US5083470A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Capacitive liquid level sensor
Assignee: Dade Behring Inc
•
Filing: 1990-09-28
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Granted: 1992-01-28
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Expires: 2010-09-28
Abstract
Abstract A capacitance liquid level sensor uses an inductance to isolate the probe of the sensor from the plastic tubing coupled to the probe thus reducing false signals generated by movement of the tubing.
Inventors
- 👤 James E. Davis
- 👤 Stephen J. Simko
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 16:08
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: 3
Claim 1
Independent Claim
154 words
In a capacitive liquid level sensor for determining the liquid level of a sample in a liquid pipetting system, having: a pipette probe for withdrawing liquid from a sample, means including tubing coupled to the pipette probe for applying suction, an oscillator coupled to the probe for applying a high frequency signal to the probe to create a second signal whose amplitude and/or phase is determined by the capacitance of the probe; and comparator means for generating a level sensor signal according to the amplitude or phase of the second signal for signaling the probe's reaching the liquid level of the sample, the improvement comprising: means exhibiting an inductive reactance positioned on the pipette probe adjacent to the suction means, thereby to electrically isolate the probe from the suction means, the tubing for applying suction being plastic tubing and a portion being coiled in a ferrite core to provide the means exhibiting inductive reactance.
Claim 2
Dependent Claim
154 words
In a capacitive liquid level sensor for determining the liquid level of a sample in a liquid pipetting system, having: a pipette probe for withdrawing liquid from a sample, means including tubing coupled to the pipette probe for applying suction, an oscillator coupled to the probe for applying a high frequency signal to the probe to create a second signal whose amplitude and/or phase is determined by the capacitance of the probe; and comparator means for generating a level sensor signal according to the amplitude or phase of the second signal for signaling the probe's reaching the liquid level of the sample, the improvement comprising: means exhibiting an inductive reactance positioned on the pipette probe adjacent to the suction means, thereby to electrically isolate the probe from the suction means, the tubing for applying suction being plastic tubing and a portion being coiled in a ferrite core to provide the means exhibiting inductive reactance.
Claim 3
Dependent Claim
25 words
The liquid level sensor of claim 1 wherein an electrically conductive piece of tubing is connected adjacent to the plastic tubing opposite to the probe.
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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) | 1995-01-27 | 1995-07-29 | 1996-01-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-01-27 | 1999-07-29 | 2000-01-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-01-27 | 2003-07-29 | 2004-01-28 | $7700.00 | Window Closed / Lapsed |