Tektronix 222 Operator's Manual page 103

More On How It Works-222 DSO Operators
AUTO LVL: This is the autolevel Trigger MODE. The positive and
negative peaks of the selected trigger signal are found, and the Trig-
ger LEVEL is set to the midpoint between those two levels. If a trigger
is not received after the update period has finished, an auto trigger is
generated. The resulting waveform is displayed, and the new signal
peaks are acquired to reset the trigger hysteresis band at the mid-
point between the two peak limits.
Table 6-4
AUTO LVL Trigger Interval Urnits
I
SECIDIV Setting
Trigger Interval for Autoleveling
I
I
5 msldiv or less
I
30 ms or less
I
I
10 msldiv to 50 msldiv
I
4
times the SECIDIV setting or less
I
I
1
100 msldiv or more
I
200 ms or less
I
Autoleveling on the trigger signal is done at the following times:
when AUTO LVL Trigger MODE is entered,
when a trigger is not received within a certain time limit after the
trigger system is armed (see Table 6-4)
when the AUTO LVL: PUSH knob is pressed.
Autoleveling may not produce a valid trigger if the signal amplitude is
less than the trigger hysteresis (114 of a minor division) or if the trigger
events do not occur often enough (see Table 6-4).
AUTO BL: The auto baseline Trigger MODE causes a trigger to be
forced if one does not occur so that a trace may be seen. Whatever
data captured by the forced acquisition is displayed. With an appro-
priate trigger signal applied, acquisition and display occurs the same
as in NORM Trigger MODE.
The STOREINONSTORE mode selection determines how the display
will behave between trigger wents. In STORE mode, the waveform is
held displayed between triggers. With NONSTORE display mode
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1989 6-1 1