JPH05119020A - Electrochemical type gas measuring device - Google Patents

Abstract

PURPOSE:To prevent an amount of electrolyte in an electrochemical type gas detector from being reduced. CONSTITUTION:A reference gas is supplied to a septum 11 which becomes an opposite pole of an electrochemical type gas detector 1 by providing openings 4 and 5 at a cell 3 which houses an electrolyte and sealing them by the septums 10 and 11 where electrodes 8 and 9 are formed at water repellent porous films 6 and 7 through a humidifying means 20. Even if water content of the electrolyte 2 is taken away by a gas to be inspected which contacts an operation pole, the water content within the reference gas contacts the septum 11 which becomes an opposite pole so that the electrolyte 2 absorbs this water content and compensates for reduction in the electrolyte.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas concentration measuring device using an electrochemical gas sensor, and more particularly to the structure of a reference gas supply path to a counter electrode.

[0002]

2. Description of the Related Art A gas sensor for electrochemically detecting a gas is provided with an opening in a cell containing an electrolytic solution and sealed with a diaphragm having an electrode such as platinum on a water-repellent porous film such as fluororesin. , Contact the electrode with the electrolytic solution, apply a constant potential to the electrode serving as the working electrode, and apply the test gas to the working electrode side.
Also, when the reference gas such as air is brought into contact with the counter electrode side and the gas to be detected enters the electrolytic solution through the diaphragm, the electrolytic current proportional to the gas concentration is generated to measure the gas concentration. Is configured to. As described above, the electrolytic solution is in contact with the outside air through the porous membrane, so that the electrolytic solution easily volatilizes with the test gas when measuring the test gas with a particularly high degree of dryness, and the electrolytic solution is frequently used. And it is necessary to replenish fresh water.

[0003]

In order to solve such a problem to some extent, it has been attempted to select the concentration of the electrolytic component higher than in the usual case, but in the case of liquid leakage. In addition to increasing the damage, the electrolytic solution needs to be prepared according to the destination, which causes a new problem of cost increase. The present invention has been made in view of such a problem, and an object thereof is to reduce the concentration of the electrolytic solution without increasing the degree of dryness of the test gas. Another object of the present invention is to provide a novel electrochemical gas measuring device capable of suppressing the decrease of the electrolytic solution.

[0004]

In order to solve such a problem, in the present invention, an opening is provided in a cell containing an electrolytic solution, and the opening is sealed by a diaphragm having an electrode formed on a water-repellent porous film. The reference gas is supplied to the diaphragm, which is the opposite electrode of the electrochemical gas detector that is stopped, through the humidifying means.

[0005]

[Function] Even if the water content of the electrolyte solution is taken away by the test gas contacting the working electrode, the water content in the reference gas comes into contact with the diaphragm serving as the counter electrode. Will be absorbed to compensate for the decrease in the electrolytic solution.

[0006]

The details of the present invention will now be described with reference to the illustrated embodiments. FIG. 1 shows an embodiment of the present invention. In the figure, reference numeral 1 is an electrochemical gas detector, in which a cell 3 accommodating an electrolytic solution 2 is provided with openings 4 and 5, and a fluororesin is provided in each of them. Electrodes 8 and 9 made of platinum or the like on the water repellent porous films 6 and 7
It is configured to be sealed by the diaphragms 10 and 11 on which is formed. The electrochemical gas detector configured as described above uses the electrode 8 of one diaphragm 10 as a working electrode and applies a constant potential thereto, and the electrode 9 of the other diaphragm 11 is supplied with a reference gas such as air. Electrode 8 that acts as a working electrode
An electrolytic current is generated by bringing the test gas into contact with the test gas, and the concentration of the test gas is known from this current value.

Reference numerals 13 and 14 denote covers attached so as to seal the diaphragms 10 and 11, respectively. The covers 13 and 14 are provided with gas inlets 15 and 16 and gas outlets 17 and 18, respectively. The gas inlet 15 on the working electrode side is extended to the environment to be measured by a pipe, and the gas inlet 16 on the counter electrode side is connected to the reference gas source via the humidifying means 20. 21 is a double reciprocating pump, the suction port 23 of one pump chamber 22 is a pipe to the gas discharge port 17 of the working electrode side cover 13 of the gas detector 1, and the other pump chamber 23 is suctioned. The ports 25 are connected to the gas outlets 18 of the counter electrode side cover 14 of the gas detector 1, respectively. In the figure, reference numeral 30 denotes a diaphragm that is reciprocated by an electromagnetic driving means (not shown), and reference numerals 31 and 32 denote discharge ports.

In this embodiment, when the pump 21 is driven, a negative pressure acts on the covers 13 and 14, the test gas flows into the cover 13, and the humidifying means 20 enters the cover 14.
A sufficiently humid reference gas, for example air, flows in through. As a result, the test gas comes into contact with the electrode 8 serving as the working electrode, and the reference gas with high humidity comes into contact with the electrode 9 serving as the counter electrode, so that an electrolytic current proportional to the gas concentration is generated.

At this time, when the relative humidity of the test gas is extremely low, the water content of the electrolytic solution that moistens the diaphragm 10 diffuses into the test gas and is carried away together with the test gas to the outside. Although the liquid level of No. 2 is lowered, since the reference gas containing sufficient water has been supplied to the diaphragm 11 serving as the counter electrode through the humidifying means 20, this water wets the diaphragm 11. Is absorbed by the electrolytic solution 2, and the loss amount and the replenished amount are balanced, and as a result, the liquid surface level of the electrolytic solution 2 is maintained constant.

FIG. 2 is a diagram showing the change over time in the electrolytic solution surface level in the above-described gas measuring device. The diagram indicated by the symbol I in the figure is an extremely dry sample having a relative humidity of 2-3%. The test gas was supplied to the working electrode in an amount of 0.5 liters per minute, and the reference gas whose relative humidity was increased to 60% through the humidifying means to the counter electrode at 1.0 liters per minute. Although a slight drop in the liquid level was observed at the stage, it remains at a constant level thereafter. On the other hand, when the humidifying means is not provided (II), the liquid level rapidly decreases with the passage of time and the concentration of the electrolytic solution is doubled, that is, the electrolytic surface level is 1/2. The equilibrium state will be maintained at the point when it drops to. As a result, it is found that supplying the humidified reference gas is extremely effective for measuring the test gas in a dry state.

Needless to say, when the humidity of the test gas is about the same as that of the atmosphere, the reference gas is directly supplied to the counter electrode without passing through the humidifying means to change the gas concentration without changing the concentration of the electrolytic solution. Therefore, it is possible to measure a test gas having a different dryness with an electrochemical gas detector having the same specifications.

In this embodiment, the test gas is forcibly introduced into the working electrode of the gas detector, but it is left in the test gas atmosphere and is naturally diffused to the working electrode. It is obvious that the same effect can be obtained even when applied to an object to be operated. Further, in this embodiment, one reciprocating pump is used to suck the test gas and the reference gas by one pump. However, independent pumps are used to supply the reference gas. The suction capacity of the pump on the suction side can be adjusted according to the dryness of the test gas.

[0013]

As described above, according to the present invention,
A reference gas is supplied via a humidifying means to a counter electrode of an electrochemical gas detector, which is formed by forming an opening in a cell containing an electrolytic solution and sealing the electrode with a water-repellent porous film. Therefore, even if the test gas in contact with the working electrode removes the water content of the electrolytic solution, it can be replenished with water from the diaphragm that serves as the counter electrode, and the liquid surface level of the electrolytic solution can be automatically kept constant for a long time. By maintaining it, it is possible to eliminate the troublesome work of supplying fresh water to the gas detector and the work of changing the electrolytic solution according to the destination.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a process of decreasing an electrolytic solution in the present invention.

[Explanation of symbols]

 1 Electrochemical Gas Detector 2 Electrolyte 3 Cell 4,5 Open 6,7 Water Repellent Porous Membrane 8,9 Electrode 10,11 Separator 13,14 Cover 20 Humidification Means 21 Gas Suction Pump

Claims (1)

[Claims] 1. A humidifying means is provided on a diaphragm serving as a counter electrode of an electrochemical gas detector in which an opening is provided in a cell containing an electrolytic solution and the opening is sealed by a diaphragm having electrodes formed on a water-repellent porous film. An electrochemical gas measuring device adapted to supply a reference gas through the device.