Appendix B: Algorithms
Appendices
AĆ10
2. It splits the histogram into two sections at the halfway point between
Min
and
Max
(also called
Mid
).
3. The level with the most points in the upper histogram is the
High
value,
and the level with the most points in the lower histogram is the
Low
value.
(Choose the levels where the histograms peak for
High
and
Low.
)
If
Mid
gives the largest peak value within the upper or lower histogram,
then return the
Mid
value for both
High
and
Low
(this is probably a very
low amplitude waveform).
If more than one histogram level (bin) has the maximum value, choose
the bin farthest from
Mid
.
This algorithm does not work well for two-level waveforms with greater than
about 100% overshoot.
HighRef, MidRef, LowRef, Mid2Ref
The user sets the various reference levels, through the Reference Level
selection of the Measure menu. They include:
HighRef — the waveform high reference level. Used in fall time and rise time
calculations. Typically set to 90%. You can set it from 0% to 100% or to a
voltage level.
MidRef — the waveform middle reference level. Typically set to 50%. You
can set it from 0% to 100% or to a voltage level.
LowRef — the waveform low reference level. Used in fall and rise time
calculations. Typically set to 10%. You can set it from 0% to 100% or to a
voltage level.
Mid2Ref — the middle reference level for a second waveform (or the second
middle reference of the same waveform). Used in delay time calculations.
Typically set to 50%. You can set it from 0% to 100% or to a voltage level.
Other Variables
The oscilloscope also measures several values itself that it uses to help
calculate measurements.
RecordLength — is the number of data points in the time base. You set it
with the Horizontal menu Record Length item.
Start — is the location of the start of the measurement zone (X-value). It is
0.0 samples unless you are making a gated measurement. When you use
gated measurements, it is the location of the left vertical cursor.
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