JPH05322837A - Galvanic cell oxygen sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a galvanic battery type oxygen sensor that is stable and can be used for a long period of time without deterioration in performance even in an atmosphere having an oxygen concentration of 0%. [Constitution] Positive electrode 5 comprising a catalytic electrode for electrolytic reduction of oxygen
In a galvanic cell type oxygen sensor basically composed of a negative electrode 8 made of lead, an electrolytic solution 7, a diaphragm 4, and a container 7, the positive electrode 5 has a function as an electrolytic solution holder and a positive electrode current collector. Carbon that has the function of the body is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a galvanic cell type oxygen sensor. More specifically, the present invention relates to a galvanic cell type oxygen sensor basically composed of a positive electrode composed of a catalytic electrode effective for electrolytic reduction of oxygen, a negative electrode composed of lead, an electrolytic solution, a diaphragm and a container.

[0002]

2. Description of the Related Art Galvanic battery type oxygen sensors are small and lightweight, operate at room temperature, and are inexpensive, so they are used for medical checkups such as check for oxygen deficiency in holds and manholes, anesthesia machines, and respirators. It is used in a wide range of fields such as the detection of oxygen concentration in equipment.

The galvanic cell type oxygen sensor is usually basically composed of a positive electrode composed of a catalyst electrode, a negative electrode composed of lead, an electrolytic solution, a diaphragm and a container.

Conventionally, a positive electrode made of a metal effective for electrolytic reduction of oxygen, for example, gold integrated with a diaphragm, and a porous cover having a function as an electrolytic solution holder and a function as a current collector. The positive electrode and the current collector are constituted by the bon and the metal wire for current collection made of titanium wire.

[0005]

However, when the conventional oxygen sensor is left in an atmosphere having an oxygen concentration of 0% for a long time, there is a problem that lead is deposited on the gold of the positive electrode and the output is reduced. The present invention has been made to solve such a problem, and an object thereof is to achieve an oxygen concentration of 0.
%, The performance does not deteriorate even in the atmosphere,
It is intended to provide a galvanic battery type oxygen sensor which is stable and can be used for a long period of time.

[0006]

Therefore, in the present invention, by using a carbon as the positive electrode without using a metal effective for the electrolytic reduction of oxygen, such as gold, the above-mentioned problems can be solved. Is to solve.

[0007]

In the atmosphere, the lead of the negative electrode of the oxygen sensor maintains the equilibrium of Pb = Pb ⁺⁺ + 2e with the electrolytic solution. However, when the atmosphere of 0% oxygen concentration is left for a long time, the gold of the positive electrode and the lead of the negative electrode are kept near the same potential for a long time, and in the conventional oxygen sensor, the lead in the electrolyte is the positive electrode. It deposits on gold, resulting in a slow oxygen sensor response and unstable output. The reason why lead is deposited on gold is not clear, but it is presumed that it is preferentially deposited on gold due to the difference in catalytic ability between gold and lead.

The oxygen sensor of the present invention does not use a metal having a large catalytic activity such as gold as the positive electrode, but has a small catalytic capacity.
The use of bon prevents the deposition of lead on the positive electrode. Here, the carbon as the positive electrode is
The type and shape are not particularly limited, but it is convenient to use a porous carbon because it has both an electrolyte holding function and a current collecting function.

[0009]

EXAMPLES The present invention will be described below with reference to preferred examples. FIG. 1 shows a sectional structure of a galvanic cell type oxygen sensor according to an embodiment of the present invention. In the figure, 1 is an ABS resin inner lid, 2 is an O-ring, 3 is a porous polytetrafluoroethylene film, 4 is a diaphragm made of tetrafluoroethylene hexafluoropropylene copolymer film, and 5 is carbon. Consisting of a positive electrode,
6 is a lead wire made of titanium wire, 7 is an electrolytic solution made of a mixed aqueous solution of acetic acid, potassium acetate and lead acetate, 8 is a negative electrode made of lead, 9 is a holder body made of ABS resin, and 10 is AB.
It is a holder lid made of S resin. The holder-body 9 and the holder-lid 10 are each threaded. The inner lid 1, the O-ring 2, the porous polytetrafluoroethylene film 3, the diaphragm 4, and the positive electrode 5 are pressed by screwing the holder-body 9 and the holder-lid 10, and a good contact state is maintained. . The inner lid 1 functions as a pressing end plate, and the porous polytetrafluoroethylene film 3 is for preventing the surface of the diaphragm 4 from being soiled. The O-ring 2 ensures air tightness and liquid tightness.

The galvanic cell type oxygen sensor obtained in the above embodiment is designated as A, and the sensor having a gold electrode integrated with the diaphragm 4 as a positive electrode in the embodiment is designated as B, and the sensor is placed in an atmosphere of 0% oxygen concentration. 2 shows the results of examining the change over time in the output voltage of the sensor by taking out into the atmosphere at regular intervals. The sensor A of the present invention had a fast response and was very stable, but the sensor B had a slow response due to the deposition of lead on the gold integrated with the diaphragm, and a decrease in output was observed. This clearly indicates the effect of the carbon positive electrode in the present invention.

[0011]

As described above, since the galvanic cell type oxygen sensor according to the present invention uses carbon that is inactive against the precipitation of lead in the positive electrode, it is long-lived in an atmosphere of 0% oxygen concentration. Lead is not deposited on the positive electrode even after a lapse of time, stable output is obtained, and its industrial value is extremely large.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross-sectional structure of a galvanic cell type oxygen sensor according to an embodiment of the present invention.

FIG. 2 is a diagram showing a change with time of an oxygen sensor.

[Explanation of symbols]

 1 Inner lid 2 O-ring 3 Porous polytetrafluoroethylene film 4 Separator 5 Carbon positive electrode 6 Lead wire 7 Electrolyte 8 Negative lead 9 Holder-Main body 10 Holder-Lid

Claims (1)

[Claims] 1. A positive electrode (5) comprising a catalytic electrode for electrolytic reduction of oxygen, a negative electrode (8) comprising lead, and an electrolytic solution (7),
In a galvanic cell type oxygen sensor basically composed of a diaphragm (4) and a container (7), the positive electrode (5) is a carbon having a function as an electrolytic solution holder and a function as a positive electrode current collector. Galvanic battery type oxygen sensor characterized by using.