Thresholds - HP 54710A User's Reference Manual

Define Measure Menu

Thresholds

Thresholds
The Thresholds menu sets the measurement points that the automatic
measurements use for calculating the timing measurement results. The
threshold points are lower, middle, and upper. For example, rise time is
measured from the lower threshold to the upper threshold, while a width
measurement is made between two middle thresholds. The two threshold
choices are the standard IEEE measurement points (10%, 50, and 90%) or
user defined.
The Upper, Middle, and Lower softkeys are displayed when user defined is
selected.
10%, 50%, 90%
These are the standard IEEE pulse measurement thresholds for all
measurements. These standard thresholds are calculated as a percentage of
the top-base values, and the top-base values are calculated from the
waveform that is on the display. Make sure that the waveform is expanded
vertically and horizontally so that the oscilloscope can accurately determine
the top and base values of the waveform. However, if too much of the top
and base of the waveform is on the display, it may reduce the number of
sample points on the edge of interest, which may reduce the repeatability of
your measurements. A good rule of thumb is to have two divisions of top and
two divisions of base.
When the oscilloscope cannot make the requested measurement, a question
mark is displayed instead of a measurement result. Usually, this is because
there are not enough sample points, an edge is not on the display, or the
specified channel is turned off. When the measurement result is followed by
a question mark, this indicates that the waveform is clipped high or low, two
points were not available for linear interpolation, or the amplitude of the
waveform is too small.
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