Detection circuit for use in various types of capacitive transducers and a transducer including such a circuit
AssigneeUniversity of Vermont and State Agricultural College
InventorGilbert P. Gianetti
Life of this patent
Estimating the term…
Abstract
A detection circuit for detecting changes in capacitance. The detection circuit includes a tuned ratio circuit and an alternating current (AC) source AC-coupled to the tuned ratio circuit. The tuned ratio circuit includes first and second tuned circuits that are tuned to, or close, to the frequency of the AC source. Output circuitry is coupled between the two tuned circuits. During use as a transducer, an active capacitive transducer is inductively coupled to the first tuned circuit. Changes in the capacitance of the active capacitive transducer cause changes in the tuning of the first tuned circuit. The output circuitry generates an output signal that is a function of the difference between the tunings of the first and second tuned circuits.
Claims22
A transducer system, comprising:
- an alternating current (AC) voltage source for providing a constant frequency voltage;
- a tuned ratio detector AC coupled to said AC voltage source, said tuned ratio detector including first and second tuned circuits each coupled to said AC voltage source by corresponding respective first and second coupling elements;
- a transducer link inductively coupled to said first tuned circuit;
- a transducer electrically coupled to said transducer link;
- and
- signal output circuitry electrically coupled between said first and second tuned circuits.
A transducer system, comprising:
- a cantilever-beam capacitive transducer for providing a transducer signal;
- a detection circuit for detecting the transducer signal and outputting a measurement signal as a function of the transducer signal, said detection circuit including:
- an alternating current (AC) voltage source for providing a constant frequency voltage;
- a tuned ratio detector AC coupled to said AC voltage source, said tuned ratio detector including first and second tuned circuits each coupled to said AC voltage source by corresponding respective first and second coupling elements;
- a transducer link inductively coupling said cantilever-beam capacitive transducer to said first tuned circuit;
- and
- signal output circuitry electrically coupled between said first and second tuned links for outputting the measurement signal;
- and
- a housing supporting said cantilever-beam capacitive transducer.
Dependencies are inferred from the claim text.