Plot Marker Parameters



Plot Markers are used to find and display specific points of interest on lines that are plotted in graphs - like Bode Plots, Input Signals, and Output Signals.

The following Bode Plot contains three Plot Markers attached to the magnitude plot of a Transfer Function of a filter circuit.

The Plot Markers in this graph show one of the uses of Plot Markers - to determine the bandwidth of a filter circuit. The first marker found the peak's maximum of 0 dB, and the other two markers found the points in the graph that pass through -6 dB.

The horizontal scale of Bode Plots is in Log(Freq) so the 'pos' values of the markers are also expressed in Log(Freq). The 'pos' values of Plot Markers will always be in the same units as the horizontal scale of the plot they are attached to.

Parameters Dialog Box

This dialog box is used to edit the behaviour of Plot Markers.



Plot Marker Behaviour

  • The "Position" edit field is used differently depending on which one of the following radio buttons is selected.

  • The "Value at position" radio button causes the Plot Marker to display the value of the plot line at the exact position in the "Position" edit field.

  • The "Slope at position" radio button causes the Plot Marker to display the slope of the plot line at the exact position in the "Position" edit field.

  • The "Find value x near postion" radio button causes the Plot Marker to search for the position on the plot line where it crosses/touches the x value. The marker will begin searching for the x value at the position in the "Position" edit field. If the x value cannot be found, then the marker will not be displayed.

  • The "Minimum near position" radio button causes the Plot Marker to search for the local minimum value of the plot line near the position in the "Position" edit field.

  • The "Maximum near position" radio button causes the Plot Marker to search for the local maximum value of the plot line near the position in the "Position" edit field.

Plot Marker Appearance

  • Select the "Visible" check box to make the marker visible. The marker will only be visible if it points to a position on the plot line that is visible within the currently displayed graph.

  • Select the "Line to horizontal axis" check box to force the display of the marker to include a vertical line from the spot of the marker down to the horizontal axis.

  • Select the "Line to vertical axis" check box to force the display of the marker to include a horizontal line from the spot of the marker over to the vertical axis.

  • Select the "Show value" check box to force the display of the marker to include the numerical vertical-scale value at the spot of the marker.

  • Select the "Show position" check box to force the display of the marker to include the numerical horizontal-scale position value at the spot of the marker.

  • The six radio buttons labeled "upper left", "left", "lower left", "upper right", "right", and "lower right" selects the position of the displayed numerical values relative to the spot of the marker.