Optics: measuring and testing – For light transmission or absorption – By comparison
Patent
1991-07-24
1993-08-31
McGraw, Vincent P.
Optics: measuring and testing
For light transmission or absorption
By comparison
250575, 356438, 356439, G01N 2159, G01N 2185
Patent
active
052413675
DESCRIPTION:
BRIEF SUMMARY
STATE OF TECHNOLOGY
The invention relates to a device for measuring the composition of fluids, in particular the components of exhaust gases from internal combustion engines. In such a device known through DE-OS 20 22 736, the light conductive bodies lead to spatially widely differing locations, with the light conductive bodies being of flexible make-up. The device is designed in such a way that a part of the light conductive bodies, together with the reflecting arrangement, is immersed in the medium which is to be measured. A further proposal suggests that the individual components of the generic type be gathered together in one single arrangement so that a compact arrangement is obtained, but this presents the difficulty that the light source will impart its light not only to the reference light receiver directly, but also to the measuring path light receiver, which would lead to a falsification of the measured result.
ADVANTAGES OF THE INVENTION
In contrast, the device in accordance with the invention has the advantage that it is of very compact construction and operates with great sensitivity, eliminating stray light and providing accurate measured results. Advantageous further developments of the device in accordance with the invention are identified by the subordinate claims. According to claims 2 and 3, a measuring error is advantageously avoided by either controlling the light source to a constant value or by comparing the actual light emission directly with the measured value of the light receiver for the measured length. A drop in the light output of the light source can be directly compensated in this arrangement.
The embodiment in accordance with claim 4 makes it possible for the light emitted from the light source to be very accurately detected, since a distribution of the reference light receiver to several receivers can detect the spatially radiated light output more accurately.
The embodiment in accordance with claim 5 provides a statistic mean value of the measured result in which it is possible for influences which affect the light transmission in only one direction, and most importantly, heat influences which can occur on one side, to be compensated.
In a simplified way, this can also be achieved with the embodiment in accordance with claim 6, and in both cases, it is also possible in the long term to take into account influences of the structural members, the light source or the light receiver, and for example, to keep drifts which are accounted for by ageing influences, small. Preferably, however, an even thermal loading of the optically active components, the light source and/or light receiver, is achieved which in turn reduces drift occurrences.
The embodiment in accordance with claim 7 provides for advantageous ascertainment of components in the fluids which cause a specific light absorption of the light cast on them. With the use of differing light wave lengths, components in the fluids can be measured selectively and accurately, which will have a particularly intensive retroaction on these particular light wave lengths. Due to its physical properties, the particular light source can, upon stimulation, produce an intensified special light source emission, or, the special light source emission will be caused by the downstream arrangement of optical filters. The equivalent will apply to light receivers.
A further advantageous embodiment is that of claim 9, in which a very compact arrangement of the device is obtained which can also be used with high exhaust gas temperatures, when temperature resistant light conductive bodies of glass are employed.
DRAWING
An embodiment example of the invention is shown in the drawing and is described below in more detail. FIG. 1 shows a simplified representation of the device in longitudinal section, and FIG. 2 shows a section of the device in accordance with FIG. 1 through II--II.
DESCRIPTION OF THE EMBODIMENT EXAMPLES
In FIG. 1, a section through an exhaust pipe 1 is shown, which is connected to the exhaust system of an internal combustio
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Dettling Hubert
Grob Ferdinand
Potschin Roger
Stutzenberger Heinz
McGraw Vincent P.
Robert & Bosch GmbH
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