Linear signal isolator and calibration circuit for electronic current transformer
First Claim
1. An improved optically-coupled data transmission channel comprising:
- means for producing optical electromagnetic radiation which varies in intensity as a substantially linear function of the sum of a variable, alternating frequency input and a first known, direct current reference signal;
means for receiving said radiation and for producing a first electrical signal in response to the intensity thereof;
variable gain means connected to process said first electrical signal; and
first negative feedback means connected to receive the output of said gain means and to stabilize the gain of said channel by furnishing a second signal to vary the gain of said variable gain means in response to the difference between a direct current component to the output of said gain means and a second known, direct current reference signal.
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Abstract
An optical data transmission system for use with current sensors on ac high voltage transmission lines comprises a light-emitting diode transmitter at line potential and a silicon photodiode receiver at ground potential. Signals are conducted from the transmitter to receiver along a fiber optic light pipe. A silicon photodiode in a feedback configuration produces a linear ac output light from the light-emitting diode in response to line current. A dc reference signal is superimposed on the ac current data signal to provide system gain calibration. The dc signal is utilized, in a feedback loop, to control the gain of an ac signal amplifier in the receiver and to thus stabilize system calibration.
106 Citations
16 Claims
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1. An improved optically-coupled data transmission channel comprising:
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means for producing optical electromagnetic radiation which varies in intensity as a substantially linear function of the sum of a variable, alternating frequency input and a first known, direct current reference signal; means for receiving said radiation and for producing a first electrical signal in response to the intensity thereof; variable gain means connected to process said first electrical signal; and first negative feedback means connected to receive the output of said gain means and to stabilize the gain of said channel by furnishing a second signal to vary the gain of said variable gain means in response to the difference between a direct current component to the output of said gain means and a second known, direct current reference signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for stabilizing the gain of an intensity modulated ac data channel which includes a transmitter connected to produce an optical radiation output which varies as a substantially linear function of an ac input signal and a receiver which produces an output signal as a substantially linear function of said intensity;
- comprising the steps of;
adding a first known dc reference signal to said ac input signal; applying said signal to said transmitter and receiving the output thereof with said receiver; and varying the gain of said receiver to minimize the difference between a dc component of said output signal and a second dc reference signal, said first reference signal being equal to said second reference signal.
- comprising the steps of;
Specification