Gas sensor

Details Gas sensor Gas sensor

1998-03-27

2000-12-26

Tung, T.

Chemistry: electrical and wave energy

Apparatus

Electrolytic

204424, 204426, 204429, 422 98, 427244, G01N 2726

Patent

active

061653365

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a sensor for detecting combustible gas, particularly carbon monoxide contained in the general atmosphere or exhaust gas of various combustion equipment using gas and petroleum for fuel, and more particularly to a gas sensor provided with excellent characteristics with respect of stability of sensor operation under severe working environment as well as with respect of durability which raises the most serious problem in chemical sensors. However, this invention is applicable to a wide variety of chemical sensor system gas sensors used for various objects with respect to various gaseous components.
2. Description of the Prior Art
Carbon monoxide is a gas which has no color, no taste, and no scent, and is slightly lighter than air but highly toxic, and even at a concentration as low as 200 ppm, breathing the gas for 2 to 3 hours causes headaches, and at a concentration higher than 3000 ppm, death results by breathing for about 10 minutes and at 6000 ppm or higher, for a few minutes.
Because even in general home, carbon monoxide is generated by an instantaneous water heater, bath boiler, petroleum space heater, gas space heater, or charcoal fire, a carbon monoxide gas detecting sensor which can be contained in these apparatus or installed indoors, and is inexpensive, small-size, and highly reliable is strongly desired.
Examples of a gas sensor, particularly chemical sensor for detecting carbon monoxide which has been proposed to date include a type in which an electrode is mounted for absorbing and oxidizing carbon monoxide in an electrolyte and detects the carbon monoxide concentration from a current value in proportion to the carbon monoxide concentration (controlled potential electrolysis type gas sensor), in which the gas sensor is further divided into two types; one is a coulometric type in which a generated current output is to be measured and the other is a potentiometric type in which a generated voltage output is to be measured. Therefore, the coulometric type can not avoid electrolytic reaction on the electrode surfaces, resulting in deterioration of the electrode leading to an effective life shorter than that of the potentiometric type;
a type for detecting gas using a sintered compact type of an N-type semiconductor oxide, for example, stannic oxide sensitized by adding traces of metallic element such as noble metals and utilizing characteristics of these semiconductors which vary electric conductivity when in contact with combustible gas (semiconductor type gas sensor);
and a type for attaching alumina to about 20-.mu.m platinum thin wire and heating it to a constant temperature by using a pair of reference elements with and without bearing noble metal and detecting a difference of heat generation when combustible gas comes in contact with this element to carry out catalytic oxidation reactions (contact combustion type gas sensor).
For example, there is a detailed description in "Reference 1," Chapter 14, Basics of Gas Sensors (written by Masaki Haruda) in "Sensor Practical Dictionary" in P. 112-130 supervised by Toyoaki Ohmori and published by Fuji Techno System (1986).
There also proposed a solid electrolyte type carbon monoxide sensor for detecting carbon monoxide by constituting a zirconia electrochemical cell and forming platinum/alumina catalyst layeron one side of the electrode [for example, see H. Okamoto, H. Obayashi, and T. Kudo; Solid State lonics, 1, 319 (1980)].
The principle of this solid electrolysis type carbon monoxide sensor relies on a kind of oxygen concentration cell formed on electrodes on the catalyst layer side and naked side, in that it utilizes that at the electrode on the catalyst side, oxygen directly reaches the electrode as it is and carbon monoxide does not reach, whereas on the naked-side electrode, both oxygen and carbon monoxide reach and this carbon monoxide reduces oxygen and forms an oxygen concentration cell across both electrodes, and the electromotive force output appears.

REFERENCES:
patent: 3514377 (1970-05-01), Spacil et al.
patent: 3526577 (1970-09-01), Molloy
patent: 3923624 (1975-12-01), Beekmans et al.
patent: 3988233 (1976-10-01), Gamer et al.
patent: 4088576 (1978-05-01), Mott
patent: 4101403 (1978-07-01), Kita et al.
patent: 4304652 (1981-12-01), Chiba et al.
patent: 4347732 (1982-09-01), Leary
patent: 4571285 (1986-02-01), Nakazawa et al.
patent: 4692354 (1987-09-01), Asaeda et al.
patent: 5082789 (1992-01-01), Morrison et al.

Affiliated with

Also associated with

Rating

Gas sensor does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Gas sensor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gas sensor will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-990962