Chapter 4 4-9
Reading Analyzer Data
Stimulus-Related Values
Stimulus-Related Values
Frequency-related values are calculated for the analyzer display. The start and stop
frequencies or center and span frequencies of the selected frequency range are available to
the programmer.
In a linear frequency range, the frequency values can be easily calculated because the
trace data points are equally spaced across the trace. Relating the data from a linear
frequency sweep to frequency can be done by querying the start frequency, the frequency
span, and the number of points in the trace.
Given that information, the frequency of point n in a linear-frequency sweep is represented
by the equation:
In most cases, this is an easy solution for determining the related frequency value that
corresponds with a data point. This technique is illustrated in “Example 3B: Data Transfer
Using FORM 4 (ASCII Transfer)” on page 7-59.
When using log sweep or a list-frequency sweep, the points are not evenly spaced over the
frequency range of the sweep. In these cases, an effective way of determining the
frequencies of the current sweep is to use the OUTPLIML command. Although this command
is normally used for limit lines, it can also be used to identify all of the frequency points in
a sweep. Limit lines do not need to be on in order to read the frequencies directly out of the
instrument with the OUTPLIML command. Refer to “Example 3D: Data Transfer Using
Frequency-Array Information” on page 7-64.
NOTE Another method of identifying all of the frequency points in a sweep is to use
the marker commands MARKBUCK<num> and OUTPMARK in a “FOR NEXT”
programming loop that corresponds to the number of points in the sweep.
MARKBUCK<num> places a marker at a point in the sweep, where <num> is the
number of the point in a sweep, and OUTPMARK outputs the stimulus value as
part of the marker data.
F StartFrequency n 1–()
Span
Points 1–()
------------------------------
×+=
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