An external signal connected to the EXT TRIG jack can be used
to trigger the sweep in the EXT position of the Trigger SOURCE
switch. The external signal must be time-related to the displayed
signals in order to obtain a stable display. An external trigger signal
of 1 volt to 20 volts can be used to provide a triggered display when
the internal signal is too low in amplitude for correct triggering, or
contains signal components on which it is desired not to trigger.
The external trigger signal is useful when signal tracing in
amplifiers, phase-shift networks, wave-shaping circuits, etc. The
signal from a single point in the circuit under test can be connected
to the EXT TRIG banana jack. Then the sweep is triggered by the
same signal at all times to allow amplitude, time relationship,
waveshape changes, or signals at various points in the circuit to be
examined without resetting the trigger controls.
Trigger Slope
The LEVEL/SLOPE control determines whether the trigger
circuit responds on the positive-going or negative going portion of
the trigger signal. When the indicator dot is to the left of center, the
trigger circuit responds on the positive-going portion of the triggering
waveform (notice the positive-going waveform on the left side of the
control). To the right of center, the trigger circuit responds to the
negative-going portion of the triggering waveform (notice the
negative-going waveform on the right side of the control). Since this
instrument does not have an internal delay line, the display might
not start on the selected slope, particularly when the displayed
waveforms have a high repetition rate.
18
212 Operators Handbook
