Back to results
US 5,844,409 AGranted
Method and system for measuring an electric current with two light signals propagating in opposite directions, using the Faraday effect
AssigneeSiemens Aktiengesellschaft
InventorsThomas Bosselmann, Peter Menke
Life of this patent
Estimating the term…
Abstract
Method and system for measuring an electric current in a current conductor, two opposing light signals are transmitted through a Faraday element surrounding the current conductor and, after the passage through the Faraday element, are split, respectively, into two partial light signals. From these partial light signals, an intensity-normalized signal is derived for each partial light signal. Provision is made of a Faraday element having a negligible circular birefringence, and a signal processing unit for deriving a vibration-independent and temperature-independent measured signal.
Claims18
A method for measuring an electric current in a current conductor, comprising the steps of:
- transmitting a first linearly polarized light signal and a second linearly polarized light signal through a Faraday element having a circular birefringence, the first and second linearly polarized light signals propagating in opposite directions and having respective first and second planes of polarization which are rotated through a Faraday measuring angle in opposite rotational directions as a result of transmitting the first and second linearly polarized light signals through the Faraday element, the Faraday measuring angle being dependent on the electric current and being larger than the circular birefringence of the Faraday element;
- after the first linearly polarized light signal is transmitted through the Faraday element, splitting the first linearly polarized light signal to generate a first set of linearly polarized partial light signals, and, after the second linearly polarized light signal is transmitted through the Faraday element, splitting the second linearly polarized light signal to generate a second set of linearly polarized partial light signals, each set of linearly polarized partial light signals having different planes of polarization;
- converting the first and second sets of linearly polarized partial light signals into corresponding first and second sets of electric intensity signals, the first set of electric intensity signals having an IS1-signal and an IS2-signal, and the second set of electric intensity signals having an IT1-signal and an IT2-signal;
- generating a first intensity-normalized signal by dividing the difference of the IS1-signal and the IS2-signal by the sum of the IS1-signal and the IS2-signal, and generating a second intensity-normalized signal by dividing the difference of the IT1-signal and the IT2-signal by the sum of the IT1-signal and the IT2-signal;
- and
- generating a vibration-independent temperature-independent measured signal from the first and second intensity-normalized signals.
3 more elements
A system for measuring an electric current in a current conductor, comprising:
- a Faraday element having a circular birefringence;
- transmission means for transmitting a first and a second linearly polarized light signal through the Faraday element, the first and second linearly polarized light signals propagating in opposite directions and having a respective first and second planes of polarization which are rotated through a Faraday measuring angle in opposite rotational directions as a result of transmitting the first and second linearly polarized light signals through the Faraday element, the Faraday measuring angle being dependent on the electric current and being larger than the circular birefringence of the Faraday element;
- splitting means for splitting the first linearly polarized light signal to generate a first set of linearly polarized partial light signals after the first linearly polarized light signal is transmitted through the Faraday element, and for splitting the second linearly polarized light signal to generate a second set of linearly polarized partial light signals after the second linearly polarized light signal is transmitted through the Faraday element, each set of linearly polarized partial light signals having different planes of polarization;
- converting means for forming first and second sets of electric intensity signals from the corresponding first and second sets of linearly polarized partial light signals, the first set of electric intensity signals having an IS1-signal and an IS2-signal, and the second set of electric intensity signal having an IT1-signal and an IT2-signal;
- generating means for forming a first intensity-normalized signal by dividing the difference of the IS1-signal and the IS2-signal by the sum of the IS1-signal and the IS2-signal, and for forming the second intensity-normalized signal by dividing the difference of the IT1-signal and the IT2-signal by the sum of the IT1-signal and the IT2-signal;
- and
- generating means for generating a vibration-independent temperature-independent measured signal from the first and second intensity-normalized signals.
4 more elements
Dependencies are inferred from the claim text.