Parameter in second row on the right bottom of the wave frame is
scroll-step,
turn knob one step; the window-address will increase a scroll-step value. The
higher the value of scroll-step is, the faster the speed of waveform rolling is, but
this may miss needed part; the lower the value of scroll-step is, the slower the
speed of rolling is, and the finer observe the waveforms. Press
【
System
】
to
select
scroll-step
, the value of the scroll-step can be set by number keys with
the range of 1~ 260 000, after the setting, press
【
←→
】
and turn the knob to roll
the waveform left and right, so that the speed of waveform rolling will change.
Setting the window-address with number keys directly enables display window to
locate in the data block needing to visit, and rolling waveforms with knob turning
can observe the change situations of a section of waveform continuously.
5.5.4. Waveform zoom
In digital systems, the changing rate of the logic level may be very different in
different data channels, in a timing waveform displaying graph; it may include 8
channels with big difference in changing rate of logic level. This brings a problem,
that is, a large number of pulse waveforms crowds together in channel with fast
changing rate of logic level and cannot be seen clearly, but in the channel with
slow changing rate, it is a line on screen. To solve this problem, can stretch the
waveforms in level direction and unfold the crowded pulse wave to visit waveform
characteristics with fast changing, also can compress the waveforms and gather
sparse pulse waveform together to visit waveform characteristics with slow
changing.
Press
【
Zoom
】
key and turn the knob to make the display waveforms stretch or
compress in horizontal direction.
“Zoom= ns/div”
in the sixth row on the left
bottom of the wave frame will change, this ratio coefficient stands for time amount
that each lattice of scale line represents, in the above and underside two rows of
waveform frame. The essence of waveform amplification is that a number in
sampling memory is displayed continuously with several points in waveform
display. So, the amplifying waveform can make dense waveform be seen more
clearly and let measurement become easy, it won’t generate any distortion to
waveform. But waveform amplification is unable to increase resolution; the
original invisible contents are still not seen after amplification. If want to observe
the detailed change, need to increase sampling velocity. The essence of
compression is taking one number to display from several data points in sampling
memory, therefore after compression, waveform’s observing scope is broadened,
but may lead to distortion and miss small changing part, more compression rate
results in more serious distortion. So compression should be made gradually, one
should not continue compressing when finds distortion. The amplifying or
compression state will be displayed in present waveform, with the turn of knob;
character indication displays on top of interface at any moment.
Because waveform zoom is taken sampling clock as the time unit, so the zoom
ratio change is spaced by step, if measure waveform’s interval with scale of
waveform frame, may have error, just a rough measurement. If need to measure
the interval of the waveform accurately, should use the method of cursor
measurement.
The zoom function of the waveform is applied in the situation that the changing
rate difference of the logic-level in every channel is very big in a group of
waveforms, if the changing rate of the logic level in a group of waveforms is
generally bigger or smaller, then should solve it by adjusting the sampling rate.
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