Tektronix 222 Operator's Manual page 57

222 DSO Operators-How It Works
4.1 5 TRIGGER LEVEL SElTING
Rotate the Trigger knob.
The control sets the voltage threshold that a trigger signal must cross
to produce triggering. The Trigger LEVEL readout appears in the
lower left corner of the display area.
The LEVEL control has enough range to trigger on any portion of a
signal that is within the dynamic range of the vertical amplifier. If the
trigger signal is off screen, the
"+"
indicator will be at the top or
bottom of the screen to show the direction (if the oscilloscope is
triggered).
Press the center
button to force a manual Trigger AUTO LVL.
When it is pressed in, the trigger signal is checked for its peakvalues,
and the Trigger LEVEL control setting is placed at the midpoint
between the peaks. This feature is useful for quickly finding a Trigger
LEVEL setting that triggers the display in NORM, AUTO BL, and SSEQ
Trigger MODES. If you have the Trigger LEVEL set for a particular
voltage that the trigger signal must cross to trigger the acquisition,
don't press the AUTO LVL button as this will change the setting to
trigger on whatever signal appears at the probe tip.
4.1 6 TRIGGER SLOPE SELECTION
Press to toggle the trigger slope.
Each press switches between triggering on the rising slope or the
falling slope of the trigger signal. The selected slope is shown in the
bottom line of the readout as a "
+"
or a
' I - "
symbol for rising and
falling slopes respectively.
Switching between
+
and
-
slope while viewing a pulse signal lets
you view the rising and falling edges of an expanded signal with only
a single control change.
REV MAR 1989
4-9