JPH06242057A - Dissolved oxygen sensor - Google Patents

Abstract

PURPOSE:To allow automatic cleaning and calibration by providing a driver for moving a dissolved oxygen sensor up and down to immerse the sensor into a liquid to be measured or lifting the sensor upto the air, a holder for containing the sensor lifted upto the air, a sequencer, etc. CONSTITUTION:The dissolved oxygen sensor 1 is immersed, at the tip thereof, into a liquid 2 to be measured and a current proportional to the partial pressure ratio of oxygen dissolved in the liquid to be measured flows between electrodes arranged in the sensor 1. An electrical signal is delivered on a cable 3 to a converter 3 where the signal is converted into a unity signal representative of a predetermined current value which is outputted through a control section 5 having a sequencer 5a. A holder section 6 functions at the time of automatic cleaning/calibration where the bottom of the holder 6 is openable by means of a bottom cover. Cleaning water or liquid medicine is fed from a metric tank to be held therein for a predetermined time and then it is discharged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dissolved oxygen sensor with an automatic calibration function for measuring the amount of dissolved oxygen existing in a liquid to be measured.

[0002]

2. Description of the Related Art Generally, a dissolved oxygen sensor has a change with time due to a substance attached to an electrode portion. Therefore, the sensor is regularly cleaned and calibrated to maintain its performance. Regarding the cleaning, there is known Japanese Utility Model Laid-Open No. 58-14280 in which a cleaning mechanism such as a cleaning timer is added so that the sensor is automatically submerged in the liquid to be measured. Each time, the sensor is manually pulled up from the liquid to be measured.

[0003]

Generally, in normal calibration, the dissolved oxygen sensor is pulled up from the liquid to be measured into the air to remove water, and the span is adjusted based on a known value of the oxygen content of the air. However, dissolved oxygen sensors are often used for controlling activated sludge treatment processes in sewage treatment and industrial wastewater treatment facilities. In such processes, for example, cleaning every few days, every 1-2 months. It was necessary to calibrate the equipment, and on-site maintenance required a lot of man-hours. The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a dissolved oxygen sensor that can be automatically cleaned and calibrated.

[0004]

In order to achieve the above object, the present invention provides a dissolved oxygen sensor for detecting the amount of dissolved oxygen in a solution to be measured, and a dissolved oxygen sensor which is moved up and down to provide the solution to be measured. A driving device for submerging or pulling in air, a holder in which the dissolved oxygen sensor pulled in air is housed and a lid at the bottom is formed to be openable and closable, an injection device for injecting a cleaning liquid into the holder, and the drive The apparatus is provided with a sequencer that drives the opening / closing operation of the lid of the holder and the injection apparatus according to a predetermined program, and is configured to clean and calibrate the dissolved oxygen sensor according to the program of the sequencer.

[0005]

The dissolved oxygen sensor is pulled up from the liquid to be measured by the driving device, and the holder accommodates the pulled up sensor. After that, the bottom lid of the holder is closed, the cleaning liquid is introduced into the holder for cleaning, and then the bottom lid is opened to discharge the cleaning liquid, and the calibration is performed in air. The sequencer commands this series of operations according to a predetermined program.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic explanatory view of a dissolved oxygen sensor showing an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes, for example, a known diaphragm galvanic dissolved oxygen sensor (hereinafter, simply referred to as a sensor). At least the tip of this sensor 1 is submerged in the liquid to be measured 2.
A current proportional to the partial pressure ratio of the dissolved oxygen in the solution to be measured flows between the electrodes arranged inside. This electric signal is transmitted to the converter 4 via the cable 3, converted into a unified signal of 4 to 20 mA, for example, and output via the control unit 5 having the sequencer 5a.

Reference numeral 6 denotes a holder portion which functions at the time of automatic cleaning or automatic cleaning / calibration, and is configured as shown in FIG. 2, for example.
In FIG. 2, 10 is a wash water tank containing a wash liquid such as tap water or a chemical solution, 11 is a measuring tank for storing a fixed amount of wash water in the wash water tank 10, and 6a is an air cylinder Cy ₁ containing the sensor _1. , Cy ₂ are provided. AS ₁ and AS ₂ are air sets, SV _{1 to} SV ₃ are solenoid valves _, CHV is a check valve _{, and} G is a lid provided at the lower end of the holder. A certain amount of liquid is supplied from the measuring tank 11 stored in the wash water tank to the check valve (C
It is injected into the holder 6a via HV).

The bottom of the holder 6a is formed so as to be openable and closable by a bottom lid G, which holds the cleaning water or the chemical liquid injected from the measuring tank 11 and discharges it after a predetermined time elapses.
The sequencer 5 has a predetermined operation sequence for these operations.
It is performed based on the signal C based on the command from a and the answer back signal D from the holder side. By this operation, the sensor 1 is pulled up or pulled down from the liquid to be measured and submerged in the cleaning liquid for a predetermined time for cleaning.

In the illustrated example, the automatic cleaning and automatic cleaning / calibration modes are switched by the trigger signal A due to the time-up of the timer incorporated in the converter 4, and the control unit 5
Sends a command signal B to the converter 4 to suspend (hold) the measurement mode. FIG. 3 shows a time chart of the signals A and B during automatic cleaning and the state of the sensor. In the figure, a signal A has a cycle T _WASH at the time of automatic cleaning, and a signal B shows a hold operation.

That is, at the same time when the trigger signal A is issued, the signal corresponding to the dissolved oxygen amount of the measured liquid is held,
The sensor 1 is pulled up from the liquid to be measured, stored in the holder 6a, and the lid G is closed. Then, after washing for t _WASH, the lid G is opened and the sensor 1 is submerged in the liquid to be measured 2. Next, after the relaxation time t ₁ , the hold signal is released and the measurement is restarted. In this example, the sensor up / down time t ₀ is included at the beginning of the cleaning time t _{WASH and} the beginning of the relaxation time t ₁ . FIG. 4 shows a time chart of signals A ′ and B during automatic calibration and the state of the sensor. In the figure,
The signal A has a period T _cal at the time of automatic calibration, and the signal B
Indicates a hold operation.

That is, at the same time when the trigger signal A'is generated, the signal corresponding to the dissolved oxygen amount of the measured liquid is held, the sensor 1 is pulled up from the measured liquid, and the holder 6a is held.
And the lid G is closed. Then, after the waiting time t _{2 has} elapsed, the automatic calibration is performed for the time t _cal1 and the lid G is opened to open the sensor 1.
Is submerged in the solution to be measured. Next, after the relaxation time t ₃ , the hold signal is released and the measurement is restarted. In this example, the sensor up / down time t ₀ is included at the beginning of the cleaning time t _{cal and} the beginning of the relaxation time t ₃ .

[0012] Figure 5 combines automatic cleaning and automatic calibration
This shows the time chart of the signals A and A'B at the time.
The invention mainly uses this combination for automatic cleaning and calibration.
Be done. In this example, automatic cleaning is followed by calibration.
After a lapse of a predetermined time, only automatic cleaning is performed,
After a lapse of time, automatic cleaning and calibration are performed again. Note that automatic washing
How many times to wash between cleaning / calibration and automatic cleaning / calibration T_cal= N × T_WASH Can be set arbitrarily.

Next, the holder for accommodating the sensor is shown in FIG.
Will be explained. FIGS. 6A and 6B are diagrams showing details of the holder. FIG. 6A is a state in which the lid G is open and the sensor is submerged in the liquid to be measured 2, and FIG. 6B is an air cylinder Cy.
₂ shows a state in which the sensor is pulled up by ₂ and the cover G is closed, and the cylinder Cy ₂ is fixed by the stopper st pushed out by the air cylinder Cy ₁ . L is a liquid tank that temporarily holds the cleaning liquid and performs cleaning.

FIG. 7 is a diagram showing details of the measuring tank.
In the figure, the liquid E in the wash water tank 10 enters the inside of the measuring tank 11 through the check valve K _{T at the} bottom of the measuring tank, and when the liquid level E ₁ reaches the lower surface of the tube B, the atmosphere opening port at the upper part of the tube B until then. The air in the measuring tank 11 coming out of B ₁ is sealed and the rise of the liquid level E ₁ stops.

In this state, when the air pressure is applied to the tube B, the check valve _KT is closed and the liquid E in the measuring tank is pressure-fed from the tube A. The volume of the difference H between the lower ends of the tubes B and A is the amount of liquid delivered once.

Next, the operation of FIG. 6 will be described. During the measurement, for example, when the signal A is emitted due to the time-up of the timer built in the converter 4, the sensor 1 submerged in the liquid to be measured 2 receives the air pressure supplied from the SV ₂ from the cylinder Cy ₁ As it rises, it is pulled up to the position shown in FIG. 6B, separated from the liquid to be measured 2 and sealed with the lid G. At the same time, the cylinder Cy ₁ is fixed by the stopper st using the cylinder Cy ₂ by the air pressure supplied from SV ₃ .

Next, the SV ₁ is opened and the cleaning liquid measured in the measuring tank 11 is pressure-fed to the holder 6a by the air pressure supplied from the air pressure source (not shown). The air pressure that pressure-feeds the cleaning liquid is continuously fed even after the liquid is fed, and the sensor 1 is cleaned by stirring the cleaning liquid. After this cleaning operation, SV ₁ is closed and cover G is opened to discharge the cleaning liquid. After this, the calibration operation t _cal is performed after a waiting time of t ₁ .

Next, the flow path of SV ₃ is switched, the cylinder Cy ₁ is driven, the stopper is released, and the cylinder Cy ₁ is lowered. Then, the time t ₀ for lowering the sensor to the liquid to be measured.
The dissolved oxygen amount is measured after a relaxation time t ₃ including the above. Next, only the automatic cleaning is performed after a lapse of a predetermined time, and further the automatic cleaning / calibration operation is performed after a lapse of the predetermined time. The number of times automatic cleaning is performed between automatic cleaning and calibration can be set arbitrarily according to each application.

[0019]

As described above in detail with the embodiments, according to the present invention, cleaning is performed with a cleaning liquid prior to calibration. Further, since the cleaning is performed after pulling it up into the holder, tap water or other optimum chemical liquid can be used as the cleaning water, so that more accurate calibration is possible. In addition, the number of times automatic cleaning is performed between automatic cleaning and calibration can be arbitrarily set according to each application, which enables fine control.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a drive device and a holder.

FIG. 3 is a time chart of signals A and B during automatic cleaning.

FIG. 4 is a diagram showing a time chart of signals A and B during automatic cleaning / calibration.

FIG. 5 is a time chart diagram when automatic cleaning and automatic calibration are combined.

FIG. 6 is a detailed explanatory view of a holder portion.

FIG. 7 is a detailed explanatory view of a lightweight tank.

[Explanation of symbols]

 1 Dissolved oxygen sensor 2 Liquid to be measured 3 Cable 4 Converter 5 Controller 5a Sequencer 6 Holder 6a Holder G Lid 11 Weighing tank

Claims (1)

[Claims] 1. A dissolved oxygen sensor for detecting the amount of dissolved oxygen in a liquid to be measured, a drive device for moving the dissolved oxygen sensor up and down to submerge the liquid in the liquid to be measured or pull it up into the air, and A holder in which the lifted dissolved oxygen sensor is housed and a lid at the bottom is formed so as to be openable and closable, an injection device for injecting a cleaning liquid into the holder, the drive device, an opening / closing operation of the lid of the holder and an injection device A dissolved oxygen sensor, comprising a sequencer driven according to the above, and configured to clean and calibrate the dissolved oxygen sensor according to a program of the sequencer.