Magnetic flow meter with buffering electrodes
First Claim
1. A magnetic flow sensor for measuring the rate of flow of a fluid along a flow direction, the sensor comprising:
- a pair of sensing electrodes that, when wetted by the fluid, define a sensing path through the fluid transverse to the flow direction;
each of the sensing electrodes having at least one buffer electrode associated therewith;
each of the sensing electrodes connected to an input of a signal processing circuit operable to provide, as separate outputs, a flow signal representative of a flow-induced voltage, and an input to a respective buffer amplifier operable to supply a respective buffer voltage to the associated at least one buffer electrode.
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Accused Products
Abstract
The flow responsive voltages detected at the electrodes of magnetic flow meters are typically reduced in magnitude by an electrical impedance shunting effect of the fluid on the electrodes. This problem is resolved by providing buffering electrodes located near, and preferably both upstream and downstream, of flow responsive sensing electrodes. The buffering electrodes are driven by amplifiers having signals detected by the flow responsive electrodes as an input. Thus, fluid in the vicinity of the flow responsive electrodes is forced to acquire an offset voltage which can reduce the shunting effect to a negligible level.
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Citations
16 Claims
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1. A magnetic flow sensor for measuring the rate of flow of a fluid along a flow direction, the sensor comprising:
- a pair of sensing electrodes that, when wetted by the fluid, define a sensing path through the fluid transverse to the flow direction;
each of the sensing electrodes having at least one buffer electrode associated therewith;
each of the sensing electrodes connected to an input of a signal processing circuit operable to provide, as separate outputs, a flow signal representative of a flow-induced voltage, and an input to a respective buffer amplifier operable to supply a respective buffer voltage to the associated at least one buffer electrode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- a pair of sensing electrodes that, when wetted by the fluid, define a sensing path through the fluid transverse to the flow direction;
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9. A method of compensating for parasitic impedance effects in a magnetic flow meter comprising at least one pair of sensing electrodes that, when wetted by a fluid, define a sensing path through the fluid transverse to a flow direction;
- the method comprising the steps of;
providing at least one buffer electrode respectively associated with each sensing electrode; causing the fluid to flow through the magnetic flow meter and to thereby induce a respective flow voltage at each sensing electrode; connecting each sensing electrode to a signal processing circuit having an output to a respective buffer amplifier to generate a respective buffer voltage responsive to the associated flow voltage, and applying the respective buffer voltage to the respective at least one buffer electrode. - View Dependent Claims (10, 11, 12)
- the method comprising the steps of;
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13. A method of measuring the rate of flow of a fluid along a flow direction by operating a magnetic flow meter comprising at least one pair of sensing electrodes that, when wetted by a fluid, define a sensing path through the fluid transverse to a flow direction;
- the method comprising the steps of;
providing at least one buffer electrode respectively associated with each sensing electrode; causing the fluid to flow through the magnetic flow meter and to thereby induce a respective flow voltage at each sensing electrode; producing a respective buffer voltage responsive to each flow voltage by connecting the associated sensing electrode to an input of a buffer amplifier; and connecting an output of the buffer amplifier to the respective at least one buffer electrode. - View Dependent Claims (14, 15, 16)
- the method comprising the steps of;
Specification