US4788488A
Expired / Lapsed
US
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Continuous condition sensing system
Assignee: Drexelbrook Controls Inc
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Filing: 1986-10-14
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Granted: 1988-11-29
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Expires: 2006-10-14
Abstract
Abstract A probe developing an admittance with a material whose condition is to be continuously measured is capacitively coupled with a variable frequency oscillator, preferably one having a digital output stage, for generating a variable frequency signal having a period varying with the admittance developed at the probe. Both the oscillator input and output are capacitively coupled to the probe. In a preferred embodiment, a set point circuit including a plurality of resistors coupled in parallel with the oscillator output and a plurality of switches coupled in parallel with the probe conductor and each with a different one of the resistor, provides easy circuit adjustment for use of the system with a variety of materials. A preferred digital circuit employing a pair of flip flops, fixed timer and one shot generate a fixed period variable duration duty cycle digital voltage level signal for transmission, if desired, or for conversion into a variable current signal.
Inventors
- 👤 L. Jonathan Kramer
- 👤 Steven R. Peterson
- 👤 Herbert A. Shauger, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 07:09
CPC Classifications
G; G01; G01R; G01R27/00; G01R27/02; G01R27/26; G01R27/2605
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
122 words
A system for continuously measuring a varying condition of a material comprising: a source of a material condition generating a variable voltage signal; oscillator means responsive to the source for generating an oscillating signal having a period varying with the variable voltage signal; a plurality of resistor means each having an end coupled to the oscillator means output for passing said oscillating signal through one or more separate resistances coupled to the oscillator means; and an equal plurality of switches each having an end coupled to the source and a remaining end coupled with a remaining end of a different one of the plurality of resistor means for selectively coupling one or more of said plurality of resistor means with the source.
Claim 2
Independent Claim
122 words
A system for continuously measuring a varying condition of a material comprising: a source of a material condition generating a variable voltage signal; oscillator means responsive to the source for generating an oscillating signal having a period varying with the variable voltage signal; a plurality of resistor means each having an end coupled to the oscillator means output for passing said oscillating signal through one or more separate resistances coupled to the oscillator means; and an equal plurality of switches each having an end coupled to the source and a remaining end coupled with a remaining end of a different one of the plurality of resistor means for selectively coupling one or more of said plurality of resistor means with the source.
Claim 3
Dependent Claim
15 words
The system of claim 1 wherein each of said resistor means is an individual resistor.
Claim 4
Dependent Claim
32 words
The system of claim 1 further comprising: an equal plurality of capacitor means each having an end coupled with a remaining end of a different one of said plurality of resistor means.
Claim 5
Dependent Claim
51 words
The system of claim 3 further comprising: reference signal generator means for generating a signal having a predetermined constant frequency; and flip-flop means responsive to said reference signal generator and said oscillating signal for generating a logic level signal having a duty cycle varying with selected ones of the capacitor means.
Claim 6
Dependent Claim
169 words
A material condition monitoring system comprising: a reference voltage source generating a fixed voltage level signal; comparator means coupled with the reference voltage source for comparing the fixed voltage level signal with a second signal; circuit means for coupling a material condition generated, variable voltage signal with the comparator means for comparison with the fixed voltage level signal; first flip flop means responsive to the comparator means for outputting a variable frequency, digital voltage level signal having a period varying with the variation in said variable voltage signal, said comparator means and first flip flop means collectively defining a first multivibrator means; second multivibrator means independently operable of the first multivibrator means for generating a fixed period, digital signal; second flip flop means clocked by said first multivibrator means and having an asynchronous input receiving the signal from the second multivibrator means; and third flip flop means clocked by said first multivibrator means and having a data input coupled with a data output of the second flip flop means.
Claim 7
Dependent Claim
169 words
A material condition monitoring system comprising: a reference voltage source generating a fixed voltage level signal; comparator means coupled with the reference voltage source for comparing the fixed voltage level signal with a second signal; circuit means for coupling a material condition generated, variable voltage signal with the comparator means for comparison with the fixed voltage level signal; first flip flop means responsive to the comparator means for outputting a variable frequency, digital voltage level signal having a period varying with the variation in said variable voltage signal, said comparator means and first flip flop means collectively defining a first multivibrator means; second multivibrator means independently operable of the first multivibrator means for generating a fixed period, digital signal; second flip flop means clocked by said first multivibrator means and having an asynchronous input receiving the signal from the second multivibrator means; and third flip flop means clocked by said first multivibrator means and having a data input coupled with a data output of the second flip flop means.
Claim 8
Dependent Claim
28 words
The apparatus of claim 5 further comprising: a one-shot clocked by the data output of the third flip flop and outputting a signal to the second flip flop.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-11-29 | 1992-05-30 | 1992-11-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-11-29 | 1996-05-30 | 1996-11-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-11-29 | 2000-05-30 | 2000-11-29 | $7700.00 | Window Closed / Lapsed |