2.6.3
Graph Mode
The Graph Mode of the PPM provides graphic capabilities for the display, plotting, and analyses of RF
pulse profiles. Most instrument pulse parameters can be set and changed directly from information
presented in menus. Features are available which allow measurement of commonly required pulse
parameters such as rise time, pulse width, and so forth.
When the system is operating satisfactorily in the Peak or Graph Mode, it is possible to toggle back and
forth between the two modes by pressing [PEAK] or [GRAPH] whenever desired. The only exception to
this is when an 8502A is being used in the dual channel mode of operation since the Graph Mode does
not allow dual channel operation. If a dual channel function is being used and it is desired to switch to
the Graph Mode, single channel operation must first be selected. See Dual Channel Operation in
Section 2.10.
The ability to toggle back and forth between Peak and Graph Modes is useful for a number of reasons.
For example, in the single channel Peak Mode, the display produces large distinct power read-out
characters that can be read from a distance (see Figure 2-6). In addition, while in the Peak Mode, the
current frequency being used for the test is directly visible on the display. In the Graph Mode, the display
is primarily for inspection of the pulse profile and the frequency is not displayed to allow room on the
display for other important pulse profile parameters (see Figure 2-7 for a typical Graph Mode display).
All operating parameters such as trigger mode, frequency, and cursor delay are maintained in both the
Peak and Graph Modes. The Graph Mode can place the cursor at a specific point on the pulse, and then
the PEAK key can be pressed to see the power reading using the large readout characters.
Selecting the Graph Mode:
If in the Peak, CW Mode, or Ratio Modes (previous Graph or Peak Mode settings will apply), press
[GRAPH]. If a menu is being displayed and you want to exit to the Graph Mode, press [CLEAR]
[GRAPH]. Then, to Autoscale the pulse, press [AUTOSCALE]
☛
NOTE: While in the Graph Mode, the Autoscale function of the GRAPH key will be active.
Under some conditions, autoscaling cannot take place due to the complex shape of the pulse or other
timing factors. The PPM will then display only a part of the pulse. The reference level will be correct for
rectangular pulses. The PPM will not have been able to set an appropriate Delay Window for the pulse. It
may be possible to subsequently autoscale by changing the initial delay value for autoscaling to be closer
to twice the actual pulse width for the pulse in question. This is done by pressing [MENU] (9) [F2]
[n.nnnn] [UNITS].
To use the Graph Mode, the triggering selection guidelines discussed Section 2.6.2 must be followed.
Operation
Manual No. 20790, Rev C, November 1998
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Summary of Contents for 8501A
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