US3778707A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Means for measuring loss tangent of material for determining moisture content
Assignee: AGRIDUSTRIAL ELECTRONICS
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Filing: 1972-12-14
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Granted: 1973-12-11
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Expires: 1992-12-14
Abstract
Abstract A-c voltage is applied through two branches to respective input circuits of a phase detector. One of the branches includes a controlled phase shifter and a capacitive impedance circuit; the capacitive impedance circuit includes a moisture test cell and in the usual manner provides phase shift dependent upon the permitivity and loss factor of material placed in the moisture test cell. The overall shift in phase of the voltage in this branch of the circuit is therefore determined by the sum of the phase shift in the controlled phase shifter and the phase shift in the capacitive impedance circuit dependent on the sample in the moisture tester. The output of the phase detector is applied to a d-c control circuit of the controlled phase shifter to control the phase shift such that the sum of the phase angles of the phase shifter and the capacitive impedance circuit is maintained at a predetermined constant. The voltage on the output circuit for controlling the phase shifter is also the voltage that is applied to an indicator to determine moisture content according to the loss tangent of the material being tested. The output readings are substantially independent of the densities of the materials placed in the test cell.
Inventors
- 👤 R Vogel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 02:22
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/22; G01N27/223
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
333 words
Electrical circuit means for testing loss tangent of material substantially independent of the density of a sample being tested comprising: a test cell of the capacitive type having first and second electrodes with a space therebetween for receiving material to be tested, a capacitive impedance circuit including said electrodes, said capacitive impedance circuit having an a-c input circuit and an a-c output circuit, the difference in phase between a-c voltage in said a-c input circuit and the resulting a-c voltage in said output circuit being a function of the permittivity and loss factor of material placed between said electrodes, a controlled phase shifter having an a-c input circuit, a control input circuit, and an a-c output circuit, a phase detector having first and second a-c input circuits and an output circuit, said phase detector responsive to application of a-c voltages to its input circuits to supply voltage from its output circuit proportional to the difference in phase of the a-c voltages applied to its input circuits, the output circuit of said phase detector being connected to said control input circuit of said phase shifter, an a-c source, first and second branch circuits connected from said a-c source to said first and second a-c input circuits respectively of said phase detector, said second branch circuit including said controlled phase shifter and said capacitive impedance circuit connected in cascade through their respective a-c input circuits and a-c output circuits, said controlled phase shifter responding to voltage applied from said output circuit of said phase detector to its control input circuit to maintain a substantially predetermined angle of phase between the voltages applied from said first and second branch circuits to said first and second input circuits respectively, and a voltage indicator circuit connected to the output circuit of said phase detector, the voltage developed in the output circuit of said phase detector being proportional to the loss tangent but being substantially independent of the density of material placed between said electrodes of said test cell.
Claim 2
Dependent Claim
333 words
Electrical circuit means for testing loss tangent of material substantially independent of the density of a sample being tested comprising: a test cell of the capacitive type having first and second electrodes with a space therebetween for receiving material to be tested, a capacitive impedance circuit including said electrodes, said capacitive impedance circuit having an a-c input circuit and an a-c output circuit, the difference in phase between a-c voltage in said a-c input circuit and the resulting a-c voltage in said output circuit being a function of the permittivity and loss factor of material placed between said electrodes, a controlled phase shifter having an a-c input circuit, a control input circuit, and an a-c output circuit, a phase detector having first and second a-c input circuits and an output circuit, said phase detector responsive to application of a-c voltages to its input circuits to supply voltage from its output circuit proportional to the difference in phase of the a-c voltages applied to its input circuits, the output circuit of said phase detector being connected to said control input circuit of said phase shifter, an a-c source, first and second branch circuits connected from said a-c source to said first and second a-c input circuits respectively of said phase detector, said second branch circuit including said controlled phase shifter and said capacitive impedance circuit connected in cascade through their respective a-c input circuits and a-c output circuits, said controlled phase shifter responding to voltage applied from said output circuit of said phase detector to its control input circuit to maintain a substantially predetermined angle of phase between the voltages applied from said first and second branch circuits to said first and second input circuits respectively, and a voltage indicator circuit connected to the output circuit of said phase detector, the voltage developed in the output circuit of said phase detector being proportional to the loss tangent but being substantially independent of the density of material placed between said electrodes of said test cell.
Claim 3
Dependent Claim
159 words
Electrical circuit means as claimed in claim 1 wherein said phase detector includes a multiplier, a low-pass filter and a d-c amplifier, said multiplier having an output circuit and first and second input circuits, said first and second input circuits of said multiplier being said first and second a-c input circuits respectively of said phase detector, the first input circuit of said multiplier being in said first branch circuit connected to said a-c source, said second input circuit of said multiplier being in said second branch circuit and being connected to said a-c output circuit of said capacitive impedance circuit, said output circuit of said multiplier being connected through said low-pass filter to the input circuit of said d-c amplifier, and the output circuit of said d-c amplifier being the output of said phase detector, the output circuit of said d-c amplifier being connected to said a-c input circuit of said phase shifter and to said voltage indicator circuit.
Claim 4
Dependent Claim
52 words
Electrical circuit means as claimed in claim 1 wherein said voltage indicator circuit in said output circuit of said phase detector includes an adjustable gain amplifier, said adjustable gain amplifier having an input circuit connected to said output circuit of said phase detector and an output circuit for connection to an indicator.
Claim 5
Dependent Claim
26 words
Electrical circuit means as claimed in claim 2 wherein said controlled phase shifter and said phase detector maintain said predetermined angle of phase at substantially 90*.
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) | 1976-12-10 | 1977-06-11 | 1977-12-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-12-10 | 1981-06-11 | 1981-12-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-12-10 | 1985-06-11 | 1985-12-11 | $7700.00 | Window Closed / Lapsed |