Sensor and sensor system for liquid conductivity, temperature and depth

• US 6,404,204 B1
• Filed: 05/01/2000
• Issued: 06/11/2002
• 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): Brown, Glenn W.
• Assistant Examiner(s): Hamdan, Wasseem H.
• Application Number:
  US09/562,849
• Time in Patent Office: 771 Days
• Field of Search: 324/693, 324/71.1, 324/439, 324/441, 324/450, 324/717, 324/442, 324/425, 298/32, 204/412, 204/433
• US Class Current: 324/441
• 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; and

a thermometer for measuring temperature of such liquid;

wherein a sensitivity field of the conductivity sensor and a sensitivity field of the thermometer are substantially collocated.

2. The apparatus of claim 1, further comprising:

a pressure sensor for measuring pressure in a pressure-measurement volume of such liquid;

wherein a sensitivity field of the pressure sensor is very generally collocated with the conductivity- and temperature-measurement sensitivity fields.

3. The apparatus of claim 2, wherein:

the conductivity sensor has a temporal response bandwidth and a spatial response bandwidth;

the thermometer has a temporal response bandwidth and a spatial response bandwidth;

the temporal bandwidths of the conductivity sensor and thermometer are effectively matched to each other; and

the spatial bandwidths of the conductivity sensor and thermometer are effectively matched to each other.

4. The apparatus of claim 1, wherein:

the conductivity sensor has a temporal response bandwidth and a spatial response bandwidth;

the thermometer has a temporal response bandwidth and a spatial response bandwidth;

the temporal bandwidths of the conductivity sensor and thermometer are effectively matched to each other; and

the spatial bandwidths of the conductivity sensor and thermometer are effectively matched to each other.

5. The apparatus of claim 4, further comprising:

a pressure sensor for measuring pressure in a pressure-measurement volume of such liquid;

wherein a sensitivity field of the pressure sensor is very generally collocated with the conductivity- and temperature-measurement sensitivity fields.

6. The apparatus of claim 1, further comprising:

a pressure sensor mounted in a common unitary assembly with the conductivity and temperature sensors.

7. The apparatus of claim 6, wherein:

the pressure sensor is a MEMS transducer.

8. The apparatus of claim 1, wherein:

the conductivity sensor is a four-terminal device.

9. The apparatus of claim 8, wherein:

the thermometer is a thermistor encapsulated within a silkscreened glass wall.

10. The apparatus of claim 1, wherein:

the thermometer is a thermistor encapsulated within a silkscreened glass wall.

11. The apparatus of claim 1, further comprising:

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

the data-acquisition and -processing system comprising a circuit for correcting at least one of the measurement signals to compensate for time lag between measurements of conductivity and temperature.

12. The apparatus of claim 1, further comprising:

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

the data-acquisition and -processing system comprising a circuit 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.

13. The apparatus of claim 1, further comprising:

a data-acquisition and -processing system fabricated in a substantially unitary assembly with the sensors, and connected to receive measurement signals from the sensors representing collocated values of conductivity and temperature;

the data-acquisition and -processing system comprising circuits for deriving from said measurement signals secondary parameters of such liquid for said substantially identical measurement volumes.

14. The apparatus of claim 13, wherein:

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

15. The apparatus of claim 13, 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.

16. Apparatus for determining parameters of liquid;

said apparatus comprising;

a conductivity sensor for measuring electrical conductivity of such liquid, said sensor having a temporal response bandwidth and a spatial response bandwidth; and

a thermometer for measuring temperature of such liquid, said thermometer having a temporal response bandwidth and a spatial response bandwidth; and

wherein;

the temporal response bandwidths of the conductivity sensor and thermometer are effectively matched; and

the spatial response bandwidths of the conductivity sensor and thermometer are effectively matched.

17. The apparatus of claim 16, further comprising:

a pressure sensor for measuring pressure, said pressure sensor having a temporal response bandwidth and a spatial response bandwidth; and

wherein;

the temporal bandwidth of the pressure sensor is effectively matched to the temporal bandwidths of the conductivity sensor and thermometer; and

the spatial bandwidth of the pressure sensor is effectively matched to the spatial bandwidths of the conductivity sensor and thermometer.

18. 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;

the data-acquisition and -processing system comprising a circuit for correcting at least one of the measurement signals to compensate for time lag between measurements of conductivity and temperature.

19. The apparatus of claim 18, wherein:

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