Fall Time
Fall time measures the transition time of the waveform's negative (falling) edge. This measurement may be compatible with PAM4 signals, depending on the PAM4 waveform.
The measurement can be restricted to a measurement region. The measurement is made using the lower, middle, and upper threshold levels, which are based on the Waveform Top and Waveform Base measurements. Annotation labels identify the threshold levels on each end of the waveform's negative (falling) edge. The fall time will not be measured until the falling edge completes the transition through all three levels. The fall time equals the lower threshold crossing time minus the upper threshold crossing time.
PAM4 Compatibility in Oscilloscope mode. Because this measurement is based on waveform top and base levels and the passing of the waveform's edge through proximal, mesial, and distal thresholds, the measurement is not designed for PAM4 signals. However, the measurement may be able to be made on PAM4 signals if the waveform top and base definitions are manual set. This can be attempted using the Top-Base Definition tab of the Configure Measurements dialog.
This measurement may be compatible with PAM4 signals, depending on the PAM4 waveform. PAM measurement capability requires the Research and Developement or Manufacturing package license or the legacy PAM-N Analysis license.
The default setting for the threshold levels are the 10% to 90% points on the transition. The top level is defined as the 100% level of the waveform. The base level is defined as the 0% level of the waveform.
The falling edge of the waveform must be displayed on the screen or measurement region for fall time measurements.
If the signal has jitter, perform the fall time measurement in Eye/Mask mode for improved accuracy.
The measurement can be performed on any waveform that is displayed in one of a Waveform content windows.
Configurable Measurement Parameters
This measurement is affected by the following settings (click Measure > Configure Meas):
- Top-Base Definition tab
- Thresholds tab
To measure
- Select Oscilloscope Mode.
- Click the toolbar's Time tab.
- Click the toolbar's More buttons to locate the Fall Time button.
- Click the button.
- If measurement regions are enabled, the Select Measurement Region, Setting dialog is displayed. Select the area over which the measurement is to be performed: a Region or the Entire Display.
SCPI Command
:MEASure:OSCilloscope:FALLtime