Signal amplifier system for controlled carrier signal measuring sensor/transducer of the variable impedance type
First Claim
1. A controlled carrier circuit measuring sensor/transducer signal amplifier system including in combination a carrier signal oscillator for providing a carrier oscillatory signal of known frequency and fixed voltage magnitude, differential amplifier means having the carrier oscillatory signal supplied to one of the inputs thereof, reference impedance means and variable impedance sensor/transducer means connected in series circuit relationship across the output of said differential amplifier means, means for feeding back a first feedback signal to a second input to said differential amplifier means, said first feedback signal comprising the sum of the voltages across said reference impedance means and said variable impedance sensor/transducer means in series, buffer amplifier means having the input thereof connected to the juncture of the reference impedance means and the variable impedance sensor/transducer means for deriving an output voltage signal representative of the instantaneous value of the voltage across said variable impedance sensor/transducer means, and means for feeding back said output voltage signal from the output of said buffer amplifier means to a third input to said differential amplifier means in opposition to said first feedback signal for regulating the current supplied through said reference impedance means and said variable impedance sensor/transducer means to a substantially constant magnitude whereby the output voltage signal from said buffer amplifier means provides a measure of the impedance of said variable impedance transducer means.
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Accused Products
Abstract
A controlled carrier current measuring sensor/transducer signal amplifier system comprising a carrier oscillator for providing a carrier voltage oscillatory signal of known frequency and fixed voltage magnitude. A differential amplifier has the carrier voltage oscillatory signal supplied to one of its inputs. A reference impedance and a variable impedance sensor transducer are connected in a series circuit across the output of the differential amplifier and a first feedback signal is fed back to a second input of the differential amplifier with the first feedback signal comprising the sum of the voltage across the reference impedance and the variable impedance sensor transducer. A buffer amplifier has its input connected to the juncture of the reference impedance and the variable impedance sensor/transducer for deriving an output voltage representative of the instantaneous value of the voltage across the variable impedance sensor/transducer. The output voltage signal from the output of the buffer amplifier is fed back to a third input to the differential amplifier in opposition to the first feedback signal for regulating the current supplied through the reference impedance and the variable impedance sensor/transducer to a substantially constant value whereby the output voltage signal from the output of the buffer amplifier provides a measure of the impedance of the variable impedance sensor/transduer. Preferably, the system further includes shielded conductors interconnected between the reference impedance and the variable impedance sensor/transducer and between the juncture thereof and the input to the buffer amplifier and the output from the buffer amplifier is fed back to the shielding of the shielded conductors whereby the effects of stray capacitance on any measurement obtained from the variable impedance sensor/transducer are minimized.
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Citations
10 Claims
- 1. A controlled carrier circuit measuring sensor/transducer signal amplifier system including in combination a carrier signal oscillator for providing a carrier oscillatory signal of known frequency and fixed voltage magnitude, differential amplifier means having the carrier oscillatory signal supplied to one of the inputs thereof, reference impedance means and variable impedance sensor/transducer means connected in series circuit relationship across the output of said differential amplifier means, means for feeding back a first feedback signal to a second input to said differential amplifier means, said first feedback signal comprising the sum of the voltages across said reference impedance means and said variable impedance sensor/transducer means in series, buffer amplifier means having the input thereof connected to the juncture of the reference impedance means and the variable impedance sensor/transducer means for deriving an output voltage signal representative of the instantaneous value of the voltage across said variable impedance sensor/transducer means, and means for feeding back said output voltage signal from the output of said buffer amplifier means to a third input to said differential amplifier means in opposition to said first feedback signal for regulating the current supplied through said reference impedance means and said variable impedance sensor/transducer means to a substantially constant magnitude whereby the output voltage signal from said buffer amplifier means provides a measure of the impedance of said variable impedance transducer means.
Specification