Operation
Precision Timing
The available Counter/Timer/Trigger
(CIT)
directly and precisely measures any
interval defined by the delayed
(B)
Sweep and the B Trigger. The
CIT
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
CIT
is active, except B Sweep
triggered by the Word Recognizer.
Indirect measurements are also displayed for
a few seconds when
~
REF
or
~
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 DL Y Mode suffer
from offset errors. Direct
delay measurements, without
~t
or
1/~t,
are
accurately calibrated
in
TRIG AFT DL Y 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.
2465A/2455A/2445A Operators 2-17
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