JPH0330850Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The present invention relates to an electrode in which an internal liquid is sealed in the electrode body, such as a diaphragm electrode for measuring dissolved oxygen. The present invention relates to an electrode that is compensated for and can perform stable measurements even when rapid temperature changes are applied to the electrode.

Problems to be Solved by Conventional Techniques and Ideas Conventionally, as a diaphragm electrode for measuring the amount of dissolved oxygen in a sample liquid, one having a structure as shown in FIG. 3, for example, is known.

That is, in FIG. 3, 1 is an electrode body formed by fixing an electrode outer tube 1b to a base 1a, and 2 is an electrode body provided to cover the tip opening of the electrode outer tube 1b of the main body 1 for transmitting dissolved oxygen gas. This gas permeable membrane 2 is attached to the tip of the electrode outer tube 1b by a ring-shaped diaphragm support 3. The tip of the base 1a of the main body 1 protrudes to the vicinity of the gas permeable membrane 2, and an indicator electrode 4 made of a noble metal such as gold or platinum is disposed at the tip of the protrusion 1c facing the gas permeable membrane 2. It is set up. In addition, 5 is the main body 1
6 is a counter electrode made of silver plated with silver chloride wrapped around the protrusion 1c, 7 is an indicator lead wire, 8 is a counter electrode lead wire, and 9 is dissolved oxygen. A connector, which is a joint for taking out the current generated by the concentration, 10
1 is a mounting screw for attaching the electrode to the electrode holder; 11 is an O-ring for sealing the electrode holder and the electrode; and 12 is a diaphragm holder for preventing the gas permeable membrane 2 from peeling off from the diaphragm support 3.

As mentioned above, when measuring dissolved oxygen using a diaphragm electrode, it is important that the positional relationship between the gas permeable membrane 2 and the membrane surface of the support electrode 4 is always constant in order to perform the measurement with good stability. This is a very important point.
When a temperature change is applied to the electrode, the internal liquid 5 and air within the electrode body 1 expand or contract, and pressure fluctuations occur within the electrode body 1, causing the gas permeable membrane 2 to move outward or inward. Due to the swelling, the positional relationship between the gas permeable membrane 2 and the membrane surface of the support electrode 4 cannot be maintained constant.

Therefore, as a means to compensate for such pressure fluctuations within the electrode body 1 and keep the pressure within the body 1 constant,
For example, as shown in FIG.
A hole 13 communicating with the gas phase 14 in the outer tube 1b is provided in the upper part of b.
A bellows 15 is disposed in the hole 13.

However, in the method of compensating pressure fluctuations within the electrode body 1 using the bellows 15 as described above, since the bellows 15 does not have sufficient elasticity, a sudden temperature change is applied to the body 1.
If there is a sudden pressure change inside, the bellows 15 cannot follow this pressure change, and the bellows 15 becomes a resistance, so it cannot fully compensate for the pressure change, and as a result, the contact between the gas permeable membrane 2 and the supporting electrode 4 membrane surface There is a drawback that the positional relationship changes, making it impossible to obtain a normal measurement signal. In this case, the gas permeable membrane 2 may come off from the diaphragm support 3 due to pressure fluctuations within the electrode body 1, and the internal liquid may leak, making measurement impossible.

As another means for compensating for pressure fluctuations within the electrode body 1, for example, as shown in FIG. However, there is a method in which only the portion below the hole 16 of the outer tube 1b is immersed in the sample liquid 17, or as shown in FIG. There is also a known method of inserting it into the body. however,
The former method has a problem in that when the entire electrode is immersed in the sample liquid, the sample liquid enters the electrode and alters the internal liquid, while the latter method has the disadvantage that the apparatus becomes complicated.

The present invention was developed in view of the above-mentioned circumstances.In electrodes such as diaphragm electrodes for measuring dissolved oxygen, in which internal liquid is sealed in the electrode body, sudden thermal changes are applied to the electrode, causing rapid pressure fluctuations within the electrode body. An object of the present invention is to provide an electrode that can reliably compensate for pressure fluctuations and maintain a constant pressure within the electrode body even when pressure fluctuations occur.

Means and operation for solving the problems That is, in order to achieve the above object, the present invention provides an electrode in which an internal liquid is sealed within the electrode body, one end of which communicates with the internal liquid within the electrode body, and the other end of which is connected to the internal liquid within the electrode body. A thin tube communicating with the outside of the electrode body is disposed in the electrode body, and this soft tube is filled with an internal liquid, so that pressure fluctuations within the electrode body are compensated for by the thin tube filled with the internal liquid. It is something.

In the electrode of the present invention, by adopting the internal structure of the electrode as described above, pressure fluctuations caused by rapid temperature changes in the measurement system can be compensated for through the thin tube filled with internal liquid. In other words, in the bellows method, the bellows acts as a resistance and cannot 100% follow sudden pressure fluctuations, and the positional relationship between the support electrode membrane surface and the gas permeable membrane becomes misaligned, resulting in a significant slowdown in response speed and a problem with indication fluctuations. In contrast, with the electrode of this invention, the internal liquid in the electrode body is connected to the test liquid via the internal liquid in the capillary and cannot create resistance, so the positional relationship between the gas permeable membrane and the support electrode membrane surface is shifted. 100% pressure compensation is achieved without any problems, allowing stable measurements. Since the test liquid communicates with the internal liquid in the electrode body via the internal liquid in the capillary, it does not enter the electrode and alter the quality of the internal liquid.

Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to the following Examples.

Embodiment FIG. 1 shows a diaphragm electrode for measuring dissolved oxygen according to an embodiment of the present invention. In FIG. 1, the same constituent parts as those of the electrode in FIG. 3 are given the same reference numerals, and the explanation thereof will be omitted.

In this electrode, a viscous internal liquid 5 is sealed in the electrode main body 1 without leaving any gas phase, and a thin tube 20 filled with the internal liquid is wound around the upper part of the protrusion 1c of the main body 1. The opening 21 at one end of the thin tube 20 is connected to the main body 1.
It communicates with the internal fluid 5 inside. Further, the base 1a of the main body 1 is provided with a pore 22 that communicates between the inside of the electrode outer tube 1b and the outside of the main body 1.
The other end of the capillary tube 20 is connected to the capillary tube 2, so that the other end opening 23 of the capillary tube 20 communicates with the outside of the electrode body 1. Note that a pair of internal liquid injection ports 24 are bored in the upper part of the electrode outer tube 1b, and these injection ports 2
4 is closed by a seal 25 to prevent internal liquid 5 from leaking.

The material of the thin tube 20 can be appropriately selected depending on the type of internal liquid, etc., and any material can be used as long as it does not alter the quality of the internal liquid, but it is particularly preferable to use a silicon tube. In addition, the thin tube 20
The length and diameter are also not limited and can be determined depending on the type of internal liquid and temperature change width, etc., but usually the content is 0.3 to 6.
It is preferable to use a material with an outer diameter of 1 to 8 mm and a length of 5 to 300 cm. Furthermore, the viscosity of the internal liquid 5 is preferably about 0.9 to 12 cps.

When assembling the above electrode, for example, after attaching the diaphragm support 3 to the tip of the electrode outer tube 1b, the internal liquid is injected from the internal liquid inlet 24 using a syringe or the like so that no gas phase remains inside the main body 1. , immediately seal 2
5 is attached, and the thin tube 20 is similarly filled with internal liquid using a syringe or the like.

The electrode of this embodiment has a thin tube 20 disposed inside the electrode body 1, one end of which communicates with the internal liquid 5 within the electrode body 1, and the other end of which communicates with the outside of the electrode body 1. By filling the internal liquid, pressure fluctuations caused by rapid temperature changes in the measurement system are reliably compensated for through the thin tube 20 filled with internal liquid, and the relationship between the gas permeable membrane 2 and the membrane surface of the indicator plate 4 is reduced. The positional relationship is always kept constant and stable measurement results can be obtained. Furthermore, since the internal liquid has viscosity, even if the sample liquid enters the thin tube 20, it is difficult for the sample liquid to permeate and diffuse into the internal liquid inside the thin tube 20. Moreover, since the thin tube is long, the test sulfur solution does not penetrate into the thin tube 20. It is reliably prevented from moving through the internal liquid inside the main body 1 and changing the quality of the internal liquid. Therefore, the entire electrode can be immersed in the sample liquid for measurement, which facilitates the measurement operation. Furthermore, since the internal liquid 5 is sealed so that no gas phase remains in the electrode body 1, pressure fluctuations due to air expansion can be eliminated, and the range of pressure fluctuations can be reduced. This can prevent the oxygen from dissolving in the internal liquid and delaying the return of the electrode to zero. That is, as shown in FIG. 3, in the electrode using the bellows 15, there is a gas phase 14 inside the main body 1, so that the pressure inside the main body 1 tends to fluctuate greatly due to air expansion due to temperature changes. Oxygen in the gas phase dissolves in the internal liquid, and the electrodes become sensitive to this oxygen, so there was a problem that it took a long time for the electrodes to return to zero, but this example solves this problem. It has been resolved.

In the above embodiment, the thin tube 20 is wound around the protruding portion 1c of the electrode body 1, but the manner in which the thin tube 20 is arranged is not limited to this. Further, a pore 22 was formed in the base 1a, and the other end of the thin tube 20 was connected to this pore 22, but the pore 22 was connected to the electrode outer tube 1.
b, and other configurations may be modified in various ways without departing from the gist of the present invention.

Hereinafter, the effects of the present invention will be specifically illustrated by experimental examples.

Example Dissolved oxygen in boiler water at a power plant was measured using an electrode of the present invention similar to that shown in FIG. 1 and a comparative electrode shown below for comparison. The results are shown in Figure 2. In addition, the outer diameter of the thin tube 20 is 1 mm,
In addition to using a silicon tube with an inner diameter of 0.5 mm,
The length was calculated from the volumetric expansion rate of water, and was set to 70 cm, which is a length that will not leak 10 ml of internal liquid even if the temperature rises by 40°C from the standard 25°C.

In Fig. 2, a shows the electrode according to the present invention. After calibrating the meter by exposing the electrode to the atmosphere at 20°C, the electrode is immediately immersed in boiler feed water with a water temperature of 40°C to measure dissolved oxygen. This figure shows the relationship between the meter reading and the elapsed time when the test was carried out. The meter indicated that the concentration had reached the control standard concentration of 7ppb or less within one hour. In the figure, b is a comparative experiment using electrodes for comparison to confirm the effect of the present invention. That is, a gas phase space is created above the internal liquid by closing the external opening of the electrode body without filling the internal liquid, and a porous gas permeable membrane is placed in place of a liquid leakage prevention seal to prevent air from flowing due to sudden temperature changes. An attempt was made to compensate for the pressure fluctuations caused by volumetric expansion using the gas permeable membrane described above, but as can be seen from the figure, it took 5.5 hours to reach the control standard concentration, making it clear that the effectiveness of this invention was achieved. It was done. The electrode according to the present invention could be used continuously for one year, but the electrode for comparison could only be used for 2 years.
After multiple uses, the gas permeable membrane peeled off from the diaphragm support, causing internal fluid leakage and rendering it unusable. From this fact, this method cannot compensate for pressure fluctuations caused by sudden temperature changes, and the position of the supporting electrode membrane and gas permeable membrane may shift, and the internal liquid may be removed from the gas phase above the internal liquid. It is expected that the response time is significantly slowed down due to factors such as reaching equilibrium while the electrode consumes the dissolved oxygen.

Effects of the Invention As explained above, the electrode of the present invention can reliably compensate for sudden pressure fluctuations within the electrode body, and can always maintain a constant pressure within the electrode body. Therefore, when the electrode of the present invention is configured as a diaphragm electrode, the positional relationship between the diaphragm and the support electrode can be kept constant at all times, and stable measured values can be obtained.

[Brief explanation of the drawing]

Figure 1 is a partial cross-sectional view showing a diaphragm electrode for measuring dissolved oxygen according to an embodiment of the present invention, and Figure 2 is a partial cross-sectional view showing dissolved oxygen in boiler feed water using the electrode of the present invention and an electrode for comparison in an experimental example. Figure 3 is a partial cross-sectional view of an example of a conventional diaphragm electrode for measuring dissolved oxygen, and Figures 4 and 5 are examples of conventional pressure fluctuation compensation means within the electrode. FIG. DESCRIPTION OF SYMBOLS 1... Electrode body, 20... Thin tube, 21... One end opening, 23... Other end opening.

Claims (1)

[Scope of utility model registration request] In an electrode with an internal liquid sealed inside the electrode body,
A thin tube having one end communicating with the internal liquid in the electrode body and the other end communicating with the outside of the electrode body is disposed in the electrode body, and this thin tube is filled with the internal liquid to cause pressure fluctuation inside the electrode body. An electrode characterized in that the electrode is configured to compensate for this by a capillary filled with the internal liquid.