Horizontal Control
TDS 420A, TDS 430A, TDS 460A & TDS 510A User Manual
3–61
CAUTION. To prevent damage to the external clock and external trigger circuitry,
do not exceed the input voltage rating of the EXT CLOCK/AUX TRIGGER
input (see Auxiliary Trigger Input, External Clock Input in your Performance
Verification manual).
2. Connect your TTL-like external clock signal to the EXT CLOCK/AUX
TRIGGER BNC at the rear of the oscilloscope. If your EXT CLK source
can drive 50W to TTL levels, use a 50W terminator. Before connecting your
external clock signal, make certain the signal has TTL levels and a 30 ms or
faster falling edge. (In External Clock mode, sampling occurs on the falling
edge of the clock.)
3. Connect the signals you wish to acquire to the input channels.
NOTE. If you set the maximum clock frequency to 1 kHz, do not connect an
external clock with a frequency greater than 1 kHz. If you do, you may need to
remove the external clock signal and turn the oscilloscope power off and
then on.
4. To bring up the Edge Trigger menu and select which source you want for the
trigger, press TRIGGER MENU
➞ Type (main) ➞ Edge (pop-up) ➞
Source
(main) ➞ Ch1, Ch2, Ch3, Ch4, AC Line, or Auxiliary (side), and
then press SET LEVEL TO 50%.
5. Set all other oscilloscope controls (the horizontal SCALE has no effect
except in ZOOM) as you would for an internally clocked acquisition.
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