Data Analysis Features
All about Markers
Keysight N9927-90001 User’s Guide                                                            599
Figure 28-1  Marker 2 is Active, marker 1 is NOT active.
About Delta Markers
A Delta marker provides X-and Y-axis readout information that is relative to a ‘reference’ marker. 
A Delta marker is created with a Δ (delta symbol) to distinguish it from the reference marker.
All six markers can be a Delta marker pair. 
Peak search functions can be performed using delta markers. 
Figure 28-2  A Delta marker and its associated reference marker. 
In the graphic above, the marker readout shows the difference between the two markers in 
frequency and amplitude.