Tektronix 6 series, Printable Help

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Reference Levels panel- fields and controls.
Field or control Description
Reference Levels Global sets whether the reference levels defined in this measurement apply to all
measurements that are set to global (the default setting).
Local sets the Reference Level parameters to apply to just this measurement.
Source Lists the source signals used for each edge of the measurement.
Set Levels In
Sets the method used to set or calculate the High, Mid, and Low reference levels. Select % or
Units and use the Multipurpose Knob to set custom reference values.
Levels Sets the reference levels as specified percentages of the Top and Base waveform
measurement.
To set custom reference values, tap Custom, tap a setting field, and use the Multipurpose Knob
to set the different % (relative) or absolute values.
High and Low references are used to calculate rise and fall times. The default High reference is
90% and Low reference is 10%.
Mid reference is primarily used for measurements between edges such as pulse widths. The
default level is 50%.
Base Top Method Sets the method to calculate the waveform Base and Top values, which is then used to
calculate the High, Mid, and Low reference levels.
Auto is the default method, and automatically determines the best Base Top method to use.
Most commonly sets the Top Base method to Histogram Mode.
MinMax Uses the minimum and maximum values in the waveform record to determine the base
and top amplitude. Useful on a waveform with low noise and free from excessive overshoot.
Histogram Mean uses histogram analysis to calculate the mean or average value using all
values above and below the waveform midpoint. Top is set to the mean high value, and Base is
set to the mean low value.
Histogram Mode uses histogram analysis to calculate the most common values above and
below the waveform midpoint. Top is set to the common high value, and Base is set to the
common low value.
Histogram Eye Center uses histogram analysis to determine the base top amplitude. Creates
a histogram of the amplitudes in the center of each bit (unit interval) while ignoring the
waveform during bit transitions. The histogram should have a peak at the nominal high level
and another peak at the nominal low level.
NOTE. If you set the Base Top Method to other than Auto, and do not change the Reference
Levels mode to Local, many existing measurements, as well as measurements that you add to
the Results bar, will use the new Base Top Method values for taking measurements. This may
result in measurement values that you are not expecting.
Menus and dialog boxes
MSO54, MSO56, MSO58, MSO58LP, MSO64 Help 167