JPS6243133B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dissolved oxygen analyzer equipped with a zero point and span point calibration device.

In order to detect not only oxygen concentration but also the concentration of gases or ions dissolved in a liquid, an electrode suitable for the substance to be detected or the properties of the liquid is buried in the liquid flow path or tank, and a predetermined voltage is applied to this electrode. The current value that flows when is applied is converted to the concentration of gas or ions. Such detection devices may produce different values even for liquids of the same concentration due to dirt on the electrode surface, subtle changes in the liquid flow path or tank, or even drift of the measuring instrument itself. May give instructions. In order to accurately measure this, it is common to measure a standard liquid and calibrate the meter by adjusting the reading on the meter to the concentration of this liquid.

When calibrating a dissolved oxygen analyzer, zero gas ( _N2 gas), which reduces the dissolved oxygen in the liquid to zero, is diffused into the liquid at the electrode to align the zero point, and then the dissolved oxygen concentration in the liquid is made constant. Span gas (N ₂ + O ₂
gas) was diffused into the liquid in the electrode area and aligned with the span point. The gases supplied into the liquid at the electrode part are called adjustment gases, and these adjustment gases are not only supplied to the sample liquid specially collected, but also to the liquid in the pipe where the detection electrode is installed. In many cases, instruments are calibrated by supplying directly to the
For example, the latter method is adopted for calibration work using water containing radioactivity at nuclear power plants and the like.

These calibrations are usually carried out manually, but water containing radioactivity as described above is difficult to handle, and calibrations must be performed more frequently in order to minimize the chance of exposure to radiation for operators. The number of meetings has decreased and is now only carried out once a week. In order to obtain accurate measurement values, it is desirable to calibrate once a day, but measurement results that are calibrated at such intervals are naturally unreliable and can lead to serious accidents. .

Furthermore, supplying the conditioning gas directly to the conduit in which the detection electrode is installed has the following disadvantages.

1. It is difficult to bring the adjustment gas to the same temperature as the measurement sample, and supplying this gas changes the temperature of the liquid, which tends to cause measurement errors due to temperature differences.

2. After the calibration work is completed, the adjustment gas tends to remain as bubbles in the flow path, causing errors during actual concentration measurements.

3. It is difficult to generate an adjustment gas containing bubbled water vapor, and the bubble-free integration of water vapor causes an error during calibration.

The present invention was made in order to eliminate the above-mentioned drawbacks, and the foamed liquid of the adjustment gas is made separately from the liquid flowing through the pipe, and only the foamed liquid is supplied to the electrode section. The purpose of the present invention is to provide a dissolved oxygen analyzer that calibrates a liquid as a concentration standard solution.

Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

The figure is a system diagram showing the configuration of a dissolved oxygen analyzer according to the present invention, in which 1 is a detection electrode, 2 is a dissolved oxygen transmission indicator, 3 is a calibration device for calibrating the transmission indicator, and 4 and 5 are sample liquid flow paths. 6 and 7 are solenoid valves that shut off the flow path of the calibration liquid;
1 is a solenoid valve for supplying zero gas, 9 is a solenoid valve for supplying span gas, 10 is a vapor-liquid balance tank for creating foamed liquid with zero gas or span gas, and 11 is a sintering valve for diffusing the gas that foams the liquid in the vapor-liquid balance tank. 12 is a pump, 13 is a constant temperature bath that keeps the temperature of the liquid passing through the corrugated pipe constant, and 14 is a control device that centrally controls all elements of the dissolved oxygen meter.

The operation of the dissolved oxygen analyzer according to the present invention configured as described above will be explained below using an example in which the sample liquid is water.

First, when measuring the oxygen concentration of sample water using a dissolved oxygen analyzer, solenoid valves 4 and 5 are opened, other solenoid valves 6, 7, 8, and 9 are closed, and of course, pump 12 is also stopped. , pure water is put into the vapor-liquid balance tank 10. Therefore, the sample water led from the main pipe system passes through the electromagnetic valve 4, is adjusted to a constant temperature by the constant temperature bath 13, and then passes through the detection electrode 1 and the electromagnetic valve 5 to be returned to the main pipe system. In this case, since the sample water at a constant temperature is supplied to the detection electrode 1, the measurement error due to the temperature difference is so small that it can be ignored, and the dissolved oxygen concentration is measured based on the value of the transmission indicator 2.

Then, to calibrate the transmission indicator 2 to the zero or span point, the solenoid valves 4 and 5 are closed, and conversely the solenoid valves 6 and 7 are opened, and at the same time the pump 1
Activate 2. Therefore, the pure water in the vapor-liquid balance tank will circulate in the order of pump 12 → solenoid valve 6 → constant temperature tank 13 → detection electrode 1 → solenoid valve 7 → gas-liquid balance tank 10, and in this case also, the constant temperature Pure water whose temperature is controlled in tank 13 passes through detection electrode 1 . In this way, at the beginning of circulating pure water, the sample water accumulated between the solenoid valves 4 and 5 mixes into the pure water, but it is very small compared to the amount of pure water in the vapor-liquid balance tank. Therefore, the effect on calibration is negligible.

Thus, to adjust the zero point of the transmission indicator 2, open the solenoid valve 8 and introduce zero gas to the sintered metal 11, and countless bubbles will pass through the sintered metal 11 and rise through the pure water. . During this time, zero gas is diffused into the pure water and dissolved oxygen is exhausted. After about 5 minutes, the oxygen gas in the gas-liquid balance tank is completely exhausted, and the detection electrode 1 is filled with sample water. An oxygen-free solution controlled at a temperature equal to is supplied. At this time, the control device 14 gives a signal for zero point calibration to the calibration device 3, causing the dissolved oxygen transmission indicator 2 to indicate zero.

After this zero point calibration is completed, the mode shifts to span point calibration mode. That is, the solenoid valve 8 is closed and the solenoid valve 9 is opened, and span gas is supplied to the vapor-liquid balance tank through this valve. In this case as well, when the span gas is continued to be supplied for about 5 minutes as described above, the vapor-liquid equilibrium tank is equilibrated with the span gas, and pure water having the target oxygen concentration passes through the detection electrode 1. At this time, a signal for span point calibration is given from the control device 14 to the calibration device 3 to instruct the dissolved oxygen transmission indicator 2 to a predetermined value.

In this way, pure water is accumulated in the vapor-liquid balance tank, gas corresponding to the target calibration point is supplied to this pure water and diffused, and when this pure water is in equilibrium with the gas, dissolved oxygen transmission instructions are issued. The meter can be calibrated. After performing such a calibration operation, the solenoid valves 6 and 7
When the solenoid valves 4 and 5 are closed and the solenoid valves 4 and 5 are opened, the state returns to the original state for measuring dissolved oxygen in the sample water. In this case as well, the amount of pure water that accumulates between the electromagnetic valves 4 and 5 is very small and does not affect the water quality of the main pipe system in any way.

In the above embodiment, the electromagnetic valves 4 and 6 and the electromagnetic valves 5 and 7 are each configured separately, but it is also possible to configure these valves with a single switching valve.

As is clear from the above explanation, according to the dissolved oxygen analyzer of the present invention, the adjustment gas, which is difficult to maintain at the same temperature as the sample, is once diffused into the liquid in the vapor-liquid equilibrium tank, and the liquid is kept in the same state as the sample. Since it can be passed through a constant temperature bath, errors due to temperature differences can be minimized. Further, since there is no need to supply the adjustment gas to the sample water for a long time, measurement errors due to absorption of the adjustment gas are negligibly small. Furthermore, since a completely saturated liquid of the adjustment gas can be created in the vapor-liquid balance tank, the calibration accuracy can be improved.

On the other hand, the solenoid valves, pumps, calibration equipment, etc. that make up the dissolved oxygen analyzer according to the present invention can all be centrally controlled, making it possible to automate the calibration operation and shorten the calibration work regardless of the properties of the sample liquid. Since the method is terminated at the end of the test, it is possible to improve the accuracy and reliability of oxygen concentration measurement, and it is particularly effective in eliminating the risk of radiation exposure to operators when applied to liquids containing radioactivity. be.

[Brief explanation of the drawing]

The figure is a system diagram showing the configuration of one embodiment of the dissolved oxygen analyzer according to the present invention. 1...Detection electrode, 2...Dissolved oxygen transmission indicator,
3... Calibration device, 4-9... Solenoid valve, 10... Gas-liquid balance tank, 11... Sintered metal, 12... Pump,
13... Constant temperature chamber, 14... Control device.

Claims (1)

[Claims] 1 In a dissolved oxygen analyzer that detects the oxygen concentration in a liquid by applying electricity to an electrode installed in the flow path of the test liquid, an adjustment gas is diffused into the liquid to keep the dissolved oxygen concentration constant. A gas-liquid balance tank for producing a saturated gas liquid; a switching valve for supplying only the saturated liquid to the electrode section; and a pump for circulating the saturated liquid through the electrode section; A dissolved oxygen analyzer characterized in that it is configured to calibrate a value.