Fluid flow apparatus with capacitive sensors
First Claim
1. Apparatus for receiving, containing and supplying a volume of liquid, the apparatus comprising:
- a vial for containing a volume of liquid, the vial constructed of nonconductive material and having an inlet/outlet tube for receiving a fixed amount of liquid flowing in a first direction through the inlet/outlet tube and supplying the first amount of liquid in an opposite direction through the inlet/outlet tube and also having a vent tube, the inlet/outlet tube and vent tube being at separate distal ends of a path for liquid flow within the vial;
first and second capacitively coupleable plates separated by an intervening first electrostatic shield, the first and second plates and the first electrostatic shield disposed proximate the outer surface of the inlet/outlet tube, the first electrostatic shield preventing between the first and second plates capacitive coupling other than that which arises by electrostatic lines of force passing through the inlet/outlet tube, the first and second plates exhibiting a varying degree of capacitive coupling therebetween dependent upon the presence or absence of liquid fluid inside the inlet/outlet tube and upon the proximity of that liquid to the location of the first shield; and
third and fourth capacitively coupleable plates separated by an intervening second electrostatic shield, the third and fourth plates and the second electrostatic shield disposed proximate the outer surface of the vent tube, the second electrostatic shield preventing between the third and fourth plates capacitive coupling other than that which arises by electrostatic lines of force passing through the vent tube, the third and fourth plates exhibiting a varying degree of capacitive coupling therebetween dependent upon the presence or absence of liquid inside the vent tube and upon the proximity of that liquid to the location of the second shield.
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Accused Products
Abstract
An automatic atmometer includes an evaporating head that is coupled to a metering vial through a three-way valve controlled by fluid sensors disposed proximate inlet and open ends of the metering vial. The three-way valve is ordinarily in a quiescient state that connects the evaporating head to the metering vial. As water evaporates from the evaporating head water is drawn by suction out of the metering vial. When a sensor proximate the inlet of the metering vial indicates that the vial is empty the three-way valve is activated. This refills the metering vial from a fluid reservoir above the metering vial. As soon as one or more sensors proximate the open end of the metering vial indicate that the vial is full the three-way valve is returned to its quiescient condition. An output signal activates a counter or other logging device to record the number of times the metering vial has been emptied and refilled. Fluid presence at various portions of the metering vial is sensed by capacitive structures each producing a varying amount of capacitance according to the presence or absence of the fluid. The amount of an RF signal coupled through each sensor is measured and compared to a reference voltage. The reference voltage is itself produced from a similar capacitve structure so that the measured voltage and the reference voltage have the same temperature coefficient.
39 Citations
24 Claims
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1. Apparatus for receiving, containing and supplying a volume of liquid, the apparatus comprising:
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a vial for containing a volume of liquid, the vial constructed of nonconductive material and having an inlet/outlet tube for receiving a fixed amount of liquid flowing in a first direction through the inlet/outlet tube and supplying the first amount of liquid in an opposite direction through the inlet/outlet tube and also having a vent tube, the inlet/outlet tube and vent tube being at separate distal ends of a path for liquid flow within the vial; first and second capacitively coupleable plates separated by an intervening first electrostatic shield, the first and second plates and the first electrostatic shield disposed proximate the outer surface of the inlet/outlet tube, the first electrostatic shield preventing between the first and second plates capacitive coupling other than that which arises by electrostatic lines of force passing through the inlet/outlet tube, the first and second plates exhibiting a varying degree of capacitive coupling therebetween dependent upon the presence or absence of liquid fluid inside the inlet/outlet tube and upon the proximity of that liquid to the location of the first shield; and third and fourth capacitively coupleable plates separated by an intervening second electrostatic shield, the third and fourth plates and the second electrostatic shield disposed proximate the outer surface of the vent tube, the second electrostatic shield preventing between the third and fourth plates capacitive coupling other than that which arises by electrostatic lines of force passing through the vent tube, the third and fourth plates exhibiting a varying degree of capacitive coupling therebetween dependent upon the presence or absence of liquid inside the vent tube and upon the proximity of that liquid to the location of the second shield. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. Apparatus for receiving, containing and supplying a volume of liquid, the apparatus comprising:
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a vial for containing a volume of liquid, the vial constructed of nonconductive material and having an inlet/outlet tube for receiving a fixed amount of liquid flowing in a first direction through the inlet/outlet tube and supplying the fixed amount of liquid in an opposite direction through the inlet/outlet tube and also having a vent tube, the inlet/outlet tube and vent tube being a separate distal ends of a path for liquid flow within the vial; first and second capacitively coupleable plates disposed proximate the outer surface of the inlet/outlet tube, the first and second plates exhibiting a varying degree of capacitive coupling therebetween dependent upon the presence or absence of liquid inside the inlet/outlet tube; third and fourth capacitively coupleable plates disposed proximate the outer surface of the vent tube, the third and fourth plates exhibiting a varying degree of capacitive therebetween dependent upon the presence or absence of liquid inside the vent tube; and an expansion chamber located between the inlet/outlet tube and the vent tube. - View Dependent Claims (23, 24)
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Specification