Diaphragm-type sensor and measurement system using the same

Abstract

Provided is a diaphragm-type sensor that has a diaphragm through which a specific substance in a sample solution passes and that detects the specific substance which has passed through the diaphragm, wherein: the diaphragm is fixed between respective facing surfaces of a container body, which contains internal liquid, a working electrode, and a counter electrode, and of an attachment member, which is attached to the container body; a depressed portion is formed on one of the facing surface of the container body and the facing surface of the attachment member; and a protruding portion is formed on the other one of the facing surface of the container body and the facing surface of the attachment member so as to correspond to the depressed portion.

Description

[Technical Field]

[0001] The present invention relates to a diaphragm-type sensor for detecting a specific substance contained in a sample solution and a measurement system using the same. [Background technology]

[0002] A known diaphragm-type sensor has a housing that houses an internal liquid, a working electrode, and a counter electrode, and a diaphragm that is fixed liquid-tightly to the housing and allows a specific substance to permeate into the housing (Patent Document 1). This diaphragm-type sensor is used by immersing the diaphragm in a sample solution, and the specific substance, such as peracetic acid, that has permeated the diaphragm undergoes an oxidation-reduction reaction on the surface of the working electrode, and the resulting change in current is measured to measure the concentration of the specific substance.

[0003] Conventionally, the diaphragm has been fixed to the container using adhesives, heat welding, etc. (hereinafter referred to as adhesives, etc.). However, fixing the diaphragm using adhesives, etc., has the problem of increasing the assembly variation between individual products. Furthermore, fixing methods using adhesives, etc., make it difficult to tension the diaphragm, which may reduce measurement accuracy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-230172 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above-mentioned problems, and has as its main object to provide a diaphragm-type sensor in which a diaphragm can be fixed liquid-tightly without using adhesives or the like and the diaphragm can be stretched in a state in which tension is applied.

[0006] That is, the diaphragm sensor according to the present invention is a diaphragm sensor having a diaphragm that allows a specific substance in a sample solution to permeate, and that detects the specific substance that has permeated the diaphragm, wherein the diaphragm is sandwiched and fixed between the opposing surfaces of a container body that contains an internal liquid, a working electrode, and a counter electrode, and an attachment member that is attached to the container body, and wherein a recess is formed on one of the opposing surfaces of the container body or the attachment member, and a protrusion corresponding to the recess is formed on the other opposing surface of the container body or the attachment member.

[0007] With this configuration, the diaphragm is sandwiched and fixed between the recessed and protruding portions formed on the opposing surfaces of the container body and the mounting member, thereby making it possible to fix the diaphragm in a liquid-tight manner without using chemical bonding such as adhesives. Furthermore, when the mounting member is attached to the container body so that the recessed and protruding portions are aligned, the diaphragm can be fixed by being pulled into the recessed portion, allowing the diaphragm to be stretched under tension.

[0008] It is preferable that the diaphragm-type sensor has an annular facing surface between the housing body and the mounting member, and the recess is configured as an annular groove formed on one of the facing surfaces between the housing body and the mounting member. In this way, by configuring the recess as an annular groove, it is possible to apply tension by pulling the diaphragm from all circumferential directions, so that the diaphragm can be stretched without wrinkles.

[0009] In order to further improve the sealing performance for the internal liquid, it is sufficient if a plurality of the grooves are formed concentrically on one of the opposing surfaces of the container body and the mounting member.

[0010] In order to be able to finely adjust the tension applied to the diaphragm and the sealing force of the diaphragm, the plurality of grooves may be formed to have different cross-sectional shapes.

[0011] Preferably, the outer grooves are formed to be deeper than the inner grooves. In this way, when the mounting member is attached to the container body, the diaphragm can be pulled in stages, starting from the outside, thereby making it possible to stretch the diaphragm with tension applied more reliably.

[0012] In the diaphragm sensor, it is preferable that the groove located at the outermost position is formed so that, in its cross section, the inclination of the outward surface of the inner surface is gentler than the inward surface opposite the outward surface. In this way, when the mounting member is attached to the container body, the convex portion can be reliably brought into contact with the inner surface of the groove, more reliably ensuring sealing. Furthermore, when the mounting member is attached to the container body, the convex portion first comes into contact with the outward surface of the inner surface of the groove, and then the convex portion can be fitted into the groove so as to pull the diaphragm outward, so that the diaphragm can be stretched with more reliable tension applied.

[0013] In an embodiment in which the effects of the present invention are particularly pronounced, the diaphragm has a laminated structure in which a plurality of different types of membranes are stacked. With this configuration, even if the diaphragm has a layered structure in which multiple types of films are layered, the diaphragm can be stretched in a state where tension is applied.

[0014] However, if a diaphragm-type sensor is left in a sample solution for a long period of time without power being applied to the measurement circuit, including the counter electrode and working electrode (when the power is cut off), the electrodes will deteriorate, causing a decrease in sensitivity. Therefore, it is preferable that the diaphragm sensor of the present invention further comprises a pseudo voltage generating circuit unit for applying a pseudo voltage simulating a predetermined measurement voltage and cleaning voltage to the counter electrode, and that the pseudo voltage generating circuit unit is configured to apply the pseudo voltage to the counter electrode when neither the measurement voltage nor the cleaning voltage is applied to the counter electrode. In this way, when the electrode is not in use, a dummy voltage is applied to cause an electrochemical reaction at the counter electrode and working electrode, thereby suppressing deterioration of the electrode.

[0015] In this case, it is desirable that the pseudo-voltage generating circuit unit be configured to alternately apply a pseudo-measurement voltage that simulates the measurement voltage and a pseudo-cleaning voltage that simulates the cleaning voltage to the counter electrode when neither the measurement voltage nor the cleaning voltage is applied to the counter electrode.

[0016] A specific configuration of the pseudo-voltage generating circuit unit includes a power supply that generates the pseudo-voltage, a first selector switch that switches on / off conduction between the power supply and the counter electrode, and a second selector switch that switches on / off conduction between the working electrode and ground, and the first selector switch and the second selector switch are configured to turn off conduction when either the measurement voltage or the cleaning voltage is applied to the counter electrode, and to turn on conduction when neither the measurement voltage nor the cleaning voltage is applied to the counter electrode.

[0017] The measurement system of the present invention is characterized by comprising the diaphragm sensor of the present invention described above, and a calculation unit that calculates the concentration of a specific substance in the sample solution based on a current value output from the diaphragm sensor when a predetermined voltage is applied between the working electrode and the counter electrode. Such a measurement system can achieve the same effects as the diaphragm-type sensor of the present invention. [Effects of the Invention]

[0018] According to the present invention configured as described above, in the diaphragm-type sensor, the diaphragm can be fixed in a liquid-tight manner without using adhesive or the like, and the diaphragm can be stretched in a state where tension is applied. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is an overall schematic diagram of a diaphragm-type sensor according to an embodiment of the present invention; [Figure 2] FIG. 2 is an exploded schematic view of the diaphragm sensor according to the embodiment. [Figure 3] FIG. 2 is a schematic cross-sectional view of a diaphragm sensor according to the embodiment. [Figure 4]FIG. 2 is a block diagram of a measurement system using the diaphragm-type sensor of the embodiment. [Figure 5] FIG. 4 is an enlarged view of part A in FIG. 3 of the embodiment, and is a view schematically showing the configuration of a diaphragm fixing part. [Figure 6] FIG. 4 is an enlarged view of part A in FIG. 3 of the embodiment, and is an exploded view showing a schematic configuration of the diaphragm fixing part. [Figure 7] FIG. 4 is an enlarged view of part A in FIG. 3 according to another embodiment, and is a view schematically illustrating the configuration of a diaphragm fixing part. [Figure 8] FIG. 4 is an enlarged view of part A in FIG. 3 according to another embodiment, and is a view schematically illustrating the configuration of a diaphragm fixing part. [Figure 9] FIG. 4 is an enlarged view of part A in FIG. 3 according to another embodiment, and is a view schematically illustrating the configuration of a diaphragm fixing part. [Figure 10] FIG. 4 is an enlarged view of part A in FIG. 3 according to another embodiment, and is a view schematically illustrating the configuration of a diaphragm fixing part. [Explanation of symbols]

[0020] 100···Diaphragm sensor 11. Container body 11s...1st facing surface 111....recess (groove) 12 Mounting member 12s...Second opposing surface 121.... Convex part (protrusion) 2...diaphragm 4...Internal fluid 5...Working electrode 6. Opposite DETAILED DESCRIPTION OF THE INVENTION

[0021] A diaphragm-type sensor 100 according to one embodiment of the present invention will be described below with reference to the drawings.

[0022] The diaphragm sensor 100 of this embodiment is immersed in a sample solution to detect specific substances in the sample solution, such as peracetic acid, hydrogen peroxide, dissolved oxygen, and residual chlorine, and measure their concentrations. Specifically, as shown in Figures 1 and 2, the diaphragm sensor 100 includes a housing 1 that houses an internal liquid 4, a working electrode 5, and a counter electrode 6, a diaphragm 2 fixed to one surface of the housing 1, and a lid member 3 that seals the housing 1.

[0023] The container 1 has a tubular (cylindrical) shape, and its inner surface forms a storage space for storing the internal liquid 4, working electrode 5, and counter electrode 6. The container 1 has openings at both ends along its axial direction (also referred to as the tip and base ends, respectively). A diaphragm fixing part 13 for fixing the diaphragm 2 is provided at the tip of the container 1, and the diaphragm fixing part 13 fixes the diaphragm 2 so as to close the opening of the container 1. The diaphragm fixing part 13 will be described in detail later.

[0024] Specifically, this housing 1 includes a housing main body 11 having a tubular shape (here, cylindrical shape), and an attachment member 12 attached to the axial tip of this housing main body 11. The attachment member 12 has an annular plate shape, and is attached to the tip of the housing main body 11 so as to be concentric with the housing main body 11. The housing main body 11 and the attachment member 12 have annular opposing surfaces (referred to as a first opposing surface 11s and a second opposing surface 12s, respectively) that face each other when attached.

[0025] The mounting member 12 may be fixed to the housing body 11 by any method, such as welding or screwing. Here, the outer edge of the first opposing surface 11s of the housing body 11 and the outer edge of the second opposing surface 12s of the mounting member 12 are welded together.

[0026] The diaphragm 2 allows specific substances in the sample solution, such as peracetic acid, hydrogen peroxide, dissolved oxygen, and residual chlorine, to pass through. The diaphragm 2 is made of a material including, for example, silicon, fluororesin, polypropylene (PP), polyethylene (PE), and polycarbonate (PC). The thickness of the diaphragm 2 is, for example, 10 μm to 200 μm, but is not limited to this.

[0027] The diaphragm 2 of this embodiment has a layered structure in which multiple different types of membranes are layered. Specifically, the diaphragm 2 has a three-layer structure in which, for example, a silicone membrane, a polymer removal membrane, and a PP membrane are layered in this order from the base end to the tip end of the container 1. This polymer removal membrane is made of a porous PE membrane as a base material with AC (acetyl cellulose) formed on the surface.

[0028] An intermediate film M may be provided between the diaphragm 2 and the working electrode 5. This intermediate film M is intended to prevent the diaphragm 2 (particularly a silicon film) from sticking to the working electrode 5, and is made of a porous material such as a porous PC film.

[0029] The lid member 3 is attached to close the opening on the base end side of the housing 1, sealing the housing space. A holding member 31 that holds the working electrode 5 and the counter electrode 6 is provided so as to protrude from approximately the center of the housing 1 side of the lid member 3. This holding member 31 is housed within the housing space of the housing 1 in a state in which the lid member 3 is attached to the housing 1. In addition, a connector 32 is provided on the opposite side to the housing 1 side for connecting external devices such as an external power supply and a computing device (not shown).

[0030] The holding member 31 is made of an insulating material and, as shown in Fig. 3, surrounds the working electrode 5 to hold it, and also wraps around it to hold the counter electrode 6. The holding member 31 is provided with a spiral groove for attaching the lid member 3 to the housing 1, and the lid member 3 can be attached to the housing 1 by fitting the groove with a screw thread (not shown) provided on the housing 1. The holding member 31 is also provided with an air hole 31a for discharging gas to the outside. A filter for separating gas and liquid is provided at one open end of the air hole 31a.

[0031] 2 and 3, the working electrode 5 is rod-shaped and disposed so that one end thereof slightly protrudes beyond the tip surface 31b of the holding member 31. The surface of the working electrode 5 is provided with minute irregularities (not shown).

[0032] The counter electrode 6 is made of a conductive material such as platinum or silver-silver chloride (Ag / AgCl), and in this embodiment, is configured to have a linear shape.

[0033] 3, the working electrode 5 and the counter electrode 6 are connected via a conductor 7, and a voltage is applied from an external power supply means via the conductor 7. The conductor 7 is also provided with an ammeter 8 that detects the current flowing through the conductor 7. The conductor 7 and the ammeter 8 may be provided outside the cover member 3.

[0034] 3, with the cover member 3 attached to the housing 1, an internal liquid 4 is contained in the space formed between the cover member 3 and the housing 1. This internal liquid 4 may be, for example, an electrolyte such as potassium chloride, a phosphate buffer solution, an acetate buffer solution, a borate buffer solution, a citrate buffer solution, or the like.

[0035] Fig. 4 shows a block diagram of a measurement system 300 using the diaphragm sensor 100 of this embodiment. Specifically, as shown in Fig. 4, this measurement system 300 includes the diaphragm sensor 100, an external power source E that applies a voltage to the diaphragm sensor 100, and a control device 200 that measures the concentration in a sample solution based on the current output from the diaphragm sensor 100.

[0036] This control device 200 is a general-purpose or dedicated computer equipped with a CPU, memory, input / output interface, etc., and performs at least the functions of an arithmetic unit 210 and a display unit 220 by having the CPU and peripheral devices cooperate in accordance with a predetermined program stored in a predetermined area of ​​the memory.

[0037] The calculation unit 210 calculates the concentration of the specific substance in the sample solution based on the current value output from the diaphragm sensor 100 when a predetermined measurement voltage is applied between the working electrode 5 and the counter electrode 6. The display unit 220 displays the calculated concentration of the specific substance on a display or the like.

[0038] More specifically, in the measurement system 300 of this embodiment, a predetermined measurement voltage and cleaning voltage are applied to the counter electrode 6 of the diaphragm sensor 100 from an external power source E. A current corresponding to the concentration of a specific substance flows between the counter electrode 6 and the working electrode 5, and this current is output to the calculation unit 210 via an operational amplifier. Note that although the block diagram of FIG. 4 shows a three-electrode polarographic sensor provided with a reference electrode (REF), the diaphragm sensor 100 of this embodiment may also be a two-electrode polarographic sensor that does not have such a reference electrode.

[0039] In the diaphragm sensor 100 of this embodiment, the diaphragm fixing portion 13 is composed of a first opposing surface and a second opposing surface, and the diaphragm 2 is fixed with its outer edge sandwiched between these opposing surfaces 11s, 12s. As shown in Figures 5 and 6, a recess 111 is formed in one of the first opposing surface 11s or the second opposing surface 12s (here, the first opposing surface 11s), and a protrusion 121 corresponding to the recess 111 is formed in the other of the first opposing surface 11s or the second opposing surface 12s (here, the second opposing surface 12s). The diaphragm 2 is pulled radially outward with its outer edge sandwiched between the recess 111 and the protrusion 121.

[0040] Specifically, when viewed from the axial direction, this recess 111 is configured as an annular (specifically, circular) groove formed in the first opposing surface 11s so as to surround the opening of the container 1. This groove 111 is formed in a position on the first opposing surface 11s corresponding to the outer edge of the diaphragm 2 so as to be concentric with the axis of the container main body 11. In addition, the groove 111 is formed continuously all around the axis of the container 1. The convex portion 121 is configured by an annular projection 121 formed on the second opposing surface 12s so as to have substantially the same cross-sectional shape as the corresponding concave portion 111.

[0041] In this embodiment, a plurality of such annular grooves 111 (two in this example) are formed concentrically on the first opposing surface 11s. These grooves 111 are separated from each other by the first opposing surface 11s, as shown in Figures 5 and 6, and are formed so that the outer grooves 111 along the radial direction are deeper than the inner grooves 111.

[0042] The plurality of grooves 111 are formed to have mutually different cross-sectional shapes. Specifically, the groove 111 located at the innermost periphery among the plurality of grooves 111 has a cross-sectional shape that is bilaterally (radially) symmetrical, and is formed so that the inclination of the outward surface 111a of the inner side surface forming the groove 111 and the inward surface 111b opposing thereto are substantially the same. In contrast, the groove 111 located at the outermost periphery has a cross-sectional shape that is bilaterally asymmetrical, and is formed so that the inclination of the outward surface 111a is gentler than the inward surface 111b. Furthermore, the outermost groove 111 is chamfered (specifically, R-chamfered) at a boundary 111c between the inward surface 111b and the first opposing surface 11s.

[0043] Furthermore, in the diaphragm sensor 100 of this embodiment, in order to make it difficult for air bubbles to remain on the measurement surface (the surface that comes into contact with the sample solution) of the diaphragm 2 during measurement, the thickness of the mounting member 12 along the axial direction is reduced, thereby reducing the step between the measurement surface of the diaphragm 2 and the tip surface 12t of the mounting member 12 (i.e., the back surface of the second opposing surface 12s). To achieve this configuration, the tip surface of the container body 11 is formed to be flush (coplanar) except for the portion where the recess 111 is formed. This reduces the unevenness on the second opposing surface 12s of the mounting member 12, allowing the thickness of the mounting member 12 to be reduced.

[0044] Furthermore, the mounting member 12 has a chamfered radially innermost edge at the tip surface 12t, thereby forming an inclined surface 123 that is inclined relative to a direction perpendicular to the axial direction. This inclined surface 123 is formed so as to face the axial center of the container 1 (i.e., so as to move radially inward toward the base end in the axial direction). This inclined surface 123 is formed over a range of approximately 0.8 mm along the radial direction from the innermost edge at the tip surface 12t of the mounting member 12. This inclined surface 123 is also formed so that its inclination angle relative to the direction perpendicular to the axial direction is approximately 45°. By providing such an inclined surface 123, air bubbles can be easily released toward the mounting member 12 during measurement without remaining on the measurement surface of the diaphragm 2.

[0045] 4, the diaphragm sensor 100 of this embodiment includes a pseudo voltage generating circuit 9 for applying pseudo voltages that simulate the measurement voltage and cleaning voltage applied from an external power source E to the counter electrode 6. This pseudo voltage generating circuit 9 is configured to apply a pseudo voltage to the counter electrode 6 when neither the measurement voltage nor the cleaning voltage is being applied to the counter electrode 6 (i.e., when the external power source E is disconnected). Specifically, it is configured to alternately apply a pseudo measurement voltage that simulates the measurement voltage and a pseudo cleaning voltage that simulates the cleaning voltage to the counter electrode 6 at predetermined time intervals.

[0046] Specifically, as shown in FIG. 4, the pseudo voltage generating circuit unit 9 includes a sub-power supply 91 that generates a pseudo voltage, a first changeover switch 92 that is connected between the sub-power supply 91 and the counter electrode 6 and that switches on / off the electrical connection between the sub-power supply 91 and the counter electrode 6, and a second changeover switch 93 that switches on / off the electrical connection between the working electrode 5 and ground GND.

[0047] The first changeover switch 92 and the second changeover switch 93 are semiconductor switches, and in this case, junction field-effect transistors are used. The first changeover switch 92 and the second changeover switch 93 are configured to turn off conduction when a voltage from an external power supply E is applied to the counter electrode 6, and turn on conduction when the external power supply E is disconnected. Therefore, when the external power supply E is disconnected, a pseudo voltage is applied from the sub-power supply 91 to the counter electrode 6, causing a current to flow between the counter electrode 6 and the working electrode 5, and this current flows through the second changeover switch 93 to ground GND.

[0048] With the diaphragm sensor 100 of this embodiment configured as described above, the diaphragm 2 can be fixed liquid-tightly without using adhesives or the like by sandwiching the diaphragm 2 between the annular groove 111 formed in the first opposing surface 11s of the housing body 11 and the annular protrusion 121 formed on the second opposing surface 12s of the mounting member 12. Furthermore, when the mounting member 12 is attached to the housing body 11 so that the positions of the annular groove 111 and the annular protrusion 121 are aligned, the diaphragm 2 can be fixed by being pulled into the groove 111, and therefore the diaphragm 2 can be stretched without wrinkles when tension is applied so that it is pulled from all around the circumference.

[0049] The present invention is not limited to the above-described embodiment.

[0050] For example, in the above embodiment, the recess 111 is formed on the first opposing surface 11s, and the protrusion 121 corresponding to the recess 111 is formed on the second opposing surface 12s, but this is not limiting. In another embodiment, as shown in Fig. 7, the recess 111 may be formed on the second opposing surface 12s, and the protrusion 121 corresponding to the recess 111 may be formed on the first opposing surface 11s.

[0051] In the above embodiment, the plurality of grooves 111 are formed so as to be separated from one another (i.e., so as to sandwich the first opposing surface 11s between them), but this is not limiting. In other embodiments, the plurality of grooves 111 may be formed so as to be continuous without being completely separated, as shown in Fig. 8.

[0052] In another embodiment, three or more annular grooves 111 may be formed concentrically as shown in Fig. 9. In this case, the depth of the grooves 111 may increase from the outer periphery toward the inner periphery.

[0053] In addition, in the diaphragm sensor 100 of the above embodiment, a plurality of annular grooves 111 and protrusions 121 are formed concentrically, but this is not limiting. In other embodiments, as shown in Fig. 10, one annular groove 111 and one protrusion 121 may be provided.

[0054] In addition, in the diaphragm sensor 100 of the above embodiment, the asymmetric groove 111 is formed such that the inclination of the outward surface 111a of the inner side surface is gentler than the inward surface 111b, but this is not limited to this. In other embodiments, as shown in Fig. 10, the groove 111 having an asymmetric cross-sectional shape may not be formed, and only the groove 111 having a symmetric cross-sectional shape may be formed.

[0055] In other embodiments, the tip surface of the housing body 11 may not be flush except for the recess 111. In other embodiments, the mounting member 12 may not have the inclined surface 123 formed thereon.

[0056] Although the groove 111 and the protrusion 121 in the above embodiment are circular, the shape is not limited to this. In other embodiments, the groove 111 and the protrusion 121 may be rectangular or have other shapes.

[0057] Furthermore, the diaphragm sensor 100 of another embodiment may not include the pseudo voltage generating circuit unit 9.

[0058] Although the membrane 2 in the above embodiment has a laminated structure in which multiple types of membranes are stacked, the present invention is not limited to this. In other embodiments, the membrane 2 may have a single layer structure made of one type of membrane.

[0059] Furthermore, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit of the present invention. [Industrial Applicability]

[0060] According to the diaphragm sensor of the present invention, the diaphragm can be fixed in a liquid-tight manner without using adhesives or the like, and the diaphragm can be stretched in a state where tension is applied.

Claims

1. A diaphragm-type sensor has a diaphragm that allows a specific substance in a sample solution to permeate, and detects the specific substance that has permeated the diaphragm, the diaphragm is sandwiched and fixed between annular opposing surfaces of a container body that accommodates an internal liquid, a working electrode, and a counter electrode and an attachment member that is attached to the container body, an annular groove is formed on one of the opposing surface of the container body or the opposing surface of the mounting member, and a convex portion corresponding to the annular groove is formed on the other of the opposing surface of the container body or the opposing surface of the mounting member, A diaphragm-type sensor in which a plurality of the grooves are formed concentrically on one of the opposing surfaces of the housing body and the mounting member, and the outer grooves are formed so as to be deeper than the inner grooves.

2. 2. The diaphragm-type sensor according to claim 1, wherein the plurality of grooves have different cross-sectional shapes.

3. 3. The diaphragm sensor according to claim 1, wherein the groove located at the outermost position is formed so that the inclination of the outward surface of the inner surface in a cross section is gentler than the inward surface opposite the outward surface.

4. 4. The diaphragm sensor according to claim 1, wherein the diaphragm has a laminated structure in which a plurality of different types of membranes are stacked.

5. a pseudo voltage generating circuit for applying a pseudo voltage simulating a predetermined measurement voltage and a predetermined cleaning voltage to the counter electrode; 5. The diaphragm sensor according to claim 1, wherein the pseudo voltage generating circuit is configured to apply the pseudo voltage to the counter electrode when neither the measurement voltage nor the cleaning voltage is applied to the counter electrode.

6. 6. The diaphragm sensor according to claim 5, wherein the pseudo voltage generating circuit is configured to alternately apply a pseudo measurement voltage that simulates the measurement voltage and a pseudo cleaning voltage that simulates the cleaning voltage to the counter electrode when neither the measurement voltage nor the cleaning voltage is applied to the counter electrode.

7. The pseudo voltage generating circuit unit a power source that generates the pseudo voltage; a first changeover switch that switches on / off conduction between the power supply and the counter electrode; a second changeover switch that switches on / off conduction between the working electrode and ground, 7. The diaphragm sensor according to claim 5, wherein the first changeover switch and the second changeover switch are configured to turn off conduction when either the measurement voltage or the cleaning voltage is applied to the counter electrode, and to turn on conduction when neither the measurement voltage nor the cleaning voltage is applied to the counter electrode.

8. The diaphragm-type sensor according to any one of claims 1 to 7, a calculation unit that calculates the concentration of a specific substance in the sample solution based on a current value output from the diaphragm sensor when a predetermined voltage is applied between the working electrode and the counter electrode.

9. A diaphragm-type sensor having a diaphragm that allows a specific substance in a sample solution to pass through, and detecting the specific substance that has passed through the diaphragm, the diaphragm is sandwiched and fixed between annular opposing surfaces of a container body that accommodates an internal liquid, a working electrode, and a counter electrode and an attachment member that is attached to the container body, an annular groove is formed on one of the opposing surface of the container body or the opposing surface of the mounting member, and a convex portion corresponding to the annular groove is formed on the other of the opposing surface of the container body or the opposing surface of the mounting member, The groove is a diaphragm sensor formed such that the inclination of the outward surface of the inner side surface is gentler than the inclination of the inward surface opposite the outward surface in its cross section.

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