Surge current measurement
First Claim
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1. A method of measuring surge current, comprising the steps of:
- (a) receiving an input signal from a current sensor;
(b) detecting a change in said input signal indicating the beginning of a current surge;
(c) acquiring said input signal for a predetermined time period following detection of said change thereby to acquire said current surge for at least a portion of its time duration;
(d) processing said current surge to determine the numerical average thereof; and
(e) displaying said numerical average.
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Abstract
A novel method of and apparatus for accurately measuring surge currents such as motor-starting inrush currents is provided. An input signal from a current sensor is monitored, and when the input signal changes and exceeds a predetermined threshold, a surge current is detected. The input signal is acquired over a predetermined time period by a fast sampling ADC, which converts the input signal into a series of digitized samples representative of instantaneous current values. These values are processed to compute average current or RMS current, which is then displayed.
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Citations
10 Claims
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1. A method of measuring surge current, comprising the steps of:
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(a) receiving an input signal from a current sensor;
(b) detecting a change in said input signal indicating the beginning of a current surge;
(c) acquiring said input signal for a predetermined time period following detection of said change thereby to acquire said current surge for at least a portion of its time duration;
(d) processing said current surge to determine the numerical average thereof; and
(e) displaying said numerical average. - View Dependent Claims (2, 3, 4)
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5. A method of measuring surge current, comprising the steps of:
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(a) receiving an input signal from a current sensor;
(b) continuously converting said input signal into digital samples representative of instantaneous current values at a predetermined rate;
(c) comparing each of said digital samples with a predetermined value representative of a surge current, and when said predetermined value is exceeded, acquiring a series of consecutive digital samples for a predetermined time period that includes at least a portion of the time duration of said surge current;
(d) processing said series of consecutive digital samples to provide a numerical indication of said surge current; and
(e) displaying said numerical indication. - View Dependent Claims (6, 7)
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8. A current measuring instrument, comprising:
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a current sensor for providing an input signal corresponding to an external current;
means for determining when the magnitude of said input signal exceeds a predetermined trigger threshold indicating a beginning a surge current;
a sampling analog-to-digital converter coupled to said current sensor for converting said input signal into a digitized samples representative of instantaneous magnitudes at sampled points of said input signal;
a processor coupled to said sampling analog-to-digital converter for receiving a series of consecutive digital samples for a predetermined time period that includes at least a portion of the time duration of said surge current, said processor computing a numerical indication of said surge current; and
a display device for displaying said numerical indication. - View Dependent Claims (9, 10)
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Specification