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Reference Levels Control Window
Access this control window from the Measure menu Reference Levels command.
Overview
Use the Reference Levels control window to define unique reference levels for each measurement.
The default reference levels serve most general-purpose measurements. However, you can
customize all measurements to use different reference levels.
To Use
Click Min-Max to derive the reference levels from the minimum and maximum values of the
waveform record. If you want to derive the reference levels based on statistical data, click the
Histogram or the Histogram mean button.
Refer to the graphic in the center of the control window and determine the reference levels that
you want to define. Click the control with the associated reference level, and use the multipurpose
knobs to adjust the value. If you want the reference levels to be measured by volts, click the
Absolute button under Units. To measure the reference levels as a percentage, click the Percentage
button.
Click either Eye or Pulse to select the signal type.
Behavior
The following reference levels are included: High Reference, Mid Reference, Low Reference, and
Mid2 Reference.
Define the reference levels as percentages of the signal amplitude or as absolute values in vertical
units by clicking the appropriate button to define the Units selection. Use
Percentage to have
reference levels track the signal. Use Absolute to set the reference levels to fixed values.
The top and base levels that the measurement system derives from a waveform influence the
fidelity of measurements. The measurement system can derive the reference levels from either the
minimum and maximum values of the waveform or from statistical data.
The Min-Max selection uses the highest and lowest values of the waveform record. This selection
is best for examining waveforms with no large, flat portions at a common value, such as sine
waves and triangle waves.
The Histogram selection sets the top and base values statistically. The most common values either
above or below the midpoint are used (depending on whether the high reference point or the low
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