| 摘要 |
An apparatus and method for digitizing a repetitive waveform using an analog oscilloscope uses a successive approximation technique. For each sample point on the repetitive waveform a digitizing level is compared with the repetitive waveform at that sample point, and the digitizing level is adjusted until it essentially equals the magnitude of the repetitive waveform at that point. The particular sample point is determined by comparing a delay level with a ramp signal that starts from an initial fixed trigger point on the repetitive waveform. Each point is digitized in this manner in one of three modes. The first mode samples the same point on successive iterations of the waveform until that point is digitized, and then the next point is digitized. The second mode samples each point once per iteration of the waveform by stepping the delay level n times during each iteration, and adjusting the digitizing level individually for each sample point until the digitization is complete. The third mode generates a fast ramp having n cycles per iteration of the waveform so that the delay level stays the same, but each sample point is sampled once each waveform iteration. Otherwise it is essentially the same as mode two. In like manner maxima and minima for segments of the waveform may be determined using a window interval rather than a sample pulse.
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