JPS6358148A - Dissolved oxygen sensor - Google Patents

Abstract

PURPOSE:To obtain an oxygen sensor suitable for measuring the concentration of dissolved oxygen in a liquid for cultivating microorganisms, by making an end of an inner tube, made of lead glass, in contact with an oxygen permeating diaphragm curve inward in the shape so as to fasten a cathode plate while an anode is set into a bottomed cell allowed to pass an electrolytic liquid. CONSTITUTION:An inner tube 4 is made of lead glass and an end thereof in contact with an oxygen permeating diaphragm is made curve inward in the shape 41 so as to fasten a cathode plate 3 with the undersurface thereof curved. Then, a cylindrical anode 5 is set into a bottomed cell 9 allowed to pass an electrolytic liquid. The bottomed cell 9 is made up of a cell wall 91 also serving as support of the anode 5, an inner wall 21 of a cylinder 2 and a bottom plate 92 for stopping a space between the cell wall 91 and the inner wall 21.

Description

Detailed Description of the Invention A.6 Purpose of the Invention Industrial Field of Application This invention relates to a sensor for measuring the dissolved oxygen concentration in a liquid, particularly in a fermenter or other liquid where microorganisms are cultured. Suitable for measuring oxygen concentration.

2. Description of the Related Art Sensors are known that measure the concentration of dissolved oxygen in a liquid using a galvanic current generated by an electrochemical reaction caused by oxygen that has diffused and permeated through an oxygen-permeable diaphragm.

The principle of such a sensor is as follows.

In this way, a current proportional to the partial pressure of oxygen is generated.

A specific example of the structure of a dissolved oxygen sensor using the above principle will be explained with reference to FIG.

Inside a cylindrical body 2 having an oxygen permeable diaphragm 1 fixed to its bottom, there is a glass inner tube 4 having a canned plate 3 fixed to its end.
is inserted to a position where it contacts the oxygen permeable diaphragm, an anode 5 is placed between the cylinder and the inner tube, and an electrolyte 8 is filled in the cylinder. The conductor 6 is connected to the cathode plate 3.
, a conductor 7 is connected to the anode 5 and led to an ammeter.

Platinum is used for the cathode plate, and lead is used for the anode. The cathode plate 3 is fixed to the cut surface of a glass tube 4 as shown in FIG. 4, and the anode 5 is formed by winding a lead wire around the glass tube in a spiral shape. There is.

When the tip of such a sensor is inserted into the liquid to be measured, dissolved oxygen in the liquid diffuses and permeates through the oxygen permeable diaphragm.
An electrochemical reaction according to the above formula (1) occurs, and a galvanic current flows between the cathode and the anode.

If the relationship between the amount of galvanic current and the amount of dissolved oxygen in the liquid is measured in advance, the amount of dissolved oxygen in the liquid can be determined from the amount of galvanic current.

Problems to be Solved by the Invention When attempting to use a dissolved oxygen sensor to measure the dissolved oxygen concentration in a fermenter or other liquid in which microorganisms are cultured, it is necessary to heat sterilize the sensor in advance. Conventional dissolved oxygen sensors such as these have problems in terms of performance and durability when used under conditions where heat sterilization is repeated.

That is, the measured values for the same sample solution fluctuated each time heat sterilization was repeated, and accidents such as falling off of the cathode plate and damage to the oxygen permeable diaphragm were likely to occur.

The present invention improves the shortcomings of conventional dissolved oxygen sensors and provides a dissolved oxygen sensor suitable for measuring the dissolved oxygen concentration in fermenters that require heat sterilization and other liquids in which microorganisms are cultured. The purpose is to

1. Means for Solving the Problems in the Structure of the Invention The dissolved oxygen sensor according to the present invention consists of a cylindrical body with an oxygen permeable diaphragm fixed to the bottom, and a platinum cathode plate fixed to the end thereof. The tube is inserted until it touches the oxygen permeable diaphragm, a lead anode is placed between the cylinder and the inner tube, and the cylinder is filled with an electrolyte. In a sensor that measures the dissolved oxygen concentration in a liquid that is in contact with the outside by using a galvanic current flowing between two poles, a cathode and an anode, the inner tube is made of lead glass, and the end that contacts the oxygen permeable diaphragm is placed inside. A cathode plate having a curved lower surface is fixed thereto, and a cylindrical anode is installed in a bottomed compartment through which an electrolytic solution can flow.

This will be explained in detail with reference to FIGS. 1 and 2. However, the explanation of the parts common to the conventional dissolved oxygen sensor shown in FIG. 4 will be omitted.

The inner tube 4 is made of lead glass, and its end in contact with the oxygen permeable diaphragm has an inwardly curved shape 41, and the cathode plate 3 having a curved lower surface is fixed thereto.

Then, the anode 5 formed into a cylindrical shape is placed in a bottomed compartment 9 through which an electrolytic solution can flow.

In FIG. 1, a bottomed compartment 9 is formed by a compartment wall 91 that also serves as a support for the anode, an inner wall 21 of the cylinder 2, and a bottom plate 92 that closes between the compartment wall 91 and the inner wall 21. , second
As shown in the figure, a bottomed compartment 9 formed by compartment walls 91 and 93 and a bottom plate 92 may be fixed inside the cylinder separately from the cylinder 2.

Further, although the anode 5 is installed on the compartment wall 91 side in FIG. 1, it may be installed on the inner wall 21 side of the cylinder body 2.

Although an anode support may be provided separately as a member constituting the bottomed compartment, the structure is easier to simplify if it is also used as a member of the bottomed compartment.

The shape of the bottomed compartment 9 is not limited to that shown in the drawings, as long as it has a structure that can prevent the anode reaction product from falling onto the surface of the oxygen permeable membrane.

The shape of the anode installed in the bottomed compartment is not particularly limited, and any shape such as a spiral shape or a cylindrical shape can be used, but a shape that is difficult to break, such as a cylindrical shape, is preferable.

If the inner tube 4 is a lead glass tube, lead glass has a coefficient of thermal expansion close to that of platinum, so that the cathode plate is prevented from falling off due to repeated heat sterilization.

The reason why the end of the inner tube is curved inwardly 41 and the cathode plate with a curved lower surface is fixed thereto is that the part in contact with the oxygen permeable diaphragm has an edge shape like a conventional dissolved oxygen sensor. This is because, if it is heated, partial stress is applied to the oxygen permeable diaphragm, and as the membrane expands and contracts due to repeated heat sterilization, the oxygen permeable diaphragm is likely to be damaged.

The reason why the anode 5 is installed in the bottomed compartment 9 through which the electrolytic solution can flow is that the reaction product [P b (OH) 2 ] generated at the anode due to the reaction of formula (1) is separated from the anode. This is to prevent f from falling and depositing on the inner surface of the oxygen permeable diaphragm and adversely affecting the measured values.

Another specific example of the dissolved oxygen sensor according to the present invention is shown in FIG.

A cylindrical anode support 94 (also serving as a wall of the bottomed compartment) on which a cylindrical anode is installed is supported inside the cylinder 2 by a support 10 .

The support 10 has a structure that allows the electrolyte to flow therethrough, and uses, for example, a left-hand washer with a small hole.

The inner tube 4 having the structure according to the present invention and having a cathode plate fixed to the end thereof penetrates the inside of the anode support 94 and passes through the oxygen permeable membrane through the support 11 (having a shape that allows the electrolyte to flow therethrough). It is inserted to the position where it touches l.

The bottomed compartment 9 is formed of a silicone material with a pedestal 12 between the lower part of the outer wall of the anode support 94 and the inner wall 21 of the cylinder body 2.
It is formed by closing with a ring 13.

In the figure, the anode 5 is guided to an ammeter (not shown) by a conductor 7, but if the anode support 94, support 10, and cylinder 2 are made of conductive material,
The anode 5 may be connected to the ammeter via the anode support 94, the support 10, and the cylinder 2 without providing the conductor 7.

The electrolyte can flow through the support 10 and the anode support 94 to the cathode.

Comparative Test When the dissolved oxygen sensor of the present invention shown in Fig. 1 and the conventional dissolved oxygen sensor shown in Fig. 4 (however, the anode is cylindrical) are repeatedly heat sterilized, the results are the same. A test was conducted to see if the measured values for the sample solution showed a constant value. The results are shown in Table 1.

Each time, the sensor was heated with steam at 1.2 atm and 120°C for 30 minutes, and then cooled to around 35°C before use.

Table 1 As is clear from Table 1, the reliability of the measured values of conventional sensors is lost after heat sterilization and reuse two to three times.
The sensor of the present invention can withstand 6 11 uses.

This is due to the overall effect of the improvements made by the present invention.

Effects of the Invention A dissolved oxygen sensor that provides stable measured values and is difficult to damage even after repeated heat sterilization is obtained, and is particularly suitable for measuring the dissolved oxygen concentration in fermenters and other liquids in which microorganisms are cultured. It is.

[Brief explanation of the drawing]

1, 2, and 3 are model diagrams showing the specific structure of the dissolved oxygen sensor of the present invention, and FIG. 4 is a model diagram showing the specific structure of the conventional dissolved oxygen sensor. l...Oxygen permeable diaphragm, 2...Cylinder, 21...Cylinder inner wall 3...Cathode plate, 4...Glass inner tube, 4
1... End of inner tube (inwardly curved shape), 5...
Anode, 6, 7... Conductor, 8... Electrolyte, 9...
- Bottomed compartment, 91.93... Compartment wall, 92... Compartment bottom plate, 94... Anode support io, ti... Support, 12... Pedestal, 13... 0 ring

Claims (1)

[Claims] An inner tube with a platinum cathode plate fixed to the end is inserted into the cylindrical body with an oxygen permeable diaphragm fixed to the bottom until it touches the oxygen permeable diaphragm, and the inner tube is inserted between the cylindrical body and the inner tube. It has a structure in which a lead anode is placed in the cylindrical body and an electrolytic solution is filled in the cylinder, and the dissolved oxygen concentration in the liquid that is in contact with the outside of the oxygen permeable diaphragm is distributed between the cathode and the anode. In a sensor that measures by a flowing galvanic current, the inner tube is made of lead glass, the end in contact with the oxygen permeable diaphragm is curved inward, and a cathode plate with a curved lower surface is fixed thereto. A dissolved oxygen sensor characterized in that the anode is installed in a bottomed compartment through which an electrolyte can flow.