HP 54540 Series - Page 249

Measurements
Making Automatic Measurements from the Front Panel
Pulse Width Measurements
A complete positive pulse must be displayed to make a +Width measurement.
A complete negative pulse must be displayed to make a -Width measurement.
Remember that an edge must pass through all three thresholds to be
recognized as an edge. Therefore, it is important that the pulse be positioned
so that all three thresholds are displayed on the screen.
Rise Time, Fall Time, Preshoot, and Overshoot Measurement
The leading (rising) edge of the waveform must be displayed for rise time
and rising edge preshoot and overshoot measurements.
The trailing (falling) edge of the waveform must be displayed for fall time and
falling edge preshoot and overshoot measurements.
Remember that an edge must pass through all three thresholds to be
recognized as an edge. Therefore, it is important that the pulse be positioned
so that all three thresholds are displayed on the screen.
Rise time, fall time, preshoot, and overshoot measurements will be more
accurate if you expand the edge of the waveform by selecting a faster sweep
speed. Expanding the waveform will provide more data points on the edge
and thus a more accurate measurement.
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