Setting A Specific Trigger Level - Tektronix 2247A Operator's Manual

Basic Applications
. 4
Table 5-1
Trigger Cursor Channel
A or B Trigger Source A or B Cursor Channel
VERT
Lowest-numbered channel
displayed ( CH 1 or CH 2)
'
CH 1 CH 1
CH 2 CH 2
CH
3
Not used
CH 4 Not used
LINE Not used
To enable the TRACK TRIG LVL cursors, press the CURSOR VOL TS button
to call up page one of the menu. The last selection in the menu Is "TO
AUTO TRACKING MENU." Press the menu select button for that choice to
display page 2 with the tracking cursor choices. All of the choices, TRACK
MEASMT, TRACK TRIG LVL, and TRACK
m,
may be underlined, but they
cannot all be displayed at the same time. Only two cursors at a time are
permitted. If enabled, but not displayed in a particular waveform, omitted
cursors will be displayed when a higher priority cursor Is turned off. TRACK
MEASMT cursors take priority over the TRACK TRIG LVL cursors. TRACK
TRIG L VL cursors take priority over TRACK
m
cursors. The cursors dis-
played when a CURSOR VOL TS measurement Is active tak~ priority over all
the Auto Tracking Cursors.
NOTE
The CLEAR DISPLAY button w/11 turn off the TRACK TRIG
LVL and TRACK
m
cursors If pressed the appropriate
number of times. To enable either or both of these, it is
necessary to re-enter the Cursor Volts menu and reselect
them.
The TRACK MEASMT cursors are also turned off by the CLEAR DISPLAY
button, but the function Is not turned off; the TRACK MEASMT cursor(s)
will be displayed again when a CH 1 /CH 2 Voltmeter measurement Is called
up.
5-20
2247 A Operators
Basic Applications
Setting Trigger Level
The trigger level readout supplied by the TRACK TRIG L VL cursor may be
used to set a specific trigger level for triggering on a displayed waveform.
As an example , assume the f ollowlng conditions:
a . The signal to be examined Is a mix of two different signal levels ( see
Figure 5-8) .
b. It Is necessary to trigger on the larger amplitude signals to make a
closer examination of their waveshape and take pulse width and/ or
rise time measurements.
To set therrlgger LEVEL to the appropriate level with no signal applied (or
with GND Input coupling) use the TRACK
m
cursor feature. (The TRACK
m
cursor menu choice is reached through the san:,e menu path as the TRACK
TRIG LVL cursor . ) The ground cursor provides feedback to the user so that
the ground level may be positioned without the need for a ground baseline
trace.
,
100 ·
I
a
.
90
I
r
.., J
I
........ J ......
I ..
~
...........
~--•···0_1 ..
V ........ ··-······ ............ -·········· ............. ·-·'····
10
- - - - 1 - ~ ~ .......
- + - -...... ---++-
1
-+-+-++--+-,' ~ ---t+---+---
1
~~
. ·I .
l l . •·
l · .
l l
l -
.l
1
~
- ·
1
1U:-~
.54
~
DC SYMBOL
6556-34
Figure 5-8. Setting a specific trigger level.
2247 A Operators
5-21