B Trigger Modes - Tektronix 2245A Operator's Manual

Controls, Connectors, and Indicators
TV LINE—Starts the A sweep at the beginning of a video signal line.
SLOPE polarity must match the composite sync polarity (i.e., - T
SLOPE for negative sync) to obtain TV LINE triggering on the horizon­
tal sync pulse. Instruments Serial Numbered B020100 or above can
have the TV SLOPE polarity preset by changing the instrument con­
figuration from the CONFIGURE menu (see " Service Menu Features"
in Section 3).
TV FIELD—Starts the A sweep at the beginning of a video signal field.
SLOPE polarity must match the composite sync polarity to obtain TV
FIELD triggering.
SGL SEQ (Single Sequence)—Sets up the A sweep for single-se­
quence operation. Each additional press of the down-arrow MODE
button, when in single-sequence mode, resets the sweep and makes
it ready to accept a trigger. As in NORM trigger MODE, the set trig­
gering level changes only when the TRIGGER LEVEL control is ad­
justed to a new level setting.
When triggered, the sweep runs to produce a single sweep of each
trace as required by the setting of the VERTICAL MODE and HORI­
ZONTAL MODE switches. Each displayed sweep in the sequence re­
quires a distinct A sweep triggering event. The READY light remains
on until the final trace in the sequence is completed. The readout and
cursors can be set to turn on briefly at the end of the sequence when
using a camera (factory setting default mode), or they can be set to
remain on by changing the instrument configuration from the CON­
FIGURE menu (see " Service Menu Features" in Section 3).
B T rig g e r M o d e s
AUTO LEVEL—Sets the range of the Trigger Level control to the
peak-to-peak limits of an adequate B Trigger-source signal and trig­
gers the B sweep.
The auto-level range is reset when triggering is lost, TRIGGER LEVEL
control is rotated to either end stop, or AUTO LEVEL Trigger MODE
Is reselected. AUTO LEVEL mode is useful for quickly locating an ap­
propriate triggering level.
The B sweep operates in RUNS AFTER mode when the trigger-source
signal amplitude is too low or the frequency is below 10 Hz. Switch to
NORM triggering if the repetition rate is too slow for auto leveling. The
A Sweep must be running (free-running or triggered) for B Sweep to
trigger.
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2245A Operators