Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Magnetic saturation
Reexamination Certificate
1999-10-29
2002-09-03
Le, N. (Department: 2858)
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Magnetic saturation
C324S142000, C324S076770, C607S066000
Reexamination Certificate
active
06445171
ABSTRACT:
The invention pertains to current sensors and particularly to magnetoresistive (MR) current sensors. More particularly, it pertains to MR sensors having low offsets.
SUMMARY OF THE INVENTION
The present current sensor is a closed-loop, non-contact, fast-responding, wide-bandwidth, field nulling current sensor. This sensor reveals parameters equivalent to other closed-loop approaches such as the closed loop Hall effect current sensor in the related art. It is the use of the MR sensor having a set/reset and offset nulling loop leads to ultra low offsets and ultra low offset drifts over all conditions in current measurement. It also has very low offset drift over wide ranges of operating temperatures. Because of the ultra low offset, the sensor provides very accurate measurements of current. It has an auto-zero offset reduction circuit, which has a separate feedback path to remove offset and offset drift from the circuit. The magnetic signal and offset signals are driven to their respective nulls by independent feedback loops. The offset feedback loop is not used in Hall effect type current sensors. The transient noise and spikes caused by the set/reset circuit are greatly reduced with this new feedback scheme. The sensor has a frequency response from DC to over 150 kHz and has a response time of less than one microsecond.
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Article “A New Perspective on Magnetic Field Sensing”, Michael J. Caruso and Tamara Bratland, Honeywell, SSEC, Carl H. Smith and Robert Schneider, Nonvolatile Electronics, Inc., Sensors Dec. 1998.
Article “Anisotropic Magnetoresistive Sensors: Theory and Applications”, Michael J. Caruso and Tamara Bratland, Honeywell, SSEC, Carl H. Smith and Robert Schneider, Nonvolatile Electronics, Inc., Sensors Mar. 1999.
Berndt Dale F.
Lenz James E.
Sandquist David A.
Abeyta Andrew A.
Hamdan Wasseem H.
Honeywell Inc.
Le N.
Shudy, Jr. John G.
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