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

Series 8500A Peak Power Meters
2.13 Special Capabilities of the PPM
2.13.1 Reference Delay
To facilitate making timing measurements relative to some event other than the trigger (such as the
falling edge of a pulse), it is possible to shift the PPM time coordinates by using Reference Delay. The
PPM subtracts the Reference Delay from the Cursor Delay and Start Delay, in effect shifting the zero
time reference from the trigger time to a time after the trigger by the amount of the Reference Delay. To
set the Reference Delay press [MENU] (4) [F1] (for Ch A or [F2] for Ch B) [nn.nn] [UNITS].
2.13.2 Single Pulse Measurements
Measurement of a single pulse can be done with the PPM by operating in the Peak Mode. (The Graph
Mode cannot be used for single pulse measuring.)
Two methods are available for making single pulse power measurements. These are discussed in the next
two sub-sections.
2.13.3 Single Pulse Measurement Using Internal Trigger
To make a single pulse measurement using the Internal Trigger, it must first be decided how long after
the trigger has occurred that the measurement should be taken. For example, in the single pulse shown in
Figure 2-16, the PPM trigger level is set to -10 dBm. If the Cursor Delay were set to 0.0000 ns, then the
power measurement would be taken at the trigger point. In this case, this is not on the top of the pulse
being measured.
To measure power at the top of the pulse as required in most applications, the Cursor Delay needs to be
set at around 5 µs. Therefore, to accurately make Peak power measurements using the Internal Trigger
mode of operation, you must have some idea of the pulse width boundaries to be tested.
In cases where the rise time of the pulse is known to be repeatable and the pulse width is known never to
be below, say, 8 µs, you could set the Cursor Delay to 5 µs. This decision would allow measurement of
all pulse widths greater than 5 µs without the necessity of altering the Cursor Delay.
Figure 2-16. Typical Pulse with -10 dBm Trigger Level
2-40 Manual No. 20790, Rev C, November 1998
Superceded by Revision D, March 2009