Measuring Waveforms
TDS 684A, TDS 744A, & TDS 784A User Manual 3–93
Histogram sets the values statistically. It selects 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, etc.), histogram is the best setting for examining pulses.
Min-max uses the highest and lowest values of the waveform record. This setting is
best for examining waveforms that have no large, flat portions at a common value,
such as sine waves and triangle waves — almost any waveform except for pulses.
Once you define the reference levels, the oscilloscope will use them for all
measurements requiring those levels. To set the reference levels, do the
following steps:
1. Press MEASURE ➞ Reference Levels (main) ➞ Set Levels (side) to
choose whether the References are set in % relative to High (100%) and Low
(0%) or set explicitly in the units of the selected waveform (typically volts). See
Figure 3–55. Use the general purpose knob or keypad to enter the values.
% is the default selection. It is useful for general purpose applications.
Units helps you set precise values. For example, if your are measuring
specifications on an RS-232-C circuit, set the levels precisely to RS-232-C
specification voltage values by defining the high and low references in units.
Figure 3–55: Measure Menu — Reference Levels
Define Reference Levels