Chapter 2 91
Front-Panel Key Reference
Display
straight line is used when interpolating 
between points in a limit table. If 
frequency interpolation is logarithmic, 
frequency values between limit points 
are computed by first taking the 
logarithm of both the table values and 
the intermediate value. A linear 
interpolation is then performed in this 
logarithmic frequency space. An exactly 
analogous manipulation is done for 
logarithmic amplitude interpolation. 
Key Access: 
Display, Limits, Limit 1 or 
Limit 2, More
Amptd Interp 
Log Lin
  Allows you to determine how limit 
trace values are computed between 
points in a limit table. The available 
interpolation modes are linear and 
logarithmic. If the linear mode is used 
for both frequency and amplitude, a 
straight line is used when interpolating 
between points in a limit table. 
Key Access: 
Display, Limits, Limit 1 or 
Limit 2, More
NOTE Interpolation modes determine how limit values are computed between 
points in the limit table. The appearance of a limit trace is also affected 
by the amplitude scale, which may be linear or logarithmic.
X Axis Units
Freq Time
Selects whether limit lines will be entered using frequency or sweep 
time to define the segments. They can be specified as a table of limit 
line segments of amplitude versus frequency, or of amplitude versus 
time. Time values are evaluated with respect to the analyzer sweep 
time. A time value of zero corresponds to the start of the sweep, which 
is at the left edge of the graticule. 
Switching the limit line definition between frequency and time will 
erase both of the current limit lines. The message Changing X axis 
units will delete all limits. If you are sure, press key 
again to change units will appear. Press 
X Axis Units Freq Time again 
to purge both limit lines and switch between frequency and time.
Key Access: 
Display, Limits