Chemistry: analytical and immunological testing – Pyrolysis – combustion – or elevated temperature conversion – With catalyst or accelerator
Patent
1991-10-07
1993-08-10
Warden, Robert J.
Chemistry: analytical and immunological testing
Pyrolysis, combustion, or elevated temperature conversion
With catalyst or accelerator
73 2331, 422 94, 422 98, G01N 2522
Patent
active
052348377
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns detecting combustible gas in a gaseous medium such as air.
A known method of detecting combustible gas in air uses a sensor device, generally called a catalytic filament explosimeter, in which a filament, usually of platinum, is heated by the Joule effect, in other words by passing an electric current through it. The combustible gas contained in the surrounding air oxidizes by catalysis in contact with the filament, so that the filament temperature increases. This increases the resistance of the filament, which is measured directly or indirectly to determine the concentration of said combustible gas in the air.
To give one example, the applicant has proposed in French patent FR-1.444.771 filed 4 May 1965 apparatus for sampling and measuring gas in the air in which the gas is metered by measuring the voltage across one diagonal of a resistive bridge comprising a detector filament and a compensator filament connected in parallel with two resistors, one of which is advantageously a variable resistor.
The applicant has also proposed in French patent FR-1.577.448 filed 22 May 1968 a method and apparatus for measuring a parameter characteristic of a gaseous medium in which the value of the parameter in question is estimated by measuring power supply data for a detector filament when the resistance of the filament is held equal to that of a compensator filament.
The applicant has also proposed in French patent FR-1.576.576 filed 6 Jun. 1968 a method and apparatus for metering combustible gas in which a substantially constant voltage is maintained across the filament despite variations in its resistance due to wear or the presence of combustible gas.
Similarly, the applicant has disclosed in French patent FR-1.579.535 filed 21 Mar. 1968 a voltage stabilizer circuit for supplying metering filaments at a substantially constant voltage.
More recently the applicant has proposed in French patent FR-2.537.722 filed 14 Dec. 1982 a measuring method and apparatus designed to eliminate the effects of diffusion of combustible gases in the air and making it possible to eliminate the effects of differences in oxidization heat between gases. To this end the changing value of a parameter representative of the supply of power to the filament is measured, the supply of power being controlled in such a way as to hold the filament resistance constant.
Although the use of a filament to catalyze combustion of methane now makes it possible to monitor very accurately the presence of methane in a mine, the power supply and measuring arrangements used until now have the disadvantage of relatively rapid ageing and relatively high electrical power consumption, making intermittent use necessary and so increasing the real response time.
In an attempt to alleviate these disadvantages other equipment has been based on catalytic beads comprising a metal detector (made of platinum, for example) coated with doped alumina and resembling a small pearl.
Use of these catalytic beads has made possible continuous monitoring of combustible gas levels through slower ageing linked to a lower combustion temperature. However, these beads suffer from significant drift in sensitivity, decreased stability and a longer response time than filaments.
An object of the invention is to alleviate the aforementioned disadvantages and to provide a new filament interrogation method with reduced electrical power consumption, slower ageing and pseudo-continuous use, that is to say use which is continuous as far as can be perceived by the user, the interrogation cycle time being much shorter than the sensor response time.
To this end the invention proposes a method for measuring the concentration in a gaseous medium of a known combustible gas in which method a resistive element in the gaseous medium having a catalytic surface or being sensitive to variations in the concentration of the combustible gas in the gaseous medium is electrically heated, the value of a parameter representative of the gas concentration is detected and there is deduced
REFERENCES:
patent: 1231045 (1917-06-01), Means
patent: 3200011 (1965-08-01), Baker
patent: 3911386 (1975-10-01), Beaudoin et al.
patent: 4538448 (1985-09-01), Boutonnat et al.
patent: 4870025 (1989-09-01), Hurley et al.
patent: 4992384 (1991-02-01), Laurs et al.
Accorsi Antoinette
Kazmierczak Marc
Wattier Andree
Charbonnages de France
Tran Hien
Warden Robert J.
LandOfFree
Pseudo-continuous process for interrogating a combustible gas de does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pseudo-continuous process for interrogating a combustible gas de, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pseudo-continuous process for interrogating a combustible gas de will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1724692