Monitoring fluid condition through an aperture
First Claim
1. A fluid condition sensor for insertion in an aperture in a fluid filled vessel comprising:
- (a) an elongated member having a distal end and a proximal end and including certain surfaces with a relatively low dielectric constant;
(b) a pair of electrically conductive members disposed on said certain surfaces in spaced spiral arrangement adjacent said distal end, each member of said pair having an electrical lead extending to said proximal end;
(c) electrical circuitry associated with the proximal end of said elongated member and operatively connected to said leads, said circuitry operable to measure the electrode surface impedance between said pair at a first (low) frequency and to measure the bulk fluid impedance at a second (high) frequency of at least one Hertz and compute the difference and compare the difference with predetermined values and determine the fluid condition.
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Accused Products
Abstract
A method for real time monitoring fluid in a vessel with a probe having a pair of electrodes immersed in the fluid. The disclosed probe has the electrodes arranged helically on a rod, sized and configured for insertion in an engine dipstick hole. Preferably, the probe has spiral electrode winding up regions different pitch to provide improved impedance response at low fractional Hertz and high (at least one Hertz) frequencies of excitation. In one version with alternating voltage the difference in current magnitude measured at the low and high frequencies is compared with stored known values for known fluid conditions and an electrical signal indicative of fluid condition is generated. Examples with engine drain oil and heavy duty transmission lubricant fluid are presented. The impedance properties measured can determine the percentage remaining useful life (RUL) of the fluid. In another version of the method the current phase shift angle is measured at the fractional Hertzian frequency; and, from known values of current phase shift angle of the fluid, at various conditions, the condition of the fluid determined. The differential current measured and the measured phase shift angle may be combined, for example, by the square of the sum of the squares procedure to provide an enhanced impedance change indicator.
78 Citations
40 Claims
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1. A fluid condition sensor for insertion in an aperture in a fluid filled vessel comprising:
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(a) an elongated member having a distal end and a proximal end and including certain surfaces with a relatively low dielectric constant;
(b) a pair of electrically conductive members disposed on said certain surfaces in spaced spiral arrangement adjacent said distal end, each member of said pair having an electrical lead extending to said proximal end;
(c) electrical circuitry associated with the proximal end of said elongated member and operatively connected to said leads, said circuitry operable to measure the electrode surface impedance between said pair at a first (low) frequency and to measure the bulk fluid impedance at a second (high) frequency of at least one Hertz and compute the difference and compare the difference with predetermined values and determine the fluid condition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of continuously monitoring the condition of fluid in a vessel having an aperture for a dipstick comprising:
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(a) providing an elongated member of relatively low permittivity having a distal and proximal end and disposing a pair of generally spirally arranged spaced electrical conductors thereon in the region of the distal end;
(b) disposing electrical circuitry on said elongated member in the region of the proximal end and connecting said circuitry to said pair of conductors and inserting said distal end through said aperture into said fluid and detecting the bulk fluid impedance between said conductors at a first frequency (low) and detecting the electrode surface impedance at a second (high) frequency of at least one Hertz; and
,(c) computing the difference in said detected impedances and comparing said difference with predetermined values for said fluid and determining the condition of said fluid and providing an electrical indication when a certain fluid condition exists. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
(a) disposing a pair of thermistors in the region of the distal end of said elongated member and connecting said thermistors to said circuitry and self heating said thermistors and determining the level of said fluid in said vessel.
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14. The method defined in claim 13, wherein said step of disposing said pair of conductors includes winding said conductors in a pair of spiral grooves formed on said elongated member.
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15. The method defined in claim 10, wherein said step of detecting the impedance change includes converting a current in said electrodes to a voltage.
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16. The method defined in claim 10, further comprising:
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(a) disposing an indicator remotely from said vessel; and
,(b) connecting said circuitry to said indicator and energizing said indicator when said impedance reaches a pre-determined value.
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17. The method defined in claim 10, wherein said step of inserting said distal end of said elongated member through said aperture includes inserting said distal end into the lubricant sump of an internal combustion engine.
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18. The method defined in claim 10, wherein said step of inserting said distal end through said aperture includes inserting said distal end through an aperture in the casing of a power transmission lubricant reservoir.
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19. A removable fluid condition monitor for insertion through a dipstick aperture in a fluid reservoir comprising:
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(a) an elongated member of relatively low permittivity having a distal end for insertion through said aperture and a proximal end for remaining exteriorly disposed with respect to said reservoir;
(b) a pair of electrical conductors disposed in spaced generally parallel spiral relationship on said member in the region of the distal end;
(c) a casing structure associated with the proximal end of said member; and
,(d) circuitry disposed within said casing and connected to said conductors and operative to determine the electrode surface impedance between said conductors at a first (low) frequency and to determine the bulk fluid impedance at a second (high) frequency of at least one Hertz, said circuitry including a computer operable to compute the difference in said impedances and compare the difference with predetermined values for various conditions of the fluid and further operable to provide an electrical indication when said comparison correlates with a certain of said conditions. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
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32. A method of monitoring fluid condition in real time comprising:
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(a) immersing a pair of closely spaced electrodes in said fluid and connecting said electrodes to a source of electrical current;
(b) flowing a fractional ampere alternating current through said electrodes at a relative low voltage sequentially at a first frequency of at least one Hertz and at a second frequency less than said first frequency and measuring the current at said first and second frequency and computing the bulk fluid impedance from said first frequency current and the surface electrode impedance from said second frequency current;
(c) measuring the temperature of said fluid and storing said measured temperature;
(d) subtracting said impedance at said second frequency from said impedance at said first frequency and storing the differential;
(e) comparing said stored differential with valves of said differential at said stored temperature for known fluid conditions at said temperature; and
,(f) providing an electrical indication when said stored differential is less than a predetermined value for critical fluid condition. - View Dependent Claims (33, 34, 35)
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36. A method of monitoring in real time the condition of a fluid in a vessel comprising:
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(a) disposing a pair of spaced generally parallel electrodes in the fluid to be monitored;
(b) exciting said electrodes with an alternating generally constant voltage at a first frequency of at least one Hertz and at a second frequency less than said first frequency;
(c) detecting the phase angle of the current in said electrodes resulting from said alternating voltage excitation;
(d) comparing the phase shift angle of said current at said first and second frequency with the phase angle of said alternating voltage and computing the phase shift of said current at said first and second frequency;
(e) computing the reactance from said phase shift angle and subtracting the reactance computed at said first frequency from the reactance computed at said second frequency;
(f) determining the condition of the fluid with said reactance difference from known values of fluid condition and reactance difference for said fluid; and
,(g) providing an electrical signal indicative of said fluid condition. - View Dependent Claims (37, 38, 39, 40)
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Specification