Reference
Measurement In
teraction with Preview. If you change a vertical or horizontal
control setting while acquisition is stopped or is waiting for trigger, measurements
track the changes and remain valid.
Taking Gray-Scale Measurements. Using cursors is often the best way to
take simple measurements on waveforms that contain significant gray-scale
informatio
n. The automatic measurements operate only on the latest acquisition,
not on the previous acquisitions that are displayed in gray scale. However, you
can set the cursors to surround and measure the gray-scale area of the waveform.
High-Low Setup. The oscilloscope determines the 10%, 50%, or 90% levels of
the waveform and then uses them to calculate the measurements. There are two
possible
methods: Histogram or Min-max. Auto Select allows the oscilloscope
to determine the method used.
Histogr
am sets the values statistically; it finds the most common value either
above or below the midpoint (depending on whether it is defining the high
or low reference level). Since this statistical approach ignores short-term
aberrations (overshoot, ringing, noise), histogram is the best method for
measuring digital waveforms a nd pulses.
Min-max uses the highest and lowest values of the waveform record. This
method is best for measuring waveforms that have no large, flat portions at a
common value, such as sine waves and triangle waves.
Auto Select chooses one of the above methods automatically depending on
the signal characteristics. Auto Select chooses the histogram method if the
his
togram contains prominent peaks. If not, Auto Select chooses the min-max
method.
Measurement Gating. You can use the gating feature to limit measurements to the
portion of the waveform that is on the screen or between the cursors.
When you turn Screen g ating on, the oscilloscope only uses the waveform points
on screen in its measurements. This function is useful at the fastest time base
settings or when you want to take measurements on a magnified waveform (when
zoom
is on).
When you turn Cursor gating on, the oscilloscope displays vertical bar cursors.
Use the general purpose knob and Select button to place the cursors around the
area of interest.
In the next example, the cursors surround the second positive-going pulse so the
oscilloscope can measure the width of that pulse.
TDS3000C Series Oscilloscope User Manual 81
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