| 摘要 |
<p>A one step RMS system in which an air core toroid coil (30) is used to measure the first differential with respect to time of a current signal waveform. The RMS value of the current signal waveform is determined directly from the first differential waveform generated by the air core toroid coil (30) by mathematically integrating the first differential waveform. The integration is performed by converting the signal into digital form and by sampling N times per piece of waveform or time period being analyzed. The value of N can be chosen so that the entire half cycle is sampled. Thus, the RMS value to be calculated will be based on the whole half cycle time period not merely a part of the half cycle time period. Alternatively, the RMS value of segments of a pulse with a long duration can be measured. As each sampling and conversion is completed, the digital number, representing the instantaneous value of the amplitude of the differential waveform, is used to determine the instantaneous value of the current at that time. This current value is squared and added to the sum of the prior squared values. Each squared value is summed until N samplings and conversions have been made. At this point, the final total is divided by N, and the square root is then taken to obtain the RMS value.</p> |
