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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

Frequency with Delta-Delay-Time

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.

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.)

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

Tektronix 2445B User Manual

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