US5495130A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Point level switch
Assignee: Magnetrol International Inc
•
Filing: 1990-09-04
•
Granted: 1996-02-27
•
Expires: 2010-09-04
Abstract
Abstract A capacitance point level switch includes a probe adapted to be disposed in a material containing vessel, the material having a capacitance value dependent upon its level in the vessel. An oscillator circuit develops a periodic signal at a select frequency. A reference network is driven by the oscillator and includes a reference capacitance for developing a periodic reference signal at the select frequency and phase displaced responsive to the reference capacitance. A probe network is driven by the oscillator and is connected to the probe to include the capacitance of the material for developing a periodic probe signal at the select frequency and phase displaced responsive to capacitance of the material. An output circuit is connected to the reference network and the probe network for developing a discrete output assuming a first or a second state according to the relative phase displacement of the periodic reference signal and the periodic probe signal.
Inventors
- 👤 Quentin L. Schneider
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 23:12
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/94; H03K17/945; H03K17/955
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
150 words
A capacitance point level switch comprising: a probe adapted to be disposed in a material containing vessel, such material having a capacitance value dependent on its level in the vessel; an oscillator circuit developing a periodic signal at a select frequency; a reference network driven by said oscillator and including a reference capacitance for developing a periodic reference signal at the select frequency and phase displaced responsive to said reference capacitance; a probe network driven by said oscillator and connected to said probe to include the capacitance of the material for developing a periodic probe signal at the select frequency and phase displaced responsive to capacitance of the material; and an output circuit connected to said reference network and said probe network for developing a discrete output assuming a first or a second state according to the relative phase displacement of said periodic reference signal and said periodic probe signal.
Claim 2
Dependent Claim
150 words
A capacitance point level switch comprising: a probe adapted to be disposed in a material containing vessel, such material having a capacitance value dependent on its level in the vessel; an oscillator circuit developing a periodic signal at a select frequency; a reference network driven by said oscillator and including a reference capacitance for developing a periodic reference signal at the select frequency and phase displaced responsive to said reference capacitance; a probe network driven by said oscillator and connected to said probe to include the capacitance of the material for developing a periodic probe signal at the select frequency and phase displaced responsive to capacitance of the material; and an output circuit connected to said reference network and said probe network for developing a discrete output assuming a first or a second state according to the relative phase displacement of said periodic reference signal and said periodic probe signal.
Claim 3
Dependent Claim
24 words
The capacitance point level switch of claim 1 wherein said select frequency varies as a function of said reference capacitance and said material capacitance.
Claim 4
Dependent Claim
17 words
The capacitance point level switch of claim 1 wherein said oscillator circuit develops a square wave signal.
Claim 5
Dependent Claim
31 words
The capacitance point level switch of claim 1 wherein each said reference network and probe network comprises an RC circuit driven by said oscillator circuit for developing a sawtooth type waveform.
Claim 6
Dependent Claim
38 words
The capacitance point level switch of claim 4 wherein said RC circuits utilize a common potentiometer and said potentiometer is adjustable to calibrate said networks to select a desired material level at which said discrete output changes state.
Claim 7
Dependent Claim
61 words
The capacitance point level switch of claim 4 wherein each said reference network and probe network further comprises a comparator connected to said RC circuit for comparing the sawtooth waveform to a reference to develop a square wave output at the select frequency and phase displaced relative to said periodic signal responsive to the capacitance of its associated said RC circuit.
Claim 8
Dependent Claim
44 words
The capacitance point level switch of claim 4 further comprising a latching circuit connected to said output circuit and said reference network including means for varying resistance of said reference network RC circuit to provide hysteresis according to the state of said discrete output.
Claim 9
Dependent Claim
47 words
The capacitance point level switch of claim 4 further comprising a resistor and a switch circuit driven by said output circuit for selectively connecting said resistor across said reference network RC circuit or bypassing said resistor to provide hysteresis according to the state of said discrete output.
Claim 10
Dependent Claim
25 words
The capacitance point level switch of claim 1 wherein said output circuit includes means for determining which of said phase displaced signals leads the other.
Claim 11
Dependent Claim
21 words
The capacitance point level switch of claim 1 wherein said output circuit includes a flip-flop circuit connected to said network circuits.
Claim 12
Dependent Claim
29 words
The capacitance point level switch of claim 1 wherein said output circuit includes means for delaying when said discrete output switches from the first state to the second state.
Claim 13
Dependent Claim
29 words
The capacitance point level switch of claim 1 wherein said output circuit includes means for delaying when said discrete output switches from the second state to the first state.
Claim 14
Dependent Claim
67 words
The capacitance point level switch of claim 1 wherein said output circuit includes first means for delaying when said discrete output switches from the first state to the second state, second means for delaying when said discrete output switches from the second state to the first state and selection means for selectively switching said first and second means into and out of operation in said output circuit.
Claim 15
Dependent Claim
23 words
The capacitance point level switch of claim 1 wherein said output circuit includes an anti-bounce circuit for preventing cycling of said discrete output.
Claim 16
Dependent Claim
28 words
The capacitance point level switch of claim 1 further comprising a protection circuit connected to said probe network including means for compensating said probe network for temperature changes.
References Cited (Backward Citations)
US3684952A
Cited
US3684953A
Cited
US3676742A
Cited
US3742347A
Cited
US3774237A
Cited
US3896374A
Cited
US3864626A
Cited
US3879660A
Cited
US4058765A
Cited
US4173398A
Cited
US4199984A
Cited
US4310794A
Cited
US4470008A
Cited
US4555941A
Cited
US4499766A
Cited
US4800755A
Cited
US4499767A
Cited
US4532419A
Cited
US4530372A
Cited
US4551785A
Cited
US4676100A
Cited
US4788488A
Cited
US4780705A
Cited
US4809129A
Cited
US4853718A
Cited
US4881025A
Cited
US5017909A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-02-26 | 1999-08-28 | 2000-02-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-02-26 | 2003-08-28 | 2004-02-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-02-26 | 2007-08-28 | 2008-02-27 | $7700.00 | Window Closed / Lapsed |