Portable fluid screening device and method

• US 6,028,433 A
• Filed: 05/14/1997
• Issued: 02/22/2000
• Est. Priority Date: 05/14/1997
• Status: Expired due to Fees

• Current Assignee: Predict, Inc.
• Original Assignee: Reid Asset Management Company
• Inventors: Bush, Wayne A., Cheiky-Zelina, Margaret A.
• Primary Examiner(s): Ballato, Josie
• Assistant Examiner(s): Solis, Jose M.
• Application Number:
  US08/855,911
• Time in Patent Office: 1,014 Days
• Field of Search: 324/663, 324/639, 324/636, 324/672, 324/637, 324/688, 324/316
• US Class Current: 324/663
• CPC Class Codes: G01N 27/026 Dielectric impedance spectroscopy electrochemical impedance spectroscopy for measuring corrosion G01N17/02
• CPC Class Codes: G01N 33/2888 Lubricating oil characteristics, e.g. deterioration lubricating properties G01N33/30

Abstract

This invention relates to a fluid screening device, comprising: an impedance sensor including a cavity for holding a fluid to be screened, an impedance of the impedance sensor being affected by conditions of the fluid; an impedance measuring circuit for measuring the impedance of the impedance sensor with respect to at least one frequency; a processor for processing impedance data taken by the impedance measuring circuit for purposes of determining a condition of the fluid; and a connector which operatively couples the impedance sensor to the impedance measuring circuit, the connector allowing the impedance sensor to be selectively detached from the impedance measuring circuit.

Claims

1. A portable fluid screening device, comprising:

a hand-held sized portable housing;

a sensor operatively coupled to the housing for holding the fluid;

circuitry within the housing and operatively coupled to the sensor for measuring a dielectric property of the fluid at each of a plurality of discrete frequency ranges, wherein at least two of the plurality of discrete frequency ranges are in the audio frequency band;

processing means within the housing for determining a condition of the fluid based on the dielectric property of the fluid measured at the plurality of discrete frequency ranges; and

a display within the housing which displays information indicative of the determined condition of the fluid.

4. The device of claim 1, wherein the condition of the fluid comprises identification of a specific contaminant, and the display displays information regarding the contamination level.

9. The device of claim 1, wherein the condition of the fluid comprises identification of a specific contaminant, and the display displays information regarding the specific contaminant.

13. The device of claim 1, wherein the condition comprises at least one of contamination, water content and oxidation, and the display displays information regarding the at least one of contamination, water content and oxidation.

14. The device of claim 1, wherein the fluid is at least one of a lubricant and a hydraulic fluid, and the processing means is programmed to analyze the at least one of a lubricant and a hydraulic fluid based on the dielectric property of the fluid measured at the plurality of discrete frequency ranges.

15. The device of claim 1, wherein the processing means performs a trending analysis on the condition of the fluid.

16. The device of claim 1, wherein the circuitry comprises a bank of different valued resistors which are selectively coupled to the sensor to form an RC circuit which defines an oscillating frequency of an oscillator included in the circuitry.

2. A method of screening a fluid for contaminants, comprising the steps of:

using the fluid as a dielectric;

measuring a dielectric property of the fluid in each of a plurality of discrete frequency ranges, wherein the measuring step further comprises;

measuring the dielectric property of the fluid at a frequency within a first discrete frequency range, wherein the first discrete frequency range is in the audio frequency band;

measuring the dielectric property of the fluid at a frequency within a second discrete frequency range wherein the second discrete frequency range is in the audio frequency band and is different than the first discrete frequency range;

determining a condition of the fluid based on the dielectric property of the fluid measured at the plurality of discrete frequency ranges; and

displaying information indicative of the determined condition of the fluid.

23. The method of claim 2, wherein measuring the dielectric property of the fluid at each of the plurality of discrete frequency ranges further comprises measuring the dielectric property of the fluid at a frequency within a third discrete frequency range, wherein the third discrete frequency range is a frequency range above the audio frequency band.

24. The method of claim 23, wherein the frequency in the first discrete frequency range is 1 KHz, the frequency in the second discrete frequency range is 10 KHz, and the frequency in the third discrete frequency range is 200 KHz.

3. A fluid screening device, comprising:

a hand-held sized portable housing;

an impedance sensor operatively coupled to the housing and including a cavity for holding a fluid to be screened, an impedance of the impedance sensor being affected by conditions of the fluid;

an impedance measuring circuit within the housing and operatively coupled to the impedance sensor for measuring the impedance of the impedance sensor at a plurality of discrete frequencies, wherein at least two of the plurality of discrete frequencies are in the audio frequency band;

a processor within the housing for processing impedance data taken by the impedance measuring circuit and determining a condition of the fluid; and

a display within the housing for displaying information indicative of the determined condition of the fluid.

5. The device of claim 3, wherein the protective body further comprises an input/output port operatively coupled to the impedance measuring circuit for communication with an external processor or memory.

6. The device of claim 5, wherein the input/output port is selected from a group consisting of a serial port, an RF port and an IR port.

7. The device of claim 3, further comprising a variable frequency generator coupled to the impedance measuring circuit, and wherein the impedance measuring circuit is operable to measure the impedance of the impedance sensor over a plurality of frequencies provided by the variable frequency generator.

8. The device of claim 3, wherein the impedance sensor comprises a capacitive sensor.

10. The device of claim 3, further comprising a memory associated with the processor for storage of analysis information.

11. The device of claim 3, further comprising input means, wherein the input means is operable to transmit desired user operations to the processor.

12. The device of claim 3, wherein the impedance sensor comprises a pair of interdigitated electrodes formed on a substrate.

17. The device of claim 3, wherein the condition of the fluid comprises a contamination level of the fluid, and the display displays information regarding the contamination level.

18. The device of claim 3, wherein the condition of the fluid comprises identification of a specific contaminant, and the display displays information regarding the specific contaminant.

19. The device of claim 3, wherein the condition comprises at least one of contamination, water content and oxidation, and the display displays information regarding the at least one of contamination, water content and oxidation.

20. The device of claim 3, wherein the processor performs a trending analysis on the condition of the fluid.

21. The device of claim 3, further comprising a connector exposed at a surface of the housing which operatively couples the impedance sensor to the impedance measuring circuit, the connector allowing the impedance sensor to be selectively detached from the housing by an operator without necessitating opening the housing.

22. The device of claim 3, wherein the processor determines the condition of the fluid by comparing the measured impedances at the plurality of discrete frequencies to one another.

25. The method of claim wherein measuring the dielectric property of the fluid at each of the plurality of discrete frequency ranges comprises:

placing the fluid in a capacitive-type sensor, wherein the fluid forms the dielectric of the capacitive-type sensor and contributes to a capacitance thereof;

coupling the capacitive-type sensor to an oscillator circuit, wherein the capacitance of the capacitive-type sensor influences an oscillation frequency of the oscillation circuit; and

identifying the oscillation frequency of the oscillation circuit in each of the plurality of discrete frequency ranges.

26. The method of claim 25, wherein determining the condition of the fluid comprises:

calculating the capacitance of the capacitive-type sensor using the identified oscillation frequency in each of the plurality of discrete frequency ranges;

identifying the condition of the fluid using the calculated capacitance in each of the discrete frequency ranges.

27. The method of claim 26, wherein identifying the condition of the fluid using the calculated capacitance in each of the discrete frequency ranges comprises:

plotting a capacitance curve over frequency using the calculated capacitance in each of the discrete frequency ranges;

comparing the capacitance curve to one or more reference capacitance curves, wherein the reference capacitance curves represent one or more fluids having known contamination conditions associated therewith; and

determining the condition of the fluid using the comparison.

28. The method of claim 27, wherein comparing the capacitance curve to one or more reference capacitance curves comprises:

identifying a rate of change of capacitance over frequency for the capacitance curve and a reference capacitance curve; and

comparing the rates of change of capacitance of the capacitance curve and the reference capacitance curve over frequency.

29. The method of claim 27, wherein comparing the capacitance curve to one or more reference capacitance curves comprises:

performing a statistical correlation between the capacitance curve and each of the one or more reference capacitance curves; and

identifying one of the one or more reference capacitance curves which has a largest correlation with the capacitance curve.

30. The method of claim 29, further comprising the steps of:

coupling a known reference capacitance to the oscillation circuit;

identifying the oscillation frequency of the oscillation circuit in each of the plurality of discrete frequency ranges;

calculating a capacitance associated with the known reference capacitance using the identified oscillation frequency in each of the plurality of discrete frequency ranges;

determining a compensation value by comparing the calculated capacitance to the known reference capacitance; and

using the compensation value in determining the condition of the fluid.