JPH0559304U - Residual chlorine meter - Google Patents

Abstract

(57) [Summary] [Purpose] It is possible to detect the absence of liquid to be measured without interrupting the measurement. [Structure] An indicator electrode and a reference electrode are immersed in a liquid to be measured introduced into a liquid tank, and a voltage is applied between these electrodes to release free available chlorine in the liquid to be measured based on a current flowing between the electrodes. In the residual chlorine meter for measuring the concentration, a circuit means (5) for applying a DC voltage and a rectangular wave AC voltage to the reference electrode (2) is provided, and the measured value of this indicator electrode is set to a voltage in the indicator electrode (1). The current-voltage conversion circuit (6) to be converted, and the voltage output of the current-voltage conversion circuit is separated into a direct current component and an alternating current component, and the presence or absence of the measured liquid is measured while continuously measuring the measured liquid. A structure provided with a circuit means for identifying.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a residual chlorine meter having a liquid shortage detection circuit.

[0002]

[Prior Art]

 As a conventional technique of this kind, there is known a residual chlorine meter as shown in the block diagram of the conventional residual chlorine meter of FIG. 4 (for example, JP-A-2-52153 and JP-A-2-98661). And Japanese Patent Laid-Open No. 2-154142).

In this type of residual chlorine meter, an indicator electrode (rotating indicator electrode) 1 and a reference electrode (counter electrode) 2 are immersed in a liquid S to be measured introduced into a liquid tank 4, and measurement is performed between these electrodes. An applied voltage is applied from the circuit 3, and the concentration of free available chlorine in the measured liquid S is measured based on the current flowing between the electrodes at this time.

The circuit means 3 is shown as being composed of an analog circuit in FIG. 4, but it may be composed of a CPU. D indicates a drain.

[0005]

[Problems to be solved by the device]

 Such conventional techniques have the following problems.

(A) In the case of the configuration of FIG. 4, the presence or absence of the liquid S to be measured cannot be identified without interrupting the measurement by using the detector of the residual chlorine meter.

(B) When a CPU (not shown) is used in the measurement circuit portion, theoretically, the applied voltage is changed to detect the change in the measurement current, and when there is no change in the current, it can be judged that the liquid has run out. It is possible. However, it is not yet a concrete and established technology to construct the technology so that it can detect water interruption continuously.

The present invention has been made in view of the above problems of the related art.

It is an object of the present invention to provide a residual chlorine meter which has a simple circuit configuration and can detect that the liquid to be measured does not enter the liquid tank without interrupting the measurement.

Another object is to add a simple circuit so that the conductivity can be measured at the same time to know an appropriate applied voltage, and residual chlorine can be stably measured or displayed. A residual chlorine meter is provided.

[0011]

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the present invention immerses an indicator electrode and a reference electrode in a liquid to be measured introduced into a liquid tank and applies a voltage between these electrodes to apply a current to the electrodes. In the residual chlorine meter for measuring the concentration of free available chlorine in the solution to be measured, (a) circuit means (5) for applying a DC voltage and a rectangular wave AC voltage to the reference electrode (2) is provided, and A current-voltage conversion circuit (6) that converts the measured value of the indicator electrode into a voltage is provided on the pole (1), and the voltage output of the current-voltage conversion circuit is separated into a direct current component and an alternating current component, and What is provided with circuit means (7 to 9) for discriminating the presence or absence of the liquid to be measured while continuously measuring the liquid to be measured (Claim 1), (b) DC voltage and rectangular wave AC to the reference electrode (2). A circuit means (5) for applying a voltage and a current for converting the measured value of the indicator electrode into a voltage on the indicator electrode (1). A voltage conversion circuit (6), display means (14) for displaying a signal proportional to the conductivity after filtering and rectifying the output from the current-voltage conversion circuit, and filtering of the current-voltage conversion circuit output. And a resistance value switching means (SS ₁ ) configured to be switchable between a plurality of resistance values to which the latter signal is guided and output to the circuit means 5 as a feedback compensation value, based on the display of the display means. The feedback compensation value of the resistance value switching means can be selected (claim 2).

[0012]

[Function] In the residual chlorine meter using the rotating platinum electrode, the conductivity between the indicator electrode and the reference electrode is measured by applying a slight AC voltage to the applied voltage (DC), and the measured The presence or absence of liquid can be detected.

According to the present invention, the presence or absence of the liquid to be measured can be identified while continuing the measurement of residual chlorine.

That is, on the comparison electrode side, a circuit for applying the polarographic DC voltage and the rectangular wave AC voltage to the comparison electrode is provided. On the indicator electrode side, a current-voltage conversion circuit that converts the measured value (current) from the indicator electrode into a voltage is provided, and the output of this current-voltage conversion circuit is separated into DC and AC components for processing. A circuit will be provided for this purpose so that the presence or absence of the liquid to be measured can be identified while performing continuous measurement on the liquid to be measured.

By the way, the AC component is passed through a filter circuit and a rectifier circuit to identify the presence or absence of the liquid to be measured from the rectified voltage. To a discriminating circuit having a function of treating the liquid to be measured, and performing a predetermined treatment to discriminate the presence or absence of the liquid to be measured.

On the other hand, the direct current component is led to a residual salt signal separation circuit and a residual salt signal is obtained by a predetermined process.

[0017]

【Example】

 The present invention will be described with reference to the drawings showing specific embodiments. In the following drawings, the same parts as those in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 is a diagram showing an outline of the residual chlorine meter of the present invention. FIG. 2 is a diagram showing a specific embodiment of the residual chlorine meter of the present invention (a circuit diagram as an example in which the configuration of FIG. 1 is further developed). FIG. 3 is a diagram for explaining another embodiment of the present invention. FIG. 4 is a block diagram of a conventional residual chlorine meter. FIG. 5 is a diagram for explaining FIG. 3 with reference to FIG.

In FIG. 1 and FIG. 2, the residual chlorine meter is a circuit means 5 for applying a DC voltage and a rectangular wave AC voltage to the indicator electrode (rotating electrode) 1, the comparison electrode (counter electrode) 2 and the comparison electrode (2). In Fig. 2, it is represented by 5 _{A. The same} applies to the following display), current-voltage conversion circuit 6, rectification circuit 7, identification circuit 8, residual salt signal separation circuit (low-pass filter) 9, filter F (further diagram 2 includes a temperature compensation circuit 10, an A / D “analog / digital conversion circuit” 11, a display unit 12 and a current output circuit 13).

Such a residual chlorine meter measures the conductivity between the indicator electrode 1 and the comparison electrode (counter electrode) 2 by applying a slight alternating voltage to the applied voltage (direct current), and The presence or absence of the measurement liquid S 1 can be detected.

R _c represents an interelectrode resistance generated between the indicator electrode and the comparison electrode.

The circuit means 5 (5 _A ) applies a polarographic DC voltage and a slight rectangular wave AC voltage to the comparison pole 2 via the connection terminal R and the resistance R ₁ (the applied voltage is a rectangular wave portion). Is added and applied to the comparison pole), and can be configured by, for example, a rectangular wave AC signal generation circuit 51 and a DC voltage circuit 52.

[0023] Then, the rectangular wave AC signal generating circuit 51 may be configured to generate a rectangular wave AC voltage Vs made of a peak value V _k.

Further, the DC voltage circuit 52 can be configured to output a polarographic DC voltage from the rectangular wave AC voltage from the rectangular wave AC signal generating circuit 51 (see the output waveform in FIG. 2). ..

In FIG. 2, instead of the feedback resistor of FIG. 1, for feedback of the applied voltage output amplifier 52U ₁ for adding and outputting the rectangular wave signal input and the applied voltage for residual chlorine concentration measurement, Shown when the buffer amplifier 52 _A is installed.

From the above results, a diffusion current I proportional to the residual chlorine concentration and a current i proportional to the conductivity of the measurement liquid flow between the indicator electrode 1 and the comparison electrode (counter electrode) 2.

The current-voltage conversion circuit 6 is composed of an input amplifier having a gain resistor R _f, and the inverting terminal of the input amplifier is connected to the connection terminal P to which the indicator electrode 1 is connected to derive the measured value (I + i). Get burned.

The current-voltage conversion circuit 6 uses a voltage component V _i (DC signal) obtained by converting the diffusion current I into a direct current component and an alternating current component, that is, a voltage V _i (applied voltage) proportional to the conductivity. Outputs an AC signal with the same frequency as the rectangular wave.

After the current-voltage conversion circuit 6, a circuit for processing the direct current component and the alternating current component, which are circuit outputs, through the filter F is provided. Regarding the filter, FIG. 2 shows a case where a high-pass filter is provided to separate the water cutoff detection signal from the input signal, or a low-pass filter is provided to separate the residual chlorine concentration signal.

The AC component is introduced to the rectifier circuit 7 / identification circuit 8.

The rectifier circuit 7 is composed of a half-wave rectifier circuit configuration such as shown in FIG. 2, the AC component V _i, a rectified voltage (water outage detection signal proportional to the square wave signal rectified by the immediately Chishirubeden rate ) Output V ₂ .

The discrimination circuit 8 is composed of, for example, a comparator for discriminating when there is a water cutoff detection signal in FIG. 2 by comparing this signal with a reference value D which is a comparison voltage for water cutoff detection (or A μP or the like having a function equivalent to a container), and a necessary identification process for identifying the presence or absence of the liquid S to be measured is performed.

The identification circuit 8 outputs a signal K when the water cutoff detection signal is present. The signal K can be used as a relay signal for contact output or a voltage signal.

The rectified voltage V ₂ to be input to the identification circuit 8 in this case, the protection resistor R _1, the R ₂ R ₁ << R _C, when the _{R 2 << R C, V 2} = V k · {R _f / (R ₁ + R _c + R ₂ )} (1) (This is approximately V _k · (R _f / R _c )). When the liquid S to be measured is lost in the measuring tank, the rectified voltage V ₂ becomes substantially “0”, so that the discrimination circuit 8 can easily detect the presence or absence of the liquid to be measured.

However, since the inter-electrode resistance R _c has a capacitance (for example, C ₁ ) when the electrodes come into contact with the liquid to be measured, the equivalent circuit at that time is the capacitance C in series with the resistor R _{c. The} circuit configuration consists of 1s connected in series. Therefore, it is necessary to set the frequency of the rectangular wave AC signal Vs at this time so that the impedance of the capacitance C ₁ is sufficiently smaller than the interelectrode resistance (liquid resistance) R _c .

On the other hand, the direct current component is a signal obtained by current-voltage converting the diffusion current I proportional to residual chlorine, and in order to obtain the residual salt concentration signal V ₁ , the residual salt signal separation circuit ( Low-pass filter) 9.

By the way, the residual salt concentration signal V ₁ is output to the DC voltage circuit 52, or is processed as it is by the output circuit means, that is, for example, via the A / D (analog / digital conversion circuit) 11, the display unit. 12 or to obtain a current output I _{out of 4} to 20 mA through a circuit means such as a current output circuit 13 or to arrange both circuits in parallel to perform the display / output processing. You can

Although not necessarily installed, in FIG. 2, in front of the output circuit means, a platinum resistor or a temperature measuring element having a good positive characteristic / linearity (in the figure, a platinum resistance temperature measuring element is shown. ) The case where the temperature compensation circuit 10 using Pt is provided is shown. The temperature compensation as used herein means compensation using the measured temperature t and the temperature coefficient α [% / ° C] with respect to the reference temperature (t _r ).

The characteristic of the temperature compensating circuit 10 shown here is that it is composed of only one amplifier, and the variable input value can be always temperature-compensated.

The configuration is such that the inverting terminal of the amplifier U is connected to the platinum resistance temperature detector Pt and the fixed resistance R _E whose other end is connected to the output terminal, and the non-inverting terminal is provided between the output terminal and the ground. The divided voltage obtained from the connection of the resistor R _L · R _R is fed back.

Here, for example, when Pt1000 is used, R _E = 300Ω ± 1%, R _L = 1 KΩ ± 1%, and R _R = variable resistance (20 ° C.), V _F is a feedback voltage, When the input is V ₁ and the output is V ₁₀ , it can be adjusted so as to satisfy the following formula.

{(V ₁₀ −V _F ) / R _E } + {(V ₁ −V _F ) / Pt} = 0 (2) and V ₁₀ {R _R / (R _R + R _L )} = V _F ... from _{(3), V 10 = {} (- (R L + R R) · R E / (R L · Pt-R R · R E)} to obtain a · V ₁ ... (4).

The temperature condition is 0 ° C. (the temperature compensation rate is 0.504 ″, the temperature compensation rate is [1- {2.48 / 100 (t ₀ -t ₂₀ )}, where 2.48 is the temperature coefficient% / ° C]. , Pt = 1000Ω), 20 ° C (Temperature compensation ratio is 1, Pt = 1077.9Ω), 40 ° C (Temperature compensation ratio is 1.496, Pt = 11 55.4Ω), between 0 ° C / 20 ° C The resistance value between R _R · R _E = 920.8435 · R _L 20 ° C / 40 ° C is R _R · R _E = 921.65 · R _L. The value (921.247Ω) can be obtained.

Next, consider the case where the offset is taken into consideration. At this time, the voltage of the non-inverting input terminal is set to V _F + V _off (offset voltage).

[{V ₁₀ − (V _F + V _off )} / R _E ] + [{V ₁ − (V _F + V _off )} / Pt] = 0 (5) From V ₁₀ · Pt = −V ₁ · R _E + (Pt + R _E ) V _off + V ₁₀ (Pt + R _E ) ... (6) is obtained.

[0046] From equation (3) and _{(6), V 10 = {(R L} + R R) / (R L · Pt-R R · R E)} · (-V 1 · R E) + obtain _{{(R L + R R)} / (R L · Pt-R R · R E)} · {(Pt + R E) V off} ... (7).

[0047] As a result, the gain of the circuit _{is, {- (R L + R} R) · R E)} / (R L · Pt-R R · R E)} ... (8) , and the positive feedback (denominator Is subtracted), a coefficient larger than the temperature coefficient of the temperature sensing element Pt can be obtained.

Further, the gain for the offset is larger than the gain of the input signal and is {(P t + R _E ) / R _E } times. However, this effect can be reduced by using an amplifier with a small offset voltage V _off or by adjusting the offset.

By the way, in the above apparatus, there is usually no concept of measuring the conductivity.

However, in a reagentless residual chlorine meter, the plateau characteristic in the residual chlorine characteristic changes in relation to the conductivity of the measurement liquid, as described in detail below. Therefore, when the conductivity of the measurement liquid changes, it is necessary to correct (change) the applied voltage in accordance with the change in the plateau characteristic.

However, since the conductivity cannot be measured with the configuration of the apparatus described above as it is, in order to make the correction, it is necessary to use the experience up to that point, use the past data, or use the measurement liquid. There is no choice but to use the measured value of the conductivity of the measurement solution after taking it back.

Here, a related technique of the conductivity and the plateau characteristic, which is a premise of the description of FIG. 3 described later, will be described with reference to FIG.

When a voltage is applied between the indicator electrode 1 and the counter electrode 2, the residual chlorine concentration characteristics A 1, B and C as shown in FIG. 5 are obtained. At this time, the polarographic change of the signal current with respect to the applied voltage is affected by the conductivity K [S / cm] of the measurement liquid (Va in FIG. 5 represents the start voltage of the applied voltage).

The reason for this is that there is a voltage drop effect due to the resistance component R _c of the liquid. In order to correct the influence of the voltage drop of the signal current due to the resistance component R _c, a voltage proportional to the increment of the signal current is applied to the applied voltage Va when the signal current is zero and applied. We have to go. As a result, an appropriate applied voltage can be applied even if the conductivity of the measurement liquid changes.

From the above, if the conductivity can be measured at the same time, an appropriate applied voltage can be known, and the residual chlorine can be measured more stably and reliably.

Therefore, specifically, as shown below, the conductivity of the measurement liquid is measured at the same time so that the optimum applied voltage can be selected in the field, or the optimum applied voltage can be automatically selected. It is also possible to do so. In this way, a structure that enables highly reliable residual chlorine measurement will be realized. A specific embodiment will be described below with reference to FIG.

In FIG. 3, a part different from FIG. 2 is that, firstly, a resistance value switching means SS ₁ capable of selectively switching the resistance value is arranged between the low pass filter 9 and the buffer amplifier 52 _A. That is what I did.

Secondly, the display unit 14 is provided to display the rectified voltage value of the rectangular wave signal proportional to the conductivity from the rectifier circuit 7. It is also possible to adjust this voltage and display it as conductivity.

At this time, by judging the display of the display unit 14, it becomes possible to switch the resistance value switching means SS ₁ and select the feedback compensation value to the buffer amplifier 52 _A. You can also

Needless to say, the above contents can be simultaneously processed as a series of operations by using the CPU.

In FIG. 3, a portion corresponding to the above-mentioned conductivity meter will be seen.

The output voltage of the buffer amplifier 52 _A (voltage for residual chlorine measurement), that is, the output of the current-voltage conversion circuit 6 for the voltage value V _k of the rectangular wave component for conductivity measurement. The relationship with the voltage value V _H of the rectangular wave component is V _H / V _k = R _f / (R ₁ + R _c + R ₂ ) ... (9) (This is approximately R _f / R _c , where R ₁ <<R _C, the R ₂ << R _C).

When the cell constant is S _k [cm ⁻¹ ], the conductivity K [S / cm] is K = S _k · (1 / R _f ) · (V _H / V _k ) ... (10) Can be represented. From this fact, the conductivity K can be obtained by measuring the voltage value V _H.

Therefore, as described above, the applied voltage compensation rate must be changed depending on the electrical conductivity. Therefore, if the compensation rate is selectively switched by the electrical conductivity obtained by the equation (10), more stable residual chlorine It will be possible to measure.

According to the above description, the presence or absence of the liquid to be measured can be discriminated while continuing the measurement of residual chlorine, and the conductivity can also be measured. In terms of reliability, it becomes possible to perform even more excellent measurements.

[0066]

[Effect of the device]

 Since the present invention is configured as described above, it has the following effects.

(A) A circuit that can identify the presence or absence of the liquid to be measured while performing continuous measurement can be simply configured and added.

(B) As a result, when the indication of the residual chlorine meter is zero, it is determined whether the measured value of the liquid to be measured is truly zero or the liquid to be measured does not flow. Is possible.

(C) Therefore, the reliability of the measurement value of the device can be dramatically improved.

(D) If the conductivity can be measured at the same time, an appropriate applied voltage can be known, so that the residual chlorine can be measured more stably and reliably.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a residual chlorine meter of the present invention.

FIG. 2 is a view showing a concrete example of the residual chlorine meter of the present invention.

FIG. 3 is a diagram for explaining another embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional residual chlorine meter.

5 is a diagram for explaining FIG. 3 with reference to FIG. 4. FIG.

[Explanation of symbols]

 1 Indicator electrode (rotation indicator electrode) 2 Comparative electrode 3 Measurement circuit 4 Liquid tank 6 Current-voltage conversion circuit 9 Residual salt signal separation circuit 10 Temperature compensation circuit

Claims (2)

[Scope of utility model registration request] 1. An indicator electrode and a reference electrode are immersed in a liquid to be measured introduced into a liquid tank, and a voltage is applied between these electrodes to release the liquid from the liquid to be measured based on a current flowing between the electrodes. In a residual chlorine meter for measuring effective chlorine concentration, the reference electrode (2)
Circuit means for applying a DC voltage and a rectangular wave AC voltage to the (5)
The indicator electrode (1) is provided with a current-voltage conversion circuit (6) for converting the measured value of the indicator electrode into a voltage, and the voltage output of the current-voltage conversion circuit is separated into a DC component and an AC component. And a circuit means for discriminating the presence / absence of the liquid to be measured while continuously measuring the liquid to be measured. 2. An indicator electrode and a reference electrode are immersed in a liquid to be measured introduced into a liquid tank, and a voltage is applied between these electrodes to release the liquid from the liquid to be measured based on a current flowing between the electrodes. In a residual chlorine meter for measuring effective chlorine concentration, the reference electrode (2)
Circuit means for applying a DC voltage and a rectangular wave AC voltage to the (5)
And a current-voltage conversion circuit (6) that converts the measured value of this indicator electrode into a voltage on the indicator electrode (1), and is proportional to the conductivity after filtering and rectifying the output from the current-voltage converter circuit. And a display means (14) for displaying the signal, and a plurality of resistance values to which the filtered signal of the output of the current-voltage conversion circuit is guided and output as feedback compensation values to the circuit means 5 are selectable. A residual chlorine meter, comprising: a resistance value switching means (SS ₁ ), wherein the feedback compensation value of the resistance value switching means can be selected based on the display of the display means.