Linear signal isolator and calibration circuit for electronic current transformer
AssigneeGeneral Electric Company
InventorHarry R. Summerhayes
Life of this patent
Estimating the term…
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.
Claims16
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.
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.
Dependencies are inferred from the claim text.