Measuring and testing – With fluid pressure – Leakage
Reexamination Certificate
1999-07-08
2001-07-24
Larkin, Daniel S. (Department: 2856)
Measuring and testing
With fluid pressure
Leakage
C073S001060
Reexamination Certificate
active
06263724
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns a gas analyser including a pump unit and autocalibration means.
The invention applies in particular to a gas analyser that is part of a tracer gas leak detector.
Tracer gas leak detectors generally include autocalibration means, i.e. means for calibrating the detector. To this end the device includes a container of tracer gas, generally helium, having a known and calibrated leakage rate.
The container is connected to the inlet of the detector by a valve which is opened during autocalibration. To enable calibration, the calibrated leakage flow is entered into an electronic circuit, for example using thumbwheels on the device, the electronic circuit adjusting the ionisation current of the gas analyser. The device carries a mass selector switch, generally selecting one of three separate possible masses, operating on the ion acceleration voltage. This is so even though the detector contains only one calibrated leakage container for a given gas.
Accordingly, if a tracer gas other than that in the calibrated leakage container inside the device is to be used, it is necessary to use a calibrated leakage cylinder of the other gas and to connect it to the inlet flange of the device and of course to open the device to set the calibrated leakage value of that cylinder on the thumbwheels. The mass selector switch must also be set to the position corresponding to the gas used.
When this has been done, the above parameters (ion acceleration voltage and ionisation current) are adjusted automatically during autocalibration so that the leak shown on the device corresponds to the calibrated leakage flow entered via the thumbwheels.
SUMMARY OF THE INVENTION
An aim of the present invention is therefore to propose a gas analyser equipped with means for automatically calibrating it in a very simple manner using a plurality of different gases.
An analyser of the above kind can be used directly to analyse a gas or as part of a leak detector that can be used with a plurality of different tracer gases by simplifying to the greatest possible degree the operations to be carried out when the tracer gas used is changed.
The invention therefore consists in a gas analyzer connected to a pump unit and including auto calibration means characterised in that it is connected to a storage tank having a calibrated leak and filled with a mixture of n gases having different masses and the leakage flow of each of said n gases which through said calibrated leak is known.
In an advantageous embodiment of the invention, the concentration of each of the n gases in the mixture is such that said partial leakage flow of each of the n gases through said calibrated leak is the same for all of them. This enables a single value of the leakage flow to be set that is valid for all the n gases.
REFERENCES:
patent: 4680956 (1987-07-01), Huszczuk
patent: 4797784 (1989-01-01), Grosse Bley
patent: 5835974 (1998-11-01), Nagy
patent: 2 366 553 (1978-04-01), None
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patent: 2 688 307 (1993-09-01), None
B. Piégay: “Les Détecteures de fuites á hélium. Conception et étallonnage” Le Vide: Science, Technique et Applications., vol. 51, No. 278, Nov. 1995, FR, pp. 443-455, XP000557206.
J.C. Legras, et al.: “Létalonnage des fuites de rérence au BNM/L.N.E.” Le Vide: Science, Technique et Applications., vol. 51, No. 278, Nov. 1995, FR, pp. 436-442, XP000557205.
Alcatel
Larkin Daniel S.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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