Operation
TRIGGER CONTROLS
For most signals, the trigger-control settings that will yield hands-
off triggering are:
Which Mode to Use
P-P AUTO/TV LINE— With this mode set, the range of the LEVEL
control is confined to the values between the triggering-signal
peaks. For example, selecting P-P AUTO and rotating the LEVEL
control to the center half of its range establishes a trigger point
that is about midway between the peaks of the triggering signal.
In this mode, the absence of a triggering signal causes the
sweep to free-run. And with signals below 20 Hz, the P-P AUTO
circuit may not find the correct level.
Whenever P-P AUTO is active and VEFfT MODE source selected,
the triggering signal is supplied by the channel that is being dis
played— or by Channel 1 in a two-channel display.
The P-P AUTO mode is effective for monitoring logic signals and
television lines having at least a 20-Hz repetition rate. Selecting
P-P AUTO at the instrument front panel also sets the TV LINE
triggering mode.
NORM— This mode produces a sweep only when the triggering
signal meets the criteria set by the LEVEL and SLOPE controls.
With NORM mode selected, range of the LEVEL control is suffici
ent to set any voltage threshold that can be displayed by the
instrument. In the absence of a triggering signal, there is no
sweep.
Use the NORM mode for viewing infrequent events and erratic
signals.
SGL SWP— When this mode is selected, the sweep is triggered
only once. Press the RESET button once to arm the trigger circuit
and illuminate the READY indicator. When a trigger event occurs,
the sweep runs once and the READY light extinguishes.
Use the SGL SWP mode to display or photograph nonrepetitive
or unstable signals.
TV FIELD— This mode triggers the sweep at the beginning of a
television field. To change the TV field being displayed, you must
interrupt the trigger signal by setting the input coupling switch
momentarily to GND then back to either DC or AC until the
desired field is displayed.
MODE
HOLDOFF
SOURCE
COUPLING
P-P AUTO
MIN
VERT MODE
DC
2225 Operators
2-9
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