HP 54645A User's And Service Manual page 168

Automatic Measurements
The oscilloscope makes automatic measurements on the first displayed event.
The following figure shows how to use delayed sweep to isolate an event for a
frequency measurement. If the measurement is not possible in the delayed
time base mode, then the main time base is used. If the waveform is clipped,
it may not be possible to make the measurement.
Figure 5-21
Isolating Event for Frequency Measurement
Making Measurements with HP 54645A/D Oscilloscopes
To find the Show Meas softkey, press the Next Menu softkey key.
When the Show Meas softkey is turned on, cursors are displayed on
the waveform, and show measurement points for the measurement
result displayed on the right-most part of the status line. If you select
more than one measurement, you can show a previous measurement
by reselecting the measurement.
To make frequency measurements automatically
5-27