JP6372302B2 - Free residual chlorine measuring device - Google Patents

Description

  The present invention relates to an apparatus for measuring free residual chlorine. More specifically, the present invention relates to a free residual chlorine measuring apparatus that can appropriately cope with a measurement abnormality without imposing an excessive burden on a user.

  Chlorination is performed to disinfect various types of water such as clean water, sewage, industrial water, waste water, food washing water, and pool water. The chlorinating agent used in this chlorination must be put in a sufficient amount to disinfect the water to be disinfected, but if it is added too much, it will adversely affect the environment and harm the human body. It is not desirable to give. Therefore, measurement of the residual chlorine concentration of water charged with a chlorinating agent is performed.

Residual chlorine includes hypochlorous acid (free residual chlorine) produced by the dissolution of the chlorine agent in water, and chloroamine (bonded chlorine) generated by combining it with ammoniacal nitrogen. Free residual chlorine concentration and combined chlorine The total concentration of residual chlorine is the sum of the concentrations.
As a manual analysis method for measuring the residual chlorine concentration, an o-tolidine colorimetric method (OT method), a diethyl-p-phenylenediamine colorimetric method (DPD method), an iodine titration method, or the like is used.
However, since the manual analysis method is complicated and measurement data can be obtained only intermittently, a residual chlorine measuring device has been conventionally used. This residual chlorine measuring device is classified into a so-called reagent type residual chlorine measuring device and a reagentless type residual chlorine measuring device.

Among these, the reagentless residual chlorine measuring device does not replace residual chlorine with iodine, but electrolyzes the residual chlorine itself in the sample solution as it is, and this causes a redox current flowing between the detection electrode and the counter electrode. Is used to measure the residual chlorine concentration.
In the reagentless type residual chlorine measuring device, free residual chlorine and bound chlorine are detected, although there is a difference in sensitivity. However, in drinking water etc., most of the residual chlorine is free residual chlorine. It is used as a measuring device.

  However, even in the case of clean water or the like, if a large amount of ammonia nitrogen is present in the raw water to be chlorinated, the combined chlorine concentration after chlorination may increase. In that case, since the reagentless residual chlorine measuring device (free residual chlorine measuring device) that has sensitivity to both free residual chlorine and combined chlorine will show a measured value higher than the actual free residual chlorine concentration, Despite the insufficient free residual chlorine concentration, there is a risk of misunderstanding that it is sufficient. As a result, there is a risk that water with insufficient free residual chlorine is supplied as clean water or the like without being aware that the free residual chlorine has become insufficient.

In order to avoid such a risk, in Patent Document 1, the presence or absence of bound chlorine is determined based on whether or not the current gradient in the plateau region (the region where the current hardly changes even when the applied voltage is slightly shifted) is increased. Technology has been proposed.
In Patent Document 1, a large current gradient in the plateau region means that bound chlorine is present. In that case, by increasing the amount of chlorinating agent, water with sufficient free residual chlorine concentration can be supplied. .

JP 02-154142 A

The technique of Patent Document 1 is premised on the presence of bound chlorine if the current gradient in the plateau region is large. However, the factor that impairs the good plateau region is not limited to the combined chlorine, and the current gradient in the plateau region may increase due to an abnormality in the electrode.
In that case, if the amount of chlorine agent injected is controlled according to the description in Patent Document 1, an excessive amount of chlorine agent will be injected even though the free residual chlorine concentration is sufficient water.
Therefore, it has been difficult to appropriately control the injection amount of the chlorine agent using the technique of Patent Document 1.
The present invention has been made in view of the above points, and provides a free residual chlorine measuring apparatus capable of taking appropriate measures against measurement abnormality based on combined chlorine and electrode abnormality without imposing an excessive burden on the user. This is the issue.

In order to achieve the above object, the present invention employs the following configuration.
[1] a detection electrode and a counter electrode immersed in the sample liquid;
A motor for rotating or vibrating the detection pole;
A polishing member capable of contacting the detection electrode;
An applied voltage mechanism for applying an applied voltage between the detection electrode and the counter electrode;
An ammeter for measuring an oxidation-reduction current flowing between the detection electrode and the counter electrode;
In the measurement mode, while the detection pole is rotated or vibrated by the motor, the redox current is measured with the applied voltage as a constant voltage in the plateau region, and the free residual chlorine concentration of the sample liquid is measured based on the obtained redox current. Seeking
In the diagnostic mode, the free residual chlorine measuring device is configured to perform the following steps.
Step 1: the rotational speed of the motor while the N _1, the applied voltage is changed in the plateau region, the absolute value of the change amount of the redox current with respect to the absolute value of the amount of change of the applied voltage ([Delta] V) ( A ratio R (= ΔI / ΔV) of ΔI) is obtained.
Step 2: When the ratio R is within a predetermined range K _{1 to} K ₂ (where K ₁ <K ₂ ), the diagnosis mode is terminated, and the ratio R is within a predetermined range K _{1 to} K ₂ . When outside, go to step 3.
Step 3: The rotational speed of the motor is changed to N ₂ (where N ₁ <N ₂ ), and the detection electrode is polished for a predetermined time.
Step 4: The rotation speed of the motor in the state returning to N _1, the applied voltage is changed in the plateau region, the absolute amount of change of the redox current with respect to the absolute value of the amount of change of the applied voltage ([Delta] V ') A ratio R ′ (= ΔI ′ / ΔV ′) of values (ΔI ′) is obtained.
Step 5: When the ratio R ′ is within the predetermined range K ₁ ′ to K ₂ ′ (where K ₁ ′ <K ₂ ′), the diagnosis mode is terminated, and the ratio R ′ is within the predetermined range K When it is outside the range of ₁ ′ to K ₂ ′, the process proceeds to Step 6.
Step 6: Generate abnormality information and end the diagnosis mode.

[2] The free residual chlorine measuring apparatus according to [1], wherein the predetermined range K _{1 to} K ₂ is determined to include the following R _b .
R _b = ΔI _b / ΔV _b
However, ΔI _b / ΔV _b is the applied voltage obtained by changing the applied voltage in the plateau region with the span solution used for span calibration as the sample solution and the rotation speed of the motor being N ₁ . It is the ratio of the absolute value (ΔI _b ) of the change amount of the oxidation-reduction current to the absolute value (ΔV _b ) of the change amount.
[3] The free residual chlorine measuring device according to [1] or [2], wherein the predetermined range K ₁ ′ to K ₂ ′ is defined to include the following R _b .
R _b = ΔI _b / ΔV _b
However, ΔI _b / ΔV _b is the applied voltage obtained by changing the applied voltage in the plateau region with the span solution used for span calibration as the sample solution and the rotation speed of the motor being N ₁ . It is the ratio of the absolute value (ΔI _b ) of the change amount of the oxidation-reduction current to the absolute value (ΔV _b ) of the change amount.
[4] The rotational speed of the motor is N ₁ in the measurement mode [1] to free residual chlorine measuring device according to any one of [3].
[5] The free residual chlorine measuring device according to any one of [1] to [4], wherein the polishing member is a granular abrasive disposed in an unfixed state in the vicinity of the detection electrode.
[6] Furthermore, a flow cell through which the sample liquid flows and liquid feeding means for flowing the sample liquid in the flow cell are provided, and the detection electrode and the non-fixed granular abrasive are stored in the flow cell. 5] The apparatus for measuring free residual chlorine according to [5].
[7] The relationship between the flow rate F ₁ of the sample liquid in the flow cell in Step 1 and Step 4 and the flow rate F ₂ of the sample liquid in the flow cell in Step 3 is F ₁ ≦ F ₂ [6] The free residual chlorine measuring apparatus described in 1.
[8] free residual chlorine measuring device according to the flow rate of the sample liquid in the flow cell is F ₁ in the measurement mode [7].
[9] The free residual chlorine measuring device according to any one of [1] to [8], wherein the diagnostic mode is started when the free residual chlorine concentration obtained in the measurement mode is out of a predetermined range. .
[10] The free residual chlorine measuring apparatus according to any one of [1] to [9], wherein the diagnostic mode is started at every predetermined time interval.

  According to the free residual chlorine measuring apparatus of the present invention, it is possible to appropriately cope with measurement abnormality based on combined chlorine or electrode abnormality without imposing an excessive burden on the user.

1 is an overall configuration diagram of a free residual chlorine measuring device according to a first embodiment of the present invention. It is a flowchart of the diagnostic mode which the free residual chlorine measuring apparatus which concerns on 1st Embodiment performs. It is sectional drawing of the sensor part in the free residual chlorine measuring apparatus which concerns on 2nd Embodiment of this invention. It is a whole block diagram of the free residual chlorine measuring apparatus which concerns on 3rd Embodiment of this invention. It is a flowchart of the diagnostic mode which the free residual chlorine measuring apparatus which concerns on 3rd Embodiment performs. It is sectional drawing of the sensor part in the free residual chlorine measuring apparatus which concerns on 4th Embodiment of this invention. It is a polarogram of samples 1-3. It is a polarogram of samples 4-6. It is a polarogram of samples 7-9. It is a polarogram of samples 10 and 11. It is a polarogram of samples 12 and 13.

<First Embodiment>
[Device configuration]
A free residual chlorine measuring apparatus according to a first embodiment of the present invention will be described with reference to FIG. The free residual chlorine measuring apparatus according to the present embodiment is generally composed of a sensor unit 1 and a main body unit 20.

  The sensor unit 1 includes a measurement cell 11 into which the sample solution S is introduced, a detection electrode support 12 in which the lower part is immersed in the sample solution S, a detection electrode 13 attached to the distal end surface of the detection electrode support 12, and a lower part in the sample. The counter electrode support 14 immersed in the liquid S, the counter electrode 15 attached to the outer peripheral surface on the lower end side of the counter electrode support 14, the motor 16 for vibrating the detection electrode 13 in a circular motion, and the detection electrode support 12 are held. A bearing 17 and a large number of beads 18 for cleaning the detection electrode 13 put in the sample solution S are provided. The measurement cell 11 is provided with a mesh-like partition plate 11a that partitions the detection electrode 13 and the counter electrode 15 so that the beads 18 do not flow out to the counter electrode 15 side.

  The main body 20 includes an arithmetic control unit 21, an applied voltage mechanism 22, an ammeter 23, and a display device 24. The detection electrode 13 and the calculation control unit 21 are connected by a wiring L1, the counter electrode 15 and the calculation control unit 21 are connected by a wiring L2, and the motor 16 and the calculation control unit 21 are connected by a wiring L3. . The ammeter 23 is provided in the middle of the wiring L1, and the applied voltage mechanism 22 is provided in the middle of the wiring L2.

Since it is easy to obtain a good plateau region, the detection electrode 13 is preferably gold, a gold alloy, or platinum. The counter electrode 15 is preferably a silver / silver chloride electrode.
The detection pole support 12 is arranged in an inclined state, and a predetermined portion in the middle in the length direction is held by the bearing 17 so that the precession can be performed with the holding portion by the bearing 17 as a fulcrum. Further, the base end portion 12a of the detection pole support 12 and the rotating shaft 16a of the motor 16 are eccentrically engaged. Therefore, rotating the rotating shaft 16a of the motor 16 causes the base end portion 12a to make a circular motion, and the detection pole 13 attached to the distal end portion of the detection pole support 12 also vibrates (circulates). . Further, the wiring L1 can be pulled out without being twisted even if the detection electrode 13 is circularly moved from the vicinity of the holding position by the bearing 17 through the detection electrode support 12.

The beads 18 are granular abrasives in the present invention, and a large number of beads 18 are arranged in the vicinity of the detection electrode 13 in an unfixed state. The beads 18 come into contact with the detection electrode 13 that vibrates (circulates), and the detection electrode 13 is polished. The material of the beads 18 is preferably ceramic or glass.
As the motor 16, a motor that can be operated at an arbitrarily set number of revolutions is used. The motor 16 can be switched between N ₁ and N ₂ (where N ₁ <N ₂ ) according to an instruction from the arithmetic control unit 21. Rotational speed N ₁ and N ₂ can be arbitrarily set in consideration of washing efficiency and the like. The set values of the rotational speeds N ₁ and N ₂ may be changed at any time or may be fixed values.
By switching the number of rotations of the motor 16 to either N ₁ or N ₂ , the vibration speed of the detection electrode 13 changes, and the speed and number of times the bead 18 contacts the detection electrode 13 also changes. The polishing efficiency of the pole 13 also changes.

[Plateau area]
In the polarogram, the region where the current hardly changes even when the applied voltage changes is the plateau region.
In the following description, an applied voltage with a stable and small change in current in the plateau region is V ₀ , and other applied voltages in the plateau region are V ₁ and V ₂ (where V ₁ > V ₀ > V ₂ ). And

In order to operate the free residual chlorine measuring apparatus of the present embodiment, it is assumed that the plateau region has been confirmed. If the material of the detection electrode and the counter electrode and the concentration of free residual chlorine in the sample solution are determined, an almost equivalent polarogram can be obtained under normal operating conditions. For this reason, in a measuring apparatus in which the material of the detection electrode and the counter electrode and the measurement range are specified, the plateau region is normally confirmed not at each individual measuring apparatus but at the design stage of the apparatus of the specification.
To determine new plateau region, free residual include chlorine bound chlorine dipping the sensing electrode 13 and counter electrode 15 in a sample solution S containing little, in a state where the rotational speed of the motor 16 and the N _1, the applied voltage It is only necessary to measure the oxidation-reduction current while sweeping and to create a polarogram. As the sample solution S at this time, it is preferable to use a sample solution containing free residual chlorine close to the upper limit of the measurement range. In order to create a polarogram, the oxidation-reduction current may be measured continuously while sweeping the applied voltage, or may be measured each time the applied voltage changes by a certain value (for example, 50 mV or 100 mV). .

[Calibration mode]
The free residual chlorine measuring apparatus of this embodiment performs zero calibration and span calibration in the calibration mode. Ordinarily, only zero calibration may be performed simply and both zero calibration and span calibration may be performed as necessary. The calibration mode may be appropriately performed in consideration of necessary management accuracy.
In the zero calibration, a zero solution having a total residual chlorine concentration of almost zero is used as a sample solution S, the detection electrode 13 and the counter electrode 15 are immersed in the sample solution S, the number of rotations of the motor 16 is N ₁ , and the applied voltage is V _0. The oxidation-reduction current _Iz is obtained. In the span calibration, the span solution selected in consideration of the measurement range or the like is used as the sample solution S, the detection electrode 13 and the counter electrode 15 are immersed in the sample solution S, the rotational speed of the motor 16 is N ₁ , and the applied voltage is V _0. As shown, the redox current _Is is obtained.

The zero solution can be obtained, for example, by filtering the sample solution or tap water with a filter capable of removing chlorine.
As the span liquid, it is preferable to use clean water or the like to be measured whose free residual chlorine concentration and combined chlorine concentration are appropriately controlled. Moreover, you may use what diluted the hypochlorous acid solution with the zero solution.
Free residual chlorine concentration f _s of free residual chlorine concentration f _z and span solution zero liquid can be confirmed by, for example, the DPD method. The free residual chlorine concentration f _z of zero liquid, without confirming with the DPD method or the like, may be regarded as zero.

If the free residual chlorine concentration f _z of zero liquid regarded as zero without confirming by the DPD method or the like, zero calibration may be automatically performed. In this case, zero calibration can be started by a timer built in the main body 20 or an external start signal.
Span calibration that requires confirmation of the free residual chlorine concentration f _s of the span solution by the DPD method or the like is performed manually. For even zero calibration, to check the free residual chlorine concentration f _z of zero liquid in the DPD method or the like is carried out manually.

Free residual chlorine concentration f _z redox current I _z of zero _calibration, by two points of free residual chlorine concentration f _s redox current I _s of the span calibration is determined, it is possible to obtain a calibration curve.
The arithmetic control unit 21 of the main body unit 20 stores two points of zero calibration and span calibration. Alternatively, a calibration curve is obtained from these two points, and the obtained calibration curve is stored.

[ _Rb calculation mode]
Values _{K 1} and _{K 2} demarcating a predetermined range _K 1 ~K ₂ in the diagnosis mode will be described later, a predetermined range _K 1 ~K ₂ is preferably defined to include the following _{R b.} Similarly, the value _{K 1} 'and _{K 2'} demarcating a predetermined range _{K 1} '~K _2' is predetermined range _{K 1} '~K _2' is preferably defined to include the following _{R b} .
R _b = ΔI _b / ΔV _b
However, ΔI _b / ΔV _b is the applied voltage obtained by changing the applied voltage within the plateau region with the span solution used for span calibration as the sample solution and the rotation speed of the motor being N ₁ . It is the ratio of the absolute value (ΔI _b ) of the change amount of the oxidation-reduction current to the absolute value (ΔV _b ) of the change amount.
As the span liquid for obtaining R _b , it is preferable to use clean water or the like to be measured whose free residual chlorine concentration and combined chlorine concentration are appropriately controlled. Moreover, you may use what diluted the hypochlorous acid solution with the zero solution.

R _b is, specifically, the R _b calculation mode, the span solution as the sample solution S, can be obtained as follows.
The detection electrode 13 and the counter electrode 15 are immersed in the span solution, and the applied voltage is swept from V _b1 to V _b2 while the state where the rotation number of the motor 16 is set to N ₁ to measure the oxidation-reduction current. However, the voltages V _b1 and V _b2 are applied voltages in the plateau region. V _b1 is preferably V ₁ , and V _b2 is preferably V ₂ .
The oxidation-reduction current may be measured continuously while sweeping the applied voltage, or may be measured every time the applied voltage changes by a certain value (for example, 50 mV or 100 mV). Alternatively, the measurement may be performed at two points when the applied voltage is V _b1 and V _b2 .

Then, the ratio of the absolute value (ΔI _b ) of the change amount of the oxidation-reduction current to the absolute value (ΔV _b ) of the change amount of the applied voltage is obtained, and this ratio is defined as R _b . An equation for obtaining R _b from two points of the oxidation-reduction current I _b1 when the applied voltage is V _b1 and the oxidation-reduction current I _b2 when it is V _b2 is as follows.
R _b = ΔI _b / ΔV _b = | I _b2 −I _b1 | / | V _b2 −V _b1 |
When measuring the oxidation-reduction current at three or more applied voltages, or when measuring the oxidation-reduction current continuously while sweeping the applied voltage from V _b1 to V _b2 , a linear function obtained by the least square method or the like The absolute value of the slope of R is _Rb .
The R _b calculation mode for obtaining R _b may be appropriately performed in consideration of necessary management accuracy and the like. For example, it can be performed after the span calibration.

The predetermined ranges K _{1 to} K ₂ are determined so as to include the obtained R _b . Specifically, it can be obtained by the following equation.
K ₁ = R _b −α
K ₂ = R _b + β
Here, α and β are values appropriately set in consideration of necessary management accuracy and the like. α and β are preferably equal, but may be different.

The predetermined range K ₁ ′ to K ₂ ′ is determined so as to include the obtained R _b . Specifically, it can be obtained by the following equation.
K ₁ '= R _b -α'
K ₂ '= R _b + β'
Here, α ′ and β ′ are values appropriately set in consideration of necessary management accuracy and the like. α ′ and β ′ are preferably equal but may be different. Further, α and α ′ are preferably equal but may be different. Similarly, β and β ′ are preferably equal but may be different.

[Measurement mode]
In the free residual chlorine measuring apparatus of this embodiment, the detection electrode 13 and the counter electrode 15 are immersed in the sample liquid S such as clean water to be measured during the measurement mode, the rotation number of the motor 16 is N ₁ , and the applied voltage is The oxidation-reduction current I _x is obtained as V ₀ (a constant voltage in the plateau region). The calculation control unit 21 of the main body 20 calculates the free residual chlorine concentration f _x corresponding to the oxidation-reduction current I _x based on the calibration curve specified by the two points stored in the calibration mode or the calibration curve stored in the calibration mode. Ask.

The value of the resulting free residual chlorine concentration f _x is given to the display device 24 as a signal D1, free residual chlorine concentration f _x is displayed on the display device 24. The value of free residual chlorine concentration f _x as a signal D2, an external recorder, transmitted data logger, memory, printers, to a computer or the like. The signal D2 may be a digital signal or an analog signal. Further, it may be transmitted by wire or wirelessly.

[Diagnostic mode]
In the diagnostic mode, the free residual chlorine measuring apparatus of the present embodiment performs the following steps.
Step 1: the rotational speed of the motor while the N _1, the applied voltage is changed in the plateau region, the absolute value of the change amount of the redox current with respect to the absolute value of the amount of change of the applied voltage ([Delta] V) ( A ratio R (= ΔI / ΔV) of ΔI) is obtained.
Step 2: When the ratio R is within a predetermined range K _{1 to} K ₂ (where K ₁ <K ₂ ), the diagnosis mode is terminated, and the ratio R is within a predetermined range K _{1 to} K ₂ . When outside, go to step 3.
Step 3: The rotational speed of the motor is changed to N ₂ (where N ₁ <N ₂ ), and the detection electrode is polished for a predetermined time.
Step 4: The rotation speed of the motor in the state returning to N _1, the applied voltage is changed in the plateau region, the absolute amount of change of the redox current with respect to the absolute value of the amount of change of the applied voltage ([Delta] V ') A ratio R ′ (= ΔI ′ / ΔV ′) of values (ΔI ′) is obtained.
Step 5: When the ratio R ′ is within the predetermined range K ₁ ′ to K ₂ ′ (where K ₁ ′ <K ₂ ′), the diagnosis mode is terminated, and the ratio R ′ is within the predetermined range K When it is outside the range of ₁ ′ to K ₂ ′, the process proceeds to Step 6.
Step 6: Generate abnormality information and end the diagnosis mode.

Hereinafter, each step will be described in detail with reference to FIG.
The diagnosis mode is started by interrupting the measurement mode at predetermined time intervals by a timer or an external start signal built in the main body unit 20. Also, free residual chlorine concentration f _x obtained in the measurement mode, when became out of the range of a predetermined control value, and starts to interrupt measurement mode.

In step 1, the detection voltage 13 and the counter electrode 15 are immersed in the sample liquid S that has been measured in the measurement mode, and the applied voltage is changed from V ₁ to V while maintaining the rotation number of the motor 16 at N _{1. The} redox current is measured by sweeping to ₂ (step A1-1).
The oxidation-reduction current may be measured continuously while sweeping the applied voltage, or may be measured every time the applied voltage changes by a certain value (for example, 50 mV or 100 mV). Further, the measurement may be performed at two points when the applied voltage is V ₁ and when it is V ₂ .

Next, the ratio R (= ΔI / ΔV) of the absolute value (ΔI) of the change amount of the oxidation-reduction current to the absolute value (ΔV) of the change amount of the applied voltage is obtained (step A1-2). An equation for obtaining the ratio R from two points of the oxidation-reduction current I ₁ when the applied voltage is V ₁ and the oxidation-reduction current I ₂ when V ₂ is as follows.
R = ΔI / ΔV = | I ₂ −I ₁ | / | V ₂ −V ₁ |
When measuring the redox current at three or more applied voltages, or when measuring the redox current continuously while sweeping the applied voltage from V ₁ to V ₂ , a linear function obtained by the least square method or the like The absolute value of the slope of is the ratio R.

In step 2, the ratio R is compared with a predetermined range K _{1 to} K ₂ (where K ₁ <K ₂ ) (step A2). As a result, when the ratio R is within the predetermined range K _{1 to} K ₂ , the diagnosis mode is terminated. On the other hand, when the ratio R is outside the predetermined range K _{1 to} K ₂ , the process proceeds to Step 3 (Step A3-1).
In FIG. 2, the case where K ₁ ≦ R ≦ K ₂ is satisfied is within the predetermined range K _{1 to} K ₂ , and the case where K ₁ ≦ R ≦ K ₂ is not satisfied is the predetermined range K _{1 to} K _2. It was out of the range _of, K 1 <R _<K where satisfying ₂ a within a predetermined range _K 1 ~K _2, K 1 <R <a predetermined range _K 1 a is not satisfied _{K 2} ~K _It may be outside the range of ₂ .

In step 3, the rotation speed of the motor 16 is changed from N ₁ to N ₂ (where N ₁ <N ₂ ) (step A3-1). The detection electrode 13 and the counter electrode 15 remain immersed in the sample liquid S that has been measured in the measurement mode. The value of the applied voltage in step A3-1 is arbitrary, and the applied voltage may not be applied. By increasing the rotation speed of the motor 16, the polishing efficiency of the detection electrode 13 by the beads 18 is increased.
Step A3-1 continues until a predetermined time elapses (step A3-2), and then proceeds to step 4. The predetermined time is set to such a time that the surface of the detection electrode 13 can be sufficiently polished.

In step 4, it returns the number of revolutions of the motor 16 from _{N 2} to _{N 1.} The detection electrode 13 and the counter electrode 15 remain immersed in the sample liquid S that has been measured in the measurement mode. Then, the applied voltage is swept from V ₁ ′ to V ₂ ′ to measure the oxidation-reduction current (step A4-1). The applied voltages V ₁ ′ and V ₂ ′ are preferably equal to the applied voltages V ₁ and V ₂ in step 1, respectively.

The oxidation-reduction current may be measured continuously while sweeping the applied voltage, or may be measured every time the applied voltage changes by a certain value (for example, 50 mV or 100 mV). Further, the measurement may be performed at two points when the applied voltage is V ₁ ′ and when it is V ₂ ′. The timing for measuring the redox current is preferably the same as the timing for measuring the redox current in Step 1.

Next, the ratio R ′ (= ΔI ′ / ΔV ′) of the absolute value (ΔI ′) of the change amount of the oxidation-reduction current to the absolute value (ΔV ′) of the change amount of the applied voltage is obtained (step A4-2). And _'redox currents I ₁ when _a' applied voltage V _1, wherein when determining the ratio R 'from two points _of' redox current I ₂ when a _'V 2 are as follows .
R ′ = ΔI ′ / ΔV ′ = | I ₂ ′ −I ₁ ′ | / | V ₂ ′ −V ₁ ′ |
When measuring the oxidation-reduction current at three or more applied voltages, or when continuously measuring the oxidation-reduction current while sweeping the applied voltage from V ₁ ′ to V ₂ ′, it was obtained by the method of least squares or the like. The absolute value of the slope of the linear function is the ratio R ′.

In step 5, the ratio R ′ is compared with a predetermined range K ₁ ′ to K ₂ ′ (where K ₁ ′ <K ₂ ′) (step A5). As a result, when the ratio R ′ is within the predetermined range K ₁ ′ to K ₂ ′, the diagnosis mode is terminated. On the other hand, when the ratio R ′ is out of the predetermined range K ₁ ′ to K ₂ ′, the process proceeds to Step 6 (Step A6).
In FIG. 2, the case where K ₁ ′ ≦ R ′ ≦ K ₂ ′ is satisfied is set within the predetermined range K ₁ ′ to K ₂ ′, and the case where K ₁ ′ ≦ R ′ ≦ K ₂ ′ is not satisfied. The predetermined range K ₁ ′ to K ₂ ′ is outside the range, but the case where K ₁ ′ <R ′ <K ₂ ′ is satisfied is set within the predetermined range K ₁ ′ to K ₂ ′, and K ₁ ′ < The case where R ′ <K ₂ ′ is not satisfied may be outside the predetermined range K ₁ ′ to K ₂ ′.

In step 6, abnormality information is generated (step A6).
The generated abnormality information is given to the display device 24 as a signal D1, and the display device 24 displays that it is in an abnormal state. Also, the abnormality information is transmitted as a signal D2 to an external recorder, data logger, memory, printer, speaker, computer, etc., and the user is notified of the abnormal state by display, recording, printing, voice, etc. .
After step 6, the diagnostic mode is terminated.

During the diagnostic mode may not seek a free residual chlorine concentration f _x of the sample solution S. Therefore, it is impossible to transmit the free residual chlorine concentration f _x display device 24 or an external printer, a computer or the like.
During the diagnosis mode, a message indicating that the diagnosis mode is being used may be displayed on the display device 24. In addition, this fact may be transmitted to an external printer, computer or the like. It can also be displayed on the display device 24 a hold value or the like of the free residual chlorine concentration f _x in the diagnosis mode start just before the dummy information may or transmitted outside of the printer, to a computer or the like.

  After ending the diagnostic mode, the measurement mode is returned to the principle. Moreover, you may start the calibration mode as needed. In addition, when the diagnosis mode is terminated after the process up to Step 6, the measurement mode may be set to a pause mode in which neither measurement nor calibration is performed.

Second Embodiment
[Device configuration]
The free residual chlorine measuring apparatus according to the second embodiment of the present invention is the same as that of the first embodiment except that the sensor unit 1 in FIG. 1 is changed to the sensor unit 2 shown in FIG.

  FIG. 3 is a cross-sectional view of the sensor unit 2. The sensor unit 2 shown in FIG. 3 is provided with a substantially cylindrical case 31, and a support base 32 having a through hole 32 a extending in the axial direction at the center at one opening of the case 31. Is fixed. A pair of upper and lower circular windows 32b and 32b are formed at a substantially central portion in the axial direction of the support base 32 so as to penetrate from one circumferential surface to the opposing circumferential surface. . A recess 32c is formed in the circumferential direction near the tip, and the counter electrode 33 is wound over the entire surface of the recess 32c.

  A cap 34 made of a mesh is screwed below the counter electrode 33 so as to cover the tip of the support base 32. In addition, a large number of beads 36 for polishing and cleaning a detection electrode 35 described later are accommodated in the cap 34. And the inner net | network 37 is provided in the position which covers the window 32b from the inner side, and the outflow of the bead 36 is prevented.

A motor 38 is attached inside the case 31, and is fixed to the rotating shaft 38 a of the motor 38 above the eccentric coupling 41. The eccentric coupling 41 is held by a coupling case 42, and the coupling case 42 is held above the support base 32 by a plurality of support columns 43.
A substantially rod-shaped connecting shaft 44 is connected to the lower side of the eccentric coupling 41. The angle formed by the rotating shaft 38a and the connecting shaft 44 is set to about 3 degrees, and the portion connected to the coupling case 42 of the connecting shaft 44 performs a circular motion by driving the motor 38.

  A portion slightly below the center in the axial direction of the connecting shaft 44 is inserted into the bearing 45. The bearing 45 includes a cylindrical tube portion 45a in the direction of the connecting shaft 44 and a flange portion 45b that spreads in the radial direction around the lower end side of the tube portion 45a, and is formed of a rubber material. The tube portion 45a is in close contact with the connecting shaft 44 in a watertight state with high pressure. The outer peripheral surface of the bearing 45 is in watertight contact with the inner peripheral surface of the support base 32.

The lower end side of the coupling shaft 44 with respect to the bearing 45 is inserted into the upper end side of a substantially cylindrical detection electrode support 46. As a result, the detection electrode support 46 is connected and fixed to the lower end side of the connection shaft 44, and is suspended in the through hole 32 a of the support base 32. A detection electrode 35 is provided at the lower end of the detection electrode support 46.
When the portion of the connecting shaft 44 connected to the coupling case 42 is circularly driven by the drive of the motor 38, the connecting shaft 44 performs precession with the portion where the flange portion 45b is located as a fulcrum. As a result, the detection pole 35 provided at the lower end of the detection pole support 46 fixed to the connecting shaft 44 also moves circularly.

The lead wire 47 of the detection electrode 35 is finally connected to the calculation control unit 21 of the main body unit 20 via the connector 48. Further, the counter electrode 33 is connected to the calculation control unit 21 of the main body unit 20 via the connector 48. The motor 38 is also connected to the arithmetic control unit 21 of the main body unit 20 via the connector 48.
In FIG. 3, the wiring of the lead wire 47 near the connector 48 is not shown. Also, the wiring from the counter electrode 33 to the connector 48 and the wiring from the motor 38 to the connector 48 are not shown.

As the detection electrode 35, the same one as the detection electrode 13 of the first embodiment can be used. The counter electrode 33 can be the same as the counter electrode 15 of the first embodiment.
As with the motor 16 of the first embodiment, the motor 38 can switch the number of rotations to either N ₁ or N ₂ (where N ₁ <N ₂ ) according to an instruction from the arithmetic control unit 21. ing.

When the lower end of the sensor unit 2 of the present embodiment is immersed in the sample solution S, the sample solution S flows in and out through the cap 34 and the window 32b. As a result, the sample liquid S comes into contact with the detection electrode 35 and also comes into contact with the counter electrode 33 wound around the support base 32. That is, the detection electrode 35 and the counter electrode 33 are immersed in the sample liquid S.
The sample liquid S is prevented from entering the case 31 above the bearing 45 by the bearing 45.

The free residual chlorine measuring apparatus according to the second embodiment operates in the same manner as the free residual chlorine measuring apparatus according to the first embodiment in each of the calibration mode, _Rb calculation mode, measurement mode, and diagnostic mode. Further, it is necessary that the plateau region is confirmed, and the confirmation method is the same as that of the free residual chlorine measuring apparatus according to the first embodiment.

<Third Embodiment>
[Device configuration]
A free residual chlorine measuring apparatus according to a third embodiment of the present invention will be described with reference to FIG. In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and detailed description thereof is omitted.
The free residual chlorine measuring apparatus according to the present embodiment is generally composed of a sensor unit 3, a main body unit 20, and a liquid feeding unit 50.

The sensor unit 3 is the same as the sensor unit 1 of the first embodiment except that the measurement cell 11 of the first embodiment is changed to the flow cell 19. The flow cell 19 is provided with a mesh-like partition plate 19a that partitions the detection electrode 13 and the counter electrode 15 so that the beads 18 do not flow out to the counter electrode 15 side.
The liquid feeding unit 50 includes an inflow path 51 for sending the sample liquid S to the flow cell 19, a discharge path 52 for discharging the sample liquid S from the flow cell 19, and a pump 53 provided in the inflow path 51. The liquid means is constituted.

The pump 53 and the calculation control unit 21 are connected by a wiring L4. The pump 53 is configured to switch the flow rate of the sample liquid S in the flow cell 19 to either F ₁ or F ₂ (where F ₁ <F ₂ ) according to an instruction from the arithmetic control unit 21. By changing the flow rate of the sample solution S in the flow cell 19, the momentum of the beads 18 that collide with the detection electrode 13 changes, and the polishing efficiency of the detection electrode 13 also changes.
As in the first and second embodiments, the polishing efficiency of the detection electrode 13 by the beads 18 also changes by changing the rotational speed of the motor 16.

[Plateau area]
Similar to the description of the first embodiment, in the following description, an applied voltage with a stable and small change in current in the plateau region is V ₀ , and other applied voltages in the plateau region are V ₁ , V ₂ (however, V ₁ > V ₀ > V ₂ ).

When operating the free residual chlorine measuring apparatus of this embodiment, it is assumed that the plateau region is confirmed. If the material of the detection electrode and the counter electrode and the concentration of free residual chlorine in the sample solution are determined, an almost equivalent polarogram can be obtained under normal operating conditions. For this reason, in a measuring apparatus in which the material of the detection electrode and the counter electrode and the measurement range are specified, the plateau region is normally confirmed not at each individual measuring apparatus but at the design stage of the apparatus of the specification.
In order to newly confirm the plateau region, the sample solution S containing free residual chlorine and containing almost no combined chlorine is circulated in the flow cell 19, the rotational speed of the motor 16 is N ₁ , and the flow rate of the sample solution S in the flow cell 19 is in a state in which the F _1, the oxidation-reduction current measured while sweeping the applied voltage, it may be creating a polarogram. As the sample solution S at this time, it is preferable to use a sample solution containing free residual chlorine close to the upper limit of the measurement range. In order to create a polarogram, the oxidation-reduction current may be measured continuously while sweeping the applied voltage, or may be measured each time the applied voltage changes by a certain value (for example, 50 mV or 100 mV). .

[Calibration mode]
The free residual chlorine measuring apparatus of this embodiment performs zero calibration and span calibration in the calibration mode. Ordinarily, only zero calibration may be performed simply and both zero calibration and span calibration may be performed as necessary. The calibration mode may be appropriately performed in consideration of necessary management accuracy.
In zero calibration, a zero solution having a total residual chlorine concentration of almost zero is used as a sample solution S, this sample solution S is circulated in the flow cell 19, the number of revolutions of the motor 16 is N ₁ , and the flow rate of the sample solution S in the flow cell 19. Is F ₁ , the applied voltage is V ₀ , and the oxidation-reduction current I _z is obtained. In the span calibration, the span solution selected in consideration of the measurement range or the like is used as the sample solution S, this sample solution S is circulated in the flow cell 19, the number of revolutions of the motor 16 is N ₁ , and the sample solution S in the flow cell 19 is measured. the flow rate _{F 1,} obtaining the redox current _{I s} the applied voltage _{V 0.}

The method or selecting process for the preparation of zero liquid and span solution, how to check the free residual chlorine concentration f _s of free residual chlorine concentration f _z and span solution zero solution is similar to the first embodiment. The calculation control unit 21 of the main body unit 20 stores two points of zero calibration and span calibration, or obtains a calibration curve from these two points and stores the obtained calibration curve as in the first embodiment. It is the same. The calibration mode can be started in the same manner as in the first embodiment.

[ _Rb calculation mode]
Values _{K 1} and _{K 2} demarcating a predetermined range _K 1 ~K ₂ in the diagnosis mode will be described later, a predetermined range _K 1 ~K ₂ is preferably defined to include the following _{R b.} Similarly, the value _{K 1} 'and _{K 2'} demarcating a predetermined range _{K 1} '~K _2' is predetermined range _{K 1} '~K _2' is preferably defined to include the following _{R b} .
R _b = ΔI _b / ΔV _b
However, ΔI _b / ΔV _b is the applied voltage in a state where the span solution used for span calibration is the sample solution, the rotational speed of the motor is N ₁ , and the flow rate of the sample solution S in the flow cell 19 is F _1. It is the ratio of the absolute value (ΔI _b ) of the change amount of the oxidation-reduction current to the absolute value (ΔV _b ) of the change amount of the applied voltage, which is obtained by changing within the plateau region.
As the span liquid for obtaining R _b , it is preferable to use clean water or the like to be measured whose free residual chlorine concentration and combined chlorine concentration are appropriately controlled. Moreover, you may use what diluted the hypochlorous acid solution with the zero solution.

R _b is, specifically, the R _b calculation mode, the span solution as the sample solution S, can be obtained as follows.
The sample solution S (span solution) was circulated in the flow cell 19, and the applied voltage was changed from V _b1 while maintaining the state where the rotational speed of the motor 16 was N ₁ and the flow rate of the sample solution S in the flow cell 19 was F _1. Sweep to V _b2 and measure the redox current. However, the voltages V _b1 and V _b2 are applied voltages in the plateau region. V _b1 is preferably V ₁ , and V _b2 is preferably V ₂ .
The oxidation-reduction current may be measured continuously while sweeping the applied voltage, or may be measured every time the applied voltage changes by a certain value (for example, 50 mV or 100 mV). Alternatively, the measurement may be performed at two points when the applied voltage is V _b1 and V _b2 .

Then, the ratio of the absolute value (ΔI _b ) of the change amount of the oxidation-reduction current to the absolute value (ΔV _b ) of the change amount of the applied voltage is obtained, and this ratio is defined as R _b . An equation for obtaining R _b from two points of the oxidation-reduction current I _b1 when the applied voltage is V _b1 and the oxidation-reduction current I _b2 when it is V _b2 is as follows.
R _b = ΔI _b / ΔV _b = | I _b2 −I _b1 | / | V _b2 −V _b1 |
When measuring the oxidation-reduction current at three or more applied voltages, or when measuring the oxidation-reduction current continuously while sweeping the applied voltage from V _b1 to V _b2 , a linear function obtained by the least square method or the like The absolute value of the slope of R is _Rb .
The R _b calculation mode for obtaining R _b may be appropriately performed in consideration of necessary management accuracy and the like. For example, it can be performed after the span calibration.

The predetermined ranges K _{1 to} K ₂ are determined so as to include the obtained R _b . Specifically, it can be obtained by the following equation.
K ₁ = R _b −α
K ₂ = R _b + β
Here, α and β are values appropriately set in consideration of necessary management accuracy and the like. α and β are preferably equal, but may be different.

The predetermined range K ₁ ′ to K ₂ ′ is determined so as to include the obtained R _b . Specifically, it can be obtained by the following equation.
K ₁ '= R _b -α'
K ₂ '= R _b + β'
Here, α ′ and β ′ are values appropriately set in consideration of necessary management accuracy and the like. α ′ and β ′ are preferably equal but may be different. Further, α and α ′ are preferably equal but may be different. Similarly, β and β ′ are preferably equal but may be different.

[Measurement mode]
In the free residual chlorine measuring apparatus of the present embodiment, the sample liquid S such as clean water to be measured is circulated in the flow cell 19 during the measurement mode, the rotation number of the motor 16 is N ₁ , and the sample liquid in the flow cell 19 is measured. The oxidation-reduction current I _x is determined with the flow rate of S as F ₁ and the applied voltage as V ₀ . The calculation control unit 21 of the main body 20 calculates the free residual chlorine concentration f _x corresponding to the oxidation-reduction current I _x based on the calibration curve specified by the two points stored in the calibration mode or the calibration curve stored in the calibration mode. Ask.

The value of the resulting free residual chlorine concentration f _x is given to the display device 24 as a signal D1, free residual chlorine concentration f _x is displayed on the display device 24. The value of free residual chlorine concentration f _x as a signal D2, an external recorder, transmitted data logger, memory, printers, to a computer or the like. The signal D2 may be a digital signal or an analog signal. Further, it may be transmitted by wire or wirelessly.

[Diagnostic mode]
The free residual chlorine measuring apparatus of the present embodiment performs steps 1 to 6 in the diagnostic mode as in the first embodiment, but the point of adjusting the flow rate of the sample liquid S in the flow cell 19 is the same as that of the first embodiment. Is different.
Hereinafter, each step will be described in detail with reference to FIG.
The diagnosis mode is started by interrupting the measurement mode at predetermined time intervals by a timer or an external start signal built in the main body unit 20. Also, free residual chlorine concentration f _x obtained in the measurement mode, when became out of the range of a predetermined control value, and starts to interrupt measurement mode.

In step 1, the sample liquid S measured in the measurement mode is circulated in the flow cell 19, and the state in which the number of revolutions of the motor 16 is N ₁ and the flow rate of the sample liquid S in the flow cell 19 is F ₁ is maintained. As it is, the applied voltage is swept from V ₁ to V ₂ to measure the redox current (step B1-1).
The oxidation-reduction current may be measured continuously while sweeping the applied voltage, or may be measured every time the applied voltage changes by a certain value (for example, 50 mV or 100 mV). Further, the measurement may be performed at two points when the applied voltage is V ₁ and when it is V ₂ .

Next, the ratio R (= ΔI / ΔV) of the absolute value (ΔI) of the change amount of the oxidation-reduction current to the absolute value (ΔV) of the change amount of the applied voltage is obtained (step B1-2). An equation for obtaining the ratio R from two points of the oxidation-reduction current I ₁ when the applied voltage is V ₁ and the oxidation-reduction current I ₂ when V ₂ is as follows.
R = ΔI / ΔV = | I ₂ −I ₁ | / | V ₂ −V ₁ |
When measuring the redox current at three or more applied voltages, or when measuring the redox current continuously while sweeping the applied voltage from V ₁ to V ₂ , a linear function obtained by the least square method or the like The absolute value of the slope of is the ratio R.

In step 2, the ratio R is compared with a predetermined range K _{1 to} K ₂ (where K ₁ <K ₂ ) (step B2). As a result, when the ratio R is within the predetermined range K _{1 to} K ₂ , the diagnosis mode is terminated. On the other hand, when the ratio R is outside the range of the predetermined range K _{1 to} K ₂ , the process proceeds to Step 3 (Step B3-1).
In FIG. 5, _{K 1} ≦ R ≦ _K where satisfying ₂ a within a predetermined range _{K 1 ~K 2, K 1 ≦} R ≦ _{If K 2} does not satisfy the predetermined range _K 1 ~K ₂ It was out of the range _of, K 1 <R _<K where satisfying ₂ a within a predetermined range _K 1 ~K _2, K 1 <R <a predetermined range _K 1 a is not satisfied _{K 2} ~K _It may be outside the range of ₂ .

In step 3, the rotational speed of the motor 16 is changed from N ₁ to N ₂ (where N ₁ <N ₂ ), and the flow rate of the sample solution S in the flow cell 19 is changed from F ₁ to F ₂ (where F ₁ < changing the F ₂₎ (step B3-1). In the flow cell 19, the sample liquid S measured in the measurement mode is kept flowing. The value of the applied voltage in step B3-1 is arbitrary, and the applied voltage may not be applied. By increasing the rotation speed of the motor 16 and increasing the flow rate of the sample solution S in the flow cell 19, the polishing efficiency of the detection electrode 13 by the beads 18 is increased.
Step B3-1 continues until a predetermined time elapses (step B3-2), and then proceeds to step 4. The predetermined time is set to such a time that the surface of the detection electrode 13 can be sufficiently polished.

In step 4, the rotational speed of the motor 16 is returned from N ₂ to N _1, and the flow rate of the sample liquid S in the flow cell 19 is returned from F ₂ to F ₁ . In the flow cell 19, the sample liquid S measured in the measurement mode is kept flowing. Then, the applied voltage is swept from V ₁ ′ to V ₂ ′ to measure the redox current (step B4-1). The applied voltages V ₁ ′ and V ₂ ′ are preferably equal to the applied voltages V ₁ and V ₂ in step 1, respectively.

The oxidation-reduction current may be measured continuously while sweeping the applied voltage, or may be measured every time the applied voltage changes by a certain value (for example, 50 mV or 100 mV). Further, the measurement may be performed at two points when the applied voltage is V ₁ ′ and when it is V ₂ ′. The timing for measuring the redox current is preferably the same as the timing for measuring the redox current in Step 1.

Next, the ratio R ′ (= ΔI ′ / ΔV ′) of the absolute value (ΔI ′) of the change amount of the oxidation-reduction current with respect to the absolute value (ΔV ′) of the change amount of the applied voltage is obtained (step B4-2). And _'redox currents I ₁ when _a' applied voltage V _1, wherein when determining the ratio R 'from two points _of' redox current I ₂ when a _'V 2 are as follows .
R ′ = ΔI ′ / ΔV ′ = | I ₂ ′ −I ₁ ′ | / | V ₂ ′ −V ₁ ′ |
When measuring the oxidation-reduction current at three or more applied voltages, or when continuously measuring the oxidation-reduction current while sweeping the applied voltage from V ₁ ′ to V ₂ ′, it was obtained by the method of least squares or the like. The absolute value of the slope of the linear function is the ratio R ′.

In step 5, the ratio R ′ is compared with a predetermined range K ₁ ′ to K ₂ ′ (where K ₁ ′ <K ₂ ′) (step B5). As a result, when the ratio R ′ is within the predetermined range K ₁ ′ to K ₂ ′, the diagnosis mode is terminated. On the other hand, when the ratio R ′ is out of the predetermined range K ₁ ′ to K ₂ ′, the process proceeds to Step 6 (Step B6).
In FIG. 5, the case where K ₁ ′ ≦ R ′ ≦ K ₂ ′ is satisfied is within the predetermined range K ₁ ′ to K ₂ ′, and the case where K ₁ ′ ≦ R ′ ≦ K ₂ ′ is not satisfied. The predetermined range K ₁ ′ to K ₂ ′ is outside the range, but the case where K ₁ ′ <R ′ <K ₂ ′ is satisfied is set within the predetermined range K ₁ ′ to K ₂ ′, and K ₁ ′ < The case where R ′ <K ₂ ′ is not satisfied may be outside the predetermined range K ₁ ′ to K ₂ ′.

In step 6, abnormality information is generated (step B6).
The generated abnormality information is given to the display device 24 as a signal D1, and the display device 24 displays that it is in an abnormal state. Also, the abnormality information is transmitted as a signal D2 to an external recorder, data logger, memory, printer, speaker, computer, etc., and the user is notified of the abnormal state by display, recording, printing, voice, etc. .
After step 6, the diagnostic mode is terminated.

During the diagnostic mode may not seek a free residual chlorine concentration f _x of the sample solution S. Therefore, it is impossible to transmit the free residual chlorine concentration f _x display device 24 or an external printer, a computer or the like.
During the diagnosis mode, a message indicating that the diagnosis mode is being used may be displayed on the display device 24. In addition, this fact may be transmitted to an external printer, computer or the like. It can also be displayed on the display device 24 a hold value or the like of the free residual chlorine concentration f _x in the diagnosis mode start just before the dummy information may or transmitted outside of the printer, to a computer or the like.

  After ending the diagnostic mode, the measurement mode is returned to the principle. Moreover, you may start the calibration mode as needed. In addition, when the diagnosis mode is terminated after the process up to Step 6, the measurement mode may be set to a pause mode in which neither measurement nor calibration is performed.

<Fourth embodiment>
[Device configuration]
The free residual chlorine measuring apparatus according to the fourth embodiment of the present invention is the same as that of the third embodiment except that the sensor unit 3 in FIG. 4 is changed to the sensor unit 4 shown in FIG.

FIG. 6 is a cross-sectional view of the sensor unit 4. The sensor unit 4 has a configuration in which a flow cell 60 is added to the sensor unit 2 of the second embodiment. 6, the same components as those in FIG. 3 are denoted by the same reference numerals as those in FIG. 3, and detailed description thereof is omitted.
A support base 32 is inserted into the flow cell 60. The inner wall of the upper end side of the flow cell 60 and the outer periphery of the support base 32 are fixed in a liquid-tight manner via an O-ring 61.
A sample liquid inflow port 60a for sample liquid inflow is provided at the center of the tip of the flow cell 60, and a sample liquid outflow port 60b for sample liquid outflow is provided on the side wall in the vicinity of the O-ring 61. An inflow path 51 is connected to the sample liquid inlet 60a, and a discharge path 52 is connected to the sample liquid outlet 60b.

  When the sample liquid S is caused to flow from the sample liquid inlet 60a of the flow cell 60 of the sensor unit 4 of the present embodiment, a part of the sample liquid S enters the cap 34 and flows out from the sample liquid outlet 60b through the window 32b. To do. Thereby, the sample solution S comes into contact with the detection electrode 35. A part of the sample liquid S flows in from the sample liquid inlet 60a, then passes through the outside of the support base 32 and flows out of the sample liquid outlet 60b. Thereby, the sample solution S comes into contact with the counter electrode 33 wound around the support base 32. That is, by flowing the sample solution S from the sample solution inlet 60 a of the flow cell 60, the detection electrode 35 and the counter electrode 33 are immersed in the sample solution S.

The free residual chlorine measuring apparatus according to the fourth embodiment operates in the same manner as the free residual chlorine measuring apparatus according to the third embodiment in each of the calibration mode, _Rb calculation mode, measurement mode, and diagnostic mode. Moreover, it is necessary that the plateau region is confirmed, and the confirmation method is the same as that of the free residual chlorine measuring device according to the third embodiment.

<Other embodiments>
In each of the above embodiments, the rotational speed of the motor in the measurement mode and the rotational speed of the motor in Step 1 are the same, but they may be different.
Further, in each of the above embodiments, the abrasive member is a granular abrasive (beads 18 and 36) arranged in a non-fixed state in the vicinity of the detection electrode. For example, a spring biased toward the detection electrode is used. An abrasive member such as a sponge or brush attached to the tip and contacting the detection electrode may be used.

Moreover, in 3rd Embodiment and 4th Embodiment, although the flow volume in step 3 was made larger than the flow volume in step 1, the flow volume of step 1 and step 3 in these embodiment may be the same. That is, only the number of rotations of the motor may be changed in step 3.
Further, in the third embodiment and the fourth embodiment, the flow rate in the measurement mode and the flow rate in step 1 are the same, but they may be different.

In the above embodiments, the diagnostic mode, and starts a predetermined time interval, even when the free residual chlorine concentration f _x obtained in the measurement mode is out of the range of the predetermined control value, the measurement mode However, the diagnosis mode may be started only at predetermined time intervals. Also, free residual chlorine concentration f _x obtained in the measurement mode, it may be initiated only when it becomes out of the range of a predetermined control value.
In addition, when initiating a diagnostic mode at predetermined time intervals, the predetermined time interval, according to the variation conditions like and seasonal etc. obtained in the measurement mode free residual chlorine concentration f _x, it may be changed.

In each of the above embodiments, the calibration mode and the _Rb calculation mode have been described as independent processes. However, for example, the span calibration and the _Rb calculation mode may be performed simultaneously.
Specifically, _Rb is calculated by continuously measuring the redox current while sweeping the applied voltage, and span calibration is performed based on the redox current when the applied voltage during sweeping becomes V _0. It can be carried out.
Further, the predetermined ranges K _{1 to} K ₂ and the predetermined ranges K ₁ ′ to K ₂ ′ may be fixed ranges. In that case, the _Rb calculation mode is unnecessary.

[Function and effect]
In the embodiments described above, if the ratio R is within a predetermined range K ₁ ~K ₂ good plateau region is maintained in step 2, it can be determined to be normal, immediate return to measurement mode it can. On the other hand, when the ratio R is a large value outside the predetermined range K _{1 to} K ₂ and a good plateau region cannot be maintained, the cause is a change (increase) in the combined chlorine concentration or an abnormality of the electrode. Conceivable. Further, when the ratio R is a small value outside the predetermined range K _{1 to} K ₂ , an abnormality of the electrode or a change (decrease) in the combined chlorine concentration can be considered.

  The present inventors have found that the abnormality of the electrode is often resolved if the detection electrode is sufficiently polished. In other words, the electrode due to an increase in the surface area of the detection electrode, such as when a part of the surface of the detection electrode is deeply shaved or a piece cut from the detection electrode is not completely detached and is hung on the surface of the detection electrode Abnormality causes measurement value abnormality. It has been found that such an abnormality can be eliminated by sufficiently polishing the detection electrode to restore the flatness of the surface or removing the hanging fragments. Therefore, in step 3, polishing is sufficiently performed with high polishing efficiency.

Thereafter, when the ratio R ′ is within the predetermined range K ₁ ′ to K ₂ ′ and the good plateau region is restored in step 5, it can be determined that the ratio has returned to normal, and the measurement mode can be immediately restored. On the other hand, if the ratio R ′ is still outside the predetermined range K ₁ ′ to K ₂ ′ and a good plateau region has not been restored, the cause can be solved by the influence of bonded chlorine or sufficient polishing. Severe abnormality of the electrode that is not performed is considered. Therefore, abnormal information is generated to prompt the user to respond.
According to this embodiment, it is possible to automatically resolve an abnormality that can be eliminated if the detection electrode is sufficiently polished, and to return to a normal state. Therefore, it is possible to greatly reduce the burden of the user visiting the site and responding.
Further, it is possible to avoid misinjecting the influence of the combined chlorine and injecting an excessive chlorine agent even though the current gradient in the plateau region is increased due to the abnormality of the electrode.

<Sample solution>
The following sample solution was created,
(Sample solution 1) Tap water was supplied from Toray Industries, Inc. Trebino (registered trademark) STC. The sample solution 1 was filtered through J.
(Sample solution 2) Sample solution 2 was prepared by adding hypochlorous acid solution (1800 mg / L) to sample solution 1 so that the concentration of free residual chlorine in the sample solution was about 0.5 mg / L.
(Sample solution 3) Sample solution 3 was prepared by adding hypochlorous acid solution (1800 mg / L) to sample solution 1 so that the concentration of free residual chlorine in the sample solution was about 1 mg / L.

(Sample solution 4) Sample solution 4 was prepared by adding hypochlorous acid solution (1800 mg / L) to sample solution 1 so that the free residual chlorine concentration of the sample solution was about 1 mg / L.
(Sample solution 5) An ammonium chloride solution (a special grade of 0.382 mg of ammonium chloride manufactured by Kanto Chemical Co., Ltd.) was added to 1 L of sample solution 1 so that the amount of ammoniacal nitrogen in the sample was 0.1 mg / L. Was dissolved). Next, approximately the same amount of hypochlorous acid solution (1800 mg / L) added in sample solution 4 (if hypochlorous acid does not react with ammonia nitrogen, the concentration of free residual chlorine in the sample solution is about 1 mg / liter). The amount of L) was added to obtain sample solution 5.
(Sample solution 6) An ammonium chloride solution (a special grade 0.764 mg of ammonium chloride manufactured by Kanto Chemical Co., Ltd.) was added to 1 L of sample solution 1 so that the amount of ammoniacal nitrogen in the sample was 0.2 mg / L. Was dissolved). Next, approximately the same amount of hypochlorous acid solution (1800 mg / L) added in sample solution 4 (if hypochlorous acid does not react with ammonia nitrogen, the concentration of free residual chlorine in the sample solution is about 1 mg / liter). The amount of L) was added to obtain sample solution 6.

(Sample solution 7) Sample solution 7 was prepared by adding hypochlorous acid solution (1800 mg / L) to sample solution 1 so that the concentration of free residual chlorine in the sample solution was about 0.5 mg / L.
(Sample Solution 8) An ammonium chloride solution (special grade 0.191 mg of ammonium chloride manufactured by Kanto Chemical Co., Ltd.) was added to Sample Solution 1 so that the amount of ammoniacal nitrogen in the sample was 0.05 mg / L. Was dissolved). Next, approximately the same amount as the amount of hypochlorous acid solution (1800 mg / L) added in the sample solution 7 (if the hypochlorous acid does not react with ammoniacal nitrogen, the concentration of free residual chlorine in the sample solution is about 0. 0). Sample solution 8 was prepared by adding 5 mg / L).
(Sample solution 9) An ammonium chloride solution (special grade 0.382 mg of ammonium chloride manufactured by Kanto Chemical Co., Ltd.) was added to the sample solution 1 so that the amount of ammoniacal nitrogen in the sample was 0.1 mg / L. Sample solution 1 dissolved in 1 L) was added. Next, approximately the same amount as the amount of hypochlorous acid solution (1800 mg / L) added in the sample solution 7 (if the hypochlorous acid does not react with ammoniacal nitrogen, the concentration of free residual chlorine in the sample solution is about 0. 0). Sample solution 6 was prepared by adding 5 mg / L).

(Sample solution 10) Sample water 10 was used as tap water.
(Sample solution 11) Tap water was prepared by Trebino (registered trademark) STC. The sample solution 11 was filtered through J.

(Sample solution 12) Tap water was used as sample solution 12.
(Sample solution 13) Tap water was prepared by Trebino (registered trademark) STC. The sample solution 13 was filtered through J.

<Polarogram creation 1>
The sensor unit 4 in FIG. 6 was used as the sensor unit. A gold electrode was used as the detection electrode 35, and a silver / silver chloride electrode was used as the counter electrode 33. The rotation speed of the motor 38 was 2800 rpm.
The sample liquids (sample liquids 1 to 9) were circulated in the flow cell 60 of the sensor unit of FIG. 6 using the head pressure of the tank so as to maintain a flow rate in the range of 100 to 300 mL / min.
In this state, a redox current flowing between the detection electrode and the counter electrode is measured while applying a voltage of 300 mV to −300 mV (sweep speed 100 mV / min) between the detection electrode 35 and the counter electrode 33, and the sample solution 1 A polarogram of ˜9 was obtained. The results are shown in FIGS.

<Polarogram creation 2>
The polarograms of the sample solutions 10 and 11 were obtained in the same manner as in the polarogram preparation 1 except that a gold electrode whose surface area was increased by deformation as the detection electrode 35 was used. The results are shown in FIG.

<Polarogram creation 3>
The polarograms of the sample solutions 12 and 13 were obtained in the same manner as in the polarogram creation 1 except that the gold electrode used in the polarogram creation 2 was re-polished as the detection electrode 35. The results are shown in FIG.

<Measurement by DPD method>
Using a pocket residual chlorine meter manufactured by HACH, the free residual chlorine concentration of each sample solution and the total residual chlorine concentration of sample solutions 4 to 9 were measured by the DPD method. The measured free residual chlorine concentration and the concentration obtained by subtracting the free residual chlorine concentration from the total residual chlorine concentration (bound chlorine concentration) are shown in FIGS. In the figure, f is the free residual chlorine concentration and c is the combined chlorine concentration. Note that N in FIGS. 8 and 9 is the amount of ammoniacal nitrogen calculated from the reagent blending amount at the time of sample solution preparation.

<Calculation of ratio R>
7 to 11, the ratio R (= ΔI / ΔV) of the absolute value (ΔI) of the change amount of the oxidation-reduction current to the absolute value (ΔV) of the change amount of the applied voltage was obtained.
The ratio R was calculated by the following equation from two points of the oxidation-reduction current I ₁ when the applied voltage was V ₁ and the oxidation-reduction current I ₂ when V ₂ was applied.
R = ΔI / ΔV = | I ₂ −I ₁ | / | V ₂ −V ₁ |
The applied voltage V ₁ was +50 mV, and the applied voltage V ₂ was −50 mV. The results are shown in Table 1.

<Discussion>
From FIG. 7, by using a gold electrode as the detection electrode and a silver / silver chloride electrode as the counter electrode, in the sample solutions 1 to 3 substantially free of bound chlorine, a plateau state in which the range of +100 to −100 mV is stable is obtained. It was confirmed that the applied voltage at the time of measurement can be selected from this range. In particular, it was confirmed that a particularly good plateau region was obtained in the range of +50 to −50 mV.
As shown in Table 1, the ratio R of the sample solutions 1 to 3 tends to increase as the free residual chlorine concentration increases.

On the other hand, as shown in FIGS. 8 and 9, in the sample solutions 5, 6, 8, and 9 in which bound chlorine is present, the ratio R tends to increase even in the range of +50 to −50 mV.
As shown in Table 1, when R of Samples 4 to 6 in which the addition amount of the hypochlorous acid solution was almost equal was compared, the ratio R increased as the amount of ammoniacal nitrogen increased. Similarly, when R of Samples 7 to 9 in which the amount of the hypochlorous acid solution added was almost equal, the ratio R increased as the amount of ammoniacal nitrogen increased.
Therefore, in clean water etc. in which the free residual chlorine concentration is managed in a substantially constant range, the ratio R is larger than the predetermined range K _{1 to} K ₂ set according to the measurement range and management accuracy. In this case, it was confirmed that it was possible to diagnose that there may be an abnormality due to the presence of bound chlorine.

Further, as shown in FIG. 10, in the sample solutions 10 and 11, a good plateau region was not obtained even though the concentration of bound chlorine was such that it did not affect the measurement. On the other hand, as shown in FIG. 11, it was confirmed that a good plateau region was obtained with the sample liquids 12 and 13 equivalent to the sample liquids 10 and 11 after polishing.
Further, as shown in Table 1, the ratio R of the sample liquid 10 is larger than the ratio R of the sample 12 having the same free residual chlorine concentration, and the ratio R of the sample liquid 11 having a free residual chlorine concentration of almost zero is free. The residual chlorine concentration was larger than the ratio R of the sample 13 which was nearly zero.

Therefore, in the case of clean water or the like in which the free residual chlorine concentration is managed in a substantially constant range, when the ratio R is outside the predetermined range K _{1 to} K ₂ set according to the measurement range and management accuracy, It was confirmed that it was possible to diagnose that there was a possibility of abnormality due to insufficient polishing of the detection electrode.
Further, if it can be confirmed that the ratio R after polishing (corresponding to the ratio R ′ in step 4 of the present invention) is within the predetermined range K ₁ ′ to K ₂ ′, the cause of the abnormality is insufficient polishing of the detection electrode. It was confirmed that it was possible to diagnose that this was not due to the presence of bound chlorine, and that the normal state was restored by polishing.

DESCRIPTION OF SYMBOLS 1-4 ... Sensor part, 11 ... Measurement cell, 12 ... Detection pole support body, 13, 35 ... Detection pole,
14 ... Counter electrode support, 15, 33 ... Counter electrode, 16, 38 ... Motor, 17, 45 ... Bearing,
18, 36 ... beads, 19, 60 ... flow cell, 20 ... main body,
21 ... Calculation control unit, 22 ... Applied voltage mechanism, 23 ... Ammeter, 24 ... Display device,
50 ... Liquid feeding part, 53 ... Pump, S ... Sample liquid

Claims (10)

A detection electrode and a counter electrode immersed in the sample liquid;
A motor for rotating or vibrating the detection pole;
A polishing member capable of contacting the detection electrode;
An applied voltage mechanism for applying an applied voltage between the detection electrode and the counter electrode;
An ammeter for measuring an oxidation-reduction current flowing between the detection electrode and the counter electrode;
In the measurement mode, while the detection pole is rotated or vibrated by the motor, the redox current is measured with the applied voltage as a constant voltage in the plateau region, and the free residual chlorine concentration of the sample liquid is measured based on the obtained redox current. Seeking
In the diagnostic mode, the free residual chlorine measuring device is configured to perform the following steps.
Step 1: the rotational speed of the motor while the N _1, the applied voltage is changed in the plateau region, the absolute value of the change amount of the redox current with respect to the absolute value of the amount of change of the applied voltage ([Delta] V) ( A ratio R (= ΔI / ΔV) of ΔI) is obtained.
Step 2: When the ratio R is within a predetermined range K _{1 to} K ₂ (where K ₁ <K ₂ ), the diagnosis mode is terminated, and the ratio R is within a predetermined range K _{1 to} K ₂ . When outside, go to step 3.
Step 3: The rotational speed of the motor is changed to N ₂ (where N ₁ <N ₂ ), and the detection electrode is polished for a predetermined time.
Step 4: The rotation speed of the motor in the state returning to N _1, the applied voltage is changed in the plateau region, the absolute amount of change of the redox current with respect to the absolute value of the amount of change of the applied voltage ([Delta] V ') A ratio R ′ (= ΔI ′ / ΔV ′) of values (ΔI ′) is obtained.
Step 5: When the ratio R ′ is within the predetermined range K ₁ ′ to K ₂ ′ (where K ₁ ′ <K ₂ ′), the diagnosis mode is terminated, and the ratio R ′ is within the predetermined range K When it is outside the range of ₁ ′ to K ₂ ′, the process proceeds to Step 6.
Step 6: Generate abnormality information and end the diagnosis mode. The free residual chlorine measuring device according to claim 1, wherein the predetermined ranges K _{1 to} K ₂ are determined so as to include the following R _b .
R _b = ΔI _b / ΔV _b
However, ΔI _b / ΔV _b is the applied voltage obtained by changing the applied voltage in the plateau region with the span solution used for span calibration as the sample solution and the rotation speed of the motor being N ₁ . It is the ratio of the absolute value (ΔI _b ) of the change amount of the oxidation-reduction current to the absolute value (ΔV _b ) of the change amount. The predetermined range K ₁ '~K _2' is, free residual chlorine measuring device according to claim 1 or 2 are determined to include the following R _b.
R _b = ΔI _b / ΔV _b
However, ΔI _b / ΔV _b is the applied voltage obtained by changing the applied voltage in the plateau region with the span solution used for span calibration as the sample solution and the rotation speed of the motor being N ₁ . It is the ratio of the absolute value (ΔI _b ) of the change amount of the oxidation-reduction current to the absolute value (ΔV _b ) of the change amount. Free residual chlorine measuring device according to any one of claims 1 to 3 rpm is N ₁ of the motor in the measurement mode.   The free residual chlorine measuring device according to any one of claims 1 to 4, wherein the polishing member is a granular abrasive disposed in an unfixed state in the vicinity of the detection electrode.   Furthermore, the flow cell which distribute | circulates a sample liquid and the liquid feeding means to distribute | circulate a sample liquid in the said flow cell are provided, The said detection electrode and the non-fixed granular abrasive | polishing agent are accommodated in the said flow cell. The apparatus for measuring free residual chlorine as described. The relationship between the flow rate F ₁ of the sample liquid in the flow cell in the step 1 and the step 4 and the flow rate F ₂ of the sample liquid in the flow cell in the step 3 is F ₁ ≦ F ₂ . Free residual chlorine measuring device. Free residual chlorine measuring device according to claim 7 flow of the sample liquid in the flow cell in the measurement mode is F _1.   The free residual chlorine measuring device according to any one of claims 1 to 8, wherein the diagnostic mode is started when a free residual chlorine concentration obtained in the measurement mode is out of a predetermined range.   The free residual chlorine measuring apparatus as described in any one of Claims 1-9 which starts the said diagnostic mode for every predetermined time interval.

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