Hot wire anemometer and pulmonary gas flow monitor combination capable of fast accurate calibration
First Claim
1. A respiratory gas flow monitor comprising:
- a) a hot wire anemometer sensor comprised of a transparent cylindrical tube, at least one pair of electrically conductive lead projecting inwardly of and mounted in the wall of said tube, one platinum wire in said tube having two ends connected, respectively, between said one pair of leads, said transparent tube having adjacent a first end thereof a first opaque region;
b) an electrical gas-flow-signal generating means having a housing and having a circuit with first and second input terminals enclosed in said housing;
c) a sensor calibration-socket means mounted in a wall of said housing for during calibration of said sensor receiving said one tube end, holding said sensor tube horizontal and rotatable in said socket means, and for blocking air flow therethrough; and
d) connecting means for electrically connecting said one pair of sensor leads to said first and second input terminals, respectively, of said electrical gas-flow-signal means, said electrical gas-flow signal generating means being for supplying a heating current through said platinum wire and for producing at a point in said circuit a signal voltage of magnitude that is related to the rate of flow of gas through said sensor tube and for adjusting said heating current to set said flow-rate voltage to a predetermined value indicative of a zero gas flow rate.
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Accused Products
Abstract
A hot wire sensor has a cylindrical light-transparent tube having two opaque patches adjacent the two tube ends, respectively, and with one platinum "hot" wire mounted about centrally therein and another platinum wire mounted adjacent thereto. A gas flow monitor includes a resistive bridge circuit, connected to the hot wire sensor. In the bridge circuit, the two platinum wires become two of the adjacent bridge branches. A DC voltage supply of the monitor is connected across the bridge at the bridge junction of the platinum wires, heating the one but not the other owing to disparate resistances in the bridge branches. A calibration socket is mounted vertically on an outer wall of the monitor housing. To calibrate the sensor, a tube end is inserted into the socket holding the tube axis horizontal and the tube is rotated until the opaque patch breaks a light beam between a LED and a photo transistor at the periphery of the socket. At that position the one "hot" wire is horizontal and the breaking of the light beam electrically enables (unlocks) the bridge so that an adjustment of one of the bridge arm resistances can be made to obtain a bridge output voltage of predetermined value corresponding to zero flow of gas through the sensor tube.
62 Citations
9 Claims
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1. A respiratory gas flow monitor comprising:
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a) a hot wire anemometer sensor comprised of a transparent cylindrical tube, at least one pair of electrically conductive lead projecting inwardly of and mounted in the wall of said tube, one platinum wire in said tube having two ends connected, respectively, between said one pair of leads, said transparent tube having adjacent a first end thereof a first opaque region; b) an electrical gas-flow-signal generating means having a housing and having a circuit with first and second input terminals enclosed in said housing; c) a sensor calibration-socket means mounted in a wall of said housing for during calibration of said sensor receiving said one tube end, holding said sensor tube horizontal and rotatable in said socket means, and for blocking air flow therethrough; and d) connecting means for electrically connecting said one pair of sensor leads to said first and second input terminals, respectively, of said electrical gas-flow-signal means, said electrical gas-flow signal generating means being for supplying a heating current through said platinum wire and for producing at a point in said circuit a signal voltage of magnitude that is related to the rate of flow of gas through said sensor tube and for adjusting said heating current to set said flow-rate voltage to a predetermined value indicative of a zero gas flow rate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A respiratory gas flow monitor comprising:
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a) a hot-wire anemometer sensor comprised of a transparent cylindrical tube, a first pair and a second pair of electrically conductive leads extending about radially from within said tube and sealingly through the wall of said tube, one and another platinum wires, the ends of each of said platinum wires connected, respectively, within said tube between said first pair and said second pair of said leads, said tube having adjacent one end thereof a first opaque region and having adjacent the opposite end thereof a second opaque region, said opaque regions having the same circumferential orientations about said tube; and b) an electrical-signal processing means having a circuit and a housing enclosing said circuit with at least one vertical panel, a socket mounted in said one panel including a solid cylindrical center portion extending outward from said one panel and having an outside diameter slightly smaller than the inside diameter of said sensor tube, having a circular ring portion extending outward from said one panel outside of and coaxial with said solid cylindrical portion, the inside diameter of said ring portion having an inside diameter slightly greater than the outside diameter of said sensor tube so that said socket is capable of accepting said one or said opposite end of said sensor tube in the groove formed between said solid center portion and said coaxial ring portion and holding said tube in a horizontal position;
said signal processing means additionally having four input terminals and a connecting means for electrically connecting said four sensor leads to said four input terminals, respectively, said socket additionally having alight source and a light detector mounted on opposite side of said groove in a circumferential position causing said one platinum wire to be held horizontally when said one tube end is held in said socket groove and rotated until said opaque region in said tube end blocks light from said source to said light detector, said signal processing means being for supplying a heating current through said platinum wire and producing a voltage of magnitude that is related to the rate of flow of gas through said sensor tube.
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Specification