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Chapter 3 177
Instrument Functions: M - O
Marker
Instrument Functions: M - O
3.1 Marker
Accesses the marker control menu. If no markers are active, pressing Marker activates the
currently selected marker as a normal type marker and places it at the center of the
display. (This will be marker 1 if you have not previously selected a different marker.)
There are five control modes for the markers:
Normal (POSition)-A single marker that can be moved to any point on the trace.
Delta (DELTa)-A fixed reference marker and a moveable marker that you can place at any
point on the trace
Delta Pair (BAND)-Bothamovabledeltaandamovablereferencemarker.Youcan
independently adjust the position of each marker.
Span Pair (SPAN)-A moveable reference and a movable delta marker. You can adjust the
center point of the markers and the frequency span between the markers.
Off (Off)-Turnsofftheactivemarkerormarkerpair.
Your instrument stores data to a high degree of resolution and accuracy. It is often difficult
to read the trace data directly from the screen to the desired accuracy. Markers are
diamond-shaped pointers that can be placed at any point on a trace to accurately read the
data at that point. Markers may also be use in pairs to read the difference (or delta)
between two data points. The marker number is indicated above the marker. Use the data
controls to position the marker. The knob and/or Up/Down keys move the marker left or
right. If a value is entered from the numeric keypad, the marker is moved to the trace
point nearest to that value.
The data for the active marker (the one currently be controlled) appears in the upper-right
corner of the display. In addition, when a marker is being actively controlled, the marker
data appears in the active function area of the display. There are four markers in your
instrument; each can be controlled as a single marker or as a reference/delta pair.
A trace is a connected series of points displayed on the instrument screen. The left-most
point is point 0 and the right-most point (default) is 600. You control markers by moving
them from trace point to trace point. Markers areshapedlikediamonds.Thelowestpoint
of the diamond shape represents the trace point that is being read. The marker number is
indicated above the active marker. The same marker number is indicated with an R (for
example, 1R) above the reference marker when in a delta mode (delta, delta pair, and span
pair).
Marker Units
• Normal markers - the display shows the value of the Y-axis position of the marker in the
current Y-axis units. (See
Amplitude, YAxisUnits.)
• Delta, Delta Pair,orSpan Pair markers - the display shows the ratio (difference when
expressed in dB) between two markers. If the Y-axis units are logarithmic (dBm, dBmV,
dBuV) the ratio is express in dB. If the Y-axis units are linear (volts, watts) the ratio is
expressed in percent (where 100% is the same as 0 dB difference). Note that the value
when the Y-axis units are watts is the square of the value when the Y-axis units are