Reference Level (Y Scale)

Reference Level sets the Y-axis value of the Reference Line for the active trace.

The Reference Line provides an easy point of reference on the trace. Use this feature to, among other things, quickly compare multiple traces.

Overview

The data shown in a trace can be moved up or down by changing the Reference Level or by changing the position of the Reference Line.

To change the Y-axis size of the trace use Y Per Division.

Using Reference Position to Move a Trace

The Reference Line is a horizontal line that is located in a fixed position on the display. The trace Y-axis scale is referenced to this line. Moving the Y-axis Reference Line up or down moves the trace up or down.

To move the reference line, change the Reference Position. Enter the Reference Position as a percentage of the height of the trace display. A value of 0% places the reference line at the bottom of the trace box; 50% places it in the center; 100% places it at the top.

Because the trace is referenced to the reference line, moving the reference line down moves the trace down by the same amount.

The reference line is shown only if the Reference Line check box is selected.

Using Reference Level to Move a Trace

The trace can also be moved by changing the Reference Level.

Because the trace is referenced to the Reference Line, increasing Reference Level pushes the trace down. Likewise, decreasing Reference Level pulls the trace up.

Auto Scale works by changing the value of Reference Level.

Examples

The following illustrations show how the VSA uses Reference Level and Reference Position to position a trace.

Turn on Reference Line and vary Reference Level and Reference Position to better understand how these parameters work.

Interaction With Other Parameters

The value of Reference Level can be forced to track input range changes if the data format is linear magnitude or log magnitude and the units are compatible. To do this, select the Range Tracking check box.

The unit specifing the Reference Level is also used as the display unit for marker values.

Reference Level and Polar/x-y Trace Formats

Reference Level can be used with polar (IQ and Const) and the Real vs. Imag trace formats. For these trace formats, Reference Level, Reference Position, and Reference Line work as described above--they all help position the trace along the y-axis.

For polar trace formats, the center value can be specified for the X axis. See Vector X Center.