Triggerpoint selection
The SLOPE switch determines whether the sweep will on a positive-going or negative-going transition of the
trigger signal (See fig. 2-4). Always select the steepest and most stable slope or edge. For example, small
changes in the amplitude of the sawtooth shown in Figure 2-4 a will cause jittering if the timebase is triggered
on the positive (ramp) slope, but have no effect if triggering occurs on the negative slope (a fast-fall edge).
In the example shown in Figure 2-4b, both leading and trailing edges are very steep trace to jitter, making
observation difficult. Triggering from the stable leading edge (+ slope) yields a trace that has only the trailing
-edge jitter of the original signal. If you are ever in doubt, or have an unsatisfactory display, try both slopes to
find the best way.
Trigger Level Control
The LEVEL control determines the point on the selected slope at which the main (A) timebase will be
triggered. The effect of the LEVEL control on the displayed trace is shown in figure 2-4 c. The "-","0", and "+"
panel-markings for this control refer to the waveform's zero crossing and points more positive (+) and more
negative (-) than this. If the trigger slope is very steep, as with square waves or digital pulses, there will be no
apparent change in the displayed trace until the LEVEL control is rotated past the most positive or most
negative trigger point, whereupon the display will free run (AUTO Sweep mode) or disappear completely
(NORM sweep mode). Try to trigger at the mid point of slow-rise waveforms (such as sine and triangular
waveforms), since these are usually the cleanest spots on such waveforms.
Fig. 2-4: Trigger-Slope Selection
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