Measuring and testing – Gas analysis – By thermal property
Reexamination Certificate
1999-09-10
2001-07-24
Williams, Hezron (Department: 2856)
Measuring and testing
Gas analysis
By thermal property
C324S201000, C324S204000
Reexamination Certificate
active
06263722
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a magnetomechanical gas analyzer and more particularly to a paramagnetic gas analyzer such as an oxygen analyzer which has a dumbbell that is rotatably suspended in the region of action of an inhomogeneous magnetic field and around which a paramagnetic gas to be measured flows and to the damping of all of the oscillations that have a negative effect on the stability of the analyzer's balance point.
DESCRIPTION OF THE PRIOR ART
Gas analyzers that have a dumbbell that is rotatably suspended in the region of action of an inhomogeneous magnetic field use the paramagnetic property of a gas such as oxygen and in effect exploit the deflection of paramagnetic gas in the inhomogeneous field.
In known arrangements of this kind, a diamagnetic dumbbell is rotatably suspended from a taut band in an inhomogeneous field. In the presence of a paramagnetic gas, such as oxygen, the body of the dumbbell is pushed out of the magnetic field. With the aid of a compensating coil, the dumbbell is turned back into its initial position. The current needed for this is a measure of the oxygen concentration in the gas to be measured flowing around the dumbbell. The rotation or counter-rotation is in this case made visible or recordable by a system involving a light beam and a mirror.
The limiting factors for the performance of this measurement method are the detectability and the speed of the measurement. The smallest possible detectable or resolvable measurement range in this case is physically dictated by the instability of the dumbbell at the balance point. The speed of the measurement essentially depends on finding the aforementioned balance point rapidly.
As an example of analyzers of the known type, DE 2339960 discloses a gas detector in which two-dimensional oversizing of the conductor tracks is provided on the body of the dumbbell and in its plane, these regions acting as eddy-current brakes under the influence of the magnetic field. Rotational oscillations about this plane are thereby damped.
However, because of shaking or vibrations which the instrument experiences, there are also oscillations in other planes. A fundamental aspect of this is that vibrational oscillations which also affect the dumbbell and cause the aforementioned instability about the balance point are a sum of linearly independent individual oscillations which from a mathematical standpoint are made up of orthogonal oscillation components. This in turn means that damping only in one oscillation plane cannot lead to any damping action of an oscillation component in a respectively orthogonal plane.
On the basis of this, the present invention dampens oscillations of all kinds which have a negative effect on stability at the balance point and increases detectability and the speed of the measurement.
SUMMARY OF THE INVENTION
The present invention uses an eddy-current brake, to settle or obtain damped motion of the dumbbell, not only in one plane, that is to say the rotational plane of the dumbbell, but also damps other oscillation planes.
This use of an eddy-current brake is based on the discovery that perpendicular oscillation planes are mathematically and physically independent of one another, so that damping in one plane does not give any damping coupling to any other of the oscillation planes. To that end, at least two electrically conductive surface segments which are essentially perpendicular to one another are arranged for eddy-current damping on the dumbbell or in the mechanical gearing on the dumbbell and in the region of action of the inhomogeneous field. The inhomogeneous magnetic field which is present has in this case field components in almost all directions. The effect of this is that magnetic action also acts on the different planes, or the eddy-current surfaces lying in different planes. This means that only one magnetic field arrangement is needed even in this case.
Consequently, efficient eddy-current induction takes place, resulting from oscillations of at least two spatial direction components. This means that considerably more effective damping in the region of the aforementioned balance point is possible.
In a further advantageous refinement, one of the electrically conductive surface segments is formed with a mirror surface which is applied or vapor deposited. This mirror surface is in this case effective as an eddy-current brake for the oscillation component lying perpendicular to the plane of the mirror. In this embodiment, the dumbbell is advantageously produced in micromechanical silicon technology or in glass.
In both embodiments, the mirror surface can be vapor deposited in a straightforward way by processes that use either PVD or CVD technology. The thickness of the vapor deposited mirror surface should be dimensioned such that it is possible to generate a current density which is required in terms of eddy-current braking in this space plane.
The other metallic surface, which acts as another eddy-current brake and is perpendicular to the mirror surface, is formed in the region of the current paths on the dumbbell. Further, the material for the eddy-current brake is advantageously a chemically stable material. Particularly suitable examples include platinum, rhodium, rhenium, aluminum, titanium or nickel.
REFERENCES:
patent: 3612991 (1971-10-01), Greene
patent: 3826974 (1974-07-01), Kocache et al.
patent: 5369980 (1994-12-01), Kocache
patent: 5932794 (1999-08-01), Fabinski et al.
Bauer Thomas
Fabinski Walter
Hartmann & Braun GmbH & Co. KG
Politzer Jay L.
Rickin Michael M.
Williams Hezron
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