Sensor and sensor system for liquid conductivity, temperature and depth

• US 6,577,134 B2
• Filed: 12/06/2001
• Issued: 06/10/2003
• Est. Priority Date: 05/01/2000
• Status: Expired due to Term

• Current Assignee: Arete Associates
• Original Assignee: Arete Associates
• Inventors: Farruggia, Guy J., Fraser, Allan B.
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): Hamdan, Wasseem H.
• Application Number:
  US10/010,936
• Publication Number:
  US 20020135377A1
• Time in Patent Office: 551 Days
• Field of Search: 324/425, 324/439, 324/441, 324/448, 324/444, 324/158.1, 324/442, 324/693, 298/32
• US Class Current: 324/425
• CPC Class Codes: G01N 27/06 of a liquid involving electrolysis G01N27/26
• CPC Class Codes: G01N 33/18 Water

Abstract

Liquid conductivity and temperature are measured in respective sensitivity fields that are collocated—i. e., in volumes that nearly match by mathematical, geometrical, or functional criteria. Collocation is as distinct from mere adjacency or proximity; and is with respect to measurement volumes, not measuring hardware. Preferably pressure too is measured with sensitivity very generally collocated to the conductivity and temperature sensitivity. Preferably, respective temporal/spatial bandwidths of the two (or three) sensors are matched. Preferably the pressure sensor is a MEMS transducer, the conductivity sensor is a four-terminal device, the thermometer is a thermistor encapsulated in a silkscreened glass wall, and circuits (1) compensate for time lag between conductivity and temperature measurement, (2) remove artifacts due to detritus in or near either sensor, and (3) derive secondary parameters of the liquid.

Claims

1. Apparatus for determining parameters of a liquid;

said apparatus comprising;

a conductivity sensor for measuring electrical conductivity of such liquid;

a thermometer for measuring temperature of such liquid; and

a data-acquisition and -processing system connected to receive measurement signals from the conductivity sensor and thermometer, representing conductivity and temperature;

the data-acquisition and -processing system comprising a circuit modifying at least one of the measurement signals to remove signal artifacts due to detritus passing by or through the conductivity sensor or the thermometer.

2. The apparatus of claim 1, wherein:

the data-acquisition and -processing system is a substantially unitary assembly with the sensors and comprises circuits deriving from said measurement signals secondary parameters of such liquid.

3. The apparatus of claim 2, wherein:

the secondary parameters comprise density of such liquid and speed of sound in such liquid.

4. The apparatus of claim 2, further comprising:

a pressure sensor for determining pressure of such liquid; and

wherein;

the data-acquisition and -processing system further receives pressure-measurement signals from the pressure sensor representing values of pressure that are associated with values of conductivity and temperature measured by the conductivity sensor and thermometer; and

the data-acquisition and -processing system further derives, from said pressure-measurement signals, depth of such liquid.

5. The apparatus of claim 4, wherein:

the pressure sensor is a MEMS transducer.

6. The apparatus of claim 5, wherein:

the transducer is embedded in a common chip that provides the data-acquisition and -processing system.

7. The apparatus of claim 1, for use with said liquid being ocean, estuarine, or brackish water;

and further comprising;

hardware for mooring the sensors in, or a vehicle and associated hardware for vehicle-mounting them in or towing them through such ocean, estuarine or brackish water.

8. The apparatus of claim 1, wherein:

the signal-modifying means comprise means for substituting a signal representative of at least one period before or after the passing of the detritus, or both, in place of signal generated in response to the detritus.

9. The apparatus of claim 8, wherein:

the substituting means comprise a circuit.

10. Apparatus for determining parameters of a liquid;

said apparatus comprising;

two conductivity sensors for measuring electrical conductivity of such liquid; and

at least one thermometer for measuring temperature of such liquid; and

a structural assembly for supporting the sensor and thermometer, said assembly comprising at least two circuit cards or ceramic cards having structural strength to provide mechanical integrity to the assembly and mutually disposed in a parallel, substantially aligned relationship and having the two conductivity sensors at mutually opposed faces of two of said cards.

11. The apparatus of claim 10, further comprising:

third and fourth circuit cards or ceramic cards also having structural strength to provide mechanical integrity to the assembly and disposed at substantially right angles to, and for structural interconnection between, the first-mentioned two cards;

the four cards forming a substantially rectangular or square frame open at two ends for circulation of such liquid therethrough.

12. The apparatus of claim 11, wherein:

the at least one thermometer comprises a resistance wire mounted across the frame.

13. The apparatus of claim 12, wherein:

the resistance wire is connected at its two ends to points on the frame respectively associated with the two conductivity sensors.

14. The apparatus of claim 11, wherein:

at least one of the two conductivity sensors has concentric electrodes; and

the at least one thermometer comprises a thermistor mounted at a centerpoint of the concentric electrodes.

15. The apparatus of claim 10, wherein:

the at least one thermometer comprises a resistance wire mounted across the frame.

16. The apparatus of claim 15, wherein:

the resistance wire is connected at its two ends to points on the frame respectively associated with the two conductivity sensors.

17. The apparatus of claim 16, wherein:

the resistance wire is connected at its two ends to centerpoints of the two conductivity sensors respectively.

18. The apparatus of claim 10, further comprising:

pillar-type standoffs also having structural strength to provide mechanical integrity to the assembly and disposed at substantially right angles to, and for structural interconnection between, the two cards;

the two cards and the pillar-type standoffs forming a substantially rectangular or square frame, generally open at four faces for circulation of such liquid therethrough.

19. The apparatus of claim 18, wherein:

the at least one thermometer comprises a resistance wire mounted across the frame.

20. The apparatus of claim 19, wherein:

the resistance wire is connected at its two ends to points on the frame respectively associated with the two conductivity sensors.

21. The apparatus of claim 19, wherein:

the resistance wire is connected at its two ends to centerpoints of the two conductivity sensors respectively.

22. The apparatus of claim 18, wherein:

at least one of the two conductivity sensors has concentric electrodes; and

the at least one thermometer comprises a thermistor mounted at a centerpoint of the concentric electrodes.

23. The apparatus of claim 10, wherein:

the maximum dimension of each conductivity electrode is 1.5 centimeter.

24. Apparatus for determining parameters of a liquid;

said apparatus comprising;

at least one conductivity sensor for measuring electrical conductivity of such liquid; and

at least one thermometer for measuring temperature of such liquid,

circuitry connected to receive and manipulate electrical signals from the sensor and thermometer; and

a common ceramic substrate holding the sensor, thermometer and circuitry, said thermometer comprising a thermistor chip applied directly to the substrate holding the circuitry.

25. The apparatus of claim 24, wherein the circuitry comprises:

an analog-to-digital converter digitizing the signals;

memory means holding calibration coefficients for each sensor and each thermometer;

a data bus transmitting the signals with the calibration coefficients embedded therein to a processing unit.

26. The apparatus of claim 25, wherein:

the processing unit is programmed for plotting and data archiving.

27. The apparatus of claim 25, wherein:

the processing unit is disposed, remote from the sensor and thermometer, in a vehicle or shore facility.

28. The apparatus of claim 24:

wherein the thermometer is a thermistor, having an asymptotic time-response function; and

the circuitry comprises a module that executes a program for calculating a limit value from early response data.

29. Apparatus for determining parameters of a liquid;

said apparatus comprising;

at least one conductivity sensor for measuring electrical conductivity of such liquid; and

at least one thermometer for measuring temperature of such liquid;

circuitry connected to receive and manipulate electrical signals from the sensor and thermometer; and

a common ceramic substrate holding the sensor, thermometer and circuitry; and

wherein the thermometer is a thermistor bead mounted in a niche in the substrate.

30. Apparatus for determining parameters of a liquid;

said apparatus comprising;

a tube for passage of such liquid therethrough;

at least one slot formed through a side wall of the tube;

a generally planar substrate mounted in the slot and extending inward from the slot across the tube interior, and also extending outward from the slot and projecting from the tube;

a conductivity sensor, formed on opposite sides of the portion of the substrate that extends across the tube interior, for measuring electrical conductivity of such liquid; and

a thermometer for measuring temperature of such liquid.

31. The apparatus of claim 30, wherein:

the conductivity sensor comprises electrodes extending along the substrate and across the tube, on said opposite sides of the substrate.

32. The apparatus of claim 31, wherein:

the electrodes comprise, on each side of the substrate, two generally parallel current-driving electrodes, and a sensing electrode generally parallel to and between the driving electrodes.

33. The apparatus of claim 32, wherein:

conductivity measurement paths extend through such liquid within and generally parallel to the tube, between the electrodes on one side of the substrate and the electrodes on the opposite side of the substrate, by passing around at least one edge of the substrate.

34. The apparatus of claim 33, wherein:

the paths comprise two paths passing around two opposite edges of the substrate; and

said two paths define two conductivity-measurement sensitivity lobes extending in opposite generally axial directions within the tube from the sensing electrode on one side of the substrate to the sensing electrode that is on the side opposite said one side.

35. The apparatus of claim 34, wherein:

the thermometer is mounted substantially between the two conductivity-measurement sensitivity lobes.

36. The apparatus of claim 34, wherein:

the thermometer comprises two temperature sensors, one on each side of the substrate, each temperature sensor disposed substantially between the two conductivity-measurement sensitivity lobes.

37. The apparatus of claim 30, wherein:

the electrodes are silkscreened on the substrate.

38. The apparatus of claim 30, wherein:

the tube is of alumina.

39. Apparatus for determining parameters of a liquid;

said apparatus comprising;

a conductivity sensor for measuring electrical conductivity of such liquid, the sensor having concentric annular electrodes; and

a thermometer for measuring temperature of such liquid, the thermometer being disposed within an innermost of the annular electrodes.

40. Apparatus for determining parameters of a liquid;

said apparatus comprising;

a conductivity sensor for measuring electrical conductivity of such liquid;

a thermometer for measuring temperature of such liquid; and

a data-acquisition and -processing system connected to receive measurement signals from the conductivity sensor and thermometer, representing conductivity and temperature;

the data-acquisition and -processing system comprising means for modifying at least one of the measurement signals to remove signal artifacts due to detritus passing by or through the conductivity sensor or the thermometer.

41. The apparatus of claim 40, wherein:

the signal-modifying means comprise a circuit.

42. The apparatus of claim 40, wherein

the data-acquisition and -processing system is a substantially unitary assembly with the sensors, and comprises means for deriving from said measurement signals secondary parameters of such liquid.

43. The apparatus of claim 42, wherein:

the deriving means comprise circuits.

44. The apparatus of claim 40, for use with said liquid being ocean, estuarine, or brackish water;

and further comprising;

means for mooring the sensors in, or means for vehicle-mounting them in or towing them through such ocean, estuarine or brackish water.

45. The apparatus of claim 44, wherein:

the mooring means comprise hardware; and

the mounting or towing means comprise a vehicle and associated hardware.

46. The apparatus of claim 40, wherein:

the signal-modifying means comprise means for substituting a signal representative of at least one period before or after the passing of the detritus, or both, in place of signal generated in response to the detritus.