An apparatus and method make use of a single shunt and two or more instrumentation amplifiers, switchably measuring voltages at the shunt. This permits current measurement. At times each instrumentation amplifier has its input shorted, which permits zeroing out many sources of offset in the signal p
An apparatus and method make use of a single shunt and two or more instrumentation amplifiers, switchably measuring voltages at the shunt. This permits current measurement. At times each instrumentation amplifier has its input shorted, which permits zeroing out many sources of offset in the signal path of that amplifier. Dynamic range is several orders of magnitude better than known current measurement approaches, permitting coulometry.
대표청구항▼
1. Apparatus for use in measuring current with respect to first and second measurement points, the apparatus comprising: a first instrumentation amplifier, said instrumentation amplifier having first and second input terminals,a first impedance means connecting the first and second measurement point
1. Apparatus for use in measuring current with respect to first and second measurement points, the apparatus comprising: a first instrumentation amplifier, said instrumentation amplifier having first and second input terminals,a first impedance means connecting the first and second measurement points to first and second terminals of a first switch, respectively, with the first and second terminals of the first switch connected respectively to the first and second input terminals of the first instrumentation amplifier;a second instrumentation amplifier, said instrumentation amplifier having first and second input terminals,a second impedance means connecting the first and second measurement points to first and second terminals of a second switch, respectively, with the first and second terminals of the second switch connected respectively to the first and second input terminals of the second instrumentation amplifier. 2. The apparatus of claim 1 further comprising a shunt with first and second terminals, the current disposed to pass between said first and second terminals, the shunt having the first and second measurement points disposed therebetween. 3. The apparatus of claim 1 wherein the first impedance means comprises a first resistor connecting the first measurement point with the first input terminal of the first instrumentation amplifier and a second resistor connecting the second measurement point with the second input terminal of the first instrumentation amplifier, and wherein the second impedance means comprises a third resistor connecting the first measurement point with the first input terminal of the second instrumentation amplifier and a fourth resistor connecting the second measurement point with the second input terminal of the second instrumentation amplifier. 4. The apparatus of claim 1 wherein the first impedance means comprises a third switch connecting the first measurement point with the first input terminal of the first instrumentation amplifier and an electrical connection connecting the second measurement point with the second input terminal of the first instrumentation amplifier, and whereinthe second impedance means comprises a fourth switch connecting the first measurement point with the first input terminal of the second instrumentation amplifier and an electrical connection connecting the second measurement point with the second input terminal of the second instrumentation amplifier. 5. The apparatus of claim 3 further comprising a control means, the control means disposed at times to open the first switch and close the second switch, and to zero any offset in the second instrumentation amplifier, while providing current-measurement information from the first instrumentation amplifier to equipment external to the apparatus;the control means disposed at other times to close the first switch and open the second switch, and to zero any offset in the first instrumentation amplifier, while providing current-measurement information from the second instrumentation amplifier to equipment external to the apparatus. 6. The apparatus of claim 4 further comprising a control means, the control means disposed at times to close the third switch and open the first switch and open the fourth switch and close the second switch, and to zero any offset in the second instrumentation amplifier, while providing current-measurement information from the first instrumentation amplifier to equipment external to the apparatus;the control means disposed at other times to open the third switch and close the first switch and close the fourth switch and open the second switch, and to zero any offset in the first instrumentation amplifier, while providing current-measurement information from the second instrumentation amplifier to equipment external to the apparatus. 7. The apparatus of claim 4 wherein the shunt, the first and second terminals thereof, and the first and second measurement points thereof, are formed on a printed circuitry board, and whereinfirst, second, and third respective soldering pads for each of the first, second, third and fourth switches are formed on the printed circuitry board, and whereinthe shunt, the first and second terminals thereof, and the first and second measurement points thereof, and the first respective soldering pad for each of the first, second, third, and fourth switches are all fabricated of a single continuous extent of copper cladding. 8. The apparatus of claim 7 wherein the first, second, third and fourth switches are closely grouped together in a small area of the printed circuitry board, adjacent to the shunt. 9. The apparatus of claim 8 wherein an air gap is cut into the printed circuitry board around the first, second, third and fourth switches, whereby the first, second, third and fourth switches tend toward the same temperature. 10. The apparatus of claim 5 wherein zeroing of an offset in a instrumentation amplifier is achieved by applying an analog offset to an output terminal thereof. 11. The apparatus of claim 5 wherein zeroing of an offset in a instrumentation amplifier is achieved by digital computation applied to a digitized output therefrom. 12. The apparatus of claim 6 wherein zeroing of an offset in a instrumentation amplifier is achieved by applying an analog offset to an output terminal thereof. 13. The apparatus of claim 6 wherein zeroing of an offset in a instrumentation amplifier is achieved by digital computation applied to a digitized output therefrom. 14. A current measurement system for use with apparatus comprising a shunt having first and second measurement points, the apparatus having first and second instrumentation amplifiers, each having a respective first input terminal and a respective second input terminal, the apparatus having first and second switches controllably connecting the respective first input terminal and the respective second input terminal of the first and second instrumentation amplifiers, the apparatus having a controller configured to turn either of the first and second switches fully on or off, with at least one of the first and second switches turned off at any point in time, each of the first and second instrumentation amplifiers having an output indicative of measured voltage, the method comprising the steps of: for a first interval, connecting the first input terminal of the first instrumentation amplifier to the first measurement point and connecting the second input terminal of the first instrumentation amplifier to the second measurement point;during the first interval, providing current-measurement information from the first instrumentation amplifier to equipment external to the apparatus;within the first interval, connecting the first input terminal of the second instrumentation amplifier to the second input terminal of the second instrumentation amplifier, and zeroing any offset in the second instrumentation amplifier;for a second interval, connecting the first input terminal of the second instrumentation amplifier to the first measurement point and connecting the second input terminal of the second instrumentation amplifier to the second measurement point;during the second interval, providing current-measurement information from the second instrumentation amplifier to equipment external to the apparatus;within the second interval, connecting the first input terminal of the first instrumentation amplifier to the second input terminal of the first instrumentation amplifier, and zeroing any offset in the first instrumentation amplifier,wherein the apparatus further comprises third and fourth instrumentation amplifiers, each having a respective first input terminal and a respective second input terminal, each of the third and fourth instrumentation amplifiers having an output indicative of measured voltage, the method further characterized in that:for the first interval, connecting the first input terminal of the third instrumentation amplifier to the first measurement point and connecting the second input terminal of the third instrumentation amplifier to the second measurement point;during the first interval, providing current-measurement information from the third instrumentation amplifier to equipment external to the apparatus;within the first interval, connecting the first input terminal of the fourth instrumentation amplifier to the second input terminal of the fourth instrumentation amplifier, and zeroing any offset in the fourth instrumentation amplifier;for a second interval, connecting the first input terminal of the fourth instrumentation amplifier to the first measurement point and connecting the second input terminal of the fourth instrumentation amplifier to the second measurement point;during the second interval, providing current-measurement information from the fourth instrumentation amplifier to equipment external to the apparatus;within the second interval, connecting the first input terminal of the third instrumentation amplifier to the second input terminal of the third instrumentation amplifier, and zeroing any offset in the third instrumentation amplifier. 15. The method of claim 14 wherein the first interval and second interval alternate continuously, whereby current-measurement information from one or another of the instrumentation amplifiers is continuously provided to equipment external to the apparatus. 16. The method of claim 14 further comprising a step, carried out within the second interval, of connecting the first input terminal of the first instrumentation amplifier to the first measurement point and connecting the second input terminal of the first instrumentation amplifier to the second measurement point, andcomparing current-measurement information from the first instrumentation amplifier with current-measurement information from the second instrumentation amplifier. 17. The method of claim 15, further comprising integrating the current-measurement information over a period of time to measure total charge passing through the shunt during that period of time. 18. The method of claim 15, further comprising acting upon the current-measurement information to open an electronic fuse, ceasing current through the shunt. 19. The method of claim 14 wherein zeroing of an offset in a instrumentation amplifier is achieved by applying an analog offset to an output terminal thereof. 20. The method of claim 14 wherein zeroing of an offset in a instrumentation amplifier is achieved by digital computation applied to a digitized output therefrom. 21. The method of claim 14 further comprising: within the first interval, disconnecting at least one of the input terminals of the second instrumentation amplifier from at least one of the first and second measurement points; andwithin the second interval, disconnecting at least one of the input terminals of the first instrumentation amplifier from at least one of the first and second measurement points.
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이 특허에 인용된 특허 (3)
Miranda, Evaldo M.; Mahony, Michelle; Cleary, John; Blake, John, Current measurement circuit.
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