Edge Triggering
3–24
TDS 420A, TDS 430A, TDS 460A & TDS 510A User Manual
Noise Rej provides lower sensitivity. It requires additional signal amplitude for
stable triggering, reducing the chance of falsely triggering on noise.
To select the slope that the edge trigger occurs on:
1. Press the TRIGGER MENU
➞ Type (main) ➞ Edge (pop-up) ➞
Slope
(main).
2. Select the rising or falling edge from the side menu.
Press the TRIGGER MENU
➞ Type (main) ➞ Edge (pop-up) ➞ Lev-
el
(main) ➞ Level, Set to TTL, Set to ECL, or Set to 50% (side).
Level lets you enter the trigger level using the general purpose knob or the
keypad. (You may also change the level using the MAIN LEVEL knob.)
Set to TTL fixes the trigger level at +1.4 V.
Set to ECL fixes the trigger level at –1.3 V.
NOTE. When you set the volts/div smaller than 200 mV, the oscilloscope reduces
the Set to TTL or Set to ECL trigger levels below standard TTL and ECL levels.
This happens 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.
Set to 50% fixes the trigger level to approximately 50% of the peak-to-peak
value of the trigger source signal.
To select the trigger mode and change the holdoff time:
1. Press the TRIGGER MENU
➞ Mode & Holdoff (main) ➞ Auto or
Normal
(side). The trigger modes operate as follows:
In Auto mode the oscilloscope acquires a waveform after a specific time
has elapsed even if a trigger does not occur. The amount of time the
oscilloscope waits depends on the time base setting.
In Normal mode the oscilloscope acquires a waveform only if there is a
valid trigger.
2. To change the holdoff time, press Holdoff
(side). Enter the value in % using
the general purpose knob or keypad.
If you want to enter a large number using the general purpose knob, press the
SHIFT button before turning the knob. When the light next to the SHIFT button
To Set Slope
To Set Level
To Set Mode & Holdoff
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