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

Operation
2.6 Mode Selection
Follow these procedures to select the desired operating mode. The modes are CW, PEAK and GRAPH.
Throughout this chapter, you will be instructed to press the MENU and MEM keys. The instruction may
be followed by a number in parenthesis. This number corresponds to the menu number and indicates the
number of times you need to press the key to reach the necessary menu.
2.6.1 CW Mode
If in the Peak or Graph mode, press [CW] to access the CW Mode.
If a menu is being displayed and you want to exit it and go to the CW Mode press [CLEAR] [CW].
If the 8502A is in the Ratio mode, selecting CW will cancel RATIO and the 8502A will display the CW
power of channel A.
In certain instances the option will be given to select the CW Mode if there is some reason that another
mode is not operating properly. For example, if a trigger had not been provided as required in the Peak
Mode. The purpose is to allow an escape from erroneous modes of operation.
Very few adjustments or menu selections are required to set up the unit for CW measurements. The two
major settings that must be specified are defined as follows:
Frequency
Press [FREQ] to select the operating frequency at which the power will be measured. Normally, the PPM
automatically adjusts for detector frequency response variations by using the factory measured frequency
response data stored in the PROM in the detector housing. Other options are available as detailed in
PROM Frequency Correction Section 2.8.2. Not compensating for the frequency response of the detector
could result in an error in the power measurement reading.
CW Averaging
This setting selects how many samples of the signal being measured will be taken and averaged to reduce
noise effects at low power levels. To adjust the averaging number, press [Menu] (2) [F1]. A number
between 1 and 999 averages must then be entered. The number of averages presently in effect is not
indicated until the averaging menu has been entered.
Low Power Level Measurements
When the PPM is used in the CW mode for power levels below -30 dBm, its dynamic range is extended
to below -40 dBm. Under low power testing conditions it is necessary to observe the correct auto-zeroing
procedures to obtain the highest measurement accuracy. Zeroing should be done more often in
environments where temperature changes are more drastic. See the Auto-Zero procedures in Section 2.7.3.
2.6.2 Peak Mode
While you are in the CW or Graph Mode, press [PEAK] to access the Peak mode.
If a menu is displayed and you want to exit and go to the Peak mode, press [CLEAR] [PEAK].
After this, follow the trigger setting guidelines given below. Lack of a trigger can freeze the display. To
exit either of these situations either the trigger can be set, or the CW Mode can again be accessed by
pressing [CW].
To make measurements in the Peak or Graph Mode, first ensure that the system is receiving a trigger
signal that will drive its timebase and crystal-based delay generator. The delay generator accurately
places a sampling window at the desired time on the pulse to be measured. The different triggering
methods are detailed below.
Manual No. 20790, Rev C, November 1998 2-11
Superceded by Revision D, March 2009