Tektronix CSA7404B, User Manual

Page: 143 / 438

Triggering
CSA7000B Series & TDS7000B Series Instruments User Manual
3- 75
Overview Control elements and resources Additional trigger parameters (Cont.)
To select a
preset trigger
level
1. Push the ADVANCED button, select the A Event tab,
and touch either of the Trigger Type buttons.
2. Select a Trigger Type, such as Edge, that uses a level
adjustment.
3. Select Level and touch the keyboard icon to display the
keyboard. Select either TTL, ECL, or USER:
H
TTL fixes the trigger level at +1.4 V.
H
ECL fixes the trigger level at --1.3 V.
H
USER fixes the trigger level at the USER preset
voltage.
When you set the volts/div smaller than 200 mV, the
instrument reduces the TTL or ECL trigger levels below
standard TTL and ECL levels. This reduction occurs
because the trigger level range is fixed at
±
12 divisions
from the center. At 100 mV (the next smaller setting
after 200 mV) the trigger range is
±
1.2 V, which is
smaller than the typical TTL (+1.4 V) or ECL (--1.3 V)
level.