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Application Notes 49
5.1.8 Automatic Measurement Sequence
The automatic measurement process analyzes the captured signal data in the following sequence:
1. Approximately 500 samples of the waveform (equivalent to one screen width) are scanned to determine the maximum
and minimum sample amplitudes.
2. The difference between the maximum and minimum sample values is calculated and stored as the Signal Amplitude.
3. The Transition Threshold is computed as one-half the sum of the maximum and minimum sample amplitudes.
4. The processor locates each crossing of the Transition Threshold.
5. Starting at the left edge of the screen, the processor classifies each Transition threshold crossing according to whether
it is positive-going (– +) or negative-going (+ –). Because the signal is repetitive, only three transitions are needed
to classify the waveform, as follows:
Type Sequence Description
0 none No crossings detected
1 Not used
2 + – One falling edge
3 – + One rising edge
4 + – + One falling, followed by one rising edge
5 – + – One rising, followed by one falling edge
6 + – + – Two falling edges
7 – + – + Two rising edges
Table 5.3 Transition Threshold Crossing
Figure 5.5 Step Waveforms