JP2005148007A - Conductivity meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductivity meter capable of stably measuring the conductivity of a liquid to be measured in spite of being manufacturable at low cost. <P>SOLUTION: The conductivity meter 10 measures the conductivity of the liquid 13 to be measured by measuring the resistance value of the liquid 13 between rod-shaped electrodes 2, 3. One of the electrodes is the measuring electrode 2, and the other is the reference electrode 3, and the conductivity meter comprises a guard 4 consisting of an insulating material electrically shielding the electrodes 2 and 3 from the outside. A communicating port 5 for the liquid 13 and a slit 6 are provided in a position C1 near the reference electrode 3 but distant from the measuring electrode 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a conductivity meter that measures the resistance (or specific resistance) of a measured liquid by measuring the resistance value of the measured liquid between two electrodes.

  For example, as a device for monitoring the purity of pure water used in a semiconductor manufacturing process, there is a conductivity meter that measures the conductivity of the pure water. FIG. 8 is a diagram showing an overall configuration of an example of the conductivity meter 10. In FIG. 8, 11 is a conductivity meter body, 12 is an electrode, and 13 is a liquid to be measured. That is, the main body 11 is configured to be able to measure various physical quantities of the liquid to be measured 13 by replacing the electrode 12 connected thereto. 8 shows an example in which one electrode 12 is connected to the main body 11, a plurality of electrodes may be connected to this.

  9A and 9B are diagrams showing an example of an electrode 12A for measuring conductivity. FIG. 9A is a perspective view, and FIG. 9B is an explanatory diagram. The electrode 12A of this example is composed of two rod-like electrodes 14 and 15 arranged in parallel, and these rod-like electrodes 14 and 15 are made of, for example, platinum or platinum black. In the following description, the electrode 12A is referred to as a parallel bar electrode. When the parallel bar electrode 12A configured as described above is subjected to an electrical disturbance as indicated by an imaginary line arrow A in FIG. 9B, it is considered that both the bar electrodes 14 and 15 are similarly affected. It is done. When a voltage is applied between the rod-shaped electrodes 14 and 15, a current corresponding to the conductivity of the liquid to be measured 13 flows as shown by a double arrow B, and a balanced signal is output from the parallel rod-shaped electrode 12A. Is done.

  FIG. 10 shows an example of another electrode 12B for measuring conductivity, which is almost the same as that shown in Patent Document 1 below, FIG. 10 (A) is a perspective view, and FIG. 10 (B) is an explanatory view. It is. The electrode 12 </ b> B of this example includes a rod-shaped internal electrode 16 and a substantially cylindrical external electrode 17 disposed coaxially with the internal electrode 16. In the following description, the electrode 12B is referred to as a coaxial electrode. As shown in FIG. 10B, the coaxial electrode 12B configured in this way enters only the external electrode 17 when it receives an electrical disturbance A, so that the liquid to be measured 13 and the outside of the detector are outside. The electrode 17 becomes the same potential.

That is, by using the coaxial electrode 12B, by directly connecting the external electrode 17 as a reference electrode to the circuit common of the main body 11 (see FIG. 8), it is possible to measure the conductivity without being affected by the disturbance A. Can be performed. Further, the signal from the coaxial electrode 12B is a non-equilibrium signal.
JP 2000-162168 A

  However, when the parallel bar electrode 12A is directly connected to the circuit common of the main body 11, as indicated by the double arrow B, the current that should flow between the electrodes 14 and 15 also flows to other portions or passes through the ground. The current flowing in the ground loop may cause a large measurement error. Therefore, in order to avoid the influence of the ground loop, it is necessary to insulate the liquid 13 to be measured from the ground, or to insulate the common of the main body 11 from the ground, both of which are functional restrictions and performance restrictions. It was.

  Further, when a plurality of parallel bar-type electrodes 12A are immersed in the same liquid to be measured 13 and the conductivity thereof is measured, interference may occur by forming a loop circuit between the plurality of electrodes. Conceivable. Therefore, in order to prevent interference between the electrodes, it is necessary to insert an insulation circuit or a balanced / unbalanced converter between the parallel bar electrode 12A and the circuit of the main body 11 to eliminate the loop circuit. There has been a problem that it causes an increase in manufacturing cost on the main body 11 side.

  On the other hand, in the coaxial electrode 12B as shown in Patent Document 1, even if the external electrode 17 is directly connected to the circuit common on the main body 11 side, there is no functional restriction or performance restriction. However, the coaxial electrode 12B has a complicated structure as compared with the simple parallel bar electrode 12A, and there is a problem that the manufacturing cost is increased accordingly.

  In particular, depending on the component of the liquid to be measured and the allowable contamination level, it may be necessary to use a very expensive material such as platinum or glass carbon for the electrodes 16 and 17. In this case, the coaxial electrode 12B has a problem that the manufacturing cost of the electrode 17 is increased because the surface area of the external electrode 17 must be larger than that of the rod-like electrodes 14 and 15.

  The present invention has been made in consideration of the above-mentioned matters, and an object of the present invention is to provide a conductivity meter capable of stably measuring the conductivity of a liquid to be measured while being inexpensively manufactured. Is to provide.

  In order to achieve the above object, the present invention provides a conductivity meter that measures the resistance of a liquid to be measured between rod-shaped electrodes and measures the conductivity of the liquid to be measured. And a guard made of an insulating material that electrically shields these electrodes from the outside, and a communication hole for the liquid to be measured at a position near the reference electrode and away from the measurement electrode It is characterized by providing. (Claim 1)

  The guard may have a cylindrical shape, and the communication hole may be formed by opening the free end of the guard, and the length of the measurement electrode may be shorter than that of the reference electrode. (Claim 2)

  The communication hole may be provided by forming a slit on the side surface of the guard along the reference electrode. (Claim 3)

  The communication hole may be provided by forming a through hole in the side surface of the base end portion of the guard. (Claim 4)

  An insulating cover may be provided on the base end side of the measurement electrode. (Claim 5)

  In the conductivity meter according to claim 1, the reference electrode is positively brought into contact with the liquid to be measured by providing a communication hole for the liquid to be measured in the vicinity of the reference electrode. The potential of the reference electrode can be considered to be the same as the potential of the liquid to be measured by treating it like an external electrode of a coaxial electrode. On the other hand, since the measurement electrode is disposed at a position away from the communication hole in the guard made of an insulating material that is electrically shielded from the outside, it can be handled like the internal electrode of the coaxial electrode. .

  In other words, in the present invention, a rod-shaped electrode having a very simple structure can be used to reduce the manufacturing cost as much as possible while providing stability comparable to that of a coaxial electrode. Rate measurements can be made. The conductivity meter of the present invention having an unbalanced sensor can be used by connecting the reference electrode to the common on the main body side of the conductivity meter. It is not necessary to provide a circuit such as a balanced converter, which not only simplifies the circuit configuration of the conductivity meter, but also interferes with each other even if measurement is performed with multiple electrodes in the same liquid to be measured. There is no.

  In the present invention, the reference electrode can be connected to the circuit common on the main body side of the conductivity meter, and this potential can be considered to be the same as the potential of the liquid to be measured. Therefore, it is also possible to ground the common of the electronic circuit that constitutes the conductivity meter with a capacitor, etc., to prevent external noise from entering the electronic circuit on the main body side of the conductivity meter, and to stabilize its operation Is possible.

  In the case where the guard has a cylindrical shape and the free end portion of the guard is opened to form the communication hole, and the length of the measurement electrode is shorter than that of the reference electrode (Claim 2). It is possible to replace the liquid to be measured in the guard using a communication hole provided at the free end of the guard and to change the length of the rod-shaped electrode, Since it can be positioned away from the communication hole compared to the reference electrode, the measurement electrode is not easily affected by noise from the outside.

  When the communication hole is provided by forming a slit along the reference electrode on the side surface of the guard (Claim 3), the contact between the reference electrode and the liquid to be measured is kept close, The liquid to be measured can be replaced more quickly.

  When the communication hole is provided by forming a through hole in the side surface of the base end portion of the guard (Claim 4), the contact between the reference electrode and the liquid to be measured is maintained, and the measurement within the guard is performed. The liquid can be replaced quickly. Further, the communication hole can be easily formed.

  When an insulating cover is provided on the base end side of the measurement electrode (Claim 5), it is possible to prevent disturbance from entering the measurement electrode through the communication hole formed in the base end portion of the guard. The value stabilizes and more accurate conductivity measurement can be performed.

  1A and 1B are diagrams showing a configuration of an electrode portion in a conductivity meter according to a first embodiment of the present invention. FIG. 1A is a perspective view and FIG. 1B is a plan view. In addition, each electrode corresponding to description of each following Example is connected to the main body 11 etc. of the conductivity meter 10 demonstrated using FIG. 8, for example, and is immersed in the to-be-measured liquid 13, and measures the electrical conductivity. Is. In each of the following embodiments, one electrode is used as a measurement electrode and the other electrode is used as a reference electrode and connected to the common on the main body 11 side, and these electrodes constitute an unbalanced sensor.

  In FIG. 1, 1 is a base, 2 and 3 are rod-shaped electrodes made of, for example, glass carbon provided on the substrate 1 and arranged in parallel. One rod-shaped electrode 2 is a measurement electrode (hereinafter, one rod-shaped electrode is measured). The other rod-shaped electrode 3 is a reference electrode (hereinafter, one rod-shaped electrode may also be referred to as the reference electrode 3). Reference numeral 4 denotes an insulating cylindrical guard made of a synthetic resin that electrically shields the rod-like electrodes 2 and 3 from external noise (disturbance) indicated by an arrow A. The guard 4 has a base end portion 4a thereof. Attached to the substrate 1. Further, in this example, the open end 4a of the guard 4 is opened, so that a communication hole 5 for the liquid 13 to be measured is formed in the guard 4, and a slit 6 (communication hole is formed along the reference electrode 3 on the side surface. ) Is formed.

In addition, the measurement electrode 2 is formed to be shorter than the reference electrode 3 by, for example, 10 mm or more, so that the communication hole 5 is formed in the vicinity of the measurement electrode 2 and at a position as far as possible from the reference electrode 3. Become. That is, the electrical contact between the rod-shaped electrodes 2 and 3 and the measured liquid 13 in the guard 4 occurs in both the rod-shaped electrodes 2 and 3, but the electrical contact with the measured liquid 13 outside the guard 4 through the communication hole 5. Such a contact is mainly generated in the reference electrode 3 disposed in the vicinity of the communication hole 5 and is not generated as much as possible in the measurement electrode 2 formed as far as possible from the communication hole 5. Therefore, the disturbance A ₁ generated in the liquid to be measured 13 outside the guard 4 can be prevented from adversely affecting the measurement electrode 2 through the communication hole 5.

  As the difference in length between the measurement electrode 2 and the reference electrode 3 is increased, the electrical contact between the measurement electrode 2 and the external liquid to be measured 13 can be reduced. The current indicated by the double-pointed arrow B flows between the electrodes 2 and 3, and the conductivity of the liquid 13 to be measured needs to be increased to a certain extent so that it can be accurately measured.

The guard 4 is made of a synthetic resin having excellent corrosion resistance and sufficient insulation, such as a fluororesin, and the guard 4 has electrodes 2 and 3 in a substantially C-shaped cross section shown in FIG. In addition, the thickness of the liquid to be measured 13 surrounding the periphery of both electrodes 2 and 3 has a mechanical strength sufficient to keep the state constant. The slit 6 is formed at the position of the intersection C ₁ closer to the reference electrode 3 among the _two intersections C ₁ and C ₂ of the straight line L connecting the electrodes 2 and 3 and the guard 4. A slit 6 is formed at a position farthest from the position of the measurement electrode 2. That is, the communication hole 6 is formed in the vicinity of the reference electrode 3 and as far as possible from the measurement electrode 2.

  When the electrodes 2 and 3 of the conductivity meter having the above configuration are immersed in the liquid to be measured 13, the liquid to be measured 13 easily enters the guard 4 through the communication hole 5, and the atmosphere in the guard 4 passes through the slit 6. It is pushed out quickly. In other words, the guard 4 can be easily filled with the liquid 13 to be measured simply by immersing the electrodes 2 and 3 in the liquid 13 to be measured. Next, by applying an alternating voltage between the electrodes 2 and 3, a current flows in the direction indicated by the double arrow B, and the conductivity of the liquid 13 to be measured is measured.

Since the guard 4 having the above-described configuration is provided, the current flowing between the electrodes 2 and 3 does not flow to the outer portion of the guard 4 and does not form a ground loop or the like, so that the measurement value is stabilized. . Further, since the slit 6 is provided in the vicinity of the reference electrode 3, the reference electrode 3 can positively come into contact with the measured liquid 13, and the reference electrode 3 has substantially the same potential as the measured liquid 13. Further, even if a disturbance as indicated by an arrow A ₂ enters from the outside through the slit 6, it is exclusively entered into the reference electrode 3, so that the disturbance A ₂ has a bad influence on the measured value. Absent.

  In this example, since the slit 6 is formed in almost the entire side surface from the base end portion 4a to the free end portion 4b of the guard 4, the measured liquid 13 can easily enter the guard 4 and easily. However, the present invention is not limited to this point. That is, when the communication hole 5 is formed in the free end portion 4 b of the guard 4, the slit 6 may be partially formed in the base end portion 4 a of the guard 4. The slit 6 is desirably formed at least in the base end portion 4a of the guard 4, so that when the electrodes 2 and 3 are immersed in the liquid 13 to be measured, the air in the guard 4 can be surely vented.

  FIG. 2 is a diagram showing the configuration of the second embodiment of the present invention. In FIG. 2, the portions denoted by the same reference numerals as those in FIG. 1 are the same or equivalent portions, and thus detailed description thereof is omitted.

In FIG. 2, 7 is a communication hole formed by a through hole opened in the vicinity of the reference electrode 3 in the base end portion 4 a of the guard 4, and 8 is a fluororesin formed on the base end portion side of the measurement electrode 2. An insulating cover made of Further, as shown in FIG. 2 (B), the communication hole 7 is formed in the vicinity of the reference electrode 3 and the farthest from the position of the measurement electrode 2 by being provided at the position of the intersection C _1. . That is, the communication hole 7 is formed at a position as far as possible from the measurement electrode 2.

  The communication hole 7 is preferably formed so as to communicate with the base end of the accommodation space of the electrodes 2 and 3 formed by the guard 4. That is, by forming the communication hole 7 at this position, the electrode 2 in which the liquid 13 to be measured that has entered from the communication hole 5 when the electrodes 2 and 3 are immersed in the liquid 13 to be measured is formed by the guard 4. The entire three accommodation spaces are easily filled.

The insulating cover 8 is for preventing, for example, a portion of about 10 mm from the base end portion of the measuring electrode 2 from coming into contact with the liquid 13 to be measured. The position can be as far away as possible. In this example, since the insulating cover 8 is provided at the base end portion of the measurement electrode 2, the position in the length direction of the communication hole 7 is formed at the base end of the guard 4 shown in FIG. For example, the position in the circumferential direction (see FIG. 2B) is not limited to the position of the intersection C ₁ .

That is, the communication hole 7 includes a plurality of locations (for example, intersections C ₃ and C ₄ between the straight line L ′ orthogonal to the straight line L and the guard 4 at equal intervals in the circumferential direction in a portion located at the base end of the guard 4, for example. Even if four positions are formed at each of the positions C _{1 to} C ₄ , the portions close to the communication holes 7 are covered by the insulating cover 8, so that the measuring electrode 2 (the measuring electrode 2 not covered by the insulating cover 8). Can be positioned away from the communication hole 7. In this case, the width for providing the insulating cover 8 is preferably about 10 mm or more.

  FIG. 3 is a diagram showing the configuration of the third embodiment of the present invention. In FIG. 3, since the part which attached | subjected the same code | symbol as FIG. 1, 2 is the same or equivalent part, the detailed description is abbreviate | omitted.

  In FIG. 3, 4 ′ is a substantially cylindrical guard made of, for example, fluororesin, and a slit 6 ′ is formed on the side surface of the guard 4 ′ so as to be able to accommodate the measurement electrode 2 along the reference electrode 3. . Reference numeral 5 'denotes a communication hole formed in the free end 4b of the guard 4' along with the formation of the slit 6 '.

  By configuring as in this example, the strength of the guard 4 ′ can be sufficiently maintained, and the current flow B to the measured liquid 13 between the measurement electrode 2 and the reference electrode 3 in the guard 4 ′ is limited. However, since this can always be kept constant, the measured value is further stabilized.

  FIG. 4 is a diagram showing the configuration of the fourth embodiment of the present invention. In FIG. 4, since the part which attached | subjected the same code | symbol as FIGS. 1-3 is the same or equivalent part, the detailed description is abbreviate | omitted.

The guard 4 in FIG. 4 has a lid portion 4c that seals the free end portion 4b. Further, in the base end portion 4 a and the free end portion 4 b of the guard 4, a through hole is formed on the side surface in the vicinity of the reference electrode 3 (position of the intersection C ₁ ), and this is formed as a communication hole 9 a for the measured liquid 13. 9b. The communication holes 9a and 9b are preferably formed at least at the end portion on the base end portion 4a side and the end portion on the free end portion 4b side of the space blocked from the outside by the guard 4. That is, by forming the two communication holes 9 a and 9 b at least at both ends of the guard 4, the liquid 13 to be measured can be easily introduced into or replaced in the guard 4.

  Moreover, when the cover part 4c which seals this is formed in the free end part 4b of the guard 4 like this example, the length of the measurement electrode 2 can be made the same as the length of the reference electrode 3. Is possible. As a result, the electrical contact of the electrodes 2 and 3 with the liquid 13 to be measured entering the guard 4 can be improved.

  FIG. 5 is a diagram showing the configuration of the fifth embodiment of the present invention. In FIG. 5, since the part which attached | subjected the same code | symbol as FIGS. 1-4 is the same or equivalent part, the detailed description is abbreviate | omitted.

The reference electrode 3 in FIG. 5 forms a bent portion 3 a that is bent so as to face the communication hole 5 formed in the free end portion 4 b of the guard 4, and an electrical disturbance A that enters the guard 4 from the communication hole 5. ₁ and received by the bent portion 3a, and the measuring electrode 2 and configured to protect from disturbances a _1. That is, the communication hole 5 is disposed in the vicinity of the reference electrode 3 and as far as possible from the measurement electrode 2 by forming the bent portion 3a.

  FIG. 6 is a diagram showing the configuration of the sixth embodiment of the present invention. In FIG. 6, since the part which attached | subjected the same code | symbol as FIGS. 1-5 is the same or equivalent part, the detailed description is abbreviate | omitted.

The reference electrode 3 in this example is constituted by two rod-like electrodes 3A and 3B arranged on both sides of the measurement electrode 2. Since the two rod-like electrodes 3A and 3B are electrically connected, they can be referred to as one reference electrode 3. Therefore, in the following description, it may be referred to as reference electrodes 3A and 3B. In addition, slits 6A and 6B (communication holes) are formed in the guard 4 along the reference electrodes 3A and 3B corresponding to the rod-shaped electrodes 3A and 3B, respectively. By configuring as in this example, the guard 4 has two intersections C ₁ and C ₂ of the straight line L connecting the reference electrodes 3A and 3B and the measurement electrode 2 and the guard 4 as shown in FIG. 6B. Since the slits 6A and 6B can be formed at opposing positions corresponding to both, there is an advantage that the liquid 13 to be measured in the guard 4 can be easily replaced.

  In this example, since the free end 4b of the guard 4 is opened to form the communication hole 5, the length of the measurement electrode 2 is formed to be about 10 mm shorter than the length of the reference electrode 3. When the free end 4b of the guard 4 is sealed as shown in FIG. 4, the length of the measurement electrode 2 can be the same as the length of the reference electrode 3.

  FIG. 7 is a diagram showing the configuration of the seventh embodiment of the present invention. In FIG. 7, since the part which attached | subjected the same code | symbol as FIG. 6 is the same or equivalent part, the detailed description is abbreviate | omitted. That is, the seventh embodiment shown in FIG. 7 is a modification of the sixth embodiment shown in FIG.

The reference electrodes 3 </ b> A and 3 </ b> B of this example are connected via a bent portion 3 b, and the overall shape of the reference electrode 2 is an inverted U shape, and is arranged so as to surround the measurement electrode 2. With this configuration, the electric disturbance A ₁ entering the guard 4 from the communication hole 5 is received by the bent portion 3b, and the measurement electrode 2 is protected from the disturbance A ₁ . . That is, the communication hole 5 is disposed in the vicinity of the reference electrode 3 and as far as possible from the measurement electrode 2 by forming the bent portion 3b.

It is a figure which shows 1st Example of the conductivity meter of this invention. It is a figure which shows the structure of 2nd Example. It is a figure which shows the structure of 3rd Example. It is a figure which shows the structure of 4th Example. It is a figure which shows the structure of 5th Example. It is a figure which shows the structure of 6th Example. It is a figure which shows the structure of 7th Example. It is a figure which shows the example of a conductivity meter. It is a figure which shows the example of the conventional balanced type electrode. It is a figure which shows the example of the conventional unbalanced type electrode.

Explanation of symbols

2 Measurement electrode 3, 3A, 3B Reference electrode 4, 4 'Guard 4a Base end 4b Free end 5, 5' Communication hole 6, 6 ', 6A, 6B Slit (communication hole)
7 Through hole (communication hole)
8 Insulation cover 9a, 9b Through hole (communication hole)
10 Conductivity meter 13 Liquid to be measured

Claims (5)

  In a conductivity meter that measures the resistance of a liquid to be measured between rod-shaped electrodes and measures the conductivity of the liquid to be measured, one electrode is used as a measurement electrode and the other electrode is used as a reference electrode. A conductivity meter provided with a guard made of an insulating material that is electrically shielded from the outside, and provided with a communicating hole for a liquid to be measured at a position near the reference electrode and away from the measurement electrode. .   The conductive structure according to claim 1, wherein the guard has a cylindrical shape, the communication hole is formed by opening the free end of the guard, and the length of the measurement electrode is shorter than that of the reference electrode. Rate meter.   The conductivity meter according to claim 1, wherein the communication hole is provided by forming a slit along a reference electrode on a side surface of the guard.   The conductivity meter according to any one of claims 1 to 3, wherein the communication hole is provided by forming a through hole in a side surface of a base end portion of the guard. The conductivity meter according to claim 4, wherein an insulating cover is provided on the base end side of the measurement electrode.

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