Electrochemical sensors and measuring devices

Abstract

To provide a technique for suppressing operations unintended by a user due to incorrect operation by the user.SOLUTION: An electrochemical sensor according to one aspect of the invention measures a concentration ratio of sodium ion and potassium ion in measuring object liquid. The electrochemical sensor comprises: a sensor head; and a calculation unit that can perform calibration operation for calculating characteristics parameter of the sensor head on the basis of sensing data of the sensor head with the sensor head being in contact with calibration agent, and measurement operation for calculating the concentration ratio on the basis of the characteristics parameter of the sensor head and sensing data of the sensor head with the sensor head being in contact with the measuring object liquid. Coupling with the calibration member brings the sensor head into contact with the calibration agent. When the calibration member is coupled, the measurement operation is restricted, and when the calibration member is decoupled, the calibration operation is restricted.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to electrochemical sensors and measurement devices. [Background technology]

[0002] Conventionally, electrochemical sensors that measure the concentration ratio between two ion species contained in a measurement target liquid are known. Some electrochemical sensors are capable of performing a calibration operation using a calibration solution to determine the characteristic parameters of the sensor head used for sensing before the measurement operation that measures the concentration ratio between two ion species contained in the measurement target liquid.

[0003] For example, Patent Document 1 describes the calculation of a reference potential for calibrating a potential difference detected in a solution to be measured using a standard solution (calibration solution) having a predetermined concentration ratio between two ion species. Patent Document 2 describes a multi-ion sensor that measures the concentration ratio of sodium ions to potassium ions in a sample solution based on the sensitivity coefficients of a sodium ion electrode and a potassium ion electrode determined by calibration. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-095675 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-095692 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional technology, when an electrochemical sensor is provided with a calibration switch for performing a calibration operation and a measurement switch for performing a measurement operation, if a user mistakenly operates each of these switches, an operation unintended by the user may be performed.

[0006] For example, if a user accidentally operates the measurement switch while the sensor head of an electrochemical sensor is in contact with a calibration solution, the measurement operation may be performed without proper calibration, resulting in an inaccurate measurement value.Also, if a user accidentally operates the calibration switch while the sensor head is in contact with the liquid to be measured, an inaccurate calibration based on the liquid to be measured may occur, resulting in an inaccurate measurement value being unable to be obtained in subsequent measurements.

[0007] In one aspect, the present invention has been made in consideration of the above-described situation, and its purpose is to provide a technology that can suppress unintended actions by a user caused by a user's incorrect operation. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention employs the following configuration.

[0009] That is, an electrochemical sensor according to one aspect of the present invention is an electrochemical sensor that measures the concentration ratio of sodium ions and potassium ions in a liquid to be measured, and comprises a sensor head and a calculation unit that is capable of performing a calibration operation that calculates characteristic parameters of the sensor head based on sensing data of the sensor head when the sensor head is in contact with a calibration agent, and a measurement operation that calculates the concentration ratio based on the characteristic parameters of the sensor head and the sensing data of the sensor head when the sensor head is in contact with the liquid to be measured, wherein the sensor head is brought into contact with the calibration agent when coupled to a calibration member, and the measurement operation is restricted when coupled to the calibration member, and the calibration operation is restricted when not coupled to the calibration member.

[0010] In the above configuration, the measurement operation is restricted when the calibration member for bringing the sensor head into contact with the calibration agent is coupled to the electrochemical sensor, and the calibration operation is restricted when the calibration member is not coupled to the electrochemical sensor. This makes it possible to prevent unintended operations caused by user error, such as performing a measurement operation with the sensor head in contact with the calibration agent or performing a calibration operation with the sensor head not in contact with the calibration agent.

[0011] In the electrochemical sensor according to the above aspect, the calibration operation can be performed when the sensor head is coupled to the calibration member, and the measurement operation can be performed when the sensor head is not coupled to the calibration member. With this configuration, the calibration operation can be performed with the sensor head in contact with the calibration agent, and the measurement operation can be performed with the sensor head not in contact with the calibration agent.

[0012] The electrochemical sensor according to the above aspect includes a calibration switch for causing the calculation unit to execute the calibration operation and a measurement switch for causing the calculation unit to execute the measurement operation, and the measurement switch is inoperable when the sensor is connected to the calibration member and inoperable when the sensor is not connected to the calibration member. With this configuration, the measurement operation can be restricted when the sensor head is in contact with the calibration agent, and the calibration operation can be restricted when the sensor head is not in contact with the calibration agent. The inoperable state means, for example, that the sensor cannot be operated in a normal manner.

[0013] In the electrochemical sensor according to the above aspect, the calibration switch is operable when the sensor head is coupled to the calibration member, and the measurement switch is operable when the sensor head is not coupled to the calibration member. With this configuration, a calibration operation can be performed when the sensor head is in contact with the calibration agent, and a measurement operation can be performed when the sensor head is not in contact with the calibration agent.

[0014] In the electrochemical sensor according to the above aspect, the calibration member may be a calibration holder that holds the electrochemical sensor with the sensor head in contact with the calibration agent. According to this configuration, the measurement operation is restricted by holding the electrochemical sensor in the calibration holder, and the calibration operation is restricted by removing the electrochemical sensor from the calibration holder after the calibration operation. Furthermore, since the user does not need to hold the electrochemical sensor, operation of the calibration switch is facilitated.

[0015] In the electrochemical sensor according to the above aspect, the calibration holder may include a storage portion for storing the calibration agent, and may hold the electrochemical sensor with the sensor head in contact with the calibration agent stored in the storage portion. According to this configuration, by holding the electrochemical sensor in the calibration holder, the sensor head is in contact with the calibration agent, and measurement operation is restricted.

[0016] In the electrochemical sensor according to the above aspect, the calibration holder may include a switch for operating the calibration switch of the held electrochemical sensor from outside the calibration holder. With this configuration, by holding the electrochemical sensor in the calibration holder, it becomes possible to operate the calibration switch from outside the calibration holder.

[0017] In the electrochemical sensor according to the above aspect, the calibration holder may include a shielding portion that shields the measurement switch of the held electrochemical sensor. With this configuration, the measurement switch can be made inoperable while the electrochemical sensor is held in the calibration holder.

[0018] In the electrochemical sensor according to the above aspect, the calibration holder may include an operating unit that operates the calibration switch by holding the electrochemical sensor. With this configuration, by holding the electrochemical sensor in the calibration holder, the sensor head comes into contact with the calibration agent, thereby restricting measurement operations and performing calibration operations.

[0019] In the electrochemical sensor according to the above aspect, the operating portion may be a magnet, and the calibration switch may be a magnetic switch. With this configuration, it is easy to design the electrochemical sensor and the calibration holder to be waterproof.

[0020] In the electrochemical sensor according to the above aspect, the sensor head is brought into contact with the liquid to be measured by coupling with the measurement holder. With this configuration, by holding the electrochemical sensor in the measurement holder, the sensor head is brought into contact with the liquid to be measured, and the user does not need to hold the electrochemical sensor himself, making it easier to operate the measurement switch.

[0021] In the electrochemical sensor according to the above aspect, the measurement holder may include a switch for operating the measurement switch of the held electrochemical sensor from outside the measurement holder. With this configuration, by holding the electrochemical sensor in the measurement holder, it becomes possible to operate the measurement switch from outside the measurement holder.

[0022] In the electrochemical sensor according to the above aspect, the measurement holder may include a shielding portion that shields the calibration switch of the held electrochemical sensor. With this configuration, the calibration switch can be made inoperable while the electrochemical sensor is held in the measurement holder.

[0023] In the electrochemical sensor according to the above aspect, the sensor head includes a sodium ion selective electrode that selectively reacts to sodium ions and a potassium ion selective electrode that selectively reacts to potassium ions, and the sensing data of the sensor head may be the potential difference between the sodium ion selective electrode and the potassium ion selective electrode.

[0024] A measuring device according to one aspect of the present invention includes the electrochemical sensor and the calibration member. [Effects of the Invention]

[0025] According to the present invention, it is possible to provide a technique that can suppress an operation that is not intended by a user due to an erroneous operation by the user. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a diagram showing the configuration of an electrochemical sensor 90 according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing an example of the external configuration of an electrochemical sensor 90. [Figure 3] FIG. 2 is a diagram showing an example of a calibration holder 60 that holds an electrochemical sensor 90. [Figure 4] 10 is a diagram showing an example of the state of the electrochemical sensor 90 and the calibration holder 60 during a calibration operation. FIG. [Figure 5] FIG. 2 is a diagram showing an example of the state of the electrochemical sensor 90 during measurement operation. [Figure 6] 10 is a diagram showing an example of a calibration holder 60 according to a second embodiment. FIG. [Figure 7] 10 is a diagram showing an example of the state of the electrochemical sensor 90 and the calibration holder 60 during the calibration operation of the second embodiment. FIG. [Figure 8] FIG. 10 is a diagram showing an example of an electrochemical sensor 90 according to a third embodiment. [Figure 9] FIG. 10 is a diagram showing an example of a calibration holder 60 according to a third embodiment. [Figure 10] 10 is a diagram showing an example of the state of the electrochemical sensor 90 and the calibration holder 60 during the calibration operation of the third embodiment. FIG. [Figure 11] FIG. 10 is a diagram showing an example of an electrochemical sensor 90 according to a fourth embodiment. [Figure 12] FIG. 10 is a diagram showing an example of a calibration holder 60 according to a fourth embodiment. [Figure 13] 10 is a diagram showing an example of the state of the electrochemical sensor 90 and the calibration holder 60 during the calibration operation of the fourth embodiment. FIG. [Figure 14] FIG. 10 is a diagram showing an example of the external configuration of an electrochemical sensor 90 according to a fifth embodiment. [Figure 15]FIG. 10 is a diagram showing an example of a measurement holder 80 that holds an electrochemical sensor 90 according to a fifth embodiment. [Figure 16] 13 is a diagram showing an example of the state of the electrochemical sensor 90 and the measurement holder 80 during the measurement operation of the fifth embodiment. FIG. [Figure 17] FIG. 20 is a diagram showing an example of a state during a calibration operation according to the sixth embodiment. [Figure 18] FIG. 20 is a diagram showing an example of a state during a measurement operation according to the sixth embodiment. [Figure 19] FIG. 20 is a diagram showing a calibration spoon 240 which is another example of the calibration member according to the sixth embodiment. [Figure 20] FIG. 20 is a diagram showing a calibration cap 250 which is yet another example of the calibration member according to the sixth embodiment. [Figure 21] FIG. 10 is a diagram showing an example of the configuration of an electrochemical sensor 90 according to a seventh embodiment. [Figure 22] 2 is a diagram showing a sensor head 30A which is an example of the sensor head 30. FIG. [Figure 23] 23 is a cross section taken along line VV in FIG. 22. [Figure 24] FIG. 2 is a diagram showing a sensor head 30A in an exploded state. [Figure 25] 23 is a perspective view showing the sensor head 30 shown in FIG. 22 together with the connector 21. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, embodiments according to one aspect of the present invention will be described with reference to the drawings.

[0028] (Embodiment 1) <Configuration of Electrochemical Sensor 90 as an Example of an Embodiment> FIG. 1 is a diagram showing the configuration of an electrochemical sensor 90 according to an embodiment. The electrochemical sensor 90 detects sodium ions (Na ions) in a liquid to be measured (e.g., human urine). + ) and potassium ions (K +) is a sensor that measures the concentration ratio. The electrochemical sensor 90 includes a sensor head 30 and a main body 10 having a housing 10a. The main body 10 is equipped with a control unit 11, a data input unit 12, an operation unit 13, and a display unit 20.

[0029] The electrochemical sensor 90 is configured as a handheld device that is used by a user holding the main body 10. The main body 10 has, for example, an elongated prismatic shape that is to be held in the user's hand.

[0030] The sensor head 30 has, for example, a substantially rectangular plate-like outer shape. The sensor head 30 has, at its tip, a sodium ion selective electrode 41 that selectively reacts to sodium ions, and a potassium ion selective electrode 42 that selectively reacts to potassium ions. Specific examples of the configuration of the sensor head 30 will be described later (see, for example, FIGS. 22 to 25).

[0031] The data input unit 12 inputs the respective potentials (or potential differences) of the sodium ion selective electrode 41 and the potassium ion selective electrode 42 of the sensor head 30 .

[0032] The control unit 11 controls the operation and performs calculations of the entire electrochemical sensor 90. The control unit 11 also has a memory 18 that temporarily stores the potentials of the sodium ion selective electrode 41 and the potassium ion selective electrode 42 input by the data input unit 12, as well as characteristic parameters related to the sodium ion selective electrode 41 and the potassium ion selective electrode 42, which will be described later.

[0033] The control unit 11 is realized by, for example, a processor and a memory that operate in cooperation with each other. The processor is, for example, a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The processor operates as the control unit 11 by reading and executing a program stored in the memory. Note that this processor may be a combination of multiple processors.

[0034] The memory is realized by a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, etc. The memory stores programs executed by the processor, data used by the processor, etc. The memory 18 is configured by, for example, a RAM.

[0035] The control unit 11 is an example of a calculation unit capable of calibration and measurement. The calibration operation is an operation for calculating characteristic parameters of the sensor head 30 based on sensing data of the sensor head 30 in a state where the sensor head 30 is in contact with a calibration liquid. The calibration liquid is an example of a calibration agent in which the concentration ratio of sodium ions to potassium ions is known.

[0036] The sensing data of the sensor head 30 is, for example, the potentials of the sodium ion selective electrode 41 and the potassium ion selective electrode 42. The characteristic parameters of the sensor head 30 are, for example, parameters related to the sodium ion selective electrode 41 and the potassium ion selective electrode 42. The characteristic parameters will be described later.

[0037] The measurement operation is an operation for calculating the concentration ratio of sodium ions to potassium ions in the liquid to be measured based on the characteristic parameters of the sensor head 30 calculated by the calibration operation and the sensing data of the sensor head 30 in a state where the sensor head 30 is in contact with the liquid to be measured. The calculation of the concentration ratio of sodium ions to potassium ions in the liquid to be measured will be described later.

[0038] The operation unit 13 is a user interface that accepts operations from the user. The operation unit 13 includes, for example, a power switch (for example, power switch 13c in FIG. 2) for the electrochemical sensor 90. The operation unit 13 also includes a calibration switch 13a for causing the control unit 11 to perform the above-mentioned calibration operation, and a measurement switch 13b for causing the control unit 11 to perform the above-mentioned measurement operation.

[0039] The display unit 20 is a user interface that displays various information such as the results of calculations performed by the control unit 11. For example, the display unit 20 is configured by an LCD (Liquid Crystal Display) or the like.

[0040] When the calibration switch 13a is operated, the control unit 11 executes the above-mentioned calibration operation and stores the characteristic parameters of the sensor head 30 calculated by the calibration operation in the memory 18. When the measurement switch 13b is operated, the control unit 11 executes the above-mentioned measurement operation using the characteristic parameters of the sensor head 30 stored in the memory 18, and controls the display unit 20 to display the concentration ratio calculated by the measurement operation.

[0041] The user first brings the calibration liquid into contact with the sensor head 30 and operates the calibration switch 13a in this state. This causes the electrochemical sensor 90 to be calibrated. Next, the user removes the sensor head 30 from the calibration liquid and discards the calibration liquid. The user then brings the sensor head 30 into contact with the liquid to be measured and operates the measurement switch 13b in this state. This causes the electrochemical sensor 90 to perform a measurement, and the concentration ratio measured by the measurement operation is displayed on the display unit 20.

[0042] <External configuration of electrochemical sensor 90> Fig. 2 is a diagram showing an example of the external configuration of electrochemical sensor 90. Front surface 90a is the front of electrochemical sensor 90. Top surface 90b is the top surface of electrochemical sensor 90. In the example of Fig. 2, a calibration switch 13a, a measurement switch 13b, a power switch 13c, and a display unit 20 are provided on housing 10a. In the example of Fig. 2, each of calibration switch 13a, measurement switch 13b, and power switch 13c is a push-button.

[0043] Specifically, the calibration switch 13a is provided on the side surface of the housing 10a. The calibration switch 13a is a push-button switch that does not protrude from the housing 10a and is small enough for the user's finger or the like, making it difficult for the user to press with the user's finger or the like. The calibration switch 13a may take various forms as long as it is difficult for the user to press with the user's finger or the like. For example, if the calibration switch 13a is recessed into the housing 10a, it will be difficult for the user to press with the user's finger or the like, even if the calibration switch 13a is large to some extent.

[0044] The measurement switch 13b is provided on the front surface of the housing 10a. The measurement switch 13b protrudes from the housing 10a and is a push-button switch that can be easily pressed by a user's finger or the like. The power switch 13c is provided on the top surface of the housing 10a. The power switch 13c protrudes from the housing 10a and is a push-button switch that can be easily pressed by a user's finger or the like.

[0045] <Calibration holder 60 for holding electrochemical sensor 90> FIG. 3 is a diagram showing an example of a calibration holder 60 that holds an electrochemical sensor 90. A front surface 60a is the front of the calibration holder 60. A top surface 60b is the top surface of the calibration holder 60. The calibration holder 60 is an example of a calibration member. The calibration holder 60 shown in FIG. 3 is a stand-type calibration holder that holds the electrochemical sensor 90 with the sensor head 30 in contact with the calibration solution. The calibration holder 60 has a holding portion 61, a sensor head insertion hole 62, an accommodation portion 63, a switch 64, and a base 69.

[0046] The holder 61 is a hole having a shape capable of holding the tip (the portion on the side where the sensor head 30 is provided) of the housing 10a of the electrochemical sensor 90. In this example, since the housing 10a of the electrochemical sensor 90 is substantially rectangular prism-shaped, the holder 61 is also a hole having a substantially rectangular prism-like shape. The holder 61 also has a bottom that supports the housing 10a from below.

[0047] The sensor head insertion hole 62 is a hole that is electrically connected from the bottom of the holding portion 61 to the accommodation portion 63 and has a shape that allows insertion of the sensor head 30 of the electrochemical sensor 90. In this example, since the sensor head 30 of the electrochemical sensor 90 has a substantially square prism shape, the sensor head insertion hole 62 is also a hole that has a substantially square prism shape.

[0048] The container 63 is a container for containing the calibration liquid. The container 63 has a portion that is electrically connected to the sensor head insertion hole 62. Except It is an enclosed space.

[0049] The switch 64 is a push-button switch for operating the calibration switch 13a of the held electrochemical sensor 90 from outside the calibration holder 60. Specifically, the switch 64 is provided on the side of the calibration holder 60 at the portion where the holding portion 61 is provided. The switch 64 also protrudes outward from the side of the calibration holder 60, and is a push-button switch that can be easily pressed by a user with a finger or the like.

[0050] The calibration holder 60 has a hole in the portion where the switch 64 is provided, which allows electrical continuity from the outside of the calibration holder 60 to the holding part 61, and the switch 64 has a pin that can slide within this hole. When the switch 64 is pressed, the tip of the pin enters the inside of the holding part 61.

[0051] The base 69 is a member with a flat bottom surface that is provided at the bottom of the calibration holder 60. The base 69 allows the calibration holder 60 to be stably placed on a flat surface such as a desk.

[0052] <State of the electrochemical sensor 90 and the calibration holder 60 during the calibration operation> 4 is a diagram showing an example of the state of the electrochemical sensor 90 and the calibration holder 60 during the calibration operation. The front surface 1a is the front of the electrochemical sensor 90 and the calibration holder 60 that are coupled to each other. The top surface 1b is the top surface of the electrochemical sensor 90 and the calibration holder 60 that are coupled to each other.

[0053] When the calibration solution 63a is poured into the accommodation portion 63 of the calibration holder 60 and the electrochemical sensor 90 is placed in the calibration holder 60, the state shown in Fig. 4 is obtained, for example. The placement of the electrochemical sensor 90 in the calibration holder 60 is an example of coupling the calibration holder 60 (calibration member) and the electrochemical sensor 90.

[0054] 4, the tip of the sensor head 30 (the portion where the sodium ion selective electrode 41 and the potassium ion selective electrode 42 are exposed) is in contact with the calibration solution 63a in the accommodation portion 63 through the sensor head insertion hole 62, and the tip of the sensor head 30 in the housing 10a is held in the holding portion 61. As a result, even if the user releases their hand from the electrochemical sensor 90, for example, the electrochemical sensor 90 is held in a state where the sensor head 30 is in contact with the calibration solution 63a.

[0055] 4, the measurement switch 13b of the electrochemical sensor 90 is shielded from the outside by the side wall of the holding part 61. That is, the side wall of the holding part 61 is an example of a shielding part that shields the measurement switch 13b of the electrochemical sensor 90 held by the calibration holder 60. Shielding the measurement switch 13b makes it difficult for the user to press the measurement switch 13b with a finger or the like.

[0056] 4, when the switch 64 is pressed, the calibration switch 13a is pressed by the tip of a pin provided on the switch 64. Therefore, the user can easily press the calibration switch 13a by pressing the switch 64 with a finger or the like.

[0057] 4 (when the electrochemical sensor 90 is connected to the calibration holder 60), the calibration switch 13a is operable and the measurement switch 13b is inoperable. Operable means that the switch can be easily operated in a normal manner (for example, by pressing it with a finger). Inoperable means that the switch cannot be operated in a normal manner (a state in which operation is difficult).

[0058] This allows the user to easily cause the electrochemical sensor 90 to perform a calibration operation by pressing switch 64, and also prevents the user from accidentally pressing the measurement switch 13b, causing the electrochemical sensor 90 to perform a measurement operation.

[0059] <State of the electrochemical sensor 90 during measurement operation> Fig. 5 is a diagram showing an example of the state of the electrochemical sensor 90 during a measurement operation. When the measurement operation in the state shown in Fig. 4 is completed, the user removes the electrochemical sensor 90 from the calibration holder 60 and holds the electrochemical sensor 90 so that the sensor head 30 contacts the measurement target liquid 70a contained in the container 70, as shown in Fig. 5.

[0060] Then, the user presses measurement switch 13b. In the state of FIG. 5, measurement switch 13b is not shielded, so the user can easily press measurement switch 13b. On the other hand, since calibration switch 13a is arranged so as not to protrude from housing 10a as described above, the user cannot easily press measurement switch 13b in the state of FIG. 5. That is, in the state of FIG. 5 (when electrochemical sensor 90 and calibration holder 60 are not coupled), measurement switch 13b is operable and calibration switch 13a is inoperable.

[0061] This allows the user to easily press the measurement switch 13b to cause the electrochemical sensor 90 to perform a measurement operation, and also prevents the user from accidentally pressing the calibration switch 13a, causing the electrochemical sensor 90 to perform a calibration operation.

[0062] In this way, in the electrochemical sensor 90, coupling the electrochemical sensor 90 to the calibration holder 60 (calibration member) brings the sensor head 30 into contact with the calibration solution 63a, and the measurement switch 13b is inoperable when the electrochemical sensor 90 is coupled to the calibration holder 60, and the calibration switch 13a is inoperable when the electrochemical sensor 90 is not coupled to the calibration holder 60. As a result, measurement operations are restricted when the electrochemical sensor 90 is coupled to the calibration holder 60, and calibration operations are restricted when the electrochemical sensor 90 is not coupled to the calibration holder 60.

[0063] This makes it possible to prevent unintended operations by the user caused by user error, such as performing a measurement operation with the sensor head 30 in contact with the calibration liquid 63a, or performing a calibration operation with the sensor head 30 not in contact with the calibration liquid 63a.

[0064] For example, it is possible to prevent a situation in which the user mistakenly operates the measurement switch 13b while the sensor head 30 is in contact with the calibration liquid 63a, resulting in a measurement operation being performed without proper calibration and an inaccurate measurement value being obtained.It is also possible to prevent a situation in which the user mistakenly operates the calibration switch 13a while the sensor head 30 is in contact with the measurement target liquid 70a, resulting in an inaccurate calibration based on the measurement target liquid 70a and an inaccurate measurement value being obtained in the subsequent measurement.

[0065] (Measurement method) In the electrochemical sensor 90, the concentration ratio of sodium ions to potassium ions in the measurement object liquid 70a is determined according to the following principle.

[0066] First, ion selective electrodes such as the sodium ion selective electrode 41 and the potassium ion selective electrode 42 generally exhibit a response proportional to the logarithm of the activity of a chemical species according to the Nernst equation as shown in equation (1).

[0067]

number

[0068] where E w is the potential of the working electrode [V], E 0 is the formal potential [V] specific to each electrode, R is the gas constant (= 8.314 [J / K·mol]), T is the absolute temperature [K], n is the ionic valence, F is the Faraday constant (≒ 96,485 [C / mol]), r is the activity coefficient representing the ion concentration of the entire solution, and C is the ion concentration to be measured [mol / L].

[0069] Here, the electrode potentials of the sodium ion selective electrode 41 and the potassium ion selective electrode 42 are E w1 , E w2 and the formal potential are expressed as follows:

[0070]

number

[0071] The concentrations of sodium ions and potassium ions to be measured by the sodium ion selective electrode 41 and potassium ion selective electrode 42 are designated C1 and C2, respectively. The sensitivities of the sodium ion selective electrode 41 and potassium ion selective electrode 42 are designated S1 and S2, respectively, as values ​​including the activity coefficients. Theoretically, the response sensitivities of the sodium ion selective electrode 41 and potassium ion selective electrode 42 are S1 = S2 = 59.2 when the measurement target is a monovalent ion and the temperature is 25°C. However, in practice, these values ​​differ due to variations in the membrane and the effects of deterioration and elution of the sensitive substance. Therefore, S1 and S2 are designated as values ​​including the activity coefficients, as described above. The influence of interfering substances on the potential of the sodium ion selective electrode 41 and potassium ion selective electrode 42 (corresponding to the selectivity of each ion selective electrode) is designated k1 and k2. Then, the electrode potential E w1 , E w2 are expressed as equations (2) and (3), respectively.

[0072]

number

[0073]

number

[0074] Here, the difference (sensitivity difference) between the sensitivity of the sodium ion selective electrode 41 and the sensitivity of the potassium ion selective electrode 42 is defined as α, as shown in equation (4).

[0075] S2=S1-α …(4)

[0076] Then, the difference (potential difference) ΔE between the electrode potential of the sodium ion selective electrode 41 and the electrode potential of the potassium ion selective electrode 42 is expressed as in equation (5).

[0077]

number

[0078] Here, the sensitivities S1 and S2 of the sodium ion selective electrode 41 and the potassium ion selective electrode 42 and the influences k1 and k2 (corresponding to the selectivity of each ion selective electrode) of interferents on the potential at the sodium ion selective electrode 41 and the potassium ion selective electrode 42 can be made to match each other by, for example, setting the materials of the sodium ion selective membrane 41i and the potassium ion selective membrane 42i described below. In this way, when the sensitivity S1 and the selectivity k1 of the sodium ion selective electrode 41 are made to match the sensitivity S2 and the selectivity k2 of the potassium ion selective electrode 42, respectively, they can be regarded as substantially formulas (6) and (7).

[0079] α=S1-S2=0 …(6)

[0080] k1=k2 …(7)

[0081] As a result, equation (5) is simplified to the following equation (8).

[0082]

number

[0083] This formula is calculated by measuring ΔE for a solution with a known concentration ratio between sodium ions and potassium ions (calibration solution 63a) and calculating the following constant V 0 If the sensitivity S1 is previously calculated, the concentration ratio M between sodium ions and potassium ions in the measurement target liquid 70a can be calculated. s (=C1 / C2) can be measured. 0 is defined as follows:

[0084]

number

[0085] In particular, the sensitivity S1 is assumed to be constant within a lot of manufactured sensor heads 30, and a known constant value measured in advance is used. 0 can be obtained by detecting the potential difference between the sodium ion selective electrode 41 and the potassium ion selective electrode 42 for the calibration solution 63a. That is, the concentration ratio (known) between sodium ions and potassium ions in the calibration solution 63a is expressed as M ref The potential difference detected for the calibration solution 63a is V ref Then, equation (8) is transformed into equation (9).

[0086] V 0 =V ref -S1log(M ref ) …(9)

[0087] On the other hand, the potential difference between the sodium ion selective electrode 41 and the potassium ion selective electrode 42 is detected for the measurement target liquid 70a. The concentration ratio between sodium ions and potassium ions in the measurement target liquid 70a is expressed as Ms The potential difference detected for the measurement target liquid 70a is V s Then, equation (8) is transformed into equation (10).

[0088] logM s =(V s -V 0 ) / S1 …(10)

[0089] Therefore, the concentration ratio M between sodium ions and potassium ions in the measurement target liquid 70a is s can be calculated as shown in equation (11).

[0090]

number

[0091] That is, in the calibration operation, the control unit 11 0 the sensitivity S1 of the sodium ion selective electrode 41 and the potential difference V detected for the calibration solution 63a. ref are calculated as characteristic parameters of the sensor head 30.

[0092] Furthermore, the control unit 11 detects the potential difference V s and the constant V 0 the sensitivity S1 of the sodium ion selective electrode 41 and the potential difference V detected for the calibration solution 63a. ref and the known concentration ratio M between sodium ions and potassium ions in the calibration solution 63a ref Based on the above equation (11), the concentration ratio M between sodium ions and potassium ions in the measurement target liquid 70a is calculated. s Calculate.

[0093] (Embodiment 2) The second embodiment will be described with respect to the differences from the first embodiment. In the second embodiment, an example of an operation unit in which the calibration holder 60 holds the electrochemical sensor 90 to operate the calibration switch 13a will be described.

[0094] <Calibration holder 60 according to the second embodiment> Fig. 6 is a diagram showing an example of a calibration holder 60 according to embodiment 2. The calibration holder 60 shown in Fig. 6 includes a switch 65 instead of the switch 64 of the calibration holder 60 shown in Fig. 3. The switch 65 is an example of an operating unit that operates the calibration switch 13a when the calibration holder 60 holds the electrochemical sensor 90.

[0095] Switch 65 is provided in a hole provided on the inside of the side wall of holding portion 61, and is biased by a spring or the like toward the inside of holding portion 61. As a result, when electrochemical sensor 90 is not inserted into holding portion 61, only the tip of holding portion 61 is exposed inside holding portion 61.

[0096] The tip of the holder 61 is inclined with respect to the insertion direction of the electrochemical sensor 90 into the holder 61 (the vertical direction in FIG. 6). In the example of FIG. 6, the tip of the holder 61 is hemispherical. This prevents the switch 65 from interfering with the insertion of the electrochemical sensor 90 into the holder 61.

[0097] <State of the electrochemical sensor 90 and the calibration holder 60 during the calibration operation of the second embodiment> Fig. 7 is a diagram showing an example of the state of the electrochemical sensor 90 and the calibration holder 60 during the calibration operation of embodiment 2. When the calibration solution 63a is poured into the container 63 of the calibration holder 60 shown in Fig. 6 and the electrochemical sensor 90 is placed in the calibration holder 60, the state shown in Fig. 7 is obtained, for example.

[0098] Specifically, when the electrochemical sensor 90 is placed in the calibration holder 60, the calibration switch 13a is pressed by the switch 65. Therefore, by placing the electrochemical sensor 90 in the calibration holder 60, the user can easily press the calibration switch 13a.

[0099] This makes it possible to easily cause the electrochemical sensor 90 to perform a calibration operation by placing the electrochemical sensor 90 in the calibration holder 60, and also prevents the user from accidentally pressing the measurement switch 13b, causing the electrochemical sensor 90 to perform a measurement operation.

[0100] The calibration operation of the second embodiment has been described, but the measurement operation of the second embodiment is performed in the same manner as in the first embodiment, for example.

[0101] (Embodiment 3) The third embodiment will be described in terms of differences from the first and second embodiments. In the second embodiment, an example of a calibration switch for causing the control unit 11 to execute a calibration operation, which is different from the above-described calibration switch 13a, will be described.

[0102] <Electrochemical Sensor 90 of Third Embodiment> FIG. 8 is a diagram showing an example of an electrochemical sensor 90 according to a third embodiment. The electrochemical sensor 90 shown in FIG. 8 includes a magnetic switch 13d instead of the calibration switch 13a of the electrochemical sensor 90 shown in FIG. 2. The magnetic switch 13d is an example of a calibration switch that causes the control unit 11 to perform a calibration operation. The magnetic switch 13d is a magnetic proximity switch that outputs a detection signal when it detects magnetism. The control unit 11 performs a calibration operation when the detection signal is output from the magnetic switch 13d.

[0103] <Calibration holder 60 according to the third embodiment> 9 is a diagram showing an example of a calibration holder 60 according to the third embodiment. The calibration holder 60 shown in FIG. 9 includes a magnet 66 instead of the switch 64 of the calibration holder 60 shown in FIG. 3. The magnet 66 is embedded in the side wall of the holder 61. Specifically, the magnet 66 is provided in a position close to the magnetic switch 13d of the electrochemical sensor 90 when the electrochemical sensor 90 is held by the holder 61. The magnet 66 is an example of an operating unit that operates the calibration switch (magnetic switch 13d of the electrochemical sensor 90) when the calibration holder 60 holds the electrochemical sensor 90.

[0104] <State of the electrochemical sensor 90 and the calibration holder 60 during the calibration operation of the third embodiment> Fig. 10 is a diagram showing an example of the state of the electrochemical sensor 90 and the calibration holder 60 during the calibration operation of embodiment 3. When the calibration solution 63a is poured into the container 63 of the calibration holder 60 shown in Fig. 9 and the electrochemical sensor 90 shown in Fig. 8 is placed in the calibration holder 60, the state shown in Fig. 10 is obtained, for example.

[0105] Specifically, when the electrochemical sensor 90 is placed in the calibration holder 60, the magnet 66 of the calibration holder 60 comes into close proximity to the magnetic switch 13d of the electrochemical sensor 90. This causes a detection signal to be output from the magnetic switch 13d, and the calibration operation is performed by the control unit 11. Therefore, by placing the electrochemical sensor 90 in the calibration holder 60, the user can easily perform the calibration operation.

[0106] This makes it possible to easily cause the electrochemical sensor 90 to perform a calibration operation by placing the electrochemical sensor 90 in the calibration holder 60, and also prevents the user from accidentally pressing the measurement switch 13b, causing the electrochemical sensor 90 to perform a measurement operation.

[0107] Furthermore, since the magnetic switch 13d and the magnet 66 can be non-contact switches, the magnetic switch 13d does not have to be exposed from the surface of the electrochemical sensor 90, and the magnet 66 does not have to be exposed from the surface of the calibration holder 60. This makes it easy to design the electrochemical sensor 90 and the calibration holder 60 to be waterproof.

[0108] The calibration operation of the third embodiment has been described, but the measurement operation of the third embodiment is performed in the same manner as in the first embodiment, for example.

[0109] (Fourth embodiment) The fourth embodiment will be described in terms of differences from the first to third embodiments. In the fourth embodiment, an example of a calibration switch for causing the control unit 11 to execute a calibration operation, which is different from the above-described calibration switch 13a and magnetic switch 13d, will be described.

[0110] <Electrochemical Sensor 90 of Fourth Embodiment> Fig. 11 is a diagram showing an example of an electrochemical sensor 90 according to the fourth embodiment. The electrochemical sensor 90 shown in Fig. 11 includes electrodes 13e and 13f and a detection circuit 13h instead of the calibration switch 13a of the electrochemical sensor 90 shown in Fig. 2. The electrodes 13e and 13f are exposed at the side surface of the housing 10a and spaced apart from each other.

[0111] When the electrodes 13e and 13f are short-circuited, the detection circuit 13h outputs a detection signal. When the detection signal is output from the detection circuit 13h, the control unit 11 performs a calibration operation. The electrodes 13e and 13f and the detection circuit 13h are an example of a calibration switch that causes the control unit 11 to perform the calibration operation.

[0112] <Calibration holder 60 according to the fourth embodiment> Fig. 12 is a diagram showing an example of a calibration holder 60 according to the fourth embodiment. The calibration holder 60 shown in Fig. 12 includes electrodes 67a, 67b and a short-circuit path 67c instead of the switch 64 of the calibration holder 60 shown in Fig. 3. The electrodes 67a, 67b are exposed on the inner side of the side wall of the holder 61 while being spaced apart from each other. Specifically, the electrodes 67a, 67b are provided at positions where they come into contact with the electrodes 13e, 13f of the electrochemical sensor 90, respectively, when the electrochemical sensor 90 is held by the holder 61.

[0113] The short-circuit path 67c is embedded in the side wall of the holder 61 and connects the electrodes 67a and 67b to each other. The electrodes 67a and 67b and the short-circuit path 67c are an example of an operating part that operates the calibration switch (electrodes 13e and 13f and detection circuit 13h of the electrochemical sensor 90) when the calibration holder 60 holds the electrochemical sensor 90.

[0114] <State of the electrochemical sensor 90 and the calibration holder 60 during the calibration operation of the fourth embodiment> Fig. 13 is a diagram showing an example of the state of the electrochemical sensor 90 and the calibration holder 60 during the calibration operation of embodiment 4. When the calibration solution 63a is poured into the container 63 of the calibration holder 60 shown in Fig. 12 and the electrochemical sensor 90 shown in Fig. 11 is placed in the calibration holder 60, the state shown in Fig. 13 is obtained, for example.

[0115] Specifically, when the electrochemical sensor 90 is placed in the calibration holder 60, the electrodes 13e and 13f of the electrochemical sensor 90 come into contact with the electrodes 67a and 67b of the calibration holder 60, respectively. This causes the above-mentioned detection signal to be output, and the calibration operation is performed by the control unit 11. Therefore, the user can easily perform the calibration operation by placing the electrochemical sensor 90 in the calibration holder 60.

[0116] This makes it possible to easily cause the electrochemical sensor 90 to perform a calibration operation by placing the electrochemical sensor 90 in the calibration holder 60, and also prevents the user from accidentally pressing the measurement switch 13b, causing the electrochemical sensor 90 to perform a measurement operation.

[0117] The calibration operation of the fourth embodiment has been described, but the measurement operation of the fourth embodiment is performed in the same manner as in the first embodiment, for example.

[0118] (Embodiment 5) The fifth embodiment will be described with respect to the differences from the first to fourth embodiments. In the fifth embodiment, a configuration will be described in which a measurement holder is used to hold an electrochemical sensor 90 with the sensor head 30 in contact with the measurement target liquid 70a.

[0119] <External Configuration of Electrochemical Sensor 90 of Fifth Embodiment> Fig. 14 is a diagram showing an example of the external configuration of the electrochemical sensor 90 of embodiment 5. In the example of Fig. 14, the measurement switch 13b is provided on the side of the housing 10a. Like the calibration switch 13a, the measurement switch 13b does not protrude from the housing 10a and is small enough for the user's finger or the like, making it a push-down switch that is difficult for the user to press with the user's finger or the like.

[0120] <Measurement holder 80 for holding electrochemical sensor 90 according to the fifth embodiment> FIG. 15 is a diagram showing an example of a measurement holder 80 that holds an electrochemical sensor 90 according to the fifth embodiment. A front surface 80a is the front of the measurement holder 80. A top surface 80b is the top surface of the measurement holder 80. The measurement holder 80 shown in FIG. 15 is a stand-type measurement holder that holds the electrochemical sensor 90 with the sensor head 30 in contact with the measurement target liquid 70a. The measurement holder 80 has a holding portion 81, a sensor head insertion hole 82, a container installation portion 83, a switch 84, and a base 89.

[0121] Similar to the holding portion 61 of the calibration holder 60, the holding portion 81 is a hole having a shape capable of holding the tip portion of the housing 10a of the electrochemical sensor 90. Similar to the sensor head insertion hole 62 of the calibration holder 60, the sensor head insertion hole 82 is a hole that is electrically connected from the bottom of the holding portion 81 to the container installation portion 83 and has a shape capable of inserting the sensor head 30 of the electrochemical sensor 90. The container installation portion 83 is a space capable of installing the container 70 containing the measurement target liquid 70a.

[0122] Switch 84 is a push-down switch for operating measurement switch 13b of the held electrochemical sensor 90 from outside measurement holder 80. The configuration of switch 84 is similar to that of switch 64 of calibration holder 60. Similar to base 69 of calibration holder 60, base 89 is provided at the bottom of measurement holder 80 and is a member with a flat bottom surface.

[0123] <States of the electrochemical sensor 90 and the measurement holder 80 during the measurement operation of the fifth embodiment> Fig. 16 is a diagram showing an example of the state of the electrochemical sensor 90 and the measurement holder 80 during the measurement operation of embodiment 5. When the container 70 containing the measurement target liquid 70a is placed in the container placement part 83 of the measurement holder 80 and the electrochemical sensor 90 is placed in the measurement holder 80, the state shown in Fig. 16 is obtained, for example.

[0124] 16 , the tip of the sensor head 30 is held in the holder 81 in a state where the tip of the sensor head 30 is in contact with the measurement target liquid 70a in the container 70 via the sensor head insertion hole 82. As a result, even if the user releases the electrochemical sensor 90, the electrochemical sensor 90 is held in a state where the sensor head 30 is in contact with the measurement target liquid 70a.

[0125] 16, the calibration switch 13a of the electrochemical sensor 90 is shielded from the outside by the side wall of the holding part 81. That is, the side wall of the holding part 81 is an example of a shielding part that shields the calibration switch 13a of the electrochemical sensor 90 held by the measurement holder 80. Furthermore, the measurement holder 80 is not provided with a push switch, such as the switch 64 of the calibration holder 60, for operating the calibration switch 13a from outside the measurement holder 80. This makes it difficult for the user to push the measurement switch 13b with a finger or the like.

[0126] 16, when the switch 84 is pressed, the measurement switch 13b is pressed by the tip of the pin provided on the switch 84. Therefore, the user can easily press the measurement switch 13b by pressing the switch 84 with a finger or the like.

[0127] 16 (when the electrochemical sensor 90 is connected to the measurement holder 80), the measurement switch 13b is operable and the calibration switch 13a is inoperable. This allows the user to easily cause the electrochemical sensor 90 to perform a measurement operation by pressing the switch 84, and also prevents the user from accidentally pressing the calibration switch 13a, causing the electrochemical sensor 90 to perform a calibration operation.

[0128] Although the measurement operation of the fifth embodiment has been described, the calibration operation of the fifth embodiment is performed in the same manner as, for example, the first embodiment. The configuration of the fifth embodiment may be combined with any of the configurations of the second to fourth embodiments.

[0129] (Sixth embodiment) The sixth embodiment will be described with respect to the differences from the first to fifth embodiments. In the above, the calibration holder 60 has been described as an example of a calibration member, but the calibration member is not limited to the calibration holder 60. In the sixth embodiment, other examples of the calibration member will be described.

[0130] <State during calibration operation in embodiment 6> Fig. 17 is a diagram showing an example of a state during calibration operation in the sixth embodiment. The calibrator case 220 is an example of a calibration member that is different from the calibration holder 60. Note that Fig. 17 shows a cross section of the calibrator case 220. In the example of Fig. 17, holes 211 and 212 are formed in the housing 10a of the electrochemical sensor 90. The calibration switch 13a is provided at the bottom of the hole 211. This makes it difficult for a user to press the calibration switch 13a with a finger or the like when using the electrochemical sensor 90 alone.

[0131] Furthermore, measurement switch 13b is provided so as to protrude from main body 10. A measurement limit release switch 13g is provided at the bottom of hole 212. When measurement limit release switch 13g is pressed and measurement switch 13b is also pressed, control unit 11 executes a measurement operation. This prevents the measurement operation from being executed when electrochemical sensor 90 is used alone, even if the user presses measurement switch 13b with a finger or the like. In other words, when electrochemical sensor 90 is connected to calibrator case 220, the measurement operation is restricted.

[0132] The calibrator case 220 is a case that stores the calibration gel 63b. The calibration gel 63b is an example of a calibrator in which the concentration ratio of sodium ions to potassium ions is known, and is different from the calibration solution 63a. In the example of Fig. 17, the calibrator case 220 has a substantially hollow rectangular prism shape, and the calibration gel 63b is applied to the upper surface of the inside.

[0133] The calibrator case 220 also has an opening 221 for inserting the sensor head 30. By inserting the sensor head 30 into the opening 221 and connecting the calibrator case 220 to the housing 10a, the sodium ion selective electrode 41 and the potassium ion selective electrode 42 of the sensor head 30 come into contact with the calibration gel 63b inside the calibrator case 220.

[0134] The calibrator case 220 also has a pin 222 that protrudes from the upper part of the opening 221. The pin 222 is formed so as to fit into the hole 211 and press the calibration switch 13a when the calibrator case 220 is connected to the housing 10a. As a result, when the user inserts the sensor head 30 into the opening 221 and connects the calibrator case 220 to the housing 10a, the sodium ion selective electrode 41 and the potassium ion selective electrode 42 come into contact with the calibration gel 63b, and the electrochemical sensor 90 performs a calibration operation.

[0135] <State during measurement operation according to the sixth embodiment> Figure 18 is a diagram showing an example of a state during measurement operation in embodiment 6. Measuring spoon 230 is a member having a substantially hollow rectangular prism shape and a dish portion 231 capable of holding measurement target liquid 70a. Note that Figure 18 shows a cross section of measuring spoon 230. Measuring spoon 230 has an opening 233 for inserting sensor head 30.

[0136] By inserting the sensor head 30 into the opening 233 and connecting the measuring spoon 230 to the housing 10a, the sodium ion selective electrode 41 and potassium ion selective electrode 42 of the sensor head 30 are exposed from the bottom of the dish portion 231 of the measuring spoon 230, and the sodium ion selective electrode 41 and potassium ion selective electrode 42 come into contact with the liquid to be measured 70a.

[0137] Furthermore, measuring spoon 230 has pin 232 protruding from the bottom of opening 233. Pin 232 is formed so as to fit into hole 212 and press measurement limit release switch 13g when measuring spoon 230 is connected to housing 10a.

[0138] As a result, when the user inserts the sensor head 30 into the opening 233 and connects the measuring spoon 230 to the housing 10a, the sodium ion selective electrode 41 and the potassium ion selective electrode 42 come into contact with the measurement target liquid 70a, and the measurement limit release switch 13g is pressed. In this state, when the user presses the measurement switch 13b, the electrochemical sensor 90 performs a measurement operation.

[0139] On the other hand, it is difficult to press the calibration switch 13a in the state shown in Fig. 18. That is, when the electrochemical sensor 90 and the calibrator case 220 are not coupled, the calibration operation is restricted.

[0140] 17 and 18, also in the sixth embodiment, the measurement operation is restricted when the electrochemical sensor 90 is connected to the calibrator case 220, and the calibration operation is restricted when the electrochemical sensor 90 is not connected to the calibrator case 220. This makes it possible to prevent unintended operations caused by user error, such as performing a measurement operation with the sensor head 30 in contact with the calibration gel 63b or performing a calibration operation with the sensor head 30 not in contact with the calibration gel 63b.

[0141] <Calibration spoon 240 as another example of the calibration member according to the sixth embodiment> Fig. 19 is a diagram showing a calibration spoon 240, which is another example of the calibration member of embodiment 6. In embodiment 6, the calibration spoon 240 may be used instead of the calibrator case 220. Note that Fig. 19 shows a cross section of the calibration spoon 240.

[0142] The calibration spoon 240, like the measuring spoon 230, is a member that has a generally hollow rectangular prism shape and has a dish portion 242 that can hold the calibration liquid 63a. The calibration spoon 240 has an opening 243 into which the sensor head 30 is inserted.

[0143] By inserting the sensor head 30 into the opening 243 and connecting the calibration spoon 240 to the housing 10a, the sodium ion selective electrode 41 and the potassium ion selective electrode 42 of the sensor head 30 are exposed from the bottom of the dish portion 242 of the calibration spoon 240, and the sodium ion selective electrode 41 and the potassium ion selective electrode 42 come into contact with the calibration solution 63a. The calibration spoon 240 also has a pin 244 that protrudes from the upper part of the opening 243. The pin 244 is formed so as to fit into the hole 211 and press down the calibration switch 13a when the calibration spoon 240 is connected to the housing 10a.

[0144] As a result, when the user inserts the sensor head 30 into the opening 243 and connects the calibration spoon 240 to the housing 10a, the sodium ion selective electrode 41 and the potassium ion selective electrode 42 come into contact with the calibration solution 63a, and the calibration operation is performed by the electrochemical sensor 90.

[0145] <Calibration cap 250 as yet another example of the calibration member according to the sixth embodiment> Fig. 20 is a diagram showing a calibration cap 250, which is yet another example of the calibration member of embodiment 6. In embodiment 6, the calibration cap 250 may be used instead of the calibrator case 220. Note that Fig. 20 shows a cross section of the calibration cap 250.

[0146] The calibration cap 250 is a hollow cap that can be attached to the electrochemical sensor 90 so as to cover the sensor head 30. A calibration gel 63b is applied to the inside of the calibration cap 250. The calibration cap 250 also has an opening 253 for inserting the sensor head 30.

[0147] By inserting the sensor head 30 into the opening 253 and connecting the calibration cap 250 to the housing 10a, the sodium ion selective electrode 41 and the potassium ion selective electrode 42 of the sensor head 30 come into contact with the calibration gel 63b inside the calibration cap 250. The calibration cap 250 also has a pin 254 that protrudes from the upper part of the opening 253. The pin 254 is formed so as to fit into the hole 211 and press down the calibration switch 13a when the calibration cap 250 is connected to the housing 10a.

[0148] As a result, when the user inserts the sensor head 30 into the opening 253 and connects the calibration cap 250 to the housing 10a, the sodium ion selective electrode 41 and the potassium ion selective electrode 42 come into contact with the calibration gel 63b, and the calibration operation is performed by the electrochemical sensor 90.

[0149] (Embodiment 7) The seventh embodiment will be described in terms of differences from the first to sixth embodiments. In the seventh embodiment, a configuration in which the sensor head 30 is attached to the housing 10a via a connector will be described.

[0150] <Configuration of Electrochemical Sensor 90 of Seventh Embodiment> 21 is a diagram showing an example of the configuration of an electrochemical sensor 90 according to the seventh embodiment. The electrochemical sensor 90 shown in FIG. 21 includes a connector 21 in addition to the configuration of the electrochemical sensor 90 shown in FIG. 1. The connector 21 is provided so as to penetrate the wall surface of the housing 10a. The sensor head 30 is detachable from the connector 21.

[0151] The electrochemical sensor 90 may further include a sensor head connection detection unit 14. The sensor head connection detection unit 14 detects whether or not the sensor head 30 is attached to the connector 21, for example, based on sensing data from a switch provided in the connector 21. Based on the detection result by the sensor head connection detection unit 14, the control unit 11 may be configured to execute the above measurement operation and calibration operation only when the sensor head 30 is attached to the connector 21.

[0152] <Configuration example of sensor head 30> Fig. 22 is a diagram showing a sensor head 30A, which is an example of the sensor head 30. Fig. 22 shows the completed sensor head 30A as seen from a direction perpendicular to the plate surface. Fig. 23 is a cross section taken along line VV in Fig. 22. Fig. 24 is a diagram showing the sensor head 30A in an exploded state.

[0153] As can be seen from Figures 22 to 24, the sensor head 30A comprises a rectangular substrate 31 having a predetermined size, a sodium ion selective electrode 41 and a potassium ion selective electrode 42 arranged spaced apart from each other along one side 31c on a mounting surface 31a, which is one of the main surfaces of the substrate 31, and a first extracted electrode 43 and a second extracted electrode 44 extending parallel to each other in the X direction from the sodium ion selective electrode 41 and the potassium ion selective electrode 42, respectively, toward the opposite side (edge) 31e of the substrate 31.

[0154] The substrate 31 is made of an insulating material such as PET (polyethylene terephthalate), glass, silicon, polyimide film, glass epoxy, polycarbonate, acrylic, etc. Therefore, the mounting surface 31a also has insulating properties.

[0155] The first extraction electrode 43 and the second extraction electrode 44 are made of a conductive material such as Pt, Ag, Au, Ir, C, or IrO2.

[0156] As can be seen from Figures 23 and 24, the sodium ion selective electrode 41 has, as a first internal electrode 41m, a conductive first core lower layer 41m' made of the same material as the first extraction electrode 43, and a first core upper layer 41m" made of AgCl and provided in direct contact with this first core lower layer 41m'.In addition, the sodium ion selective electrode 41 has a sodium ion selective membrane 41i provided in direct contact with the first internal electrode 41m (more precisely, the first core upper layer 41m").

[0157] Similarly, the potassium ion selective electrode 42 has, as a second internal electrode 42m, a conductive second core lower layer 42m' made of the same material as the second extractor electrode 44, and a second core upper layer 42m" made of AgCl and provided in direct contact with the second core lower layer 42m'. In addition, the potassium ion selective electrode 42 has a potassium ion selective membrane 42i provided in direct contact with the second internal electrode 42m (more precisely, the second core upper layer 42m").

[0158] The area where the first internal electrode 41m and the sodium ion selective membrane 41i contact each other, and the area where the second internal electrode 42m and the potassium ion selective membrane 42i contact each other are defined by the size (in this example, a diameter of approximately 4 mm) of openings 51, 52 provided in an insulating base material 50 (made of a photo-curable or thermosetting resist, or an insulating seal, sheet, tape, etc.).

[0159] The sodium ion selective membrane 41i is a membrane that selectively selects sodium ions (Na + The potassium ion selective membrane 42i has the property of selectively permeating potassium ions (K + ) has the property of selectively permeating.

[0160] As can be seen from FIG. 22, in the electrode pad portion 30x, which is the portion of the sensor head 30A that is not covered by the insulating base material 50, the first extracted electrode 43 and the second extracted electrode 44 are exposed.

[0161] The sensor head 30A described above has relatively few components, and in particular, is formed in a substantially rectangular flat plate shape and does not have the internal liquid that is found in general ion selective electrodes. Furthermore, the only electrodes that come into contact with the liquid to be measured are the sodium ion selective electrode 41 and the potassium ion selective electrode 42. Therefore, the sensor head 30A can be constructed in a small size and at a low cost.

[0162] 22 is a perspective view showing the sensor head 30 together with the connector 21. figure > figure25 is a perspective view showing the sensor head 30 shown in FIG. 22 together with the connector 21. As shown in FIG. 25, the connector 21 shown in FIG. 21 has a slot 22 into which the electrode pad portion 30x of the sensor head 30A is to be inserted. Contact members 23, 24 made of dogleg-shaped leaf springs are provided in the slot 22 at positions corresponding to the first extracted electrode 43 and the second extracted electrode 44 of the sensor head 30A. When a user inserts the electrode pad portion 30x of the sensor head 30A into the slot 22, the first extracted electrode 43 and the second extracted electrode 44 come into contact with the contact members 23, 24, establishing electrical continuity. As a result, the potential difference or current between the sodium ion selective electrode 41 and the potassium ion selective electrode 42 of the sensor head 30A can be detected by the main body 10 via the connector 21.

[0163] The shape of the sensor head 30 is not limited to the shape of the sensor head 30A shown in Figures 22 to 25, and various other shapes may be used. For example, the sodium ion selective electrode 41 and the potassium ion selective electrode 42 may be arranged along the longitudinal direction of the sensor head 30A.

[0164] The configuration of the sensor head 30A shown in FIGS. 22 to 25 can also be applied to a configuration in which the sensor head 30 is directly connected to the main body 10 without providing the connector 21, as in the first to sixth embodiments.

[0165] (Variation 1) Although the calibration liquid 63a and calibration gel 63b have been described as examples of the calibration agent, the calibration agent is not limited to a liquid or gel, and may be, for example, an absorbent material impregnated with a liquid.

[0166] (Variation 2) Although the electrochemical sensor 90 has been described as having a power switch 13c, the present invention is not limited to this configuration. For example, the calibration switch 13a may also function as a power switch. That is, when the calibration switch 13a is pressed, the electrochemical sensor 90 may be powered on and start a calibration operation.

[0167] (Variation 3) The control unit 11 restricts the measurement operation when the calibration member and the electrochemical sensor 90 are connected, and restricts the calibration operation when the calibration member and the electrochemical sensor 90 are not connected, by software processing. Even if I go For example, the control unit 11 may include a detection unit that detects the coupling between the calibration member and the electrochemical sensor 90, and when the calibration member and the electrochemical sensor 90 are coupled, the control unit 11 does not execute a measurement operation even if the measurement switch 13b is pressed, and when the calibration member and the electrochemical sensor 90 are not coupled, the control unit 11 does not execute a calibration operation even if the calibration switch 13a is pressed.

[0168] In this case, there is no need for a configuration that disables the measurement switch 13b when the calibration member and the electrochemical sensor 90 are connected (for example, a side wall portion of the holding portion 61 of the calibration holder 60), or a configuration that disables the calibration switch 13a when the calibration member and the electrochemical sensor 90 are not connected (for example, a configuration in which the calibration switch 13a does not protrude from the housing 10a).

[0169] (Variation 4) The arrangement, shape, and size of each of the above switches can be changed as appropriate. For example, in the electrochemical sensor 90 shown in FIG. 2, the measurement switch 13b is not limited to being provided on the front surface of the housing 10a, but may also be provided on a side surface or rear surface of the housing 10a. Also, in the electrochemical sensor 90 shown in FIG. 2, the calibration switch 13a is not limited to being provided on the side surface of the housing 10a, but may also be provided on the front surface or rear surface of the housing 10a. Also, the shapes and sizes of the housing 10a and the sensor head 30 are not limited to the above configurations and can be changed as appropriate.

[0170] (Variation 5) The calibration holder 60 may have a configuration in which, instead of the accommodation portion 63, a space similar to the container installation portion 83 of the measurement holder 80 can be installed in which a container containing the calibration liquid 63a can be installed. [Explanation of symbols]

[0171] 1a, 60a, 80a, 90a Front 1b,60b,80b,90b Top surface 10 Main Unit 10a housing 11 Control section 12 Data entry section 13 Control section 13a Calibration switch 13b Measurement switch 13c Power switch 13d Magnetic Switch 13e,13f,67a,67b electrode 13g Measurement limit release switch 13h detection circuit 14 Sensor head connection detection unit 18 Memory 20 Display section 21 Connector 22 slots 23, 24 Contact member 30,30A sensor head 30x electrode pads 31 PCB 31a Mounting surface Around 31c 41 Sodium ion selective electrode 41i Sodium ion selective membrane 41m First inner electrode 41m' First core lower layer 41m″ First core upper layer 42 Potassium ion selective electrode 42i Potassium ion selective membrane 42m Second inner electrode 42m' Second core lower layer 42m″ Upper layer of second core material 43 1st extraction electrode 44 2nd extraction electrode 50 Insulating substrate 51,52 aperture 60 Calibration holder 61,81 Holding part 62,82 Sensor head insertion hole 63 Storage unit 63a Calibration solution 63b Calibration gel 64,65,84 switches 66 Magnet 67c Short-circuit path 69,89 Base 70 containers 70a Measurement target liquid 80 Measurement holder 83 Container installation section 90 Electrochemical Sensors 211,212 holes 220 Calibrator Case 221,233,243,253 Openings 222,232,244,254 pins 230 Measuring Spoon 231,242 dish part 240 Calibration Spoons 250 Calibration Cap

Claims

1. An electrochemical sensor for measuring the concentration ratio of sodium ions to potassium ions in a measurement target liquid, A sensor head; a calculation unit capable of a calibration operation of calculating characteristic parameters of the sensor head based on sensing data of the sensor head in a state where the sensor head is in contact with a calibration agent, and a measurement operation of calculating the concentration ratio based on the characteristic parameters of the sensor head and sensing data of the sensor head in a state where the sensor head is in contact with the liquid to be measured; a calibration switch for causing the calculation unit to execute the calibration operation; a measurement switch for causing the calculation unit to execute the measurement operation; Equipped with By coupling with the calibration member, the sensor head is brought into contact with the calibration agent, When the calibration member is connected, the measurement switch is inoperable, and when the calibration member is not connected, the calibration switch is inoperable. Electrochemical sensors.

2. 10. The electrochemical sensor of claim 1, The calibration operation can be performed when the calibration member is coupled to the calibration device, and the measurement operation can be performed when the calibration member is not coupled to the calibration device. Electrochemical sensors.

3. An electrochemical sensor according to claim 1 or 2, When the calibration member is connected, the calibration switch is operable, and when the calibration member is not connected, the measurement switch is operable. Electrochemical sensors.

4. An electrochemical sensor according to any one of claims 1 to 3, the calibration member is a calibration holder that holds the electrochemical sensor with the sensor head in contact with the calibration agent; Electrochemical sensors.

5. The electrochemical sensor of claim 4, The calibration holder includes: a storage section for storing the calibration agent; holding the electrochemical sensor in a state where the sensor head is in contact with the calibration agent contained in the container; Electrochemical sensors.

6. The electrochemical sensor according to claim 4 or 5, the calibration holder includes a switch for operating the calibration switch of the held electrochemical sensor from outside the calibration holder; Electrochemical sensors.

7. An electrochemical sensor according to any one of claims 4 to 6, the calibration holder includes a shielding portion that shields the measurement switch of the held electrochemical sensor; Electrochemical sensors.

8. An electrochemical sensor according to any one of claims 4 to 7, the calibration holder includes an operating portion that holds the electrochemical sensor to operate the calibration switch; Electrochemical sensors.

9. The electrochemical sensor of claim 8, the operating unit is a magnet, the calibration switch is a magnetic switch; Electrochemical sensors.

10. An electrochemical sensor according to any one of claims 1 to 9, By coupling with the measurement holder, the sensor head is brought into contact with the liquid to be measured. Electrochemical sensors.

11. The electrochemical sensor of claim 10, the measurement holder includes a switch for operating the measurement switch of the held electrochemical sensor from outside the measurement holder; Electrochemical sensors.

12. The electrochemical sensor according to claim 10 or 11, the measurement holder includes a shielding portion that shields the calibration switch of the held electrochemical sensor; Electrochemical sensors.

13. An electrochemical sensor according to any one of claims 1 to 12, comprising: the sensor head includes a sodium ion selective electrode that selectively responds to sodium ions and a potassium ion selective electrode that selectively responds to potassium ions; The sensing data of the sensor head is a potential difference between the sodium ion selective electrode and the potassium ion selective electrode. Electrochemical sensors.

14. An electrochemical sensor according to any one of claims 1 to 13, the calibration member; A measuring device comprising:

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