Spectrum Analyzer Measurement Guide : Spectrum Analyzer : Limit Menu
Limit Menu
Key Sequence: Shift > Limit (6) key
The Limit menu keys are shown in the following figures.
Two types of limit lines can be specified, lower limit lines and upper limit lines. Limit lines can be used for visual reference only, or for pass/fail criteria by using the limit alarm (Figure: SPA Limit Menu). Limit alarm failures are reported whenever a signal is above the upper limit line or below the lower limit line. By using save‑on‑event, a signal that exceeds the limit alarm can be automatically saved. For details, see the User Guide for your instrument.
Each limit line can consist of a single segment, or as many as 40 segments across the entire frequency span of the instrument. These limit segments are retained regardless of the current frequency span of the instrument, which allows the configuring of specific limit envelopes at various frequencies of interest without having to re‑configure them each time the frequency is changed.
SPA Limit Menu
Limit Upper/Lower
This submenu key selects which limit line is active for editing. The limit line that is currently selected for editing is underlined.
This submenu key turns the active limit (upper or lower) on or off.
Limit Edit
This submenu key displays the Edit Menu (Limit) that allows creating or editing of single or multi‑segment limit lines. The currently active limit point is marked by a red circle on the display.
Limit Move
Press this submenu key to display the Limit Move Menu.
Limit Envelope
A limit envelope is very useful when you want to easily detect new signals in the presence of other preexisting signals. Use the limit envelope function to automatically create upper or lower limit lines that are based upon the on‑screen measured spectrum analysis values. Refer to Figure: Square Limit Envelope for an example limit envelope. Press this submenu key to open the Limit Envelope Menu.
Limit Advanced
Press this submenu key to open the Limit Advanced submenu key menu. The advanced limit line section offers several useful functions. In this section, you can create either an absolute limit line (which is one based upon the frequencies that are entered for each inflection point) or a relative limit line (which is based upon the delta frequencies between the center frequency and the inflection points). Both types of limit lines can be saved and recalled. Press this submenu key to open the Limit Advanced Menu.
Limit Alarm On/Off
Pressing this submenu key toggles the alarm function ON and OFF for the currently active limit line. When ON, an alarm beep sounds when a data point exceeds the limit.
Set Default Limit
Pressing this submenu key deletes all limit points for the currently active limit line and sets the default limit line value, which is a single limit whose position is 2.5 grid lines from the top of the screen (for the upper limit line) or 2.5 grid lines from the bottom of the screen (for the lower limit line), depending upon which limit is active. The inactive limit line is not altered.