MULTIPLE FREQUENCY GRAIN MOISTURE SENSOR FOR COMBINES
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Abstract
A grain moisture sensor is disclosed having a sensor cell that includes a driven plate, a sense plate proximate to and substantially parallel with the driven plate for capacitive measurement across a spacing between the driven plate and the sense plate, and a fill plate adjacent the sense plate and substantially parallel with the driven plate for sensing whether the spacing is filled with grain. Optionally, the sensor cell includes a guard proximate to the parallel to the sense plate such that the sense plate is between the driven plate and the guard. The grain moisture sensor provides for measuring real and imaginary components of an excitation voltage applied to the driven plate, measuring real and imaginary components of a sense current sensed at the sense plate, calculating a complex admittance of the cell, calculating a complex admittance of a reference admittance, and calculating a grain complex permittivity.
6 Citations
26 Claims
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1-21. -21. (canceled)
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22. A grain moisture sensing system comprising:
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an excitation signal source for producing an excitation signal;
a sensor cell having a driven plate for applying the excitation signal and a sense plate proximate to and substantially parallel with the driven plate for capacitive measurement across a spacing between the driven plate and the sense plate such that a sense current is produced at the sense plate;
the excitation signal source electrically connected to the driven plate of the sensor cell;
a first synchronous detector adapted for measuring components of the excitation signal, the synchronous detector electrically connected to the excitation source; and
a second synchronous detector adapted for measuring components of the sense current, the second synchronous detector operatively connected to the sense plate. - View Dependent Claims (23, 24, 25, 26)
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Specification