JP2001066275A - Electrochemical sensor device and measurement method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the abnormality of a device caused by a fault when the fault such as disconnection and short-circuiting occurs in an electric wiring system from each operation electrode, counter electrode, and reference electrode to an electric signal processing part, in an electrochemical sensor device that gives the specific potential difference between a sensor element with the operation, counter, and reference electrodes, and the operation and reference electrodes of the sensor element, changes the potential of the counter electrode so that the potential difference is kept constantly, and has the electric signal processing part for specifying the concentration of a substance to be measured according to current flowing between the operation and counter electrodes at that time. SOLUTION: For an electric signal processing part 20 of an electrochemical sensor device, at least one of a circuit 29A for detecting a reference electrode potential and a circuit for detecting a counter electrode potential is provided, and it is judged whether the value of detected potential exceeds a preset, specific range or not. Or, a means for judging whether current flowing between the operation and counter electrodes exceeds the preset value or not is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochemical sensor device having a working electrode, a counter electrode and a reference electrode, and a measuring method using the same. The present invention relates to a technology for detecting an abnormality of a device caused by a failure of a part.

[0002]

2. Description of the Related Art In an electrochemical sensor device, three electrodes of a working electrode, a counter electrode and a reference electrode are immersed in a sample solution, and an appropriate potential difference selected between the working electrode and the reference electrode in accordance with a substance to be measured. When the potential applied to the counter electrode is changed so that the potential difference is kept constant, the measurement principle is to determine the concentration of the target substance in the sample solution from the value of the current flowing between the working electrode and the counter electrode. Basically, a sensor unit including a sensor element in which three electrodes of a working electrode, a counter electrode, and a reference electrode are formed, and the sensor unit (specifically, the three electrodes described above)
And an electric signal processing unit for supplying power and processing signals, for example, by applying a potential required for measurement and measuring a current flowing between electrodes of the sensor element.

FIG. 4 shows an example of a sensor element. FIG.
4A shows a plan view, and FIG. 4B shows X in FIG.
FIG. 4 shows a cross-sectional view taken along the line -x. Referring to FIG. 4, a sensor element 1 shown in FIG. 4 includes a rectangular reference electrode 3, a counter electrode 4, and a working electrode 5 arranged on one surface of an insulating substrate 2 in order from the left to the right in FIG. In this structure, lead wires 6 drawn out one by one and contact electrodes 7 provided one by one at the end of each lead wire are formed. The three electrodes have, for example, a structure in which a counter electrode 4 and a working electrode 5 are composed of a titanium layer and a platinum layer covering the same, and the reference electrode 3 has a structure in which a silver layer and a silver chloride layer are further laminated thereon in this order. Has become.

The above-described sensor element 1 is sealed in an outer cylinder 11 as shown in FIG. 5 to form a cartridge structure which can be exchanged for an electric signal processing section. Alternatively, it is simply referred to as a cartridge) 10. Referring to FIG. 5, in this sensor cartridge 10, an opening 13 is provided on the distal end side (left side of the paper surface) of outer cylinder 11, and sensor element 1 has a working electrode,
The counter electrode and the reference electrode are located below the opening, and the lead wire 6 and the contact electrode 7 are accommodated so as to be located on the rear end side (right side in the drawing). On the rear end side of the sensor element in the outer cylinder, a contact pin 14 for connecting to an external electric signal processing unit is provided. The space between the inside of the opening of the outer cylinder 11 and the sensor element 1 is sealed with a sealant 12. The contact electrode 7 and the contact pin 14 of the sensor element described above are electrically connected by contact, so that a lead is provided between the working electrode, the counter electrode, and the reference electrode to the electric signal processing unit. A current path (electrical wiring system) including the line 6, the contact electrode 7, and the contact pin 14 is configured.

At the time of measurement, the opening of the above-described sensor cartridge is immersed in a sample solution.
Although the sample solution that has entered the cartridge from comes into contact with the working electrode, counter electrode, and reference electrode of the sensor element,
Intrusion into other portions is prevented by the sealing material 12. Therefore, between the sealing material 12 and the lead wire 6, the contact electrode 7, the contact pin 14, and the input point of the electric signal processing unit, the electric wiring systems are not short-circuited by the sample solution.

Hereinafter, a method for measuring the concentration using an electrochemical sensor will be described with reference to an example in which the concentration of a hydrogen peroxide solution in a sample solution is measured. FIG. 6 is a circuit diagram when the sensor cartridge 10 is connected to an example of the electric signal processing unit. Referring to FIG. 6, electric signal processing unit 20 shown in FIG. 6 includes a DC voltage source 21, a current detection circuit 22 for detecting a current flowing through the working electrode, and an analog current value detected by the current detection circuit. , An A / D converter 23 for converting the data into digital data, a CPU 24,
It comprises an OM 25 and a RAM 26, an LCD 27, and a potential control circuit 28B using an operational amplifier 28. The operational amplifier 28 has a non-inverting input point connected to the voltage source 21, an output point connected to the counter electrode, and an inverted input point connected to the reference electrode.

When measuring the concentration, first, the opening side of the above-described sensor cartridge is immersed in a storage solution containing, for example, an electrolyte and a pH buffer substance as main components, and a power switch (not shown) of the sensor device is turned on. Turn on to put the device into operation. Next, the sensor cartridge is immersed in the sample solution. Then, the output voltage of the voltage source 21 is set to -700.
mV, and the potential control circuit 28B applies a potential to the counter electrode such that the potential difference between the working electrode and the reference electrode becomes 700 mV (working electrode potential = 0 V, reference electrode potential = -700 mV). As the potential difference between the working electrode and the reference electrode, an appropriate value is selected according to the substance to be measured. By the above operation, the working electrode maintains a positive constant potential with respect to the sample solution, and an anodic oxidation reaction represented by the following reaction formula occurs on the working electrode. An oxidation current corresponding to the concentration flows from the working electrode toward the counter electrode. H ₂ O ₂ → 2H ⁺ + O ₂ + 2e ^-The above-mentioned oxidation current is detected by the current detection circuit 22. Since the current flows between the working electrode and the counter electrode, the current detection circuit 22 may be provided on either the working electrode side or the counter electrode side. CP
The U 24 converts the detected current value into digital data by the A / D converter 23 according to the firmware stored in the ROM 25, and stores it in the RAM 26.
The CPU 24 further calculates the concentration of the hydrogen peroxide solution based on the relational expression between the current value stored in the ROM 25 and the concentration of the hydrogen peroxide solution, and displays it on the LCD 27.

[0008]

It is well known that it is important to control the sensitivity of a sensor element in order to obtain accurate measurement results in an electrochemical sensor device.
Several techniques have been developed for sensitivity management as described below.

[0009] That is, Japanese Patent Publication No. Hei 7-119727 (publication 1) discloses a method of refreshing an electrode in a biosensor which is a kind of electrochemical sensor element. The enzyme electrode used in the biosensor described in the above publication 1 is composed of a working electrode and a counter electrode made of Pt and a reference electrode made of Ag, and a predetermined physiologically active substance is fixed on each electrode. In the biosensor described in the above publication 1, such a sensor element is used to measure the concentration of the substance to be measured in a state where a forward bias voltage is applied to the working electrode with reference to the counter electrode. A current blocking film such as an oxide film is formed on the surface of the working electrode, and the activity of the working electrode is reduced. Therefore, after the measurement is performed a certain number of times, during the period in which the measurement is not performed, a reverse bias is applied to remove the above-mentioned current-carrying film, thereby restoring (refreshing) the activity of the working electrode. In the refresh method disclosed in this publication, when a working electrode is refreshed, a predetermined reverse bias voltage is applied for a predetermined time according to a conventional method, and then a forward bias voltage higher than a forward bias voltage at the time of measurement is applied. Supply, the time until the measurement can be resumed after the refresh is reduced.

[0010] On the other hand, Japanese Patent Application Laid-Open No. Hei 4-230843 discloses a technique for predicting the life of a sensor element in an electrochemical gas sensor. In the gas sensor described in the above publication 2, a target gas detection unit for detecting a detection target gas and a reference gas detection for detecting a reference gas existing at a certain concentration in a use environment are provided on the same one insulating substrate. Parts are provided. Each of the target gas detector and the reference gas detector has a pair of a working electrode, a counter electrode, and a reference electrode.
Each pair is equipped. By doing so, the temporal change characteristic of the sensitivity of the target gas detecting unit and the temporal characteristic of the sensitivity of the reference gas detecting unit are made equal. Then, when the detection current of the reference gas detection unit (current flowing between the working electrode and the counter electrode) becomes equal to or less than a predetermined current and it is determined that the life of the sensor of the reference gas detection unit has come, The sensor of the gas detector is also determined to have reached the end of its life.

As described above, several techniques have been considered for managing the change over time of the sensor element in the electrochemical sensor device. However, these techniques are based on the premise that there is no failure such as disconnection or short circuit in the electric wiring system from the working electrode, counter electrode and reference electrode of each sensor element to the electric signal processing unit. None of the conventional electrochemical sensor devices have any means for detecting such a failure. As a result, even when the above-described failure of the electric signal system occurs in the device, the measurement is performed as it is, and an erroneous measurement result may be output.

Accordingly, the present invention provides a sensor element having three electrodes of a working electrode, a counter electrode and a reference electrode, and a predetermined potential difference between the working electrode and the reference electrode of the sensor element, and keeps the potential difference constant. In the electrochemical sensor device including an electric signal processing unit that changes the potential applied to the counter electrode and specifies the concentration of the substance to be measured from the current flowing between the working electrode and the counter electrode at that time, each working electrode, the counter electrode, and It is an object of the present invention to reliably detect an abnormality of a device based on a failure such as a disconnection or a short circuit in an electric wiring system from a reference electrode to an electric signal processing unit.

[0013]

According to the present invention, there is provided an electrochemical sensor device comprising a sensor element having a working electrode, a counter electrode and a reference electrode, and a predetermined potential difference between the working electrode and the reference electrode of the sensor element. And an electric signal processing unit that changes the potential applied to the counter electrode so as to keep the potential difference constant, and then specifies the concentration of the substance to be measured from the current flowing between the working electrode and the counter electrode. In the sensor device,
Detecting at least one of the potential of the reference electrode and the potential of the counter electrode,
Means for judging the presence or absence of an abnormality in the device based on a disconnection of a current path from each of the electrodes to the electric signal processing unit or a short circuit between the current paths depending on whether or not the detected value is outside a predetermined range. Is provided. Further, by detecting that the current flowing between the working electrode and the counter electrode is greater than a predetermined value, a device based on a short circuit between current paths from each of the electrodes to the electric signal processing unit is detected. Characterized in that a means for detecting an abnormality is provided.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a block diagram illustrating a configuration of an electrochemical sensor device according to an embodiment. Referring to FIG. 1, the apparatus according to the present embodiment includes a reference pole potential detection circuit 29A for detecting the potential of a reference pole, and converts an analog reference pole potential detected by the circuit into an A / D converter 23. Is different from the conventional electrochemical sensor device shown in FIG. In the present embodiment, the DC voltage source 21 in the conventional device is replaced with the D / A converter 21A.
, And takes in a digital signal from the CPU 24 and converts it into an analog DC voltage, thereby making it easy to control the presence or absence of an output and the voltage value.

The reference pole potential detection circuit 29A is composed of an operational amplifier 29 having a non-inverting input point connected to the reference pole and an output point and an inverting input point directly connected. The output point of the operational amplifier 29 is A / A. It is connected to the input point of the D converter 23. The output of the operational amplifier 29 is also connected to the inverting input of the opposing operational amplifier 28. Therefore, the reference pole is equivalently directly connected to the inverting input point of the operational amplifier 28 by the total feedback from the output point of the operational amplifier 29 to the inverting input point.

In this embodiment, the electrochemical sensor device shown in FIG.
The effect of the invention was confirmed. As the sensor element, one manufactured as described below was used. Referring to FIGS. 4 and 5,
First, on a 60 × 70 mm glass substrate, a titanium layer (0.02 to 0.2 μm) and a platinum layer (0.1 to
1.0 μm) and a silver layer (0.1 to 1.0 μm) are formed by a sputtering method.

Next, patterns of the reference electrode 3, the counter electrode 4, the working electrode 5, the lead wire 6, and the contact electrode 7 are formed by photolithography. At this time, only the reference electrode 3 is left with the uppermost silver layer remaining, and the silver layer is removed for the other electrodes and lead wires so that the platinum layer is exposed. Note that the shape of each electrode and lead wire is
Is 0.4 × 2.0 mm, the counter electrode 4 is 0.4 × 2.0 mm,
The working electrode 5 has a size of 1.2 × 2.0 mm, the lead wire 6 has a size of 1.2 × 2.8 mm, and the contact electrode 7 has a size of 1.6 × 0.8 mm per electrode.

Next, a silver chloride layer is formed on the surface of the silver layer on the reference electrode 3 by treating with an aqueous solution of iron chloride (3). Thereafter, the insulating substrate 2 is divided into individual sensor elements (6 × 9 mm),
Further, this sensor element is housed in an outer cylinder to form a cartridge structure shown in FIG.

The insulating substrate 2 is not limited to glass, but may be a silicon substrate having a silicon oxide film formed thereon, quartz, polyimide, polycarbonate, or a glass epoxy substrate. For the electrodes 3, 4, 5, 7 and the lead wires 6, conductive materials such as carbon, gold, iridium and the like can be used in addition to platinum. As a method for depositing the conductive material, a vapor deposition method, a screen printing method, a plating method, or the like can be employed in addition to the sputtering method. For the formation of the silver chloride layer on the reference electrode, a method of treating with an aqueous solution of chromium chloride (3) can be used in addition to a method of treating with an aqueous solution of iron chloride (3). Alternatively, it can be formed by a method of electrolysis in a chloride aqueous solution.

In measuring the concentration of the hydrogen peroxide solution, the sensor cartridge is immersed in a sample solution containing the hydrogen peroxide solution. Then, the CPU 24 causes the D / A converter 21A to output a voltage of -700 mV, and the potential control circuit 28A (the operational amplifier 28 and the reference pole potential detection circuit 29A).
) Is applied to the counter electrode such that the potential difference between the working electrode and the reference electrode becomes 700 mV. afterwards,
Before measuring the actual working electrode current, the reference electrode potential detection circuit 29A detects the potential of the reference electrode. CPU 24
According to the firmware stored in the ROM 25, the detected reference pole potential is converted into digital data by the A / D converter 23, taken in, and stored in the RAM 26. The CPU 24 further refers to the conditions stored in the ROM 25 to determine whether or not the reference electrode potential is within a predetermined range. In the case of, "abnormal" is determined. In the case of "abnormal", the CPU 24 stops the output of the D / A converter 21A as a voltage source, stops the potential control circuit 28A to suspend the application of the potential to the reference electrode and the counter electrode,
A message such as "sensor replacement" is displayed on the CD 27.

In this embodiment, if the sensor element is normal and there is no abnormality in the electric wiring system from the working electrode, the counter electrode and the reference electrode to the electric signal processing section, the reference electrode potential is -700 ± 10 mV. Was confirmed. Accordingly, if the measurement result of the reference electrode potential prior to the measurement of the working electrode current is −710 to −690 mV, the CPU 24 determines that the device is “normal”, and measures the working electrode current, Move on to the calculation of concentration.

On the other hand, the electrical wiring system from the reference electrode (in FIGS. 4 and 5, the lead wire 6 of the sensor element, the contact between the contact electrode 7 and the contact pin 14, and the input point of the contact pin 14 and the electrical signal processing unit) Is broken, the reference electrode potential should be -700 m
Drifts gradually from V to the plus or minus side,
For example, it shows an unstable behavior approaching 0 mV. It is considered that this is because when the electric wiring system from the reference electrode is disconnected, an indefinite potential such as the leakage potential of the insulating substrate 2 of the sensor element or the reference electrode is input to the operational amplifier 29. On the other hand, even when the sealing property of the sealing material 12 inside the sensor cartridge is poor and the electric wiring system of the reference electrode and the electric wiring system of the working electrode are short-circuited,
It was observed that the reference pole potential became unstable.

From the above, in the present embodiment,
When the reference electrode potential is a value outside the range of the set value -700 ± 10 mV, at least there is a disconnection of the electric wiring system from the reference electrode or a short circuit between the electric wiring systems due to insufficient sealing in the sensor cartridge. You can judge it.

Next, a second embodiment of the present invention will be described. FIG. 2 is a block diagram showing a configuration of the electrochemical sensor device according to the second embodiment of the present invention.
Referring to FIG. 2, the electrochemical sensor device according to the present embodiment includes a counter electrode potential detection circuit 30A for detecting the potential of the counter electrode, instead of the reference electrode potential detection circuit,
This is different from the electrochemical sensor device according to the first embodiment. The counter electrode potential detection circuit 30A includes an operational amplifier 30 in which a non-inverting input point is connected to a counter electrode, and an output point and an inverting input point are directly connected, and the output point of the operational amplifier 30 is A / D
It is connected to the input point of the converter 23.

In this embodiment, a sensor cartridge having the same structure as that of the first embodiment is used to measure the concentration of hydrogen peroxide solution. That is, the above-described sensor cartridge is immersed in a sample solution containing a hydrogen peroxide solution, and the D / A converter 21A receives a −70 from the CPU 24.
A voltage of 0 mV is output, and the potential control circuit 28A (consisting of the operational amplifier 28 of the counter electrode and the operational amplifier 29 of the reference electrode)
Thus, the potential is applied to the counter electrode such that the potential difference between the working electrode and the reference electrode becomes 700 mV. Thereafter, before measuring the actual working electrode current, the counter electrode potential was detected by the counter electrode potential detection circuit 30A. In this case, if the sensor element and the electric wiring system are normal, the counter electrode potential is 0 to 800 m.
It was confirmed that the value was within the range of V.

On the other hand, when the electric wiring system from the reference electrode is disconnected, the counter electrode potential is 1.0 V or -1.0 V
To saturate. This is because if the sensor element is normal and there is no abnormality in the electric wiring system, a potential corresponding to the potential of the reference electrode -700 mV is applied to the counter electrode by the potential control circuit 28A. If the electric wiring system of the pole is disconnected, the input potential of the operational amplifier 29 of the reference pole becomes indefinite, and the potential control circuit 28A gives a potential corresponding to this undetermined potential to the counter electrode, and finally the operation is performed. It is considered that the voltage will saturate to any of ± 1.0 V which is the power supply voltage of the amplifier 28.

On the other hand, even when the electric wiring system from the counter electrode is disconnected, the counter electrode potential saturates to a potential of 1.0 V or -1.0 V. This is because the potential control circuit 28A tries to apply a potential to the counter electrode so that the potential difference between the working electrode and the reference electrode is 700 mV, but the electrical wiring system to the counter electrode is disconnected, and the potential control circuit 28A It is presumed that the voltage between the reference electrode and the reference electrode cannot be maintained at 700 mV, and that the voltage eventually saturates to any of ± 1.0 V, which is the power supply voltage of the operational amplifier 28.

From the above, in the present embodiment,
If the potential of the counter electrode is out of the range of 0 to 800 mV, the device may be faulty. In particular, when the potential of the counter electrode indicates a large voltage equal to the power supply voltage of the operational amplifier, the electric wiring system of the reference electrode Alternatively, it can be said that disconnection has occurred in at least one of the electrical wiring systems of the counter electrode.

Next, a third embodiment of the present invention will be described. FIG. 3 is a block diagram showing a configuration of the electrochemical sensor device according to the third embodiment of the present invention.
Referring to FIG. 3, in the present embodiment, the current flowing between the working electrode and the counter electrode, that is, the current value detected by current detection circuit 22 is compared with the electric wiring system to the electric signal processing unit. An upper limit for determining the presence or absence of a failure is provided. For example, in the sensor cartridge shown in FIG. 5, if the sealing property of the sealing material 12 is incomplete and the sample solution penetrates to the contact pins 14, the contact pins are short-circuited. In this case, if the contact pin of the working electrode and the contact pin of the reference electrode are short-circuited, the potential control circuit 28A cannot make the potential difference between the working electrode and the reference electrode 700 mV, and the counter electrode has the operational amplifier 28 A large positive or negative potential such as the power supply voltage of As a result, electrolysis of water occurs on the working electrode or the counter electrode, and if the sensor element and the electric wiring system are normal between the working electrode and the counter electrode, the measurement should be within about 1000 nA, for example, 5000 nA. A large current that greatly exceeds the range of system error flows. According to the present embodiment, it is possible to detect such an abnormality of the device mainly due to a short circuit of the electric wiring system in the sensor cartridge.

Heretofore, the reference electrode potential detecting circuit,
Although the example of the sensor device individually including the counter electrode potential detection circuit has been described, it is needless to say that both the detection circuits can be provided in one device. Further, a function of determining whether or not the working electrode current exceeds the upper limit as in the third embodiment may be added.

Although the sensor element having a cartridge structure has been described as an example, it will be apparent that the function and effect of the present invention will not be impaired even if the sensor element has no cartridge structure.

[0032]

As described above, the present invention provides a sensor element having a working electrode, a counter electrode, and a reference electrode, and a predetermined potential difference between the working electrode and the reference electrode of the sensor element. The potential applied to the counter electrode is changed so as to keep the potential difference constant, and then an electric signal processing unit for specifying the concentration of the substance to be measured from the current flowing between the working electrode and the counter electrode. Means for detecting at least one of the potential of the reference electrode and the potential of the counter electrode and determining whether or not the detected value is outside a predetermined range. Alternatively, there is provided means for detecting that the current flowing between the working electrode and the counter electrode is larger than a predetermined value.

Thus, according to the present invention, in the electrochemical sensor device, even if there is a failure such as disconnection or short circuit in the electric wiring system from the working electrode, the counter electrode and the reference electrode to the electric signal processing section, It is possible to reliably detect an abnormality of the device based on the failure.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an electrochemical sensor device according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of an electrochemical sensor device according to a second embodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration of an electrochemical sensor device according to a third embodiment of the present invention.

4A and 4B are a plan view and a cross-sectional view illustrating a structure of an example of a sensor element.

FIG. 5 is a plan view, a side view, and a cross-sectional view illustrating a structure of an example of a sensor cartridge.

FIG. 6 is a block diagram of a circuit for explaining a measuring method of the electrochemical sensor device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensor element 2 Insulating substrate 3 Reference electrode 4 Counter electrode 5 Working electrode 10 Sensor cartridge 11 Outer cylinder 12 Sealing material 13 Opening 14 Contact pin 20 Electric signal processing unit 21 Voltage source 21 A D / A converter 22 Current detection circuit 23 A / D converter 24 CPU 25 ROM 26 RAM 27 LCD 28, 29, 30 Operational amplifier 28A, 28B Potential control circuit 29A Reference pole potential detection circuit 30A Counter pole potential detection circuit

Claims (6)

[Claims] 1. A sensor element having three electrodes of a working electrode, a counter electrode and a reference electrode, and a predetermined potential difference between a working electrode and a reference electrode of the sensor element, and a counter electrode for maintaining the potential difference constant. And an electric signal processing unit for specifying the concentration of the substance to be measured from the current flowing between the working electrode and the counter electrode at that time, the potential of the reference electrode, the potential of the counter electrode, Detect at least one,
Means for judging the presence or absence of an abnormality in the device based on a disconnection of a current path from each of the electrodes to the electric signal processing unit or a short circuit between the current paths depending on whether or not the detected value is outside a predetermined range. An electrochemical sensor device comprising: 2. A sensor element having three electrodes of a working electrode, a counter electrode and a reference electrode, and a predetermined potential difference between a working electrode and a reference electrode of the sensor element, and a counter electrode for maintaining the potential difference constant. In the electrochemical sensor device comprising an electric signal processing unit for specifying the concentration of the substance to be measured from the current flowing between the working electrode and the counter electrode at that time, between the working electrode and the counter electrode Means for detecting a device abnormality based on a short circuit between current paths from each of the electrodes to the electric signal processing unit by detecting that a flowing current is greater than a predetermined value. An electrochemical sensor device. 3. A sensor element having three electrodes of a working electrode, a counter electrode and a reference electrode, and a predetermined potential difference between a working electrode and a reference electrode of the sensor element, and a counter electrode so as to keep the potential difference constant. And an electric signal processing unit for specifying the concentration of the substance to be measured from the current flowing between the working electrode and the counter electrode at that time, the electric signal processing unit comprising: a DC voltage supply unit; Potential control means for controlling the potential difference between the working electrode and the reference electrode to be equal to the output voltage of the DC voltage supply means, and reference electrode potential detection means for detecting the value of the potential of the reference electrode. Current detection means for detecting a value of a current flowing between a working electrode and a counter electrode; analog / digital for converting an output value of the current detection means and an output value of the reference electrode potential detection means from an analog value to a digital value conversion And determining whether or not the potential of the reference electrode is outside a predetermined range based on the output value of the analog / digital conversion means, and determining the concentration of the substance to be measured in accordance with the determination result. An electrochemical sensor device. 4. A sensor element having three electrodes of a working electrode, a counter electrode and a reference electrode, and a predetermined potential difference between a working electrode and a reference electrode of the sensor element, and a counter electrode so as to keep the potential difference constant. And an electric signal processing unit for specifying the concentration of the substance to be measured from the current flowing between the working electrode and the counter electrode at that time, the electric signal processing unit comprising: a DC voltage supply unit; Potential control means for controlling the potential difference between the working electrode and the reference electrode to be equal to the output voltage of the DC voltage supply means; counter electrode potential detection means for detecting the value of the potential of the counter electrode; Current detection means for detecting the value of the current flowing between the pole and the counter electrode; and analog / digital conversion means for converting the output value of the current detection means and the output value of the counter electrode potential detection means from an analog value to a digital value. Means for determining whether or not the potential of the counter electrode is outside a predetermined range based on the output value of the analog-to-digital conversion means, and for specifying the concentration of the substance to be measured in accordance with the result of the determination. An electrochemical sensor device comprising: 5. A sensor element provided with three electrodes of a working electrode, a counter electrode and a reference electrode, and a predetermined potential difference between a working electrode and a reference electrode of the sensor element, and a counter electrode so as to keep the potential difference constant. And an electric signal processing unit for specifying the concentration of the substance to be measured from the current flowing between the working electrode and the counter electrode at that time, the electric signal processing unit comprising: a DC voltage supply means; Potential control means for controlling the potential difference between the working electrode and the reference electrode to be equal to the output voltage of the DC voltage supply means, and detecting the value of the current flowing between the working electrode and the counter electrode. Current detection means, analog-to-digital conversion means for converting the output value of the current detection means from an analog value to a digital value, and between the working electrode and the counter electrode based on the output value of the analog-to-digital conversion means. The electrochemical sensor apparatus characterized by comprising a means for identifying the concentration of the analyte in accordance with the determination result together with the current to determine whether a predetermined value or more to be. 6. The method according to claim 1, further comprising the step of, prior to the measurement of the concentration of the substance to be measured, a step of judging the presence or absence of an abnormality in the device, using the electrochemical sensor device according to claim 1 or 2. Method for measuring the concentration of a substance.