APPARATUS AND METHOD FOR MEASURING THE LEVEL OF A CONTAINED LIQUID

• US 3,832,900 A
• Filed: 06/28/1971
• Issued: 09/03/1974
• Est. Priority Date: 06/28/1971
• Status: Expired due to Term

• Current Assignee: Gerald F. Ross
• Original Assignee: Gerald F. Ross
• Inventors: Ross, Gerald F.
• Primary Examiner(s): Queisser, Richard C.
• Assistant Examiner(s): Shoon, F.
• Application Number:
  US05/157,248
• Time in Patent Office: 1,163 Days
• Field of Search: 73/29R,29V,34C,34R 324/188,58.5R,58.5B 343/5DP,13R 333/10
• US Class Current: 73/290.00R
• CPC Class Codes: G01F 23/284 Electromagnetic waves

Abstract

A method and apparatus for measuring the level of a contained liquid, which include a device for generating a baseband pulse signal of subnanosecond duration that is coupled into a transmission line which is immersed in the contained liquid. The surface of the liquid creates a discontinuity at a point on the transmission line which produces a reflection of the baseband pulse signal that propagates back along the transmission line and is coupled into a receiver unit which includes a plurality of coincident detectors. A timing signal produced synchronously with the baseband pulse signal is coupled through a pulse circuit and a delay circuit in the receiver unit. The receiver unit establishes the level of the contained liquid by sensing the space-time coincidence between the baseband pulse signal and the timing signal. A display unit which includes a plurality of indicator lights associated respectively with the plurality of coincident circuits in the receiver unit provides a visual indication of the level of the contained liquid.

Claims

1. An apparatus for measuring the level of a contained liquid comprising generator means for producing a subnanosecond pulse signal on a first output terminal and a synchronizing pulse signal on a second output terminal, coupling means having first, second and third terminals, said first terminal being coupled to said first output terminal on said generator means, transmission line means having one end coupled to said second terminal on said coupling means and its other end partially immersed in said liquid for conducting said subnanosecond pulse signal from said generator means through said liquid and conducting reflections of said subnanosecond pulse signal back to said coupling means, receiver means including first receiver transmission line means coupled to said third terminal on said coupling means for receiving said subnanosecond pulse signal and said reflection of said subnanosecond pulse signal, second receiver transmission line means coupled to said second output terminal on said generator means for receiving said synchronizing pulse signal, and coincident detector means coupled between said first and second receiver transmission line means for providing an output signal when said synchronizing pulse signal and said reflections of said subnanosecond pulse signal are spatially and temporally coincident within said first and second receiver transmission lines respectively, duplexing means including delay means coupled between said first output terminal on said generator means and said second receiver transmission line means having a delay time greater than the time required for said subnanosecond pulse signal to propogate through said first receiver transmission line means, and display means coupled to said coincident detector means for producing a visual output indicative of said level of said liquid.

2. An apparatus for measuring the level of a contained liquid as described in claim 1 in which said coincident detector means includes a plurality of AND gates connected in parallel between said first and second receiver transmission line means each of said AND gates having a first input terminal connected to said first receiver transmission line means and a second input terminal connected to said second receiver transmission line means, pulse circuit means coupled to said AND gates for providing a longer duration output pulse, and multivibrator means responsive to said longer duration output pulse for producing an output signal indicative of coincidence and for feeding back said longer duration output signal to said pulse circuit means thereby automatically resetting said pulse circuit means.

3. An apparatus for measuring the level of a contained liquid as recited in claim 1 in which said delay means includes a length of delay line having a delay time greater than the delay time in said first receiver transmission line means.

4. An apparatus for measuring the level of a contained liquid as recited in claim 1 further including second transmission line means having an effective length d2 being coupled between said first output terminal on said generator means and said first terminal on said coupliNg means, third transmission line means having an effective length d1 being coupled between said third terminal on said coupling means and said first receiver transmission line means wherein said first receiver transmission line means has an effective length L, fourth transmission line means having an effective length d being coupled between said second output terminal on said generator means and said second receiver transmission line means, said delay means in said duplexing means having an effective delay length X whereby the total time delay in effective delay lengths X + d is greater than the total time delay in effective delay lengths d1 + d2 + L.

5. A method for determining the level of a contained liquid comprising the steps of exciting a transmission line partially immersed in said liquid with a baseband pulse of subnanosecond duration, generating a synchronized pulse signal simultaneous with said baseband pulse, delaying said synchronized pulse signal for a predetermined time with respect to said baseband pulse, propagating said baseband pulse and a reflection of said baseband pulse produced at said level of said contained liquid from said excited transmission line through a first receiver transmission line in a specified direction, propagating said delayed synchronized pulse through a second receiver transmission line in a direction opposite said specified direction after said baseband pulse has propagated through said first receiver transmission line, detecting spatial and temporal coincidence between said delayed synchronized pulse signal and said reflected pulse signal in one of a plurality of pulse detector circuits connected in parallel between said first and second receiver transmission lines, producing an output signal from said one of a plurality of pulse detector circuits in which said pulses are spatially and temporally coincident, establishing the level of said contained liquid from said detector output signal, and displaying a visual indication of said level of said contained liquid.

6. A method for determining the level of a contained liquid comprising the steps of applying a baseband pulse of subnanosecond duration to one end respectively of first and second transmission lines, said first transmission line having its other end at least partially immersed in said liquid, generating a synchronized pulse signal which is time coincident with said baseband pulse, coupling a reflection of said baseband pulse produced at the surface of said liquid into the same end of said second transmission line as said baseband pulse, delaying said synchronized pulse signal for a period of time greater than the propagation time of said baseband pulse along said second transmission line, coupling said synchronized pulse signal to one end of a third transmission line substantially similar to said second transmission line so that it propagates in a direction opposite to said reflection in said second transmission line, sensing spatial and temporal coincidence between said reflection in said second transmission line and said synchronized pulse signal in said third transmission line in one of a plurality of AND gates in which each gate has one input coupled to said second transmission line and another input coupled to said third transmission line, and providing a coincidence signal from said one AND gate which is indicative of said level of said contained liquid.

7. A method for determining the level of a contained liquid as described in claim 6 which further includes the step of illuminating an indicator light associated with said one AND gate which provided said coincident signal indicative of said level of said contained liquid.