JPH0619089Y2 - Residual chlorine meter with automatic calibration function - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a residual chlorine meter with an automatic calibration function.

<Prior Art> Conventionally, automatic calibration is not performed in a residual chlorine meter. The conventional calibration method is a manual analysis using an ortho-tolidine method (OT method), a diethyl-p-phenylenediamine method (DPD method), an iodometric titration method, an amperometric titration method, etc., using a sample solution of known content. It is calibrated so that the indicated value of the residual chlorine meter agrees with this measured value. Calibration work by manual analysis is complicated and time-consuming.

The main reason why automatic calibration is not possible with a residual chlorine meter is that chlorine water as a calibration standard solution is unstable and its concentration changes over time, so chlorine water cannot be stored for a long time.

<Problems to be Solved by the Invention> A technical problem to be solved by the present invention is to enable automatic calibration in the residual chlorine meter without resorting to complicated manual analysis.

<Means for Solving the Problems> The structure of the present invention comprises a sensor for measuring the effective chlorine concentration in a liquid to be measured by a polarographic method, and a constant concentration of NaCl.
A salt water supply means for supplying the aqueous solution at a constant flow rate and a flow path through which the NaCl aqueous solution from the salt water supply means flows are provided.
Provided with a metal inert cathode on the upstream side of this flow path, a chlorine generation flow cell provided with a metal inert anode on the downstream side thereof,
A constant current generation source for flowing a constant current between the electrodes of this chlorine generation flow cell, and a flow path switching means for connecting the measured liquid side flow path and the chlorine generation flow cell side to the sensor,
Provided with an operation control unit for performing various operations on the detection signal from the sensor and generating various control signals, and at the time of calibration, a current from the constant current source is passed between the electrodes of the chlorine generation flow cell to obtain a constant effective chlorine concentration. A standard solution is generated and the standard solution is supplied to the sensor for span calibration.

<Operation> The above-mentioned technical means operates as follows. That is, when a calibration start signal is applied, the flow path is switched, and a NaCl aqueous solution having a constant concentration is flowed from the salt water supply means to the chlorine generation flow cell at a constant flow rate. At the same time, a constant current is made to flow from the constant current source between the electrodes of this chlorine generation flow cell,
Cl ₂ is generated at the anode by electrolysis. This Cl ₂
Is a constant amount determined by the concentration of the NaCl aqueous solution, the flow rate and the electrolytic current. Since the anode is provided on the downstream side of the cathode, Cl ₂ generated at the anode is not reduced by the reverse electrolysis at the cathode. An aqueous solution containing a constant known amount of available chlorine generated in the chlorine generation flow cell is added to the sensor as a calibration standard solution, and span calibration is performed.

<Embodiment> An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram showing the basic configuration of the device of the present invention. In the figure, 1 is a flow path through which the solution to be measured M is supplied, 2 is a three-way solenoid valve that switches between the flow path 1 and the flow path 3 through which the calibration standard solution S is flown, and 4 is on the downstream side of the three-way solenoid valve 2. A constant flow pump provided, 5 is a residual chlorine sensor for measuring the effective chlorine concentration in the measurement liquid by a polarographic method, and 6 is a drainage channel of this sensor.

Reference numeral 7 denotes a tank for storing a NaCl aqueous solution having a constant concentration, and the NaCl aqueous solution from this tank is supplied to a chlorine generation flow cell 8 at a constant flow rate by a constant flow rate pump 4. 9 is a constant current source for supplying a constant current between the electrodes of the chlorine generation flow cell 8,
An arithmetic control unit 10 performs various arithmetic processes (including sensitivity adjustment) on the detection signal of the sensor 5, and gives a control signal to the constant current source 9, the three-way solenoid valve 2 and the like.

The chlorine generation flow cell 8 which is the main part of the apparatus of the embodiment of the present invention will be described with reference to the sectional view of FIG. In the figure, 801 is a body, and 802 is NaC with a constant concentration and a constant flow rate from the tank 7.
l Inflow port into which the aqueous solution flows, 803 is a flow path through which the NaCl aqueous solution flows, 804 is an outflow port, 805 is a cathode provided on the upstream side of the flow path 803, and 805a is a tip provided with, for example, platinum or the like. Metal inert electrode tip, 805
b is a platinum lead from this electrode tip.

Reference numeral 806 denotes an anode having the same structure as that of the cathode 805, which is provided on the downstream side of the cathode 805 at regular intervals, 806a is a metal inert electrode tip, and 806b is a platinum lead from this electrode tip.

Next, the operation of the apparatus of the embodiment of the present invention constructed as above will be described. At the time of measurement, the three-way solenoid valve 2 is switched to the flow path 1 side, and the measured liquid M is supplied to the sensor 5 by the constant flow rate pump 4. The detection output S ₁ from the sensor 5 is the calculation control unit 1
1 and is subjected to various kinds of arithmetic processing, and then output as an instruction output S ₂ .

At the time of calibration, when a calibration start signal is input, a NaCl solution having a constant concentration and a constant flow rate flows from the tank 7 into the chlorine generation flow cell 8 through the inlet 802. At the same time, three-way solenoid valve 2
Is switched to the chlorine generation flow cell 8 side, and a constant current is passed from the constant current generation source 9 to the electrodes 805 and 806. The concentration of Cl ₂ generated in the anode 806 by electrolysis is represented by the following formula.

c = η · {i / (F · G)} · {35.5 × 60 × 10 ⁶ } (1) where c: effective chlorine concentration [mg /] generated, η: generation efficiency, i: electrolysis Current [A] = [coul / sec],
F: Faraday constant, Q: NaCl flow rate [m
/ Min].

Since the anode 806 is provided on the downstream side of the cathode 805, Cl ₂ generated at the anode 805 is not reversely electrolyzed at the cathode 805, and N containing a certain known amount of available chlorine is always present.
The aCl aqueous solution is supplied to the sensor 5 from the chlorine generation flow cell 8.

Although the effective chlorine concentration of the aqueous solution first introduced to the sensor 5 is not stable, the automatic calibration is performed when it becomes stable.
An instruction output S ₂ c corresponding to the available chlorine concentration c is preset in the arithmetic and control unit 10. 'When is changed _{to, (S 2 c) / (} S 2 c' instruction output performs calibration _S 2 c to calibrate the sensitivity by) = G ... (2) comprising calculation was carried out G. All this work is done automatically.

It should be noted that the zero-point calibration is performed in a state where no current is passed from the constant current source 9 to the chlorine generation flow cell 8 prior to the above-mentioned sensitivity calibration.

<Effect of the Invention> According to the present invention, NaCl is stable and its concentration does not change with time.
The aqueous solution was stored, and when it was calibrated, it was electrolyzed to generate chlorine and a standard solution for calibration with a constant effective chlorine concentration was made, so that calibration of the residual chlorine meter could be automated. Also, the anode of the chlorine generation flow cell is provided on the downstream side of the cathode, and Cl ₂ generated at the anode is not reduced by the reverse electrolysis, and it is possible to always prepare a calibration standard solution having a constant effective chlorine concentration.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing an essential part of a device of the present invention, and FIG. 2 is a block diagram showing a basic configuration of the device of the present invention. 1: Flow path through which the liquid M to be measured flows, 2: Three-way solenoid valve, 3:
A flow path through which the calibration standard solution S flows, 5: residual chlorine sensor,
7: Tank for storing NaCl aqueous solution, 8: Chlorine generation flow cell, 803: Flow path, 805: Cathode, 806: Anode, 9: Constant current source, 10: Arithmetic control unit

Claims (1)

[Scope of utility model registration request] 1. A sensor for measuring an effective chlorine concentration in a liquid to be measured by a polarographic method, a salt water supply means for supplying an NaCl aqueous solution of a constant concentration at a constant flow rate, and a flow of the NaCl aqueous solution supplied from the salt water supply means. A flow path is provided, a metal inert cathode is provided at the upstream side of this flow path, and a metal inert anode is provided at the downstream side of this flow path, and a constant current is generated by flowing a constant current between the electrodes of this flow cell. Source, flow path switching means for switching the measured liquid side flow path and the chlorine generation flow cell side to connect to the sensor, and arithmetic control for performing arithmetic operation on detection signals from the sensor and generating various control signals. When a calibration is performed, a current is made to flow between the electrodes of the chlorine generation flow cell from the constant current generation source to generate a standard solution having a constant effective chlorine concentration, and this standard solution is supplied to the sensor. Automatic calibration function with residual chlorine meter to perform the bread calibration.