Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Magnetic saturation
Patent
1995-06-30
1996-12-17
Karlsen, Ernest F.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Magnetic saturation
324127, G01R 3307, G01R 120
Patent
active
055857159
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an electric current sensor device for measuring the current flowing in a primary conductor comprising at least one magnetic circuit arranged for being coupled with the primary conductor, this circuit having an airgap in which a Hall cell is arranged which provides a signal as a function of the magnetic field in the airgap, at least one electric coil being coupled with the magnetic circuit, the Hall cell and said coil being part of an electric measuring circuit fed from a current source, this measuring circuit comprising at least a current supply circuit for the coil so as to cause a compensating current to circulate therein and a control circuit for controlling this supply circuit as a function of the Hall cell signal for aiming at cancelling the magnetic field in the airgap of the magnetic circuit, this field resulting from the effect of the current to be measured and of the compensating current circulating in the coil, and means for measuring said compensating current.
SUMMARY OF THE INVENTION
The invention aims at providing a current sensor device of this type allowing the measurement of a bidirectional current while being fed from a unipolar current source. Such a requirement exists in particular in an electric car in which a single battery, for example of 12 volt, feeds the auxiliary devices and the headlights.
The sensor device according to the invention is characterized in that, the current source being unipolar with respect to ground, the current supply circuit for the coil is constructed in the form of a four-branch bridge circuit, in which the coil is connected so as to constitute a diagonal, the current source and a measuring resistor being connected in series between a common connection pointof two first branches of the bridge which are connected, on the other hand, to respective terminals of the coil, and the ends of the two further branches of the bridge, controlled variable conduction elements being mounted, respectively, in the four branches of the bridge, said control circuit of the current supply circuit of the coil being arranged for controlling said variable conduction elements so as to cause the compensating current to flow in the coil, in one direction or the other depending on the the direction of the residual flux detected by the Hall cell, through two respective opposite branches of the bridge circuit, the other two opposite branches being non-conducting.
In another embodiment of the invention the variable conduction elements are transistors (8, 9, 15, 16), the conduction paths of which form the branches of the bridge circuit and the control electrodes of which are controlled through the signal from the Hall cell (3) so that one of the transistors (8 or 9) in two opposite branches of the bridge is more or less conductive as a function of the magnitude of this signal, that the other of these transistors (15 or 16) is conductive and has a minimum resistance, and that the two other transistors of the bridge are non-conductive.
In another embodiment of the invention, the two transistors (8, 9) of the bridge, one of which is more or less conductive at one and the same time, are connected, directly or through a measuring resistor (R), to the same terminal (V.sub.+ or O) of the current source.
In another embodiment of the invention, the control circuit comprises an amplifier (7) having two inputs connected to the output terminals of the Hall cell (3), the output of this amplifier being connected, on the one hand, for controlling a first (9) or a second (8) of the transistors connected to the same terminal of the current source depending on whether the output voltage of the amplifier (7) is higher or lower than a reference voltage and, on the other hand, for controlling the transistors (16, 15) connected in the opposite branches of the bridge to render conductive or non-conductive, respectively, one or the other of these latter transistors depending on whether the output voltage of the amplifier (7) is higher or lower than the reference voltage.
In anoth
REFERENCES:
patent: 3323057 (1967-05-01), Haley
patent: 3422351 (1969-01-01), Phil
patent: 3885212 (1975-05-01), Herbert
patent: 5451865 (1995-09-01), Coburn
Browning Clifford W.
Karlsen Ernest F.
Liaisons Electroniques- Mechaniques LEM S.A.
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