achieve the above object, the electrode contact resistance measuring device according to the present invention has at least two active electrodes and one inactive electrode serving as a reference electrode. A constant current source for measuring a resistance value for supplying a constant current, respectively, and a differential amplifier having a large input impedance for differentially amplifying the terminal voltage of each electrode,
A resistance value display device for obtaining and displaying a resistance value from the output voltage of the differential amplifier, and a current supply from the constant current source to two electrodes of the three electrodes, including electrodes whose resistance values are to be measured. And a changeover switch for selectively switching the system path and selectively connecting the differential input side of the differential amplifier to another electrode that does not supply current and the electrode whose resistance value is to be measured. And

(Operation) According to the electrode contact resistance measuring device of the present invention, in the state where the above electrodes are placed in contact with the living body, the current supply path from the constant current source to each electrode is selected via the switch, When the terminal voltage between any one of the selected two electrodes and the other electrode that does not supply the current is detected, a voltage drop due to contact resistance does not occur in the other electrode that does not supply the current. The voltage due to the contact resistance of the electrodes that are in contact is detected, and this voltage is amplified. The changeover switch selects two of the three electrodes to which a constant current should be supplied, and switches the remaining electrode that does not supply a current to one input terminal of the differential amplifier and connects the other input. Of the two electrodes, one electrode whose resistance value is to be measured is selected and connected to the terminal. If the amplified voltage is solved while sequentially operating the changeover switch, the supply current is known, so that the contact resistance value of each electrode as a function of the voltage can be obtained and displayed.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an outline of an electrode contact resistance measuring device according to the present invention. In FIG. 1, (Ea),
(Eb) is a pair of active electrodes, and (Ec) is an inactive electrode serving as a reference electrode, which is grounded in this example. (Ra), (R
b) and (Rc) are contact resistances of the electrodes (Ea), (Eb) and (Ec), and (B) is a constant current source for resistance value measurement, and in this example, one terminal is grounded. . (A) is a resistance value display device, and these are the same as the above-mentioned conventional example shown in 5.

(C) is a differential amplifier, and this differential amplifier (C) differentially amplifies the terminal voltage of each electrode (Ea), (Eb), (Ec) so that the bias current can be ignored compared to the constant current. The input impedance is high.

(D) is an absolute value circuit, which calculates the absolute value of the output voltage of the differential amplifier (C) and uses it to display the resistance value display device (A).
To enter. (SW1) and (SW2) are changeover switches.
2) is two electrodes (Ea) and (Ea) from the constant current source (B).
b) Switching the current supply with, (SW1) is a differential amplifier (C)
The differential input side of the is switched to the voltage difference measurement between the two electrodes (Ea) and (Eb) and the voltage difference measurement between the two electrodes (Eb) and (Ec) (ground side). (SW3) is an amplifier (F) for measuring bioelectric phenomenon and the constant current source (B).
And a differential amplifier (C) with a pair of active electrodes (Ea),
(Eb) is an analog type switching switch that can be selectively switched and connected to switch between the bioelectric phenomenon measurement mode and the contact resistance value measurement mode of each electrode. These switches (SW1), (SW2) ), (SW3) is a logic circuit or CPU
Are automatically switched via a control circuit (E) controlled by

Next, the operation of the above configuration will be described.

When the switch (SW3) is in the contact resistance measurement mode as shown by the solid line in Fig. 1, and the switch (SW1) is connected to the side and the switch (SW2) is connected to the side, the circuit shown in Fig. 2 is obtained. Is established. In this state, the current (i) supplied from the constant current source (B) has a very large input impedance of the differential amplifier (C), so almost all of it passes through the electrode (Ea) as shown by the arrow in the figure. It flows. Therefore, the voltage between the terminals of the electrode (Ea) at this time, that is, the output voltage (Vout) becomes Vout = Ra · | i |, and since (i) is known, the output voltage (Vout)
Is a function of the contact resistance (Ra), and this contact resistance (Ra) is obtained and displayed on the display device (A).

Next, when the switch (SW1) is switched to the side and the switch (SW2) is switched to the side, the circuit as shown in FIG. 3 is established. In this state, the current (i) supplied from the constant current source (B) is the same as in the case of FIG. 2 in the differential amplifier (C).
It does not flow to the side, but flows through the electrode (Eb) as shown by the arrow in the figure. Therefore, the terminal voltage of the electrode (Eb) at this time, that is, the output voltage (Vout) becomes Vout = Rb · | i |, and the display device can be obtained by calculating the contact resistance value (Rb) from the output voltage (Vout). Displayed in (A).

Further, when the switch (SW1) is switched to the side and the switch (SW2) is switched to the side, a circuit as shown in FIG. 4 is established. In this state, the current (i) supplied from the constant current source (B) does not flow to the differential amplifier (C) side as in the case of FIGS. 2 and 3, and the electrode (Ec )
Flowing through. Therefore, the terminal voltage of the electrode (Ec) at this time, that is, the output voltage (Vout), becomes Vout = Rc · | i |, and the contact resistance value (Rc) is calculated from the output voltage (Vout). Displayed in (A).

As described above, the contact resistance values (Ra), (Rb) and (Rc) of the electrodes (Ea), (Eb) and (Ec) can be measured.

Further, as shown by the dotted line in FIG. 1 of the switching switch (SW3), the bioelectric phenomenon can be measured through the amplifier (F) by switching to the bioelectric phenomenon measurement mode. By setting both switches (SW1) and (SW2) above to the electrode side to be measured, and then switching the switch (SW3) to the contact resistance measurement mode, simple operation is possible even during the measurement of bioelectric phenomena. It is possible to measure the contact resistance value of the electrode easily and quickly in a short required time only by performing.

In addition, as a concrete configuration example of the measured value display device (A) in the above-mentioned embodiment, the output voltage (Vo
ut) to A / D converter to convert to digital value and this A / D
Even if it consists of a logic circuit that controls the operation of the converter and a display unit that latches and displays the digital value converted by the above converter, the digital value converted by the A / D converter is read by the CPU. It may be configured to display on a monitor or the like.

Further, the switches (SW1), (SW2), (SW3) may be manually switched.

Further, it is of course possible to apply the present invention to an induction reaction meter having three or more active electrodes, for example, three electrodes as one unit, and a plurality of sets of these are provided.

(Effect of device) As is clear from the above description, when the device according to the present invention is used, the contact resistance values of a plurality of electrodes can be individually measured, so that the electrodes are not properly mounted, disconnection, opening, etc. If there is a state, it can be accurately detected and the contact resistance values of all the electrodes can be measured very accurately.

Further, even if the contact resistance value of each electrode can be measured easily and quickly by performing a simple switch operation during the measurement of the bioelectric phenomenon, it has a practical effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of an electrode contact resistance measuring apparatus according to the present invention, FIGS. 2 to 4 are equivalent circuit diagrams at the time of measuring contact resistance of each electrode, and FIG. It is a block diagram showing an outline of a contact resistance measuring device. (Explanation of symbols) (Ea), (Eb) ... Active electrode, (Ec) ... Inactive electrode,
(Ra), (Rb), (Rc) ... Contact resistance value, (A) ... Resistance value display device, (B) ... Constant current source, (C) ... Differential amplifier, (E) ... … Amplifier for bioelectric phenomenon measurement (SW
1), (SW2), (SW3) ... Switching switch.

Claims (3)

[Scope of utility model registration request] 1. At least two active electrodes for measuring a bioelectric phenomenon, and one inactive electrode serving as a reference electrode,
A contact resistance measuring device for electrodes configured to measure resistance values of these electrodes, wherein a constant current source for measuring a resistance value for supplying a constant current to each of the electrodes and a terminal voltage of each of the electrodes are different from each other. A differential amplifier having a large input impedance for dynamic amplification, a resistance display device for obtaining and displaying a resistance value from the output voltage of the differential amplifier, and a resistance value of the three electrodes from the constant current source. The current supply system path to two electrodes including the electrode to be measured is selectively switched, and the differential input side of the differential amplifier is selected as another electrode that does not supply current and the electrode whose resistance value is to be measured. A contact resistance measuring device for an electrode, comprising: a changeover switch that is electrically connected. 2. The contact resistance measuring device for an electrode according to claim 1, wherein the changeover switch is automatically changed over through a control circuit. 3. A contact resistance measuring device for an electrode according to claim 2, further comprising a switch capable of switching between a bioelectric phenomenon measuring mode and a resistance measuring mode of each electrode by the control circuit. .