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US 4,829,833 AGranted
Liquid impedance flow monitors
OwnerMurray F. Fellerinventor
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OwnerMurray F. Fellerinventor
Estimating the term…
Flow monitors are disclosed for liquid like tap water having limited electrical conductivity, including a flow sensor and a circuit connected to electrodes in the flow sensor for producing flow-representing signals. Vanes of a flow-activated rotor made of insulation displace part of the pattern of current paths between the flow-sensor's electrodes. Circuits connected to the electrodes include a d-c or a-c excitation source and an impedance in series with the electrodes for providing amplitude-varying signal output. The steady-state excitation voltage at the electrodes is maintained constant despite diverse resistivities of various liquids, and the series impedance is much higher than the resistance between the electrodes. D-c excitation promotes economical utilization of a long-life circuit-energizing battery. With d-c excitation, the positive electrode is of platinum or other material that serves as an electro-chemically inert anode in the liquid.
Apparatus for monitoring the flow of liquid such as tap water having limited electrical conductivity, including means defining a flow passage, a rotor having a hub and multiple vanes projecting from said hub to outer edges and disposed in the passage so as to be driven by flowing liquid, the electrical resistivity of the vanes being much higher than of the liquid whose much higher than that of the liquid whose flow is to be monitored, a sensing electrode having an active face exposed to the liquid and disposed opposite to the path of the vanes'outer edges, the extent of said active face of the sensing electrode along said path being only a small portion of the arcuate spacing between the edges of successive vanes of the rotor, a return electrode exposed to the liquid and disposed so that a pattern of electric current paths develops through the liquid between the sensing electrode and the return electrode when excitation is applied thereto and so that the pattern of current paths is modified by said vanes, and an electric circuit including impedance means connected in series with said electrodes and excitation means and output signal deriving means both of which are connected to said electrodes for developing and utilizing amplitude-varying signals in response to turning of the rotor, said return electrode being disposed in relation to said active face of the sensing electrode so that, in use, maximum resistance between the electrodes develops only as the edge of each vane passes into and out of alignment with the sensing electrode and so that only one vane-representing signal excursion is developed across said electrodes for each vane during the rotation of the rotor, the sensing electrode being spaced from the path of the vanes'edges so that, for all widths of the sensing electrode from narrower than to much wider than the thickness of a vane when measured along said path of the vanes, the duration of each vane-representing signal excursion that develops across the electrodes as each vane passes the sensing electrode has an electrical angle at least several times the electrical angle represented by the thickness of each vane at and near its outer edge.
Flow monitoring apparatus for liquid that exhibits limited electrical conductivity, including a flow sensor comprising a localized sensing electrode and a return electrode having a much larger area than said sensing electrode exposed to the liquid and a flow-activated device having portions movable at flow-representing frequency in the space between said electrodes for modifying the resistance between said electrodes, and a circuit responsive to said flow sensor for providing flow-representing signals, said circuit including direct-current supply means for providing said electrodes with direct-current excitation arranged to render said localized sensing electrode positive relative to said return electrode, at least the portion of said localized sensing electrode that is exposed to the liquid being of a material that is essentially inert electrochemically during excitation while in the liquid whose flow is monitored.
Flow monitoring apparatus for liquid that exhibits limited electrical conductivity, including means defining a flow passage, a flow sensor comprising a localized sensing electrode and a return electrode disposed in relation to the liquid in the flow passage for developing distributed current paths through the liquid and a flow-activated device in the passage having portions movable at flow-representing frequencies in the space between said electrodes where said current paths are developed for modifying the resistance of the liquid in the passage between said electrodes, and a circuit responsive to said flow sensor for providing flow-representing signals, said circuit including self-adjusting excitation means coupled to said electrodes for providing sustained excitation voltage of an essentially single value across said electrodes regardless of which liquid may be in the passage among diverse liquids having a range of different resisitvities, said excitation means having substantial impedance at flow-representing frequencies, so that there is a composite voltage across the electrodes including said sustained excitation voltage and flow-representing modulation representing the operation of the flow-activated device.
Flow monitoring apparatus for liquid that exhibits limited electrical conductivity, including a flow sensor comprising a localized sensing electrode and a return electrode disposed in relation to the liquid for developing distributed current paths through the liquid and a flow-activated device having portions movable at flow-representing frequency in the space between said electrodes for modifying the resistance between said electrodes, and a circuit responsive to said flow sensor for providing flowrepresenting signals, said circuit including an operational amplifier haveing (+) and (-) inputs, the (+) input being coupled to one of said electrodes, a biasing and gain-control feedback network between the output and the (-) input of the operational amplifier, and dual means for both providing the electrodes with excitation and providing impedance at flow-representing frequencies in series with said electrodes, said dual means comprising a first resistor connected to the output of said operational amplifier, a second resistor and a capacitor in parallel therewith having first and second connections to said first resistor and a d-c supply terminal, respectively, and a phase-inverting device having a control electrode connected to said first connection and having an output connection to said (+) input of the operational amplifier.
Flow monitoring apparatus for liquid that exhibits limited electrical conductivity, including:
Flow monitoring apparatus including means defining a flow passage, flow sensing means secured to said passage means, and a flow-activated device in the passage movable cyclically at flow-representing frequencies into proximity to said flow sensing means, said flow sensing means characteristically producing flow-representing signals as a modulation on applied excitation voltage and characteristically developing diverse ratios of excitation-voltage-to-current under diverse sustained operating conditions of the sensing means, and a circuit for providing flow-representing signals as a composite of an excitation voltage and a signal varying at flow-representing frequencies in response to cyclic movement of the flow activated device past the flow sensing means, said circuit including said flow sensing means and impedance means in series therewith and having self-adjusting excitation means for applying excitation voltage to said flow sensing means and for maintaining the excitation voltage across said flow sensing means essentially constant regardless of which of said diverse operating conditions may be in effect, wherein said self-adjusting excitation means includes an operational amplifier having an input connected to said flow sensor, a load impedance connected to the operational amplifier's output, a filtering impedance having a connection to the load impedance and being interposed between said connection and a d-c supply terminal, and a high-gain amplifier providing a coupling between said input of the operational amplifier and said connection for developing said impedance means in series with the flow sensor, the foregoing being so related that said load impedance imparts to said impedance means an essentially constant-current characteristic at flow-representing frequencies.
Flow monitoring apparatus including:
Dependencies are inferred from the claim text.