B Trigger Modes - Tektronix 2247A Operator's Manual

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Controls, Connectors, and Indicators
the A Trigger source signal amplitude is too low or the frequency is
less than 1 O Hz or the Trigger LEVEL Is not appropriate. The triggering
level changes only when the Trigger LEVEL control is adjusted to a
new level setting.
NORM-Triggers the A sweep when the A Trigger LEVEL control Is
set within the peak-to-peak limits of an adequate trigger ~ignal. When
the A sweep is not triggered, no baseline trace is display°ed.
TV LINE-Starts the A sweep at the beginning of a video signal line.
SLOPE polarity must match the composite sync polarity to obtain TV
LINE triggering on the horizontal sync pulse.
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-
sequence 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
adjusted 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 Horizontal
MODE switches. Each displayed sweep in the sequence requires a
distinct A sweep triggering event. The READY light r emains 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 settings default mode), or they can be set to remain
on by changing the Instrument configuration from the CONFIGURE
menu ( see "Service Menu Features" In Section 3) .
B Trigger Modes
AUTO LEVEL-Sets the range of the Trigger LEVEL control to the
10% and 90% levels of the B Trigger source signal, sets the Trigger
LEVEL, and triggers the B sweep and CIT.
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2247 A Operators
®
Controls, Connectors, and Indicators
NOTE
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 autoleveling. The A sweep must be run-
ning (free-running or triggered) for B sweep to trigger.
Once set, autoleveling Is repeated only if triggering is lost, if the
Trigger LEVEL control Is rotated to either end stop, or if AUTO
LEVEL Trigger MODE is reselected. AUTO LEVEL MODE is useful for
quickly locating an appropriate triggering l~vel.
RUNS AFTER-Starts the B sweep immediately after the delay time
selected by the It- OR DELAY control.
NORM-The B sweep Is triggered when an adequate trigger signal is
received aft~r the delay time condition has been met. When there is
no trigger sjgnal, there ls no B sweep trace.
TV ·LINE FROM A SOURCE-Starts the B sweep at the beginning of _
the video signal line received after the delay time has been met.
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NOTE
SLOPE polarity defaults to the A Trigger' SLOPE. This must
match the composite sync polarity (same as .A Trigger
SLOPE) to obtain correct triggering on the horizontal sync
pulse.
SOURCE (Up-Arrow and Down-Arrow) Buttons and Indi-
cators-Select the trigger source for either the A or the B Trigger
system as directed by the A/B SELECT button. Pressing the
Up-/Down-Arrow SOURCE buttons selects the trigger source (for A
or B trigger system) as shown by SOURCE lights. For the
Counter /Timer system, all measurement sources are selected from
the SET MEAS'MT CHANNEL menus; the B trigger SOURCE lights
stay off.
2247 A Operators
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