Tektronix 2445B - Precision Timing

Operation
Precision Timing
The available Counter/Timer/Trigger (CTT) directly and precisely measures any
interval defined by the delayed (B) Sweep and the B-Trigger. The CTT also reduces
the effort required for repetitive measurements or measurements on changing signals.
Direct and Indirect Measurements
As the counter completes each direct measurement, the last character of the
units symbol blinks. If the readout includes the word "SET," it indicates an
indirect measurement of delay-time, including delta-delay-time or 1/delta-delay-
time. Indirect measurements are inferred from the A Sweep and control
settings.
Indirect delay-time measurements are displayed when any Count. Delay-by-
Events, or Logic-Trigger function of the C7Tis active, except B Sweep
triggered by the Word Recognizer. Indirect measurements are also displayed for
a few seconds when A REF or A are adjusted. Moving any control that affects
direct measurements produces an indirect reading until a new, direct
measurement is complete.
Direct, counted measurements may be different from indirect {"SET
-
')
measurements for any of the following reasons:
1. Direct measurements are more accurate and show more digits of
resolution;
2. When B Sweep is triggered, both the waveform display and the direct
measurement respond to the signal. Indirect measurements respond
only to control settings, regardless of the signal, and they include a
question mark when B Sweep is triggered;
3. Both direct and indirect measurements in RUN AFT DLY Mode suffer
from offset errors. Direct delay measurements, without At or 1/At, are
accurately calibrated in TRIG AFT DLY Mode, from the A-Trigger event
to the B-Trigger event.
Condition Messages
One of the following messages, indicating the described condition, may
appear instead of a measurement:
AVERAGING The selected resolution requires more sweeps.
NO A TRIGGER The A-Trigger event has not occurred.
MISSING B TRIG At least one A Sweep occurred without a
B-Trigger event during the A Sweep.
NO ATRG VERT SRC Multiple A-Trigger sources are selected.
2-22
2465B/2455B/2445B Operators