Tektronix TDS 500C User Manual
TDS 500C, TDS 600B, & TDS 700C User Manual
B–1
Appendix B: Algorithms
The TDS Oscilloscope can take 25 automatic measurements. By knowing how it
makes these calculations, you may better understand how to use your oscillo-
scope and how to interpret your results.
makes these calculations, you may better understand how to use your oscillo-
scope and how to interpret your results.
Measurement Variables
The oscilloscope uses a variety of variables in its calculations. These include:
is the value used as the 100% level in measurements such as fall time and
rise time. For example, if you request the 10% to 90% rise time, then the
oscilloscope will calculate 10% and 90% as percentages with
rise time. For example, if you request the 10% to 90% rise time, then the
oscilloscope will calculate 10% and 90% as percentages with
representing
100%.
is the value used as the 0% level in measurements such as fall time and rise
time.
time.
The exact meaning of
and
depends on which of two calculation
methods you choose from the High-Low Setup item of the Measure menu.
These are Min-max and Histogram.
These are Min-max and Histogram.
Min-Max Method — defines the 0% and the 100% waveform levels as the lowest
amplitude (most negative) and the highest amplitude (most positive) samples.
The min-max method is useful for measuring frequency, width, and period for
many types of signals. Min-max is sensitive to waveform ringing and spikes,
however, and does not always measure accurately rise time, fall time, overshoot,
and undershoot.
amplitude (most negative) and the highest amplitude (most positive) samples.
The min-max method is useful for measuring frequency, width, and period for
many types of signals. Min-max is sensitive to waveform ringing and spikes,
however, and does not always measure accurately rise time, fall time, overshoot,
and undershoot.
The min-max method calculates the High and Low values as follows:
=
and
=
High, Low