7-82
Operating Concepts
Limit Line Operation
Limit Line Operation
This menu can be accessed by pressing within the system
menu.
You can have limit lines drawn on the display to represent upper and lower limi ts or device
specifications with which to compare the test device. Limits are defined in segments,
where each segment is a portion of the stimulus span. Each limit segment has an upper
and a lower starting limit value. Three types of segments are available: flat line, sloping
line, and single point.
Limits can be defined independently for the four channels, up to 22 segments for each
channel. These can be in any combination of the three limit types.
Limit testing compares the measured data with the defined limits, and provides pass or
fail information for each measured data point. An out-of-limit test condi tio n is i nd ica ted in
five ways: with a FAIL message on the screen, with a beep, by changing the color of the
failing portions of a trace, with an asterisk in tabular listings of data, and with a bit in the
GPIB event status register B. (The analyzer also has a BNC rear panel output that
includes this status, but is only valid for a single channel measurement.)
NOTE The limit test output has three selectable modes. For more information, refer
to “Using Limit Lines to Test a Device” on page1-72.
Limit lines and limit testing can be used simultaneously or independently. If limit lines are
on and limit testing is off, the limit lines are shown on the display for visual comparison
and adjustment of the measurement trace. However, no pass/fail information is provided.
If limit testing is on and limit lines are off, the specified limits are still valid and the
pass/fail status is indicated even though the limit lines are not shown on the display.
Limits are entered in tabular form. Limit lines and limit testing can be either on or off
while limits are defined. As new limits are entered, the tabular columns on the displ a y a re
updated, and the limit lines (if on) are modified to the new definitions. The complete limit
set can be offset in either stimulus or amplitude value.
Limits are checked only at the actual measured data points. It is possible for a devi ce to be
out of specification without a limit test failure indication if the point density is insufficient .
Be sure to specify a high enough number of measurement points in the stimulus menu.
Limit lines are displayed only on Cartesian formats. In polar and Smith chart formats,
limit testing of one value is available: the value tested depends on the marker mode and is
the magnitude or the first value in a complex pair. The message NO LIMIT LINES
DISPLAYED is shown on the display in polar and Smith chart formats.
The list values feature in the copy menu provides tabular listings to the display or a
printer for every measured stimulus value. These include limit line or limit test
information if these functions are activated. If limit testing is on, an asterisk is listed next
to any measured value that is out of limits. If limit lines are on, and other listed data
allows sufficient space, the upper limit and lower limit are listed, together with the margin
by which the device data passes or fails the nearest limit.
LIMIT MENU
LIMIT LINE