Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1998-09-02
2000-08-29
Le, Que T.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250577, 73291, G01N 1506
Patent
active
061112631
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a bubble detector of the kind defined in the preamble of the following Claim 1.
BACKGROUND OF THE INVENTION
Earlier known technology is described in FR-A1-2 660 755, which discloses a bubble detector that includes a conduit through which a first fluid having a first refractive index passes, a light source which directs a light beam through a first transparent wall part of the conduit, through the conduit cavity, and out through a second transparent wall part of said conduit, and a detector means which receives the light beam after it has passed through the conduit and the first fluid present therein. It is also disclosed in FR-A1-2 660 755 that the light beam shall be directed in a plane normal to the axis of the circular-cylindrical conduit and be directed non-diametrically through said conduit. With this construction, it is necessary to accurately adjust the position and direction of the light source with respect to refractive index (the first fluid/liquid concerned), and the position of the detector must be adjusted to receive the light beam. This known arrangement presumes that the refractive index of the fluid is constant and will record error functions already at relatively small variations in the refractive index of the fluid. The reliability of the known arrangement is also relatively poor, because the presence of bubbles in the fluid is detected by non-detection of a light beam by the detector. When the light beam passes a bubble, the beam is split and spreads so that no clear light beam will leave the conduit.
Among other drawbacks with the known arrangement is that it gives no clear indication of malfunctioning of the main components.
The object of the present invention is to reduce or eliminate at least one of these drawbacks.
This object is achieved with a bubble detector according to the accompanying Claim 1.
SUMMARY OF THE INVENTION
The dependent Claims define further embodiments of the detector.
The invention is based on the fundamental concept that the two transparent conduit wall-parts that are trans-illuminated by the light beam shall be essentially flat and parallel and that the light beam is directed through the conduit at an oblique angle, e.g. 45 degrees, to the nearest plane of the trans-illuminated wall-part, so that the light beam will be broken into different paths depending on whether the beam in the conduit passes through the first fluid or through bubbles of a second fluid having a different refractive index. The detector means is therewith adapted to be impinged upon by the light beam exiting from the conduit independently of refractive index for the fluid or fluid mixture present between the two conduit wall-parts. The detector means is adapted to deliver an output signal that depends on the position at which the light beam meets the detector means, so as to enable the presence of bubbles of said second fluid in said first fluid to be identified by corresponding variations in the detector output signal.
In a preferred embodiment of the invention, the detector means includes a difference photodiode which delivers a signal that depends on the position at which the light beam meets the diode surface. A detector means of this nature can be readily calibrated; the first fluid, e.g. a liquid, can be passed through the conduit while ensuring that the first fluid is free from bubbles or the like. The signal that defines a bubble-free state of the first fluid is noted at the same time. A given deviation from this output signal will indicate a change in the refractive index of the medium in the conduit, that the detector means is malfunctioning, or that the alignment of the light source in relation to the conduit and/or the detector has been changed. Because the change in output signal is the result of a displacement in the distance of the position of contact of the light beam from the calibrating position, there will always be obtained an output signal from the detector means provided that the light source is operative and said arrangement has not broke
REFERENCES:
patent: 4344429 (1982-08-01), Gupton et al.
Le Que T.
Octagon AB
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