Operation
Delta-Delay- Time
Use the delayed (B) sweep to magnify both ends of a time interval for the best
measurement accuracy available. Appendix D gives relative accuracies of the various
time-measurement techniques.
Measure
Time
or
Frequency with Delta-Delay-Time
1.
Display the time interval or signal period with the A Sweep running as
fast as possible, unmagnified, up to one speed slower than the fastest
SEC/DIV setting. If the interval is a propagation delay or other two-
signal measurement, display the signals on CH 1 and CH 2 and trigger
A Sweep on the earlier of the two.
2.
Pull SEC/DIV out to activate B Sweep and light the A SWP and B SWP
indicators (INTEN mode). (If you inadvertently chose the fastest
A-Sweep speed, the CH2 Delay Match function will be active. See the
"Operator Checks and Adjustments" section.)
3. If a B-Trigger Mode indicator is on, select RUN AFT DLY. (If an
A-Trigger Mode indicator is on, the B-Trigger has been set previously to
RUN AFT DLY.)
4.
Select At or 1/At while the SEC/DIV knob is out.
5. Adjust A REF OR DLY POS and A to place the pair of intensified zones
at the beginning and end of the interval of interest. If the A Sweep
terminates just after the intensified zones, you can move the HOLDOFF
control and set it at MIN.
6. Turn SEC/DIV clockwise with the knob pulled out to magnify the ends
of the interval on the B Sweep while observing the entire interval on the
A Sweep (ALT mode). Use TRACE SEP to separate the A-Sweep and
B-Sweep traces as desired.
7. Set A REF and A to superimpose the magnified displays of the
beginning and end of the interval. The readout shows the interval.
Without the
CTT,
make delta-delay-time measurements only in the RUN AFT
DLY trigger mode, where the B Sweep runs immediately after the set delays. If
the B Sweep is triggered (TRIG AFT DLY), it waits for a trigger after the set
delay, so the actual delay time may differ from the delay or At readout by as
much as twice the signal period.
2465B/2455B/2445B Operators
2-19
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