US3684954A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Single frequency moisture gauge with logarithmic feedback
Assignee: Industrial Nucleonics Corp
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Filing: 1970-12-21
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Granted: 1972-08-15
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Expires: 1990-12-21
Abstract
Abstract For quantitively determining a property of a dielectric material, in particular its relative moisture content, an alternating current electrical signal at a constant frequency is applied to a capacitive probe coupled to the material. The effect of the capacitance of the empty probe is balanced out, and a detection signal is produced from the imbalance occasioned by the dielectric material. A first logarithmic signal is derived logarithmically related to the detection signal and used to vary the applied signal in a direction opposite to changes in the detection signal to reduce the demands upon the dynamic range of system components. A second logarithmic signal is derived logarithmically related to the applied signal. The first and second logarithmic signals are then combined to produce a third logarithmic signal logarithmically related to the ratio of said detection and applied signals, and indicative of the property of the material.
Inventors
- 👤 Henry T Jaggers
- 👤 Donald R Theado
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 21:16
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/22; G01N27/223
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
275 words
Apparatus for the quantitative determination of a property of a dielectric material, said apparatus comprising a source of alternating current electrical signal at a constant frequency, said source including control means responsive to a control signal for controlling the magnitude of said signal from said source, detecting means, capacitive probe means coupled to said source and having spaced electrodes arranged for applying said electrical signal from said source to at least a portion of said material and coupling said detecting means to said portion, said detecting means including means for deriving a detection signal resulting from the signal as applied to said portion from said source, as this applied signal is influenced by said material, balancing circuit means connected in circuit with said probe means to balance out from said detection signal any component developed by said probe means in the absence of said material, a first logarithmic converter coupled to said detecting means and responsive to said detection signal by producing a first logarithmic signal logarithmically related to said detection signal, means for applying said first logarithmic signal to said control means as a control signal to change the magnitude of said signal from said source oppositely from any change in the magnitude of said detection signal, a second logarithmic converter coupled to said source and responsive to said signal from said source by producing a second logarithmic signal logarithmically related to said signal from said source, and means for combining said first and second logarithmic signal to produce a third logarithmic signal logarithmically related to the ratio of said detection signal and said signal from said source and hence indicative of said property.
Claim 2
Dependent Claim
275 words
Apparatus for the quantitative determination of a property of a dielectric material, said apparatus comprising a source of alternating current electrical signal at a constant frequency, said source including control means responsive to a control signal for controlling the magnitude of said signal from said source, detecting means, capacitive probe means coupled to said source and having spaced electrodes arranged for applying said electrical signal from said source to at least a portion of said material and coupling said detecting means to said portion, said detecting means including means for deriving a detection signal resulting from the signal as applied to said portion from said source, as this applied signal is influenced by said material, balancing circuit means connected in circuit with said probe means to balance out from said detection signal any component developed by said probe means in the absence of said material, a first logarithmic converter coupled to said detecting means and responsive to said detection signal by producing a first logarithmic signal logarithmically related to said detection signal, means for applying said first logarithmic signal to said control means as a control signal to change the magnitude of said signal from said source oppositely from any change in the magnitude of said detection signal, a second logarithmic converter coupled to said source and responsive to said signal from said source by producing a second logarithmic signal logarithmically related to said signal from said source, and means for combining said first and second logarithmic signal to produce a third logarithmic signal logarithmically related to the ratio of said detection signal and said signal from said source and hence indicative of said property.
Claim 3
Dependent Claim
32 words
Apparatus according to claim 1, wherein said control means changes the magnitude of said signal from said source by substantially the same factor as the change in magnitude of said detection signal.
Claim 4
Dependent Claim
35 words
Apparatus according to claim 1, wherein the characteristic of said control means makes the range of said signal from said source substantially equal to the range of said detection signal over the range of measurement.
Claim 5
Dependent Claim
28 words
Apparatus according to claim 1, including means for adjusting the calibration of the system to offset the effect of changes in the mass of the material being measured.
Claim 6
Dependent Claim
32 words
Apparatus according to claim 1, including means for combining a calibrating signal with said third logarithmic signal to offset the effect on the measurement of the mass of the material being measured.
Claim 7
Dependent Claim
46 words
Apparatus according to claim 1, wherein said control means includes a source of reference signal and means for combining said reference signal and said control signal to produce a modified control signal, and said source includes a voltage controlled amplifier controlled by said modified control signal.
Claim 8
Dependent Claim
41 words
Apparatus according to claim 6, wherein said source of reference signal is adjustable and said means for combining said reference signal and said control signal comprises a summing amplifier having a variable input resistor to which said control signal is applied.
Claim 9
Dependent Claim
28 words
Apparatus according to claim 7, including clamping means for clamping the output of said summing amplifier to a predetermined voltage level whenever it would otherwise exceed that level.
Claim 10
Independent Claim
165 words
A method for the quantitative determination of a property of a dielectric material, said method comprising applying a constant frequency alternating current electrical signal of controlled magnitude to a pair of spaced electrodes of a capacitive probe, deriving a detection signal resulting from the applied signal as this applied signal is influenced by said material while at the same time balancing out from said output signal any effect of the capacitance between said electrodes in the absence of said material, deriving from said detection signal a first logarithmic signal logarithmically related thereto, utilizing said first logarithmic signal to control the magnitude of said applied signal by changing said magnitude oppositely from any change in the magnitude of said detection signal, deriving from said applied signal a second logarithmic signal logarithmically related thereto, and combining said first and second logarithmic signals to produce a third logarithmic signal logarithmically related to the ratio of said detection signal and said applied signal and hence indicative of said property.
Claim 11
Independent Claim
165 words
A method for the quantitative determination of a property of a dielectric material, said method comprising applying a constant frequency alternating current electrical signal of controlled magnitude to a pair of spaced electrodes of a capacitive probe, deriving a detection signal resulting from the applied signal as this applied signal is influenced by said material while at the same time balancing out from said output signal any effect of the capacitance between said electrodes in the absence of said material, deriving from said detection signal a first logarithmic signal logarithmically related thereto, utilizing said first logarithmic signal to control the magnitude of said applied signal by changing said magnitude oppositely from any change in the magnitude of said detection signal, deriving from said applied signal a second logarithmic signal logarithmically related thereto, and combining said first and second logarithmic signals to produce a third logarithmic signal logarithmically related to the ratio of said detection signal and said applied signal and hence indicative of said property.
Claim 12
Dependent Claim
27 words
The methoD according to claim 9, wherein the magnitude of said applied signal is changed by substantially the same factor as the magnitude of said detection signal.
Claim 13
Dependent Claim
34 words
The method according to claim 9, wherein the magnitude of the applied signal is controlled to vary over a range substantially equal to the range of the detection signal over the range of measurement.
Claim 14
Dependent Claim
31 words
The method according to claim 9, wherein a reference signal is added to said first logarithmic signal to form a modified control signal for controlling the magnitude of said applied signal.
Claim 15
Dependent Claim
32 words
The method according to claim 9 wherein a compensating signal is combined with said third logarithmic signal to offset the effect on the measurement of the mass of the material being measured.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-08-15 | 1976-02-14 | 1976-08-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-08-15 | 1980-02-14 | 1980-08-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-08-15 | 1984-02-14 | 1984-08-15 | $7700.00 | Window Closed / Lapsed |