Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Magnetic saturation
Reexamination Certificate
1999-09-28
2002-06-11
Nguyen, Vinh P. (Department: 2858)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Magnetic saturation
C324S127000
Reexamination Certificate
active
06404180
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to sensors for determining a level of current in a conductor, and particularly to a Hall effect current sensor system that is substantially immune to electrical noise.
BACKGROUND OF THE INVENTION
A variety of sensors are used to measure the amount of current flowing through a conductor. One such example is an open loop Hall effect current sensor. An open loop Hall sensor that measures current flowing through a conductor and provides an output signal proportional to the level of current. Such a Hall effect current sensor can include a gapped, ferrous-based core which surrounds the conductor and a Hall generator. The Hall generator is placed within the gap of the core.
Such an open loop configuration is typically susceptible to electrical noise on the conductor. Thus, the accuracy of the Hall generator potentially suffers due to electrical noise on the conductor being indirectly coupled through the core to the Hall generator.
The metallic core typically has a significant amount of surface area in parallel with the conductor, and a measurable amount of electrical noise can be capacitively coupled from the conductor to the floating core. Additionally, when a typical Hall generator is positioned in a core gap, the ends of the core have a significant amount of surface area in parallel with the generator. This allows noise on the core to be capacitively coupled to the generator. If the level of noise coupled indirectly from the conductor to the generator (via the core) is significant, the Hall effect current sensor provides an output signal that inaccurately represents the level of current in the conductor.
It would be advantageous to utilize an open-loop system in which the Hall generator is substantially immune from direct or indirect electrical noise.
SUMMARY OF THE INVENTION
The present invention features a system for measuring current flowing through a conductor. The system includes a core having a general ring-shape. The gap within the gapped core is defined by a pair of parallel faces. The core contains a central opening for receiving a conductor therethrough. The system further includes a Hall generator disposed in the gap and a ground. The core is electrically connected to the ground.
According to another aspect of the invention, a system is provided for detecting a current level in a conductor. The system includes a metallic core having an opening therethrough. The metallic core further includes a gap extending from the opening to an outer surface of the core. The system also includes at least one conductor extending through the opening, and a sensor disposed in the gap. The sensor cooperates with the core in detecting a current in at least one conductor and outputs a voltage proportional to the current. The system further includes a ground and an electrical connection between the core and the ground.
According to another aspect of the present invention, a method is provided for detecting a current level or change in current level in a conductor. The method includes locating a core about a conductor such that the core does not physically contact the conductor. The method further includes placing a gap in the core, and inserting a Hall generator in the gap. The Hall generator is arranged such that it cooperates with the core to output a signal proportional to the current in the conductor. The method further includes electrically grounding the core to provide immunity from electrical noise.
REFERENCES:
patent: 5041761 (1991-08-01), Wright et al.
patent: 5530937 (1996-06-01), Sugiyama
patent: 5583429 (1996-12-01), Otaka
patent: 6005383 (1999-12-01), Savary et al.
Gerasimow Alexander M.
Nguyen Vinh P.
Rockwell Automation Technologies Inc.
VanSomeren Robert A.
Walbrun William R.
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