Liquid gaging system multiplexing

• US 4,451,894 A
• Filed: 05/25/1983
• Issued: 05/29/1984
• Est. Priority Date: 05/14/1980
• Status: Expired due to Fees

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Dougherty, William R., Fahley, Jerome A., Van Dyke, Martin J., Colby, Dwight D.
• Primary Examiner(s): Krass, Errol A.
• Application Number:
  US06/496,984
• Time in Patent Office: 370 Days
• Field of Search: 364/509, 364/550, 364/551, 364/424, 364/431, 364/442, 364/571, 73/290 R, 73/304 R, 73/304 C, 340/603, 340/612, 340/620, 324/51
• US Class Current: 702/52
• CPC Class Codes: G01F 23/263 by measuring variations in capacitance of capacitors

Abstract

A liquid gaging system comprising a plurality of sensors, each sensor providing a liquid measurement signal relating to a liquid depth at a particular location in a tank. The invention also comprises apparatus for selectively monitoring individual sensors one at a time. The apparatus for selectively monitoring is connected to the sensors.

Claims

1. In a liquid gaging system, apparatus for monitoring individual sensors one at a time, comprising:

a plurality of sensors, each sensor providing a range of liquid measurement signals relating to liquid depth at a particular location in a tank; and

means for selectively monitoring individual sensors one at a time for a unique signal in the range relating to actual liquid depth at the particular location in the tank, the means for selectively monitoring being connected to the sensors.

2. The apparatus of claim 1 wherein at least one of the sensors comprises a capacitive probe.

3. The apparatus of claim 2 wherein the means for selectively monitoring comprises means for selectively providing individual sensors with an excitation signal.

4. The apparatus of claim 3 wherein the means for selectively providing further comprises means for grounding predetermined sensors not receiving the excitation signal, the means for grounding being connected to the means for selectively providing.

5. The apparatus of claim 2, 3, or 4 wherein the capacitive probe has an essentially uniform capacitance per unit length.

6. The apparatus of claim 1 wherein the means for selectively monitoring comprises means for selectively providing individual sensors with an excitation signal.

7. The apparatus of claim 6 wherein the means for selectively providing further comprises means for grounding predetermined sensors not receiving the excitation signal, the means for grounding being connected to the means for selectively providing.

8. The apparatus of claim 7 wherein at least one of the sensors comprises a capacitive probe.

9. The apparatus of claim 8 wherein the capacitive probe has an essentially uniform capacitance per unit length.

10. In a liquid gaging system, apparatus for selectively monitoring individual sensors one at a time, comprising:

a plurality of sensor systems, each sensor system comprising a plurality of sensors applicable to a particular tank, each sensor providing a range of liquid measurement signals relating to liquid depth at a particular location in a particular tank; and

means for selectively monitoring individual sensors one at a time for a unique signal in the range relating to actual liquid depth at the particular location in the tank, the means for selectively monitoring being connected to the sensors.

11. The apparatus of claim 10 wherein at least one of the sensors comprises a capacitive probe.

12. The apparatus of claim 11 wherein the means for selectively monitoring comprises means for selectively providing individual sensors with an excitation signal.

13. The apparatus of claim 12 wherein the means for selectively providing further comprises means for grounding predetermined sensors not receiving the excitation signal, the means for grounding being connected to the means for selectively providing.

14. The apparatus of claim 13 wherein the capacitive probe has an essentially uniform capacitance per unit length.

15. The apparatus of claim 10 wherein the means for selectively monitoring comprises means for selectively providing individual sensors with an excitation signal.

16. The apparatus of claim 15 wherein the means for selectively providing further comprises means for grounding predetermined sensors not receiving the excitation signal, the means for grounding being connected to the means for selectively providing.

17. The apparatus of claim 16 wherein at least one of the sensors comprises a capacitive probe.

18. The apparatus of claim 17 wherein the capacitive probe has an essentially uniform capacitance per unit length.

19. In a liquid gaging system, apparatus for monitoring individual probes one at a time, comprising:

a plurality of probe systems, each probe system comprising a plurality of probes for mounting in a tank;

means for selectively providing an individual probe in a probe system with an excitation signal, the means for selectively providing being connected to the probes;

means for selectively grounding predetermined probes not receiving the excitation signal, the means for selectively grounding being connected to the probes; and

means for selecting a probe system for liquid measurement and for monitoring the individual probe for a unique signal in a range of signals provided by the probe, each signal relating to an actual liquid depth at the particular location in the tank, the means for selecting a probe system being connected to the probe systems.

20. The apparatus of claim 19 wherein at least one of the probes comprises a capacitive probe.

21. The apparatus of claim 20 wherein the capacitive probe has an essentially uniform capacitance per unit length.

22. Apparatus for monitoring an individual sensor in a multiple-tank, multiple-sensor liquid gaging system, comprising:

a plurality of capacitive sensors for mounting in a plurality of tanks, there being a plurality of capacitive sensors for each tank, each capacitive sensor having a first electrode and a second electrode, each capacitive sensor providing a liquid measurement signal variable in dependence on the portion of the sensor immersed in liquid and on the dielectric constant of the liquid, the sensors for a particular tank comprising a particular sensor system;

excitation signal means having an output for providing an excitation signal having a voltage;

excitation multiplexer means for selectively controlling application of the excitation signal to the first electrode of a predetermined sensor in each sensor system, the excitation multiplexer means having a first input connected to receive the excitation signal and having a plurality of outputs, each output being connected to the first electrode of a predetermined capacitive sensor in each sensor system;

a plurality of input amplifier means for converting current to voltage, each input amplifier means having an input, there being for each sensor system an input of an input amplifier means connected to the second electrode of each capacitive sensor in the sensor system, the input amplifier means also having an output; and

input multiplexer means for selectively monitoring a predetermined probe system, the input multiplexer means having a plurality of first inputs, each first input being connected to the output of a predetermined input amplifier means, the input multiplexer means also having an output for providing a signal corresponding to the predetermined sensor in the predetermined sensor system.

23. The apparatus of claim 22 wherein:

at least one of the capacitive sensors in each sensor system comprises a capacitive probe for use in providing a wetted sensor length signal; and

one of the capacitive sensors in at least one sensor system comprises a capacitive dielectric sensor.

24. The apparatus of claim 23 wherein the capacitive probe has an essentially uniform capacitance per unit length.

25. The apparatus of claim 22 wherein a predetermined number of the capacitive sensors each comprise a capacitive probe having an essentially uniform capacitance per unit length.

26. The apparatus of claim 23, 24 or 25 wherein:

the apparatus further comprises a microcomputer for providing input control signals to control to input multiplexer means; and

the input multiplexer means also has a plurality of second inputs for receiving the input control signals.

27. The apparatus of claim 23, 24 or 25 wherein:

the apparatus further comprises a microcomputer for providing excitation control signals to the excitation multiplexer means; and

the excitation multiplexer means also has a plurality of second inputs for receiving the excitation control signals.

28. The apparatus of claim 22 wherein:

the apparatus further comprises a microcomputer for providing input control signals to control to input multiplexer means; and

the input multiplexer means also has a plurality of second inputs for receiving the input control signals.

29. The apparatus of claim 28 wherein:

at least one of the capacitive sensors in each sensor system comprises a capacitive probe for use in providing a wetted sensor length signal; and

one of the capacitive sensors in at least one sensor system comprises a capacitive dielectric sensor.

30. The apparatus of claim 29 wherein the capacitive probe has an essentially uniform capacitance per unit length.

31. The apparatus of claim 28 wherein a predetermined number of the capacitive sensors each comprises a capacitive probe having an essentially uniform capacitance per unit length.

32. The apparatus of claim 22 wherein:

the apparatus further comprises a microcomputer for providing excitation control signals to the excitation multiplexer means; and

the excitation multiplexer means also has a plurality of second inputs for receiving the excitation control signals.

33. The apparatus of claim 32 wherein:

at least one of the capacitive sensors in each sensor system comprises a capacitive probe for use in providing a wetted sensor length signal; and

one of the capacitive sensors in at least one sensor system comprises a capacitive dielectric sensor.

34. The apparatus of claim 33 wherein the capacitive probe has an essentially uniform capacitance per unit length.

35. The apparatus of claim 32 wherein a predetermined number of the capacitive sensors each comprise a capacitive probe having an essentially uniform capacitance per unit length.