Scan lock and track fluid characterization and level sensor apparatus and method

• US 7,650,785 B1
• Filed: 01/08/2007
• Issued: 01/26/2010
• Est. Priority Date: 11/17/2006
• Status: Active Grant

• Current Assignee: Meggitt Safety Systems, Inc. (Meggitt PLC)
• Original Assignee: Vibro-Meter, Inc.
• Inventors: Miskell, Thomas, Rizzo, Vincent J.
• Primary Examiner(s): Williams; Hezron
• Assistant Examiner(s): Frank; Rodney T
• Application Number:
  US11/650,841
• Time in Patent Office: 1,114 Days
• Field of Search: 733/04.R, 732/90.R, 732/90.V
• US Class Current: 73/290.00R
• CPC Class Codes: G01F 23/284 Electromagnetic waves
• CPC Class Codes: G01S 13/10 using transmission of interrupted, pulse modulated waves determination of distance by phase measurement G01S13/32
• CPC Class Codes: G01S 13/87 Combinations of radar systems, e.g. primary radar and secondary radar
• CPC Class Codes: G01S 13/88 Radar or analogous systems specially adapted for specific applications electromagnetic prospecting or detecting of objects, e.g. near-field detection, G01V3/00
• CPC Class Codes: G01S 7/032 Constructional details for solid-state radar subsystems

Abstract

A liquid characterization and level sensor with a coaxial probe attached to a closed loop servo circuitry combined with a DSP and novel algorithms to scan, lock and track signals to ascertain the level and purity of fluid in a container.

Claims

1. A liquid level sensing apparatus, comprising:

a coaxial probe;

a transceiver for generating and receiving electrical pulses, connected to the probe; and

a digital signal processor connected to the transceiver to process electrical pulses,

wherein the transceiver and digital signal processor form scan, lock, and track closed loops, and

wherein the digital signal processor comprises a receiver gate control to control receiver gate operation.

2. The apparatus of claim 1, wherein a transmitter portion of the transceiver includes a delay to delay transmit line electrical pulses.

3. The apparatus of claim 2 further comprising a transistor and capacitor to permit transmission of falling edges of the transmit line electrical pulses and to prevent transmission of rising edges of electrical pulses to the probe.

4. The apparatus of claim 1, wherein the transceiver includes a charge pump for moderating the frequency of the electrical pulses.

5. The apparatus of claim 1, wherein the digital signal processor includes a crystal-based clock for generating electrical pulses.

6. The apparatus of claim 5, wherein the transceiver includes at least one low pass filter for filtering pulses generated by the clock.

7. The apparatus of claim 6, wherein the transceiver comprises a receiver switch and a comparator to control the receiver switch.

8. The apparatus of claim 1, wherein the digital signal processor further comprises an integrate and limit algorithm to control intervals between receiver gate opening events.

9. The apparatus of claim 8, wherein the digital signal processor further comprises a low pass/high pass filter algorithm to refine and clarify shapes of electrical pulses.

10. A method of scanning, locking, and tracking electrical impulses to determine fluid levels in a container comprising the steps of:

providing a transceiver including a receiver switch connected to a coaxial probe positioned in the container, wherein the transceiver transmits electrical pulses guided by the probe into the container and receives electrical pulses reflected back from the container and guided by the probe;

providing a DSP comprising a clock connected to the transceiver for generating electrical pulses and a receiver gate control for generating voltage command signals;

generating an electrical pulse and transmitting to the probe into the container;

generating and transmitting a control voltage from the DSP;

controlling operation of the receiver switch with the control voltage;

comparing the control voltage with the transmitted electrical pulses to determine a time differential between the transmit pulses and receiver gate operation;

producing a dc output to represent the time differential;

detecting an electrical pulse reflected back from the container; and

,

processing the reflected pulse to determine fluid level.

11. The method of claim 10 further comprising:

converting the dc output to a digitized signal;

summing the digitized signal with a digitized voltage command signal from the receiver gate control to produce a voltage input.

12. The method of claim 10 further comprising multiplying the voltage input by a constant K1 to produce a voltage output.

13. The method of claim 12 further comprising adding the voltage output to an immediately preceding voltage output to produce a final voltage output.

14. The method of claim 13 further comprising delaying the immediately preceding voltage output before adding to the voltage output.

15. The method of claim 14 further comprising checking the final voltage output magnitude against a pre-selected voltage limit and adjusting the final voltage output to the voltage limit if above the limit.

16. The method of claim 15 further comprising transmitting the final voltage output to set the width in a pulse width modulator in the DSP, which produces a pwm output.

17. The method of claim 16 further comprising controlling the receiver gate switch with the pwm output.

18. The method of claim 10 further comprising converting the reflected pulse to a digitized signal.

19. The method of claim 18 further comprising refining and clarifying the digitized signal with low pass/high pass filters.

20. The method of claim 19 further comprising multiplying the digitized signal by constant K3 to produce a reflected pulse voltage input.

21. The method of claim 20 further comprising adding the reflected pulse voltage output to an immediately preceding reflected pulse voltage output to product a final reflected pulse voltage output.

22. The method of claim 21 further comprising delaying the immediately preceding reflected pulse voltage output before adding to the reflected pulse voltage output.

23. The method of claim 22 further comprising checking a final reflected pulse voltage output magnitude against a pre-selected reflected pulse voltage limit and adjusting the final reflected pulse voltage output to the reflected pulse voltage limit if above the limit.

24. The method of claim 23 further comprising transmitting the final reflected pulse voltage output to a transmit pulse shaper to produce a shaped transmit pulse.

25. The method of claim 24 further comprising comparing the shaped transmit pulse to a reference signal, if higher than the reference signal, the shaped transmit pulse is processed to determine a fluid level.

26. The method of claim 23 further comprising transmitting the final reflected pulse voltage output to a fluid level and bottom pulse shaper to produce a shaped fluid level and bottom pulse shaper.

27. The method of claim 26 further comprising comparing the shaped fluid level and bottom pulse shaper to a fluid level reference signal, if lower than the fluid level reference signal, the shaped fluid level and bottom pulse is processed to determine fluid level.

28. The method of claim 27 further comprising transmitting the calculated fluid level to a user interface.