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Markers
The
marker_)
key displays a movable active marker on the screen and provides access to a
series of menus to control up to five display markers for each channel. Markers are used to
obtain numerical readings of measured values. They also provide capabilities for reducing
measurement time by changing stimulus parameters, searching the trace for specific values, or
statistically analyzing part or all of the trace. Figure 6-28 illustrates the displayed trace with all
markers on and marker 2 the active marker.
CHl
S21
log MAG
10
dB/
REF -50
de
21
-23.689
dB
PRm
CENTER
134.000 000
MHz
SPAN
50.000 000
MHz
Figure
6-28.
Bbkers
on Trace
Markers have a stimulus value (the x-axis value in a Cartesian format) and a response value
(the y-axis value in a Cartesian format). In a polar or Smith chart format, the second part of a
complex data pair is also provided as an auxiliary response value. When a marker is activated
and no other function is active, its stimulus value is displayed in the active entry area and can
be controlled with the knob, the step keys, or the numeric keypad. The active marker can be
moved to any point on the trace, and its response and stimulus values are displayed at the top
right comer of the graticule for each displayed channel, in units appropriate to the display
format. The displayed marker response values are valid even when the measured data is above
or below the range displayed on the graticule.
Marker values are normally continuous: that is, they are interpolated between measured
points.
Or,
they can be set to read only discrete measured points. The markers for the four
channels normally have the same stimulus values, or they can be uncoupled so that each
channel has independent markers, regardless of whether stimulus values are coupled or dual
channel display is on.
If both data and memory are displayed, the marker values apply to the data trace. If only
memory is displayed, the marker values apply to the memory trace. In a memory math display
(data/memory or data-memory), the marker values apply to the trace resulting from the
memory math function.
6-64
Application and Operation Concepts