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

Operation
4. To change the Cursor Delay for channel B, press the up or down arrow key. The spin knob can
then be used to alter the channel B Cursor Delay. To lock out the spin knob and keyboard, press
any UNITS key. To reactivate the spin knob and keyboard, press the up or down arrow key.
5. If there are any difficulties due to timing factors, it is recommended that External Triggering be
used. The trigger signal should occur slightly before the RF pulses to be measured. The Cursor
Delays can then be used to place the Cursors on the pulses to allow readings to be taken.
2.10.3 Peak, Peak Measurements: Method 2
This method utilizes the Graph Mode to facilitate placing Cursors on the pulses of interest. Signal timing
should be considered first of all. For purposes of discussion, assume the timing of the signals to be
measured are similar to those shown in Figure 2-11.
As can be seen in Figure 2-11, the Measurement Port 1 pulse occurs before the Measurement Port 2
pulse. If Measurement Port 2 were used to generate an Internal Trigger, it would be impossible to set the
Cursor on the leading edge of the displayed Measurement Port 1 pulse because the minimum Cursor
Delay of 0 ns would be the trigger point (leading edge of the Measurement Port 2 pulse).
Figure 2-11. Typical Signal Timing
Therefore, this situation would require that either Measurement Port 1 be used to generate an Internal
Trigger, or that an External Trigger be used. Doing this would ensure that readings could be taken at any
desired points on the pulses being measured.
In cases where the pulses at each detector input are essentially occurring at the same time, this problem
could be ignored. However, it is generally the case that using the External Trigger results in more
satisfactory performance.
The preceding information is provided mainly to emphasize the importance of knowing the timing
relationships of the signals to be measured. If there is any doubt or confusion, the rear panel Monitor
Output of the PPM can be connected to an oscilloscope to quickly ascertain the timing relationships.
Assuming an autoscalable pulse greater than the current trigger level is to be measured by channel A for
this example, the procedure for Dual Channel operation in the Peak Mode via the Graph Mode would be:
Manual No. 20790, Rev C, November 1998 2-33
Superceded by Revision D, March 2009