Manual - 8500A Series Peak Power Meter - Giga-tronics

Operation
decrease the Delay Window in a 1, 2, 5 sequence as required until the trailing edge no longer disappears
from view off of the right side of the graphics area. The cursor next to DLY WIND means that the spin
knob or keypad can be used to adjust the Delay Window value.
REF PWR
The PPM’s Reference Power nomenclature refers to the manner in which the pulse profile is displayed.
Referring to the graphics area of Figure 2-7, there are four horizontal tic (division) marks on the left
vertical axis of the display. These tic marks correspond from top to bottom to the 100%, 90%, 50%, and
10% power points on the pulse profile with respect to the Reference Power. The pulse profile is always
displayed in linear units. The default Reference Power is 1 mW. However, once the Autoscale function
has been used, the Reference Power is automatically adjusted to whatever the power level is at the middle
of the pulse. Therefore, the Autoscale feature not only serves to center the pulse on the time (or
horizontal) axis, it also optimizes the display positioning on the power (or vertical) axis by setting the
highest power level as the 100% Reference point.
The adjustable Reference Power level is provided to give the user flexibility in displaying the pulse, and
measuring pulse timing parameters using the markers. This is important because it means that the PPM
can be set up to accommodate the various types of test parameters that different users might need for
their specific measurement requirements.
NOTE: The reference power level is used as the 100% power level in the marker sub-mode, but is not
used in the cursor or pulse parameter sub-modes. See the descriptions of marker sub-mode in
Section 2.8.10 and cursor sub-mode in Section 2.8.8 for a more detailed explanation.
There are two ways to set the Reference Power Level on the PPM.
The first way is to move the cursor to the REF PWR (next to last) line of the displayed parameters (use
either the up or down arrow key). Then, enter the desired Reference Power level and press the appropriate
Units key (dBm for logarithmic units; mW, W, or kW for linear units).
The second way is to move the cursor to the CSR DLY line and move the cursor to the point on the
displayed pulse profile that is desired to be 100% reference. Next, move the cursor to the REF PWR line
of the display. Then pressing any Units key will shift the pulse vertically on the screen, resulting in the
selected point lining up with the 100% tic mark on the display.
Reference Power cannot be changed with the spin knob.
TRIGGER
This display indicates the present triggering mode of the PPM. TRIG LEV = -10 dBm (A TRIG =
-10 dBm in the 8502A) is the default setting. It means that the PPM will trigger when the leading edge of
the RF pulse rises above -10 dBm at the (channel A) detector input. B TRIG = (8502A only) indicates
that the PPM is triggering off the channel B detector.
To change the Trigger Level, use either the up or down arrow key to move the cursor beside the TRIG
LEV indication. The spin knob can then be used to alter the Trigger Level, or a desired number can be
entered through the keypad and terminated with the dBm or mW key.
EXTERNAL means that the PPM is triggering off the TTL trigger input on the back panel regardless of
which channel is being displayed.
Selecting External Trigger or changing the internal trigger channel is accessed through Menu-1. See
Triggering in Section 2.6.2.
Manual No. 20790, Rev C, November 1998 2-25
Superceded by Revision D, March 2009