Material level detector and control

• US 4,589,281 A
• Filed: 09/20/1984
• Issued: 05/20/1986
• Est. Priority Date: 09/20/1984
• Status: Expired due to Fees

• Current Assignee: ASI Instruments, Inc
• Original Assignee: Keystone International, Inc. (Johnson Controls International plc)
• Inventors: Aldrich, Joe L.
• Primary Examiner(s): Smith, Robert I.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/653,028
• Time in Patent Office: 607 Days
• Field of Search: 73/290 R, 73/290 V, 73/304 R, 73/304 C, 340/617, 340/620, 361/284, 324/61 P
• US Class Current: 73/290.00R
• CPC Class Codes: G01F 23/22 by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water involving the use of floats G01F23/30

Abstract

Disclosed is a monitoring system and method for detecting the presence or absence of material at a location. The apparatus may generally be constructed to include a sensing unit, including an antenna probe for positioning at the location wherein material is to be detected, and a control unit for responding to signals from the sensing unit indicating the presence of material at the antenna probe. The control unit may include an indicator to inform an operator of the presence or absence of material at the antenna probe, and also an output which enables peripheral equipment to operate only under selected conditions at the antenna probe. The sensing signal from the sensing unit is dc, with fluctuations indicating the presence of material at the antenna probe. The sensing signal may be communicated a considerable distance to the control unit over ordinary electrical lead lines without electrical shielding, and the control unit responds to a break in such communication lines by not permitting enabling of such peripheral equipment.

Claims

1. Apparatus for detecting the presence or absence of material at a location comprising sensing means, including:

a. oscillator means for providing an oscillatory output signal;

b. reference means, for receiving said oscillatory output signal and providing a reference;

c. sensor means, including antenna probe means for positioning at said location, and for receiving said oscillatory output signal;

d. switching means for alternately permitting said oscillatory output signal to be applied to said reference means and to said antenna probe means;

e. an electrical energy source for providing electrical energy for application to said oscillator means by connection means whereby the absence of material, to be sensed, at said location, is accompanied by substantially the same rate of electrical energy consumption by said oscillator means when said oscillatory output signal is applied to said antenna probe means as when said signal is applied to said reference, and, with such material present at said location, electrical energy is consumed by said oscillator means at a greater rate when said signal is applied to said antenna probe means compared to when said signal is applied to said reference; and

f. means for detecting a change in the rate of energy consumption from said electrical power source whereby the presence or absence of said material at said location may be determined.

2. Apparatus as defined in claim 1 wherein:

a. said sensor means further comprises gate means for receiving said oscillatory output signal and operational by said switching means for periodically providing an output of frequency equal to that of said oscillatory signal for forwarding to said antenna probe means; and

b. said reference means further comprises gate means for receiving said oscillatory output signal and operable by said switching means for periodically providing an output of frequency equal to that of said oscillatory signal for forwarding to said reference.

3. Apparatus as defined in claim 2 wherein said switching means comprises an oscillator whose output is communicated to said sensor means gate means and to said reference means gate means.

4. Apparatus as defined in claim 3 wherein said switching means oscillator output is a constant frequency signal, and said oscillatory output signal has a frequency higher than said frequency of said switching means oscillator output.

5. Apparatus as defined in claim 1 wherein said means for detecting a change in rate of energy consumption comprises:

a. amplitude detector for providing a voltage level in response to an increased rate of electrical energy consumption by said oscillator means with material present at said location; and

b. indicator means for indicating the presence or absence of material at said location as determined by said amplitude detector.

6. Apparatus as defined in claim 5 further comprising open connection detector means for sensing a lack of energy consumption by said oscillator means indicative of a break in said connection means.

7. Apparatus as defined in claim 6 further comprising logic means for providing an output control signal which may be zero or non-zero, and switch means for selectively configuring said logic means in a first configuration in which said control signal is zero when material is detected at said antenna probe means, and may be non-zero otherwise, and a second configuration in which said output control signal may be non-zero when material is detected at said antenna probe means, but which is zero otherwise.

8. Apparatus as defined in claim 7 wherein said output control signal is provided by said logic means as zero in either said first configuration or said second configuration when said open connection detector means determines that said connection means is open.

9. Apparatus as defined in claim 7 further comprising relay means for receiving said output control signal from said logic means and operating in response to said control signal.

10. Apparatus as defined in claim 9 further comprising time delay means for delaying the change in operating of said relay means in response to said control signal changing between zero and non-zero.

11. Apparatus as defined in claim 5 further comprising sensitivity adjustment means for selectively adjusting the sensitivity of said means for detecting a change in the rate of energy consumption from said electric power source.

12. Apparatus as defined in claim 1 further comprising sensitivity adjustment means for selectively adjusting the sensitivity of said means for detecting a change in the rate of energy consumption from said electric power source.

13. Apparatus as defined in claim 1 further comprising open connection detector means for sensing a lack of energy consumption by said oscillator means indicative of a break in said connection means.

14. Apparatus as defined in claim 1 further comprising logic means for providing an output control signal which may be zero or non-zero, and switch means for selectively configuring said logic means in a first configuration in which said control signal is zero when material is detected at said antenna probe means, and may be non-zero otherwise, and a second configuration in which said output control signal may be non-zero when material is detected at said antenna probe means, but which is zero otherwise.

15. Apparatus as defined in claim 14 further comprising relay means for receiving said output control signal from said logic means and operating in response to said control signal.

16. Apparatus as defined in claim 15 further comprising time delay means for delaying the change in operating of said relay means in response to said control signal changing between zero and non-zero.

17. Apparatus as defined in claim 1 further comprising control means for operating in response to said means for detecting a change in the rate of energy consumption from said electric power source to provide an output signal depending, at least in part, on the detected presence or absence of material at said location.

18. Apparatus as defined in claim 1 wherein said oscillator means, reference means, sensor means and switching means are positioned remote from said energy source and means for detecting a change in the rate of energy consumption, which are connected to said oscillator means, reference means, sensor means and switching means by said connection means.

19. A system for monitoring the level of material in a container comprising:

a. sensing means for locating at said container, including;

i. a first oscillator for providing a first oscillatory signal of a first frequency;

ii. a second oscillator for providing a second oscillatory signal of a second frequency smaller than said first frequency;

iii. first gate means, and antenna probe means for positioning at a location within such container and couped to the output of said first gate means; and

iv. second gate means with an open output for providing a reference;

v. wherein said first oscillatory signal is communicated to first inputs of each of said first and second gates, said second oscillatory signal is communicated to a second input of one of said first and second gates and to an inverter, the output of said inverter being communicated to the second input of the other of said first and second gates, whereby said first and second gates alternately provide an output signal of said first frequency with the output signal from said first gate being communicated to said antenna probe coupled thereto; and

b. control means, connected to said sensing means by conductor means, and including;

i. electrical power means for providing an electrical voltage communicated along said conductor means to said sensing means;

ii. detector means for responding to changes in the electrical current drawn by said sensing means from said power means due to the presence of material at said antenna probe means compared to the electrical current so drawn by said sensing means from said power means in the absence of such material at said antenna probe means; and

iii. indicator means for displaying information indicative of the presence or absence of material at said antenna probe means as determined by said detector means.

20. A system as defined in claim 19 wherein said control means further comprises open connection detector means for sensing the lack of electrical energy communicated between said power means and said sensing means associated with the opening of said conductor means.

21. Apparatus as defined in claim 20 wherein said control means further comprises:

a. logic means for responding to the presence or absence of material at said antenna probe means as determined by said detector means, and the detection of the opening of said conductor means between said control means and said sensing means, to provide an output signal; and

b. output means, for receiving said output signal of said logic means, to control the energizing of means for affecting the level of material in such container.

22. Apparatus as defined in claim 21 wherein said control means further comprises time delay means for receiving said output signal from said logic means and delaying change in the operation of said output means to so effect change in energization of means for affecting the level of material in said container.

23. Apparatus as defined in claim 19 wherein said control means further comprises:

a. logic means for responding to the presence or absence of material at said antenna probe means as determined by said detector means; and

b. output means, for receiving said output signal of said logic means, to control the energizing of means for affecting the level of material in such container.

24. Apparatus as defined in claim 23 wherein said control means further comprises time delay means for receiving said output signal from said logic means and delaying change in the operation of said output means to so effect change in energization of means for affecting the level of material in said container.

25. Apparatus as defined in claim 19 wherein said control means further comprises sensitivity adjustment means for selectively adjusting the sensitivity of response of said detector means for responding to changes in the electrical current drawn by said sensing means from said power means.

26. A material detector and control system comprising:

a. sensing means, including;

i. a signal generator for generating a sensing signal;

ii. first and second drivers for receiving said sensing signal;

iii. an antenna probe for positioning at a predetermined location where the presence or absence of material is to be detected, said antenna probe being coupled to said first driver whereby an output signal from said first driver may be impressed on said antenna probe; and

iv. switch means for alternately enabling said first an second drivers at a switching frequency for providing output signals in response to said sensing signal received thereby, respectively;

v. wherein said second driver operates as a reference when enabled, by said switching means, to provide an output signal in response to said sensing signal so that, with no such material present at said antenna probe, the rate of electrical energy consumption by said signal generator is substantially constant, and, with detectable material at said antenna probe, said energy consumption fluctuates as said switching means alternately enables said first and second drivers, said rate of energy consumption thus providing a data signal indicating the presence or absence of material at said antenna probe; and

b. control means comprising;

i. electrical power means, in communication with said sensing means by connector means, for providing electrical energy for consumption by said sensing means such that said data signal comprises fluctuations in the rate of energy transmission by said connector means with material at said antenna probe, and comprises a substantially constant rate of energy transmission by said connector means when no detectable material is present at said antenna probe;

ii. amplifier means coupled to said connector means for receiving said data signal and providing an amplifier output signal varying between two voltage levels at said switching frequency when material is detected at said antenna probe, and which is otherwise of constant value;

iii. amplitude detector means for receiving and integrating said amplifier output signal, comparing the integration of said signal to a reference and providing an output voltage level whenever said reference is exceeded, signaling detection of the presence of material at said antenna probe;

iv. indicator means, in communication with said amplitude detector means, for providing a display indicating the presence of material at said antenna probe whenever said output voltage level is provided by said amplitude detector means;

v. logic means, in communication with said amplitude detector means, for providing a logic output signal depending on said amplitude detector means output; and

vi. relay means for receiving said logic output signal as an enabling signal whereby said relay means provides switching control means to open or close peripheral circuitry in response to said logic output signal.

27. A system as defined in claim 26 wherein said control means further comprises open connection detector means coupled to said connector means for determining whether said connector means between said control means and said sensing means is closed, and providing an open connection detector means output signal to said logic means whereby said logic means fails to provide an enabling signal to said relay means when said open connection detector means determines that said connector means is open.

28. A system as defined in claim 27 wherein said logic means may be selectively moved between a first configuration, in which said logic means does not provide an enabling signal to said relay means when said amplitude detector means signals the detection of the presence of material at said antenna probe, and a second configuration, in which said logic means does not provide an enabling signal to said relay means when said amplitude detector means does not signal the detection of the presence of material at said antenna probe.

29. A system as defined in claim 28 wherein said control means further comprises sensitivity adjustment means for selectively adjusting the response of said amplifier means to said data signal to vary the integration of said amplifier output signal by said amplitude detector means in response to change in energy consumption rate by said sensing means in the presence of material at said antenna probe.

30. A system as defined in claim 28 wherein said control means further comprises delay means for selectively delaying the response of said relay means to change in said enabling signal from said logic means.

31. A system as defined in claim 26 wherein said logic means may be selectively moved between a first configuration, in which said logic means does not provide an enabling signal to said relay means when said amplitude detector means signals the detection of the presence of material at said antenna probe means, and a second configuration, in which said logic means does not provide an output enabling signal to said relay means when said amplitude detector means does not signal the detection of the presence of material at said antenna probe means.

32. A system as defined in claim 26 wherein said control means further comprises sensitivity adjustment means for selectively adjusting the response of said amplifier means to said data signal to vary the integration of said amplifier output signal by said amplitude detector means in response to change in energy consumption rate by said sensing means in the presence of material at said antenna probe.

33. A system as defined in claim 26 wherein said control means further comprises delay means for selectively delaying the response of said relay means to change in said enabling signal from said logic means.

34. A system as defined in claim 26 wherein said signal generator comprises an oscillator for providing said sensing signal as a square wave signal of frequency higher than said switching frequency.

35. A system as defined in claim 34 further comprising capacitive coupling for so coupling said antenna probe to said first driver.

36. A system as defined in claim 26 wherein said switching means comprises an oscillator for providing an enabling signal to said first and second drivers as a square wave of said switching frequency whereby each such driver may be enabled to provide an output signal when receiving one-half cycle of said enabling signal square wave, and an inverter by which said square wave is provided to one or the other of said first and second drivers so that while one such driver receives one half of said square wave cycle, the other of said drivers receives the other half to so alternately enable said drivers.

37. A method of monitoring the quantity of material at a location comprising the following steps:

a. providing an antenna probe at the location, coupled to a probe driver;

b. providing a dummy driver serving as a reference;

c. providing an oscillator for generating an oscillatory sensing signal at a first frequency and communicating the oscillatory signal to each of the drivers;

d. periodically and alternately enabling each of the drivers at a second frequency to output a signal of the first frequency;

e. monitoring the rate of electrical energy consumption by the oscillator to detect fluctuations of increased energy consumption by the oscillator as the probe driver is enabled to output its signal to the antenna probe in the presence of material at the antenna probe, and providing an output amplifier signal at the second frequency in response to such detection of material at the antenna probe;

f. integrating the output amplifier signal and comparing the integration level with a reference level and, whenever the integration level exceeds the reference level, providing an output voltage level.

38. A method as defined in claim 37 further comprising the following additional steps:

a. applying said output voltage level to logic circuitry; and

b. providing an enabling voltage by the logic circuitry to control peripheral equipment depending upon the presence or absence of detectable material at said antenna probe.

39. A method as defined in claim 38 further comprising the step of selectively configuring said logic circuitry to either provide said enabling voltage only when material is detected at said antenna probe or only when material is not detected at said antenna probe.

40. A method as defined in claim 39 further comprising the step of monitoring the energy consumption by the oscillator to monitor the integrity of the connection between the oscillator and its power source, and, in the event of a determination of a break in that connection, providing a signal to operate the logic circuitry to prevent presentation of the enabling voltage.

41. A method as defined in claim 38 further comprising the step of monitoring the energy consumption by the oscillator to monitor the integrity of the connection between the oscillator and its power source, and, in the event of a determination of a break in that connection, providing a signal to operate the logic circuitry to prevent presentation of the enabling voltage.

42. A method as defined in claim 37 further comprising the step of selectively adjusting the sensitivity of the amplifier to provide the output amplifier signal to achieve a selected integration level in response to a selected amplitude of fluctuations in energy consumption by the oscillator in conjunction with the presence of material at the antenna probe.

43. A method as defined in claim 37 further comprising the step of applying said output voltage level to an indicator to actuate the indicator to reveal the detection of material at the antenna probe.