JPS59619Y2 - gas detector - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a gas detector for measuring the concentration of chlorine gas and oxygen gas and for detecting these gases.

Conventional gas detectors of this type using electrochemical methods include the amperometric method, which uses a plastic film as a diaphragm, and the amperometric method, which uses electrolysis between two electrodes in which an electrolytic solution is passed through a reaction cell. It is said to be based on the metric method.

The former has poor sensitivity because it uses a diaphragm.

Furthermore, maintenance is troublesome because the diaphragm and electrolyte must be replaced.

Furthermore, the structure is complicated because of the seal portion.

The latter is large in size to allow the electrolyte to flow through it.

Unfortunately, the electrolyte needs to be replenished and maintenance is troublesome.

An object of the present invention is to solve the above problems and provide a highly sensitive gas detector that is small and easy to maintain.

The present invention will be explained in detail below using the drawings.

FIG. 1 is a configuration showing an embodiment of a gas detector for chlorine gas according to the present invention, and FIG. 2 is a cross-sectional view taken along line AA' in FIG.

In the figure, 1 is a substrate made of an insulating material such as ceramic, 2 and 3 are electrodes formed on the substrate 1 by thick film printing technology, and the electrodes 2 and 3 function as an indicator electrode and a counter electrode, respectively. be.

4 is a porous body formed on the surfaces of the electrodes 2 and 3 and on a part of the surface of the substrate 1 by mixing ceramic (alumina or the like) and glass and firing the mixture.

This porous body 4 is formed as follows.

First, a liquid glass paste and a ceramic powder (for example, alumina powder) having a particle size of 50 to 300 mesh are mixed and then heated and dried at about 150°C.

This brings the glass and ceramic into a bonded state.

Thereafter, the glass-ceramic combination is again pulverized into particles.

Then, a binder such as starch paste is mixed with the mixed powder of glass and ceramic to form a paste, which is applied to the surface of the substrate 1 so as to cover the electrodes 2 and 3 formed on the substrate 1.

Thereafter, it is dried to evaporate water, and the dried substrate 1 and the like are fired at a temperature (600 to 850° C.) higher than the melting point of glass and lower than the melting point of ceramic.

Since the melting point of ceramic is sufficiently higher than that of glass, the glass melts and forms ceramic powder, substrate 1 and electrode 2.
, 3.

As a result, a porous body 4 made of ceramic powder and molten glass is formed on the surface of the substrate 1 on which the electrodes 2 and 3 are formed.

This porosity. The particle 4 contains CaCl2. Ca(NO3)2
・A deliquescent salt such as 4H20, NaOH9CH3COONH4 as a drying prevention agent and a certain amount of electrolyte are impregnated.

5 is a power supply that applies a constant voltage between the electrodes 2 and 3, and 6 is an indicator that gives an instruction corresponding to the magnitude of the current flowing through the electrodes 2 and 3.

In the case of chlorine gas measurement, all electrodes 2 and 3 are formed and electrode 2
A DC voltage of -0.35 V is applied to the sample, and a potassium iodide solution is used as the electrolyte.

This gas detector is based on the polarographic method, and its operation when measuring chlorine gas will be explained next.

The chlorine gas in the atmosphere around the gas detector reacts with potassium iodide in the electrolyte that has penetrated into the porous body 4, and liberates iodine (C12+2→2■2+2C).

The liberated iodine (2) is reduced by the voltage applied between the electrodes 2 and 3, and the following reaction occurs on the indicator electrode 2 side.

(2+2e-→2I-) Therefore, a current flows between the electrodes 2 and 3 according to the chlorine gas concentration, and the value is indicated on the indicator.

Therefore, the chlorine gas concentration can be determined from this value.

In addition, although the above explanation was for the case where the gas to be measured was chlorine gas, the gas to be measured may also be trace oxygen.

In this case, the counter electrode 3 is made of silver, potassium chloride is used instead of potassium iodide, and oxygen diffused into the electrolyte is directly electrolyzed by the polarographic method.

Furthermore, when used for gas detection, the indicator 6 may not be used, and the structure may be such that an alarm is generated when the current flowing through the electrodes 2 and 3 reaches a constant value.

As explained above, the gas detector of the present invention does not use a diaphragm.

Furthermore, there is no need to drain the electrolyte, and there is no need to replace or replenish it.

Therefore, according to the present invention, it is possible to realize a highly sensitive gas detector that is small and easy to maintain.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of a gas detector according to the present invention, and FIG. 2 is a sectional view taken along line AA' in FIG. 1...Substrate, 2...Indicator electrode, 3...Counter electrode, 4...
-Porous body, 5...power supply, 6...indicator.

Claims (1)

[Scope of utility model registration request] A substrate made of an insulating material such as ceramic, a pair of electrodes made of a thick film provided on this substrate, and ceramic and glass are mixed and fired to form a coating on the surface of the electrode and a part of the substrate. It comprises a porous body formed on a surface, an electrolytic solution and a deliquescent salt soaked into the porous body, and a power source that applies a constant voltage between the electrodes, and the current flowing through the electrodes is controlled by the power source. A gas detector that detects gas based on its size.