JPH048360Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a device for determining the deterioration state of an electrode for measuring dissolved oxygen concentration used for water quality management of industrial wastewater, urban sewage, etc.

[Conventional technology]

BACKGROUND ART Dissolved oxygen concentrations are measured for purposes such as monitoring water quality in treatment facilities for industrial wastewater and urban sewage, as well as in swamps and rivers. To measure this dissolved oxygen concentration, for example, an electrode for measuring dissolved oxygen concentration (hereinafter referred to as a DO electrode) as shown in FIG. 3 is used.

This DO electrode rod 1 has a detection end 2 at its tip.
is immersed in a liquid to be measured 3 such as sewage. The dissolved oxygen concentration of the liquid to be measured 3 detected by the detection end 2 is sent as a current value to the DO meter 4 and recorded by the recording device 5. As shown in an enlarged view in FIG. 4, this detection end 2 accommodates an electrolyte 7 in contact with an electrode 6, and a diaphragm 8 separates the electrolyte 7 from the liquid to be measured 3. .

[Problem that the invention attempts to solve]

When the DO electrode rod 1 is used to continuously measure the dissolved oxygen concentration DO over a long period of time, the electrode 6, diaphragm 8, electrolyte 7, etc. deteriorate, and the response speed of the electrode decreases. FIG. 5 shows an example of this reduction in response speed. In other words, as shown in curve A, the response speed of the DO electrode rod 1, which was designed to have a response rate of 90% in a measurement time of 30 seconds, changes as the dissolved oxygen concentration DO is continuously measured. A
→Decrease from B→C. Due to such deterioration, conventional maintenance work such as replacing the diaphragm and electrode solution and inspecting the electrodes has been performed every one to three months.

However, the degree of progress of deterioration inside the electrode is greatly influenced by the properties of the liquid to be measured. For this reason, the maintenance period that was roughly set was not enough to provide adequate support, and the response speed sometimes dropped significantly during measurements, making measurements impossible.

In order to solve these problems caused by DO electrode deterioration, the present invention detects the progress of electrode deterioration at an early stage by periodically checking the response of the electrode while measuring dissolved oxygen concentration. The purpose of the present invention is to provide a device that can notify a measurer of maintenance time.

[Means for solving problems]

In order to achieve the purpose of the deterioration determination device of the present invention, a bowl-shaped container is attached to an electrode for measuring dissolved oxygen concentration immersed in a liquid to be measured, and air is pumped into the bowl-shaped container to drain the air. A pump is connected to the bowl-shaped container via an air tube, an air supply valve is arranged in the middle of the air tube, and a signal for starting/stopping the air pump and opening/closing the air supply valve is transmitted. A timer circuit for generating the air is connected to the air supply valve, and a microcomputer is provided for calculating the response speed based on the dissolved oxygen concentration signal.

〔Example〕

Hereinafter, the features of the present invention will be specifically explained with reference to embodiments shown in the drawings.

FIG. 1 shows the configuration of equipment in the deterioration determination apparatus of this embodiment. Components corresponding to those shown in FIGS. 3 and 4 are designated by the same reference numerals in FIG. 1.

In this deterioration determination device, a DO electrode rod 1 is attached to a bowl-shaped container 11 immersed in a liquid 3 to be measured. Then, the DO concentration signal obtained by amplifying the detection signal from this DO electrode rod 1 is sent from the DO meter 4 to the microcomputer 12.
The microcomputer 12 calculates the response speed of the electrode based on the DO concentration signal, and outputs the calculation result to the recording device 5. Furthermore, depending on the value of the calculation result, a maintenance signal is output to the alarm device 13. Also,
To periodically check the electrode response speed,
A check command is output to the microcomputer 6. Furthermore, an air tube 14 connected to the inside of the bowl-shaped container 11 is connected to an air pump 15,
A three-way air valve 16 is interposed in the middle of the air tube 14, and a timer circuit 17 is connected to the air pump 15 for outputting a command to start or stop the air pump 15 that injects air into the bowl-shaped container 11.
is connected to. This timer circuit 17 is also connected to the three-way air valve 16.

Next, the operation of this deterioration determination device will be explained to clarify the effect of the present invention.

Normal DO measurement is performed as follows.

The DO concentration of the liquid to be measured 3 is determined by the detection end 2 of the DO electrode rod 1 attached to the bowl-shaped container 11 immersed in the liquid.
detected by. This DO concentration detection signal is amplified in the DO meter 4 and transmitted to the microcomputer 12 as a current or voltage signal. The signal is converted into a DO concentration value in the microcomputer 12, and the result is sent to the recording device 5.
recorded in

When performing this normal measurement, the bowl-shaped container 1
1 is filled with the liquid to be measured 3 because the three-way air valve 16 connected to the air tube 14 is open to the atmosphere.

On the other hand, when the preset DO electrode response speed check time comes, the next step is taken to perform the check operation.

From the timer circuit 17, three-way air valve 1
6, a flow path switching command, a start command to the air pump 15, and an electrode response speed calculation command to the microcomputer 12, respectively.

This output starts the air pump 5 and pumps air into the bowl-shaped container 11. the result,
The liquid to be measured 3 that has been filled in the bowl-shaped container 11 until now
is expelled to the outside of the bowl-shaped container 11, and the detection end 2
is exposed to air. As a result, the DO concentration signal begins to rise rapidly and exceeds the full scale of the DO meter 4.

At this time, the microcomputer 12 selects two preset points as shown in FIG.
DO concentration, e.g. DO concentration set point P ₁ (15mg/)
The time T ₂ during which the detection signal travels between and the DO concentration set point P ₂ (10 mg/) is measured, and this is taken as the response time of the DO electrode.

The response time at the start of use, which is determined for each commercially available electrode, is 90%/30 seconds.
The deterioration limit response time _T0 is set in advance to be slightly longer than the response time between the set DO concentrations corresponding to 95%/3 minutes, that is, the initial electrode response time _T1 .
This is compared with the response time _T2 during check measured as described above.

When the response time T ₂ shows a value larger than the deterioration limit response time T ₀ , it is determined that the deterioration of the detection end portion of the DO electrode rod 1 (diaphragm 8, electrode 6, electrolyte 7 in FIG. 4) has progressed significantly. , sends a signal to the alarm device 13. In response to receiving this signal, the alarm device 13 issues an alert regarding the need for maintenance work.

When a certain period of time has elapsed from the time set for the check, the three-way valve 16 is switched, the air pump 15 is stopped, and the timer circuit 17 is reset. As a result, the air in the bowl-shaped container 11 is released into the atmosphere from the three-way valve 16, and the liquid to be measured instead enters the bowl-shaped container 11, and normal DO concentration measurement is resumed.

Thereafter, the above operation is repeated every time the DO electrode response check time comes. In this way, it is possible to grasp the deterioration state of the DO concentration detection electrode during use.

[Effects of the invention] As explained above, when the deterioration determination device of the present invention is used, the response speed of the DO electrode is calculated during the period of measuring the dissolved oxygen concentration, and the deterioration status can be quantitatively detected at an early stage. This allows the operator to be informed of the timing of maintenance work. Furthermore, since maintenance work is performed in accordance with the properties of the liquid to be measured, it is possible to obtain stable DO measurement data and reduce maintenance costs.

[Brief explanation of the drawing]

FIG. 1 shows an example of a deterioration determination device according to the present invention, and FIG. 2 is a graph illustrating changes in response speed according to deterioration. Furthermore, Fig. 3 shows a conventional electrode for measuring dissolved oxygen concentration, Fig. 4 shows an enlarged view of its detection end, and Fig. 5 shows the response speed of the electrode for measuring dissolved oxygen concentration as it deteriorates. It is a graph explaining the change.

Claims (1)

[Scope of utility model registration request] A bowl-shaped container is attached to the electrode for measuring dissolved oxygen concentration immersed in the liquid to be measured, and an air pump that pumps air into the bowl-shaped container to drain water is connected to the bowl-shaped container via an air tube. An air supply valve is arranged in the middle of the air tube, and a timer circuit is connected to the air supply valve to issue a signal for starting/stopping the air pump and opening/closing the air supply valve. A deterioration determination device for an electrode for measuring dissolved oxygen concentration, characterized in that it is provided with a microcomputer that calculates its response speed based on an oxygen concentration signal.