Measuring and testing – Gas analysis – With compensation detail
Patent
1989-03-17
1990-11-27
Williams, Hezron E.
Measuring and testing
Gas analysis
With compensation detail
324639, G01N 2200
Patent
active
049726994
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of analyzing gaseous media by means of microwave absorption, particularly for the determination of gas concentrations, wherein a microwave is generated at at least one frequency. The invention also relates to an apparatus for analyzing gaseous media by means of the absorption of microwaves, particularly for a determination of concentrations, primarily for implementing the method and comprising at least one microwave transmitter, at least one measuring cell, at least one detector, amplifying and display devices for the measurement signal as well as a control device for the microwave transmitter.
It is known to analyze gaseous media, possibly also after conversion of a solid or a liquid into the gaseous state, by absorption of microwaves within certain characteristic frequency ranges by the excitation of rotational transitions in molecules of the media to be examined. In order to reduce the line width, the examination takes place in the low pressure range. The absorption lines are split by means of the Stark effect, with an alternating Stark voltage preferably being applied to increase detection sensitivity. Such a process is highly selective, in principle, but does not require prior modifications, such as ionization or chemical reactions, of the substances to be examined.
In the past, this examination method could be used practically only in a laboratory setting. Industrially usable devices were not available since the known devices were expensive because of their structural, mechanical as well as electrical configuration, sometimes included sensitive components and it was difficult or expensive to stay within critical parameters.
For example, it is necessary to stabilize and thus regulate (in its actual sense) the frequency of the transmitted microwave with respect to the absorption maximum of the molecule of interest, possibly under consideration of the Stark voltage that is acting on it. For this purpose, it has been proposed to feed part of the high frequency of the microwave radiation, with the aid of directional coupler, to a mixer diode, to there compare it with the harmonic of a stable low frequency transmitter generated, for example, by a quartz crystal, to bind it to the harmonic of the low frequency by synchronization by means of a PLL [phase locked loop] circuit and thus stabilize the high frequency of the microwave on the absorption line of the component to be measured. It has also been proposed to additionally modulate the microwave transmitter, to send part of the microwave radiation through a reference cell containing the component to be measured, with the splitting of the microwave radiation again requiring the use of a directional coupler. With the aid of the derivation signal at the detector of the reference cell, which is required in addition to the detector at the measuring cell, the microwave transmitter is fixed on the absorption line of the component to be measured.
The drawback of transmitter modulation becomes evident on the basis of the increased noise power in the detector as a result of it. The prior art microwave methods and devices were too expensive, particularly because of the complicated frequency stabilization, so that competing different types of measuring methods and devices were more economical.
It is the object of the invention to provide a method of this type which provides an economical analysis of gaseous media, particularly a determination of their concentration while avoiding the stated drawbacks and which provides prerequisites for an industrially usable microwave analyzer.
According to the invention this stated object is attained by a method of the above-mentioned type which is characterized in that the microwave frequency is continuously swept over the absorption frequency of an anticipated gas and the intensity of the absorption is integrated. A device according to the invention has such a configuration that the microwave frequency is continuously swept over the absorption frequency of an anticipated gas and the intensity of t
REFERENCES:
patent: 3973186 (1976-08-01), Uehara et al.
patent: 4607521 (1986-08-01), Saito et al.
Archiv fur Elektronik und Ubertragungstechnik; vol. 40, No. 5i pp. 313-320.
Instruments and Experimental Techniques; vol. 17, No. 3, Part II, pp. 777-778.
Berger Lutz
Krieg Gunther
Schmitt Gerhard
Kernforschungszentrum Karlsruhe GmbH
Roskos Joseph W.
Williams Hezron E.
LandOfFree
Method and apparatus for analysis by means of microwaves does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for analysis by means of microwaves, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for analysis by means of microwaves will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1025282