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US4912976A Expired / Lapsed US ⏱️ 0.0 years remaining

Liquid level sensing apparatus

Assignee: Beckman Coulter Inc
•
Filing: 1987-06-26
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Granted: 1990-04-03
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Expires: 2007-06-26
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Abstract

Abstract A liquid level sensing system comprising a probe and a reactive element carried by the probe. The reactive element forms a portion of a tuned circuit in a voltage-controlled oscillator. The output of the voltage-controlled oscillator is compared to a fixed frequency reference signal and a frequency/phase detector generates a signal indicative of any difference. The frequency/phase detector output is applied to the voltage-controlled oscillator to maintain the output frequency of the oscillator at the frequency of the reference signal. The output of the frequency/phase detector is also differentiated to develop a pulse when the frequency/phase detector output signal varies rapidly, indicating initial contact between the probe and the surface of a liquid held within a container.

Inventors

  • 👤 II Donald P. Labriola

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-30 16:57
CPC Classifications
G; G01; G01N; G01N35/00; G01N35/10; G01N35/1009; G01F; G01F23/00; G01F23/22; G01F23/26; G01F23/263; G01F23/266; G01N2035/1025

Claims Analysis

Total Claims: 31
Claim 1
Independent Claim 93 words
A liquid level sensing apparatus comprising: a conductive sensing member; a reactive element disposed on the member; oscillator means having an output and a tuned circuit including at least a portion of the member and the reactive element, the tuned circuit controlling the frequency of the oscillator means output; and detecting means responsive to the output of the oscillator means for detecting the oscillator means output frequency and generating a predetermined output when the detecting means detects a shift in the oscillator means output frequency indicating contact between the member and a liquid.
Claim 2
Dependent Claim 93 words
A liquid level sensing apparatus comprising: a conductive sensing member; a reactive element disposed on the member; oscillator means having an output and a tuned circuit including at least a portion of the member and the reactive element, the tuned circuit controlling the frequency of the oscillator means output; and detecting means responsive to the output of the oscillator means for detecting the oscillator means output frequency and generating a predetermined output when the detecting means detects a shift in the oscillator means output frequency indicating contact between the member and a liquid.
Claim 3
Dependent Claim 66 words
Apparatus as in claim 1 wherein the detecting means further includes means for generating a frequency control signal which varies with the frequency of the oscillator means output as compared to a signal from a reference signal generator, and the oscillator means includes means for varying an element of the tuned circuit in response to the frequency control signal to adjust the oscillator means output frequency.
Claim 4
Dependent Claim 46 words
Apparatus as in claim 2 wherein the detecting means further includes means for differentiating the frequency control signal and generating an output when a rate of change of the frequency control signal indicates initial contact between the conductive sensing member and the surface of a liquid.
Claim 5
Dependent Claim 174 words
A liquid level sensing apparatus comprising: a conductive probe adapted to aspirate liquid; a reactive element disposed on the probe; oscillator means having an output and a tuned circuit including at least a portion of the probe and the reactive element, the tuned circuit controlling the frequency of the oscillator means output, the oscillator means further including means for varying an element of the tuned circuit in response to a frequency control signal to adjust the oscillator means output frequency; a reference signal generator generating an output having a predetermined fixed frequency; detecting means responsive to the output of the oscillator means and the reference signal generator for generating a frequency control signal which varies with the frequency of the oscillator means output as compared to the signal from the reference signal generator; and differentiating means responsive to the frequency control signal for differentiating the frequency control signal and generating an output when the rate of change of the frequency control signal indicates initial contact between the probe and the surface of a liquid.
Claim 6
Dependent Claim 174 words
A liquid level sensing apparatus comprising: a conductive probe adapted to aspirate liquid; a reactive element disposed on the probe; oscillator means having an output and a tuned circuit including at least a portion of the probe and the reactive element, the tuned circuit controlling the frequency of the oscillator means output, the oscillator means further including means for varying an element of the tuned circuit in response to a frequency control signal to adjust the oscillator means output frequency; a reference signal generator generating an output having a predetermined fixed frequency; detecting means responsive to the output of the oscillator means and the reference signal generator for generating a frequency control signal which varies with the frequency of the oscillator means output as compared to the signal from the reference signal generator; and differentiating means responsive to the frequency control signal for differentiating the frequency control signal and generating an output when the rate of change of the frequency control signal indicates initial contact between the probe and the surface of a liquid.
Claim 7
Dependent Claim 93 words
A liquid level sensing apparatus comprising: a conductive sensing probe; a reactive element disposed on the probe; oscillator means having an output and a tuned circuit including at least a portion of the probe and the reactive element, the tuned circuit controlling the frequency of the oscillator means output; and detecting means responsive to the output of the oscillator means for detecting the oscillator means output frequency and generating a predetermined output when the detecting means detects a shift in the oscillator means output frequency indicating contact between the probe and a liquid.
Claim 8
Dependent Claim 93 words
A liquid level sensing apparatus comprising: a conductive sensing probe; a reactive element disposed on the probe; oscillator means having an output and a tuned circuit including at least a portion of the probe and the reactive element, the tuned circuit controlling the frequency of the oscillator means output; and detecting means responsive to the output of the oscillator means for detecting the oscillator means output frequency and generating a predetermined output when the detecting means detects a shift in the oscillator means output frequency indicating contact between the probe and a liquid.
Claim 9
Dependent Claim 46 words
Apparatus as in claim 5 wherein the detecting means further includes means for generating a frequency control signal and the oscillator means includes means for varying an element of the tuned circuit in response to the frequency control signal to control the oscillator means output frequency.
Claim 10
Dependent Claim 47 words
Apparatus as in claim 6 wherein the detecting means further includes means for differentiating the frequency control signal and for generating an output when a rate of change of the frequency control signal indicates initial contact between the conductive sensing member and the surface of a liquid.
Claim 11
Dependent Claim 36 words
Apparatus as in claim 7 including means for generating a reference frequency signal and wherein the frequency control signal is responsive to variations between the frequency of the oscillator means output and the reference frequency signal.
Claim 12
Dependent Claim 14 words
Apparatus as in claim 6 wherein the element for varying is a variable capacitor.
Claim 13
Dependent Claim 13 words
Apparatus as in claim 5 wherein the probe includes a passage for liquid.
Claim 14
Dependent Claim 15 words
Apparatus as in claim 5 wherein the reactive element includes a plurality of conductive beads.
Claim 15
Dependent Claim 172 words
A liquid level sensing apparatus comprising: a conductive probe; a reactive element disposed on the probe; oscillator means having an output and a tuned circuit including at least a portion of the probe and the reactive element, the tuned circuit controlling the frequency of the oscillator means output, the oscillator means further including means for varying an element of the tuned circuit in response to a frequency control signal to control the oscillator means output frequency; a reference signal generator generating an output having a predetermined fixed frequency; detecting means responsive to the output of the oscillator means and the reference signal generator for generating a frequency control signal which varies in response to the frequency of the oscillator means output as compared to the signal from the reference signal enervator; and differentiating means responsive to the frequency control signal for differentiating the frequency control signal and generating an output when the rate of change of the frequency control signal indicates initial contact between the probe and the surface of a liquid.
Claim 16
Dependent Claim 172 words
A liquid level sensing apparatus comprising: a conductive probe; a reactive element disposed on the probe; oscillator means having an output and a tuned circuit including at least a portion of the probe and the reactive element, the tuned circuit controlling the frequency of the oscillator means output, the oscillator means further including means for varying an element of the tuned circuit in response to a frequency control signal to control the oscillator means output frequency; a reference signal generator generating an output having a predetermined fixed frequency; detecting means responsive to the output of the oscillator means and the reference signal generator for generating a frequency control signal which varies in response to the frequency of the oscillator means output as compared to the signal from the reference signal enervator; and differentiating means responsive to the frequency control signal for differentiating the frequency control signal and generating an output when the rate of change of the frequency control signal indicates initial contact between the probe and the surface of a liquid.
Claim 17
Dependent Claim 103 words
A liquid level sensing apparatus comprising: a conductive sensing member; a reactive element disposed on the member; oscillator means having an output and a tuned circuit including at least a portion of the member and the reactive element, the tuned circuit controlling the frequency of the oscillator means output; and detecting means responsive to the output of the oscillator means for detecting the oscillator means output frequency and generating a predetermined output when the detecting means detects a shift in the oscillator means output frequency indicating contact between the member and a liquid, the frequency shift being detected in a non-radio frequency range.
Claim 18
Dependent Claim 103 words
A liquid level sensing apparatus comprising: a conductive sensing member; a reactive element disposed on the member; oscillator means having an output and a tuned circuit including at least a portion of the member and the reactive element, the tuned circuit controlling the frequency of the oscillator means output; and detecting means responsive to the output of the oscillator means for detecting the oscillator means output frequency and generating a predetermined output when the detecting means detects a shift in the oscillator means output frequency indicating contact between the member and a liquid, the frequency shift being detected in a non-radio frequency range.
Claim 19
Dependent Claim 46 words
Apparatus as in claim 13 wherein the detecting means further includes means for generating a frequency control signal, and the oscillator means includes means for varying an element of the tuned circuit in response to the frequency control signal to control the oscillator means output frequency.
Claim 20
Dependent Claim 196 words
A liquid level sensing apparatus comprising: a conductive sensing member; a reactive element disposed on the member; oscillator means having an output and a tuned circuit including at least a portion of the member and the reactive element, the tuned circuit controlling the frequency of the oscillator means output; and detecting means responsive to the output of the oscillator means for detecting the oscillator means output frequency and generating a predetermined output when the detecting means detects a shift in the oscillator means output frequency indicating contact between the member and a liquid wherein the detecting means further includes means for generating a frequency control signal which varies with the frequency of the oscillator means output as compared to a signal from a reference signal generator, and the oscillator means includes means for varying an element of the tuned circuit in response to the frequency control signal to adjust the oscillator means output frequency, and wherein the detecting means further includes means for differentiating the frequency control signal and generating an output when a rate of change of the frequency control signal indicates initial contact between the conductive sensing member and the surface of a liquid.
Claim 21
Dependent Claim 196 words
A liquid level sensing apparatus comprising: a conductive sensing member; a reactive element disposed on the member; oscillator means having an output and a tuned circuit including at least a portion of the member and the reactive element, the tuned circuit controlling the frequency of the oscillator means output; and detecting means responsive to the output of the oscillator means for detecting the oscillator means output frequency and generating a predetermined output when the detecting means detects a shift in the oscillator means output frequency indicating contact between the member and a liquid wherein the detecting means further includes means for generating a frequency control signal which varies with the frequency of the oscillator means output as compared to a signal from a reference signal generator, and the oscillator means includes means for varying an element of the tuned circuit in response to the frequency control signal to adjust the oscillator means output frequency, and wherein the detecting means further includes means for differentiating the frequency control signal and generating an output when a rate of change of the frequency control signal indicates initial contact between the conductive sensing member and the surface of a liquid.
Claim 22
Dependent Claim 177 words
A liquid level sensing apparatus comprising: a conductive sensing probe; a reactive element disposed on the probe; oscillator means having an output and a tuned circuit including at least a portion of the probe and the reactive element, the tuned circuit controlling the frequency of the oscillator means output; and detecting means responsive to the output of the oscillator means for detecting the oscillator means output frequency and generating a predetermined output when the detecting means detects a shift in the oscillator means output frequency indicating contact between the probe and a liquid, wherein the detecting means further includes means for generating a frequency control signal and the oscillator means includes means for varying an element of the tuned circuit in response to the frequency control signal to control the oscillator means output frequency, and wherein the detecting means further includes means for differentiating the frequency control signal and for generating an output when a rate of change of the frequency control signal indicates initial contact between the conductive sensing member and the surface of a liquid.
Claim 23
Dependent Claim 177 words
A liquid level sensing apparatus comprising: a conductive sensing probe; a reactive element disposed on the probe; oscillator means having an output and a tuned circuit including at least a portion of the probe and the reactive element, the tuned circuit controlling the frequency of the oscillator means output; and detecting means responsive to the output of the oscillator means for detecting the oscillator means output frequency and generating a predetermined output when the detecting means detects a shift in the oscillator means output frequency indicating contact between the probe and a liquid, wherein the detecting means further includes means for generating a frequency control signal and the oscillator means includes means for varying an element of the tuned circuit in response to the frequency control signal to control the oscillator means output frequency, and wherein the detecting means further includes means for differentiating the frequency control signal and for generating an output when a rate of change of the frequency control signal indicates initial contact between the conductive sensing member and the surface of a liquid.
Claim 24
Dependent Claim 36 words
Apparatus as in claim 16 including means for generating a reference frequency signal and wherein the frequency control signal is responsive to variations between the frequency of the oscillator means output and the reference frequency signal.
Claim 25
Dependent Claim 14 words
Apparatus as in claim 16 wherein the element for varying is a variable capacitor.
Claim 26
Dependent Claim 99 words
A liquid level sensing apparatus comprising: a conductive sensing probe; a reactive element including a plurality of conductive beads disposed on the probe; oscillator means having an output and a tuned circuit including at least a portion of the probe and the reactive element, the tuned circuit controlling the frequency of the oscillator means output; and detecting means responsive to the output of the oscillator means for detecting the oscillator means output frequency and generating a predetermined output when the detecting means detects a shift in the oscillator means output frequency indicating contact between the probe and a liquid.
Claim 27
Dependent Claim 99 words
A liquid level sensing apparatus comprising: a conductive sensing probe; a reactive element including a plurality of conductive beads disposed on the probe; oscillator means having an output and a tuned circuit including at least a portion of the probe and the reactive element, the tuned circuit controlling the frequency of the oscillator means output; and detecting means responsive to the output of the oscillator means for detecting the oscillator means output frequency and generating a predetermined output when the detecting means detects a shift in the oscillator means output frequency indicating contact between the probe and a liquid.
Claim 28
Dependent Claim 46 words
Apparatus as in claim 19 wherein the detecting means further includes means for generating a frequency control signal and the oscillator means includes means for varying an element of the tuned circuit in response to the frequency control signal to control the oscillator means output frequency.
Claim 29
Dependent Claim 47 words
Apparatus as in claim 20 wherein the detecting means further includes means for differentiating the frequency control signal and for generating an output when a rate of change of the frequency control signal indicates initial contact between the conductive sensing member and the surface of a liquid.
Claim 30
Dependent Claim 36 words
Apparatus as in claim 21 including means for generating a reference frequency signal and wherein the frequency control signal is responsive to variations between the frequency of the oscillator means output and the reference frequency signal.
Claim 31
Dependent Claim 14 words
Apparatus as in claim 20 wherein the element for varying is a variable capacitor.

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USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1993-04-02 1993-10-02 1994-04-03 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1997-04-02 1997-10-02 1998-04-03 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 2001-04-02 2001-10-02 2002-04-03 $7700.00 Window Closed / Lapsed

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