The commands in the Lines define limits for the measurement results, visualize them in the diagrams and activate/deactivate the limit check. Besides the menu provides a horizontal line for each trace.
A limit line is a set of data to specify the allowed range for some or all points of a trace. Typically, limit lines are used to check whether a DUT conforms to the rated specifications (conformance testing).
The upper limit line defines the maximum value for the trace points.
The lower limit line defines the minimum value for the trace points.
A limit check consists of comparing the measurement results to the limit lines and display a pass/fail indication. An acoustic warning and a TTL signal at the USER CONTROL port can be generated in addition if a limit is exceeded.
Upper and lower limit lines are both defined as a combination of segments with a linear dependence between the measured quantity and the sweep variable (stimulus variable). The limit lines can be stored to a file and recalled. Data or memory traces can be used to define the segments of a limit line. Moreover it is possible to modify the limit lines globally by adding an offset to the stimulus or response values.
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Show Limit Line displays or hides the limit line associated to the active trace.
Limit Check On activates or deactivates the limit check.
Fail Beep On activates or deactivates the acoustic signal indicating a limit excess.
Define Limit Line opens a dialog to define, save or recall limit lines.
TTL Out Pass 1/2 activates or deactivates a TTL output signal at the USER CONTROL connector indicating whether the trace was passed or failed.
Horizontal Line displays or hides the horizontal line of the active trace and changes its position.
Global Limit Check activates a global (composite) limit check on all traces in the active setup.
Limit lines are available for all Cartesian diagram types (Trace – Format). For polar diagrams, the functions of the Lines submenu are grayed. The limit lines are hidden and the limit check is disabled when a Cartesian trace format is replaced by a polar diagram.
Shows or hides the limit line associated to the active trace in a Cartesian diagram area. A checkmark appears next to the menu item when the limit line is shown.
In the diagram, upper and lower limit lines can be displayed with different colors. Limit line segments with disabled limit check (see Define Limit Line) can also be colored differently. The limit line colors are defined in the Define User Color Scheme dialog (Display – Display Config. – Color Scheme...).
Display of the limit line and limit check are independent
of each other: Hiding the limit line does not switch off the limit check.
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Switches the limit check of the active trace on or off. A checkmark appears next to the menu item when the limit check is enabled.
When the limit check is switched on, a PASS or FAIL message is displayed in the center of the diagram. If the limit check fails at a measurement point, the two trace segments to the left and right of the point can change their color. The Limit Fail Trace color is defined in the Define User Color Scheme dialog (Display – Display Config. – Color Scheme...). An acoustic signal (Fail Beep) and a TTL signal indicating pass or fail can be generated in addition.
Limit check and display of the limit lines
are independent of each other: With disabled limit check, the limit line
can still be displayed, however, no display elements indicating a limit
excess will appear.
Limits are checked at the actual measurement
points, whereas a limit failure is indicated for the trace segments on
both sides of a failed point. A small number of points causes wide trace
segments so that the out-of tolerance regions can appear wider as they
are.
If no limit lines are defined for the active
trace, the limit check can be switched on but will always PASS
the trace.
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CALCulate<Chn>:LIMit:STATe
ON | OFF |
Activates or deactivates the fail beep. The fail beep is a low-tone acoustic signal that is generated each time the analyzer detects an exceeded limit. No fail beep can be generated if the limit check is switched off. A checkmark appears next to the menu item when the fail beep is enabled.
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Opens a dialog to define the limit line for the active trace on a segment-by-segment basis. In each segment the limit line is defined as a straight line connecting two points.
Creating
limit lines with minimum effort
Choose one of the following methods to efficiently create and handle limit lines:
To define a limit line with only a few segments, use Add Segment and edit each segment in the segment table individually.
Use the multiselection feature to edit several limit line segments at the same time.
Select a data or memory trace as a limit line (Import Trace) or import a trace stored in a file (Import File).
Save your limit lines to a file so you can re-use or modify them later sessions (Save Limit Line, Recall Limit Line).
The Define Limit Line dialog contains a table to edit the individual segments of the limit line; see below. The active trace is indicated in the title bar of the dialog. The three buttons below the table extend or shorten the segment list.
The buttons to the right of the table are used to import and export limit line data.
opens a box to select a trace that can be used to define a limit line.
The box contains all data or memory traces of the active channel. As soon as a trace is selected, the Properties of Imported Segmentsdialogwith further global import options is opened.
Calls up a standard Import File dialog to load a limit line from a trace file. The limit line import is analogous to the import of traces. Trace files are ASCII files with selectable file format. After the trace file is selected, the Properties of Imported Segmentsdialogwith further global import options is opened.
Imported traces are polygonal curves with n points and n – 1 segments. The number of points n is set via Channel – Sweep – Number of Points. The n – 1 segments are appended to the current segment table for further editing. Existing limit line segments are not overwritten.
To import a limit line file (*.limit) you can also use
the Windows Explorer and simply double-click the file or drag and drop
the file into the NWA application. You have to switch on the limit check
separately. Use the paste
marker list
for convenient entry of Start
and Stop
values.
Columns
in the segment table
The table contains an automatically assigned current number for each segment plus the following editable columns:
Type indicates whether the segment belongs to an Upper or a Lower limit line, or if the limit check at the segment is switched Off. Switching off the limit check does not delete the segment but changes its screen color.
Start Stimulus is the stimulus (x-axis) value of the first point of the segment (not necessarily smaller than Stop Stimulus).
Stop Stimulus is the stimulus (x-axis) value of the last point of the segment (not necessarily larger than Start Stimulus).
Start Response is the response (y-axis) value of the first point of the segment.
Stop Response is the response (y-axis) value of the last point of the segment.
The limit line segment is calculated as a straight line connecting the two points (<Start Stimulus>, <Start Response>) and (<Stop Stimulus>, <Stop Response>); see Rules for Limit Line Definition.
In the Define Limit Line dialog it is possible to edit several limit line segments at the same time. Selection of two or more segments (use the left mouse key and the Shift key of an external keyboard) and a right-click on the dark grey Seg. area opens a context menu:
The context menu provides the following functions:
Modification of all entries in the segment table: Type, start and stop values for the stimulus and response variable.
Definition of an offset for response and stimulus values in analogy to the Properties of Imported Segments dialog.
Delete the selected segments.
Merge the selected segments to a single new segment.
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The analyzer places very few restrictions on the definition of limit line segments. The following rules ensure a maximum of flexibility:
Segments don't have to be sorted in ascending or descending order (e.g. the Start Stimulus value of segment no. n doesn't have to be smaller than the Start Stimulus value of segment no. n+1).
Overlapping segments are allowed. The limit check in the overlapping area refers to the tighter limit (the pass test involves a logical AND operation).
Gaps between segments are allowed and equivalent to switching off an intermediate limit line segment.
Limit lines can be partially or entirely outside the sweep range, however, the limits are only checked at the measurement points.
The following figure shows a limit line consisting of 3 upper and 2 lower limit line segments. To pass the limit check, the trace must be confined to the shaded area.
As a consequence of the limit line rules, the limit check will always pass a DUT if no limit lines are defined.
The Properties of Imported Segments dialog appears before a trace is imported into the Define Limit Line dialog.
The dialog assigns common properties to all limit line segments generated by the imported trace.
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CALCulate<Chn>:LIMit:LOWer:FEED
<stimulus_offset>,<response_offset>[,<trace_name>] |
The analyzer uses a simple ASCII format to export limit line data. By default, the limit line file has the extension *.limit and is stored in the directory shown in the Export Limit Line and Import Limit Line dialogs. The file starts with a preamble containing the channel and trace name and the header of the segment list. The following lines contain the entries of all editable columns of the list.
The limit line:
is described by the limit line file:
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MMEMory:LOAD:LIMit
"Trc_name","file_name"
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Assigns the active trace to the low-voltage (3.3 V) TTL output signals at the USER CONTROL connector. To select TTL Out Pass 1 / 2, the limit check of the active trace must be switched on.
If TTL Out Pass 1 is selected and the active trace is within limits, then the TTL signal is applied to pin 13 of the USER CONTROL connector.
If TTL Out Pass 2 is selected and the active trace is within limits, then the TTL signal is applied to pin 14 of the USER CONTROL connector.
If the active trace exceeds the limits, then no TTL signal is generated. It is possible to activate both pass/fail signals for the same trace or assign several traces to a signal.
Extension:
Monitoring several traces
If a channel contains several traces, is possible to assign them one after another to each pass/fail signal. The procedure divides the traces of the channel into four groups that are either assigned to signal A, to signal B, to both signals, or to none of them.
If several traces with independent limit check are assigned to a pass/fail signal, then the TTL signal is generated only if all traces are within limits. It is switched off as soon as one trace exceeds the limits.
Application:
Graduated limit check
The two pass/fail signals can be used to distinguish three quality levels of a DUT. The test is performed with a looser and a tighter set of limit lines that are assigned to two traces with identical channel and trace settings. The limit check for the two traces is monitored by means of the signals TTL Out Pass 1 /TTL Out Pass 2, respectively.
If the DUT is passed in both limit checks, the quality is good.
If the DUT is failed in the limit check with tighter limits, the quality is still sufficient.
If the DUT is failed in both limit checks, the quality is poor.
Instead of using two traces, it is possible to consider two groups of traces that are assigned to TTL Out Pass 1 and TTL Out Pass 2.
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Shows or hides the horizontal line associated to the active trace in a Cartesian diagram area. A checkmark appears next to the menu item when the horizontal line is shown.
The horizontal line (or display line) is a red line which can be moved to particular trace points in order to retrieve the response values.
Pressing Horizontal Line for a first time shows the line for the active trace and opens the numeric entry bar to define its position (response value). The (rounded) position is displayed near the left edge of the screen.
Pressing Horizontal Line for a second time hides the horizontal line for the active trace.
Use the analyzer's
drag-and-drop functionality to move the horizontal line symbol to the
desired position.
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Performs a composite limit check on all traces of the current setup. The result of the global check appears in a popup box whenever Global Limit Check is pressed.
or 
PASS represents pass for all traces for which the limit check is enabled. A trace without limit lines or with disabled individual limit check always passes the composite limit check.
FAIL means that the limit checks for one or more traces failed.
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