Self-compensating optical drop count apparatus for measuring volumetric fluid flow
First Claim
1. A self-compensating optical drop count apparatus for measuring volumetric fluid flow comprising:
- (a) a drop chamber including;
(1) a hollow body, having a radiation transmission path therethrough,(2) fluid inlet means coupled to an upper end of said hollow body for allowing a fluid to flow into said hollow body,(3) drop formation means coupled to said fluid inlet means for causing said fluid to break up into drops of an approximate uniform volume before said fluid passes through said hollow body, said drop formation means being positioned so that said drops pass through said hollow body along a longitudinal drop path that intersects with said radiation transmission path, and(4) fluid outlet means coupled to a lower end of said hollow body for allowing said fluid to flow away from said hollow body after passing therethrough;
(b) a light emitter adapted to continuously emit a directional light beam along said radiation transmission path, said light beam having an intensity that is controlled by an input control signal to said light emitter;
(c) a light detector optically coupled with said light beam after said light beam has passed through said hollow body along said radiation transmission path, said light detector being adapted to generate an output signal that indicates the presence and intensity of said light beam at said light detector;
(d) counting means coupled to said output signal of said light detector for counting interruptions that occur in said output signal, said interruptions being caused by said drops of fluid as said drops pass through said hollow body and interrupt said light beam, said counting means including single count protection means for counting only one interruption of a plurality of interruptions occurring in said output signal as a result of one of said drops breaking up into a plurality of smaller drops as it passes through said hollow body, said counting means thus adapted to count the number of drops of said liquid that pass through said chamber, said count, in combination with the approximate known volume of said drops, thus providing a measure of the volumetric flow of said fluid; and
(e) compensating means coupled to said output signal of said light detector and said input control signal of said light emitter for compensating the intensity of said light beam as emitted from said light emitter so that the intensity of said light beam as detected at said light detector is maintained at an average constant level regardless of any matter that may, on a long-term basis, tend to block said radiation transmission path.
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Abstract
A self-compensating optical drop count apparatus for measuring volumetric fluid flow by optically counting the number of drops of fluid that pass through a drop chamber, each drop being formed so as to be of approximate equal volume. Optical counting circuitry is designed to count each drop only once. The count is accumulated in a holding register where it may interface with external instrumentation equipment adapted to display the count and/or convert it to a volumetric measurement by multiplying it by the average volume of fluid contained in each drop. A compensation technique is utilized to maintain the intensity of a light beam, through which the drops must pass, at a constant level. Compensation is achieved in a closed loop system which varies the drive current to the light emitter to compensate for long-term variations that occur in the intensity of the light beam as sensed at a light detector. Compensation techniques are also utilized in converting the count to a volumetric measurement to account for known changes in drop volume as a function of drop rate.
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Citations
19 Claims
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1. A self-compensating optical drop count apparatus for measuring volumetric fluid flow comprising:
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(a) a drop chamber including; (1) a hollow body, having a radiation transmission path therethrough, (2) fluid inlet means coupled to an upper end of said hollow body for allowing a fluid to flow into said hollow body, (3) drop formation means coupled to said fluid inlet means for causing said fluid to break up into drops of an approximate uniform volume before said fluid passes through said hollow body, said drop formation means being positioned so that said drops pass through said hollow body along a longitudinal drop path that intersects with said radiation transmission path, and (4) fluid outlet means coupled to a lower end of said hollow body for allowing said fluid to flow away from said hollow body after passing therethrough; (b) a light emitter adapted to continuously emit a directional light beam along said radiation transmission path, said light beam having an intensity that is controlled by an input control signal to said light emitter; (c) a light detector optically coupled with said light beam after said light beam has passed through said hollow body along said radiation transmission path, said light detector being adapted to generate an output signal that indicates the presence and intensity of said light beam at said light detector; (d) counting means coupled to said output signal of said light detector for counting interruptions that occur in said output signal, said interruptions being caused by said drops of fluid as said drops pass through said hollow body and interrupt said light beam, said counting means including single count protection means for counting only one interruption of a plurality of interruptions occurring in said output signal as a result of one of said drops breaking up into a plurality of smaller drops as it passes through said hollow body, said counting means thus adapted to count the number of drops of said liquid that pass through said chamber, said count, in combination with the approximate known volume of said drops, thus providing a measure of the volumetric flow of said fluid; and (e) compensating means coupled to said output signal of said light detector and said input control signal of said light emitter for compensating the intensity of said light beam as emitted from said light emitter so that the intensity of said light beam as detected at said light detector is maintained at an average constant level regardless of any matter that may, on a long-term basis, tend to block said radiation transmission path. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A self-compensating method for optically measuring volumetric fluid flow comprising the steps of:
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(a) inserting a drop chamber in series with a tube through which a fluid to be measured is flowing; (b) inserting means inside of said tube to break said fluid up into drops of an approximate uniform known volume before said fluid passes through said drop chamber along a drop path; (c) optically coupling a light emitter that emits a beam of light, with a light detector, that generates an output signal which indicates the presence and intensity of said beam of light as detected at said light detector, through a light transmission path that passes through said drop chamber and intersects said drop path; (d) compensating the intensity of said light beam as emitted by said light emitter so that the intensity of said light beam as detected at said light detector is maintained at a constant level regardless of any matter that might on a long-term basis optically interfere with said light beam along said light transmission path; (e) monitoring said output signal of said light detector for pulses, said pulses indicating the absence of said light beam and thus indicating that said light beam has been interrupted by said drops as said drops pass through said drop chamber; (f) electrically counting the number of pulses that occur in said output signal in such a way that one count is assigned to each drop of fluid that passes through said drop chamber; and (g) converting the number of pulses thus counted to a volumetric measurement by multiplying the number of pulses, which corresponds to the number of drops of fluid that have passed through the drop chamber, by the compensated volume of each drop, said compensated volume being determined by monitoring the rate at which said drops fall through said chamber, a larger volume assigned to drops that fall at a fast rate, and a smaller volume assigned to drops that fall at a slower rate.
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Specification