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2. Trigger coupling
The LF-HF-DC switch determines the method of coupling
the signal into the trigger circuit. LF coupling blocks
undesired d.c. levels and h.f. interference but responds
to Lf. triggering signals.
HF coupling blocks d.c. and 1-f. signals, e.g. hum, but
respond to h.f. triggering signals.
DC coupling makes the full signal bandwidth available
for triggering.
3. Automatic triggering
Automatic triggering, when the LEVEL knob is pulled
out, is most often used on account of its simple
operation. In this position it is possible to display a
large number of wave forms having different amplitude
and shape, without it being necessary to operate any of
the trigger controls. If no triggering signal is present, a
time-base line remains visible on the screen. This is useful
for reference purposes. In this trigger mode, the level can
be adjusted over approximately 3 cm of the trace.
4. Trigger level
Incase of a complicated signal in which a number of
non-identical voltage shapes occur periodically, the time
axis should always be started with the same voltage
shape, so as to obtain a stationnary trace. This is possible
when one of the details has a deviating amplitude. By
means of knob LEVEL, the trigger level can then be
adjusted so that only this larger voltage variation passes
this level. The LEVEL setting is also useful for the study
ofa leading edge. Then the trigger level can be set in
such way that the time-base is already started at the
beginning of this leading edge, owing to the delay line.
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5. External triggering
External triggering is applied for signals having a strongly
varying amplitude, if a signal having a fixed amplitude
and equal frequency is available. This obviates the
necessity of readjusting the level setting at every
variation of the input signal.
E. TIME-BASE MAGNIFIER
The magnifier is operated by a push-pull switch. When
this switch is in position x5, the time-base is increased
5 times. In position x5 of the magnifier, the sweep time
of the sawtooth is determined by dividing the indicated
TIME/cm value by 5.
F. Z-MODULATION
In order to bring extra information in the c.r.t. display
without changing the wave form, the intensity of the
trace can be varied by an externally applied voltage.
The external signal must, therefore, be fed to the socket
Z-MOD on the rear side of the instrument. The vol tage
required for visible intensity modulation dependson the
position of the INTENS control. With an average bright-
ness of the trace, a 5 Vp-p voltage is amply sufficient for
obtaining a good visible Z-modulation.
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