CN112268947A - Self-calibration structure and method of miniature electrochemical sensor - Google Patents

Abstract

The invention discloses a self-calibration structure and a self-calibration method of a miniature electrochemical sensor, and the self-calibration structure comprises a sensor main body, a working electrode, a main reference electrode and a first electrolyte, wherein the working electrode and the main reference electrode are arranged in the sensor main body; the calibration of the main reference electrode is realized by measuring the electrode potential difference between the main reference electrode and the self-calibration reference electrode, wherein the self-calibration reference electrode is independently arranged in a closed container; the invention belongs to the technical field of sensors, and aims to solve the problems of reduced measurement precision and limited service life caused by potential fluctuation or potential drift of a reference electrode of a sensor in the prior art; the technical effects achieved are as follows: the invention can realize the self-calibration work of the sensor without an external calibration device, user intervention and pause of experiment or measurement.

Description

Self-calibration structure and method of miniature electrochemical sensor

Technical Field

The invention relates to the technical field of sensors, in particular to a self-calibration structure of a miniature electrochemical sensor.

Background

The electrochemical sensor is a sensor for sensing and detecting based on the electrochemical property of an object to be detected and converting the chemical quantity of the object to be detected into electric quantity, and the electrochemical property of the object to be detected is characterized by measuring the change of electric signals such as electric potential, current and the like generated in the target electrochemical reaction when in use.

Among many sensor types, the electrochemical sensor has the advantages of relatively small size, low power consumption, simple structure, low cost, etc., and has gradually become the key point of the research field and wide application range. But it also has the problems of measurement drift, measurement accuracy degradation, need of regular calibration and maintenance, etc. With further miniaturization, miniaturization and intellectualization of the electrochemical sensor, the electrochemical sensor can be more widely applied to the fields of scientific research, medical treatment, industry, national defense, environment and the like.

Electrochemical sensors are typically composed of an electrode assembly, an electrolyte, and a permeable membrane. The electrode assembly may employ 2 electrodes (2 electrode system) or 3 electrodes (3 electrode system), including a reference electrode (reference electrode), a working electrode (working electrode), and sometimes an auxiliary electrode (counter electrode). The reference electrode is typically used to provide a known solution potential, and is typically of the type used such as a standard hydrogen electrode, calomel electrode, and most typically a silver/silver chloride electrode. The working electrode is typically made of an inert metal, such as platinum, gold, etc. The auxiliary electrode is also typically made of an inert metal, but the electrode area needs to be much larger than the working electrode. The electrolyte provides an ion-exchangeable environment that enables the targeted electrochemical reactions (e.g., redox reactions) to occur and efficiently transfer ionic charges to the electrodes. The electrolyte environment needs to remain stable and compatible with the electrode material, forming a stable reference potential with the reference electrode. The change in the electrolyte ion concentration directly affects the stability of the reference potential and thus the actual measurement result. In addition, in order to control the interference caused by other substances or reactions, some electrochemical sensors incorporate a filter membrane (gas permeable membrane) to selectively pass the substance to be detected and generate the target electrochemical reaction.

Electrochemical sensors generally employ chronoamperometry, in which an electrode set is in the same electrolyte solution, and when a specific voltage is applied between the electrode sets (working electrode and reference electrode), a target electrochemical reaction occurs in the electrode set, thereby generating a certain current between the electrodes. This reaction current is directly related to the reaction rate in solution, specifically to the rate of diffusion of the dissolved molecules to the surface of the working electrode, determined by its diffusion model, and is generally linear. The diffusion model is related to the concentration of ions to be measured and the shape and size of the electrode. Therefore, a specific voltage is applied to the sensor electrode, the reaction current is measured, and a specific target concentration value can be obtained after calibration calculation. Typical sensors are for example dissolved oxygen concentration sensors.

In addition, some electrochemical sensors characterize physical quantities by measuring the potential difference between electrodes. Such sensors typically employ a selective electrode for a particular ion as a working electrode, in combination with a reference electrode to form an electrode assembly. The electrode potential is the potential difference between the plate and the solution in the electrode, and different types of electrodes will have different potentials. The reference electrode can be generally considered to have stable potential and does not change along with the change of the measurement environment, but the working electrode can generate different potentials in solutions with different ion concentrations, so that the potential difference between the working electrode and the reference electrode is measured by comparing with the reference electrode, and the concentration value of the ions to be measured in the solution can be obtained after calibration calculation.

As mentioned above, the performance and stability of a micro electrochemical sensor is related to a number of factors, among which is directly related to the state, properties, stability of the reference electrode. Whether measured using chronoamperometry or electrode potential difference, a stable reference electrode is required as the reference potential. However, in the actual measurement process, the reference electrode is affected to some extent, and thus is degraded to some extent, and thus fluctuating drift of the electrode potential is generated. In particular, the reference electrode in a micro electrochemical sensor is difficult to use due to the limited volume.

Such as a silver/silver chloride reference electrode commonly used in miniature electrochemical sensors, the surface of which undergoes a redox reaction, as shown below. The equilibrium is between silver metal (Ag) and its salt, silver chloride (AgCl), maintaining a relatively stable electrode potential. The standard electrode potential E0 was 0.230V. + -. 10mV relative to the Standard Hydrogen Electrode (SHE).

In order to improve the stability of the silver/silver chloride reference electrode, the requirement of having as many metal silver substrates and silver chloride as possible is met on the premise of ensuring a certain proportion between the metal silver and the silver chloride, so that the stability of the electrode can be obviously improved by increasing the surface area and the thickness of the electrode. However, the reference electrodes integrated in miniature electrochemical sensors typically have a small surface area and a silver substrate of limited thickness. And therefore will be affected during actual measurement, causing fluctuations and drift, and also as the surrounding environment changes. Several cases are listed below for further explanation.

When measured by amperometry using a 2-electrode microsensor, the resulting reaction current will flow through the reference electrode, which will affect the equilibrium of the redox reactions at the reference electrode, thus causing fluctuations in the electrode potential. In order to reduce the current passing through the reference electrode as much as possible, some micro-sensors adopt a 3-electrode system, and an auxiliary electrode is added to shunt the generated reaction current, but the current passing through the reference electrode during measurement is difficult to completely eliminate due to the existence of leakage current of a sensor driving circuit. Miniature electrochemical sensors based on measuring the potential difference between electrodes suffer from similar problems due to the presence of drive circuit leakage currents.

In addition, the silver/silver chloride reference electrode also generates electrode potential changes along with changes of ion concentration and temperature in the external environment. As shown in the table below.

It can be seen that different environments with different concentrations of chloride ions can generate different reference electrode potentials, thereby causing fluctuations in the reference electrode potential, which directly affect the measurement result of the sensor.

Therefore, in order to make the reference electrode as stable as possible, the following needs to be satisfied:

1. the reference electrode needs to operate in a stable electrolyte environment. If the electrolyte environment is isolated from the solution to be tested, the connection needs to be made via a salt bridge.

2. The reference electrode itself needs to have a large area and volume so that the current passing through the reference electrode will remain stable.

3. With the use of a reference electrode, measurement calibration of the reference electrode potential is required to be performed periodically. The current electrode potential of the reference electrode is obtained through measurement, and the magnitude of the applied voltage in a chronoamperometry or the potential difference result in an electrode potential difference measurement method needs to be adjusted and calibrated, so that accurate measurement can be obtained.

The existing miniaturized electrochemical sensor generally has a glass cylindrical electrode or a flat electrode manufactured based on a photoetching method, but the existing miniaturized electrochemical sensor has the problems of limited sensor volume and fluctuation and drift of a reference electrode. Calibration needs to be performed periodically, manual intervention is required for calibration, and an external calibration device needs to be used.

Electrochemical sensors have been described so far as the following are available:

1. the Chinese patent application: miniature electrochemical sensor based on direct forming mesoporous carbon technology and manufacturing method

Application publication No.: CN104502428A

2. The Chinese patent application: electrochemical sensor for detecting blood enzyme

Application publication No.: CN111638256A

3. The Chinese patent application: preparation method of miniature electrochemical sensor for detecting dopamine

Application publication No.: CN110940712A

4. The Chinese patent application: dissolved oxygen electrochemical sensor

Application publication No.: CN101042365A

5. The Chinese patent application: dissolved oxygen electrochemical sensor

Application publication No.: CN104698045A

6. Polarography dissolved oxygen sensor

The prior art has the following defects:

1. due to the fact that the size and the area of the miniature electrochemical sensor are limited, the area of the reference electrode is small, the size is limited, the stability of the reference potential is not high when the miniature electrochemical sensor is used for measurement, potential drift exists, and the service life is limited.

2. In addition, there is no relatively stable ion concentration environment around the reference electrode, and potential fluctuation is generated along with the change of the ion concentration around, which affects the measurement accuracy, so that the stability is not high.

3. In performing calibration, an externally referenced reference electrode is required for calibration.

4. In performing calibration, a user is required to perform calibration of the reference electrode, and no experiment or measurement can be performed at the same time.

Disclosure of Invention

Therefore, the invention provides a self-calibration structure and a self-calibration method of a miniature electrochemical sensor, which are used for solving the problems of measurement drift, measurement accuracy reduction, limited service life, need of regular calibration and maintenance and the like of the electrochemical sensor in the prior art.

In order to achieve the above purpose, the invention provides the following technical scheme:

according to a first aspect of the present invention, a self-calibration structure of a micro electrochemical sensor comprises a sensor body, a working electrode, a main reference electrode and a first electrolyte, wherein the working electrode and the main reference electrode are arranged in the sensor body, and the sensor body is filled with the first electrolyte, and the self-calibration structure is characterized by further comprising a self-calibration reference electrode arranged in the sensor body; and calibrating the main reference electrode by measuring the potential difference of the electrodes between the main reference electrode and the self-calibration reference electrode.

Further, the sensor further comprises a closed container, the closed container is arranged in the sensor main body, the self-calibration reference electrode is independently packaged in the closed container, and the first electrolyte is arranged on the periphery of the closed container.

And further, the self-calibration reference electrode also comprises a second electrolyte, wherein the second electrolyte is filled in the closed container and is arranged around the self-calibration reference electrode.

Further, a porous substance is arranged on the side wall of the closed container, and the closed container is connected with the first electrolyte filled in the sensor body through the porous substance, so that an ion channel is established.

Further, the inside of the closed container is filled with a mesh-like porous structure for stabilizing the ion concentration in the second electrolyte. The reticular porous structure can adopt electrolyte colloid (hydrogel) or use sponge, filter paper and the like.

The sensor comprises a sensor body, and is characterized by further comprising an auxiliary electrode, wherein the auxiliary electrode is packaged in the sensor body and arranged on the left side of the working electrode, the working electrode is arranged in the middle of the sensor body, the closed container is located on the right side of the working electrode, and the main reference electrode is arranged between the closed container and the working electrode.

Furthermore, the bottom of the sensor main body is provided with a small hole.

Furthermore, a communicating interface is arranged on the small hole and used for communicating an external substance to be detected with the sensor main body, wherein the communicating interface is a breathable film or a porous substance and the like.

The self-calibration measuring device further comprises a signal conversion circuit and a measuring circuit, the main reference electrode and the self-calibration reference electrode are connected to one end of the signal conversion circuit through a connecting wire, one end of the measuring circuit is connected to the other end of the signal conversion circuit, and the other end of the measuring circuit is connected to the main reference electrode and the working electrode through a connecting wire.

According to a second aspect of the present invention, a method for self-calibration of a micro-electrochemical sensor, using the self-calibration structure of the micro-electrochemical sensor of any one of the first aspects of the present invention, comprises the following steps:

step 1, a reference electrode in a sensor body and a reference electrode for self-calibration are connected into a signal conversion circuit, and the signal conversion circuit converts potential difference signals of the two reference electrodes into measurement signals;

and 2, feeding back the result of the measurement signal to a measurement circuit of the sensor, and adjusting the measurement signal or calibrating the measurement result by the measurement circuit, thereby realizing high-precision measurement.

The invention has the following advantages:

1. the self-calibration reference electrode is arranged, so that the self-calibration work of the sensor can be realized, an external calibration device is not needed, the user intervention is not needed, and the experiment or the measurement is not needed to be suspended.

2. The invention solves the problems of reduced sensor measurement precision and limited service life caused by the problems of degradation and drift of the reference electrode of the miniature electrochemical sensor through the timing self-calibration or the real-time self-calibration of the miniature electrochemical sensor. By realizing the self-calibration function of the sensor, the measurement accuracy of the sensor is maintained as much as possible, and the service life is prolonged.

3. The invention solves the problem of measurement precision reduction caused by more potential fluctuation of the reference electrode in the measurement process of the miniature electrochemical sensor; the measurement precision of the sensor is improved by realizing the real-time self-calibration function of the sensor.

4. The invention can solve the problems of limited measurement precision and limited service life caused by limited volume of the reference electrode in the miniature electrochemical sensor by using the self-calibration reference electrode and the main reference electrode in a matching way.

5. The invention has simple structure, convenient production and assembly, and easy realization and integration into various miniature electrochemical sensors.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.

The structures, ratios, sizes, and the like shown in the present specification are only used for matching with the contents disclosed in the specification, so as to be understood and read by those skilled in the art, and are not used to limit the conditions that the present invention can be implemented, so that the present invention has no technical significance, and any structural modifications, changes in the ratio relationship, or adjustments of the sizes, without affecting the effects and the achievable by the present invention, should still fall within the range that the technical contents disclosed in the present invention can cover.

Fig. 1 is a schematic diagram of an implementation of a self-calibration structure of a micro electrochemical sensor according to some embodiments of the present invention.

Fig. 2 is a schematic diagram of an implementation manner of a self-calibration structure of a micro electrochemical sensor according to another embodiment of the present invention.

In the figure: 1. the sensor comprises a working electrode, 2, a main reference electrode, 3, an auxiliary electrode, 4, a sensor body, 5, a first electrolyte, 6, a communication interface, 7, a self-calibration reference electrode, 8, a closed container, 9, a second electrolyte, 10, a porous substance, 11, a measurement circuit, 12, a differential amplifier, 13, a signal conditioning circuit, 14, an analog-to-digital converter, 15 and a self-calibration module.

Detailed Description

The present invention is described in terms of particular embodiments, other advantages and features of the invention will become apparent to those skilled in the art from the following disclosure, and it is to be understood that the described embodiments are merely exemplary of the invention and that it is not intended to limit the invention to the particular embodiments disclosed. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

As shown in fig. 1 and fig. 2, the self-calibration structure of the micro electrochemical sensor in this embodiment includes a sensor body 4, a working electrode 1, a main reference electrode 2, and a first electrolyte 5, wherein the working electrode 1 and the main reference electrode 2 are disposed in the sensor body 4, the sensor body 4 is filled with the first electrolyte 5, and further includes a self-calibration reference electrode 7, and the self-calibration reference electrode 7 is disposed in the sensor body 4; calibration of the main reference electrode 2 is achieved by measuring the electrode potential difference between the main reference electrode 2 and the self-calibrating reference electrode 7.

The technical effect that this embodiment reaches does: the calibration of the main reference electrode 2 is realized by measuring the electrode potential difference between the main reference electrode 2 and the self-calibration reference electrode 7; the self-calibration work of the sensor is realized through the arrangement of the self-calibration reference electrode, an external calibration device is not needed, user intervention is not needed, and the experiment or measurement is not needed to be suspended. By means of timing self-calibration or real-time self-calibration of the miniature electrochemical sensor, the problems of reduction of measurement accuracy and limited service life caused by potential fluctuation or potential drift of a reference electrode of the sensor can be solved, the measurement accuracy of the sensor is maintained as much as possible, and the service life is prolonged; in addition, the invention has simple structure, convenient production and assembly, and easy realization and integration into various miniature electrochemical sensors.

Example 2

As shown in fig. 1 and fig. 2, the self-calibration structure of a micro electrochemical sensor in this embodiment includes all the technical features of embodiment 1, and in addition, further includes a sealed container 8, the sealed container 8 is disposed in the sensor body 4, the self-calibration reference electrode 7 is separately packaged in the sealed container 8, and the first electrolyte 5 is disposed around the sealed container 8.

Optionally, the self-calibration reference electrode further comprises a second electrolyte 9, the inside of the closed container 8 is filled with the second electrolyte 9, and the second electrolyte 9 is arranged around the self-calibration reference electrode 7.

Optionally, the side wall of the closed container 8 is provided with a porous substance 10, and the closed container 8 is connected with the first electrolyte 5 filled in the sensor main body 4 through the porous substance 10, so as to establish an ion channel, where the provision of the porous substance 10 on the closed container 8 is not the only implementation manner, and may also be a salt bridge structure such as a porous substance 10 or a small hole provided on the closed container 8.

Optionally, the inside of the closed container 8 is filled with a mesh-like porous structure for stabilizing ions in the second electrolyte 9, wherein the mesh-like porous structure may be electrolyte colloid (hydrogel) or sponge, filter paper, or the like.

Optionally, the sensor further comprises an auxiliary electrode 3, the sensor body 4 is internally sealed with the auxiliary electrode 3, the auxiliary electrode 3 is arranged on the left side of the working electrode 1, the working electrode 1 is arranged in the middle of the sensor body 4, the closed container 8 is positioned on the right side of the working electrode 1, and the main reference electrode 2 is arranged between the closed container 8 and the working electrode 1.

Optionally, a small hole is formed in the bottom of the sensor main body 4, a communication interface 6 is arranged on the small hole, the communication interface 6 is used for realizing communication between an external substance to be detected and the sensor main body 1, and the communication interface is a breathable film or a porous substance 10.

The beneficial effect that this embodiment reached does: the measurement of the first electrolyte 5 in the sensor body 4 over a long period of time may cause some degree of ion diffusion with the environment to be measured, thus changing the concentration of the first electrolyte 5 in the sensor body 4 and affecting the stability of the main reference electrode 2. The second electrolyte 9 in the closed container 8 where the self-calibration reference electrode 7 is located is far away from the external environment to be measured, and is not in direct contact with the external environment to be measured, and due to the isolation of the two layers of porous materials 10 and the one layer of first electrolyte 5, ion diffusion in the second electrolyte 9 is far weaker than that in the first electrolyte 5 in the sensor body 4, so that the change of the electrolyte concentration is weaker and slower, and the self-calibration reference electrode 7 has better stability.

Example 3

As shown in fig. 1 and fig. 2, the self-calibration structure of a micro electrochemical sensor in this embodiment includes all the technical features of embodiment 1, and in addition, further includes a signal conversion circuit and a measurement circuit 11, wherein a main reference electrode 2 and the self-calibration reference electrode 7 are connected to one end of the signal conversion circuit through a connection line, one end of the measurement circuit 11 is connected to the other end of the signal conversion circuit, and the other end of the measurement circuit 11 is connected to the main reference electrode 2 and the working electrode 1 through a connection line.

As shown in fig. 1, the signal conversion circuit of the present embodiment includes a differential amplifier 12, a signal conditioning circuit 13; the specific implementation mode is as follows: the main reference electrode 2 and the self-calibration reference electrode 7 are connected to one end of a differential amplifier 12 through connecting lines, the other end of the differential amplifier 12 is connected to one end of a signal conditioning circuit 13 through connecting lines, the other end of the signal conditioning circuit 13 is connected to one end of a measuring circuit 11 through connecting lines, the other end of the measuring circuit 11 is connected to the main reference electrode 2 and the working electrode 1 through connecting lines, and the differential amplifier 12 is used for reducing the electrode potential difference for extracting the main reference electrode and the self-calibration reference electrode.

As shown in fig. 2, the signal conversion circuit of the present embodiment includes a differential amplifier 12, a signal conditioning circuit 13, an analog-to-digital converter 14, and a self-calibration module 15; the specific implementation mode is as follows: the main reference electrode and the self-calibration reference electrode are connected into a differential amplifier 12, differential signals of electrode potentials of the two reference electrodes enter an analog-digital converter 14 after being conditioned by a signal conditioning circuit 13, the analog signals are converted into digital signals, and then conversion results are input into a self-calibration module 15. The result of the self-calibration is fed back to a measuring circuit (11) of the sensor to adjust the measuring signal or calibrate the measuring result, thereby realizing high-precision measurement.

The beneficial effects in this embodiment are:

firstly, a main reference electrode 2 and a self-calibration reference electrode 7 form a differential signal of an electrode potential through a differential amplifier 12, the differential signal is conditioned through a signal conditioning circuit 13 and then directly fed back to a measuring circuit 11 of the sensor to realize real-time calibration of the reference electrode, so that high-precision measurement is realized, in addition, the potential difference of the electrode between the reference electrode in a sensor main body and the reference electrode for self-calibration is measured in real time to realize calibration of the main body reference electrode, and then the main body reference electrode and the reference electrode are fed back to a control circuit of the sensor to ensure good measurement precision of the sensor, prolong the service life and reduce the requirement of external calibration;

secondly, the arrangement of the differential amplifier 12 can inhibit the influence on the circuit caused by the change of external conditions, further ensure the measurement precision of the sensor, reduce the requirement of external calibration and prolong the service life of the sensor;

thirdly, the design of the analog-to-digital converter 14 and the self-calibration module 15 realizes that the electrode potential difference between the reference electrode in the sensor main body 4 and the self-calibration reference electrode 7 is measured regularly or in real time, so that the calibration of the main reference electrode 2 is realized, and then the main reference electrode is fed back to a control circuit of the sensor;

fourthly, the analog-to-digital converter 14 is arranged to realize that the analog signal can be digitized and then fed back to the sensor control circuit or directly fed back to the sensor control circuit during self calibration;

example 4

The method for self-calibration of a micro electrochemical sensor in this embodiment uses the structure for self-calibration of a micro electrochemical sensor as in any one of embodiments 1 to 3, and includes the following steps:

step 1, a reference electrode in a sensor body and a reference electrode for self-calibration are connected into a signal conversion circuit, and the signal conversion circuit converts potential difference signals of the two reference electrodes into measurement signals;

and 2, feeding back the result of the measurement signal to a measurement circuit 11 of the sensor, and adjusting the measurement signal or calibrating the measurement result by the measurement circuit 11, thereby realizing high-precision measurement.

Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

In the present specification, the terms "upper", "lower", "left", "right", "middle", and the like are used for clarity of description, and are not intended to limit the scope of the present invention, and changes or modifications in the relative relationship may be made without substantial changes in the technical content.

Claims (10)

1. A self-calibrating structure of a miniature electrochemical sensor, comprising a sensor body (4), a working electrode (1), a primary reference electrode (2) and a first electrolyte (5), wherein the working electrode (1) and the primary reference electrode (2) are arranged in the sensor body (4), and the sensor body (4) is filled with the first electrolyte (5), characterized by further comprising a self-calibrating reference electrode (7), wherein the self-calibrating reference electrode (7) is arranged in the sensor body (4); calibrating the main reference electrode (2) is achieved by measuring the electrode potential difference between the main reference electrode (2) and the self-calibrating reference electrode (7).

2. The self-calibration structure of a miniature electrochemical sensor according to claim 1, further comprising a closed container (8), wherein the closed container (8) is arranged in the sensor body (4), the self-calibration reference electrode (7) is separately packaged in the closed container (8), and the first electrolyte (5) is arranged around the closed container (8).

3. The self-calibration structure of a miniature electrochemical sensor according to claim 2, further comprising a second electrolyte (9), wherein the inside of the closed container (8) is filled with the second electrolyte (9), and the second electrolyte (9) is disposed around the self-calibration reference electrode (7).

4. The self-calibration structure of a miniature electrochemical sensor according to claim 2, characterized in that the side wall of the closed container (8) is provided with a porous substance (10), and the closed container (8) is connected with the first electrolyte (5) filled in the sensor body (4) through the porous substance (10) so as to establish an ion channel.

5. The self-calibration structure of a micro-electrochemical sensor according to claim 3, wherein the closed container (8) is filled with a mesh-like porous structure for stabilizing the ion concentration in the second electrolyte (9), and the mesh-like porous structure is one or more of an electrolyte colloid, a sponge and a filter paper.

6. The self-calibration structure of the miniature electrochemical sensor according to claim 2, further comprising an auxiliary electrode (3), wherein the auxiliary electrode (3) is encapsulated in the sensor body (4), the auxiliary electrode (3) is arranged at the left side of the working electrode (1), the working electrode (1) is arranged in the middle of the sensor body (4), the closed container (8) is arranged at the right side of the working electrode (1), and the main reference electrode (2) is arranged between the closed container (8) and the working electrode (1).

7. The self-calibration structure of the micro electrochemical sensor according to claim 1, wherein a small hole is formed at the bottom of the sensor body (4), a communication interface (6) is disposed on the small hole, the communication interface (6) is used for realizing communication between an external substance to be measured and the sensor body (1), and the communication interface (6) is one of a gas permeable membrane and a porous substance.

8. The self-calibration structure of a miniature electrochemical sensor according to claim 1, further comprising a signal conversion circuit and a measurement circuit (11), wherein the main reference electrode (2) and the self-calibration reference electrode (7) are connected to one end of the signal conversion circuit through a connection line, one end of the measurement circuit (11) is connected to the other end of the signal conversion circuit, and the other end of the measurement circuit (11) is connected to the main reference electrode (2) and the working electrode (1) through a connection line.

9. The self-calibration structure of a miniature electrochemical sensor according to claim 8, wherein the signal conversion circuit comprises a differential amplifier (12), a signal conditioning circuit (13), an analog-to-digital converter (14) and a self-calibration module (15), the main reference electrode (2) and the self-calibration reference electrode (7) are connected to one end of the differential amplifier (12) through connecting wires, the other end of the differential amplifier (12) is connected to one end of the signal conditioning circuit (13) through connecting wires, the other end of the signal conditioning circuit (13) is connected to one end of the measurement circuit (11) through connecting wires, the other end of the measurement circuit (11) is connected to the main reference electrode (2) and the working electrode (1) through connecting wires, and the differential amplifier (12) is used for extracting the electrode potential difference of the main reference electrode and the self-calibration reference electrode, the analog-to-digital converter (14) is connected between the signal conditioning circuit (13) and the measurement circuit (11) by a connection line, and the self-calibration module (15) is connected between the analog-to-digital converter (14) and the measurement circuit (11) by a connection line.

10. A method for self-calibration of a micro-electrochemical sensor, wherein a self-calibration structure of a micro-electrochemical sensor according to any one of claims 1 to 9 is used, comprising the following steps:

step 1, a reference electrode in a sensor body and a reference electrode for self-calibration are connected into a signal conversion circuit, and the signal conversion circuit converts potential difference signals of the two reference electrodes into measurement signals;

and 2, feeding back the result of the measurement signal to a measurement circuit (11) of the sensor, and adjusting the measurement signal or calibrating the measurement result by the measurement circuit (11), thereby realizing high-precision measurement.

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