Fluid condition monitor
First Claim
1. A method of monitoring the condition of a fluid in a fluid system comprising:
- (a) forming a pair of electrodes and disposing said electrodes in spaced generally parallel arrangement;
(b) immersing said electrodes at least partially in said fluid;
(c) applying an oscillating substantially constant peak supply voltage sequentially at a first frequency of at least one Hertz and at a second frequency of less than one Hertz across said electrodes;
(d) measuring the current flow at said first frequency representative of the bulk impedance of the fluid and said second frequency representative of the surface impedance of the electrodes and calculating the difference of said measured currents; and
, (e) comparing said difference in measured currents with a reference level for a predetermined acceptable fluid condition and determining whether said comparison indicates a non-acceptable fluid condition and providing an electrical indication of the determination.
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Accused Products
Abstract
A fluid condition monitor suitable for real time monitoring of a fluid in a fluid system such as on-board vehicle monitoring of engine oil and transmission fluid to determine contamination. A capacitive spaced array electrode probe is immersed in the fluid and an oscillating voltage is applied at a first frequency of at least one hertz and the current IB measured as an analog of the bulk fluid impedance. The voltage is also applied to the probe at a second frequency of less then one hertz and the current Is measured as an analog of the electrode surface impedance. The difference in measured currents ΔI is determined electrically compared with a predetermined threshold value; and, the measured first frequency current IB is compared with an upper and lower limit value for IB determined empirically for the known baseline fluid. If ΔI is below the threshold or IB is not within the upper and lower limits, a fault condition is declared and an indicator is activated to warn that the fluid is not suitable for continued operation of the system. An alternate embodiment includes a fluid level sensor.
81 Citations
19 Claims
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1. A method of monitoring the condition of a fluid in a fluid system comprising:
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(a) forming a pair of electrodes and disposing said electrodes in spaced generally parallel arrangement;
(b) immersing said electrodes at least partially in said fluid;
(c) applying an oscillating substantially constant peak supply voltage sequentially at a first frequency of at least one Hertz and at a second frequency of less than one Hertz across said electrodes;
(d) measuring the current flow at said first frequency representative of the bulk impedance of the fluid and said second frequency representative of the surface impedance of the electrodes and calculating the difference of said measured currents; and
,(e) comparing said difference in measured currents with a reference level for a predetermined acceptable fluid condition and determining whether said comparison indicates a non-acceptable fluid condition and providing an electrical indication of the determination. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of monitoring the condition of a fluid in a fluid system comprising:
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(a) forming a pair of electrodes and disposing said electrodes in spaced generally parallel arrangement;
(b) immersing said electrodes at least partially in said fluid;
(c) flowing an oscillating current of a substantially constant peak magnitude sequentially at a first frequency of at least one Hertz and a second frequency of oscillation less than one Hertz through said electrodes for a certain period of time;
(d) measuring the magnitude of voltage developed across said electrodes by said current at said first frequency representative of the bulk impedance of the fluid and at a second frequency representative of the impedance of the electrode surface and determining the difference of said measured voltages;
(e) comparing said difference in measured voltages with a reference level for a predetermined acceptable fluid condition and determining whether said comparison indicates a non-acceptable fluid condition and indicating the results of said determining. - View Dependent Claims (11, 12, 13)
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14. A method for sensing the condition of a fluid system comprising:
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(a) forming a pair of electrodes and disposing said electrodes in spaced arrangement;
(b) immersing said electrodes at least partially in said fluid;
(c) applying an oscillating voltage of a certain constant peak magnitude and certain oscillating frequency across said electrodes;
(d) applying said voltage at a first frequency of oscillation of at least one Hertz for a certain period of time and measuring the magnitude of the current representative of the bulk impedance of the fluid;
(e) applying said voltage at a second frequency of oscillation less than one Hertz for a certain period of time and measuring the magnitude of the current representative of the impedance of the electrode surface;
(f) calculating the difference in magnitudes of said measured currents; and
,(g) comparing the said difference in magnitudes of the measured currents to a reference level characteristic of a predetermined fluid condition and providing an electrical indication of the comparison and determining whether the comparison indicates a change in the condition of the fluid. - View Dependent Claims (15, 16)
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17. A method for sensing the condition of a fluid in a fluid system comprising:
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(a) forming a pair of electrodes and disposing said electrodes in spaced apart substantially parallel arrangement;
(b) immersing said electrodes at least partially in said fluid;
(c) applying an oscillating voltage of a certain constant peak magnitude and oscillating frequency;
(d) applying said voltage at a first frequency of oscillation of at least ten (10) Hertz for measuring the bulk impedance of said fluid for a certain length of time and measuring the magnitude of the current developed at said first frequency for such certain length of time;
(e) applying said voltage at a second frequency of oscillation less than said first frequency for measuring the surface impedance of the electrode and measuring the magnitude of the current at said second frequency for said certain length of time;
(f) calculating the difference between said measured magnitudes of current at said first and second frequencies;
(g) comparing the said difference in magnitudes of current to a reference level characteristic of a predetermined fluid condition to provide an electrical indication of the comparison and determining whether said comparison indicates a change in the condition of the fluid. - View Dependent Claims (18)
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19. A method for sensing the condition of a fluid in a fluid system comprising:
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(a) forming a pair of electrodes and disposing said electrodes in spaced apart substantially parallel arrangement;
(b) immersing said electrodes at least partially in said fluid;
(c) applying an oscillating voltage of a certain constant peak magnitude and certain frequency across said electrodes;
(d) applying said voltage at a first relatively high frequency of oscillation for a certain length of time for measuring the bulk impedance of said fluid;
(e) measuring the magnitude of current at said first frequency and comparing said measured current with measured currents at said first frequency of acceptable fluid and determining if said current measured at said first frequency is within acceptable limits;
(f) applying said voltage at a second relatively low frequency of oscillation for measuring the electrode surface impedance;
(g) measuring the magnitude of current at said second frequency of oscillation and calculating the difference in said current measured at said first and second frequencies;
(h) comparing said calculated difference in currents to a reference level characteristic of a predetermined fluid condition and providing an electrical indication of the comparison and determining whether said comparison indicates a significant change in the condition of the fluid.
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Specification