Giga-tronics 8650A Series, Operation Manual

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Front Panel Operation
Manual 31470, Rev. E, April 2001 2-33
2.3.13 Crest Factor
The Crest Factor feature is very similar to the peak hold feature, in that it holds on to the maximum
level until a reset occurs, but in this case the displayed value is expressed (in dB) as a ratio of the held
maximum power to the
average power.
The Crest Factor feature is available in the CW, MAP, PAP, or BAP modes only. It can be enabled
from the front panel under the Display Data Line Configuration setup menu, or over the GPIB. The
Crest Factor feature is reset by pressing [
Reset Line n ] of the appropriate line or, in remote control, by
sending the GPIB command which activates the Crest Factor feature (see Section 3.8).
In Figure 2-19, the same power input trace is used in two graphs to illustrate the effect of a drop in
average power, with and without a reset. In the top graph, the power drop is followed by a reset. The
held value drops to the current measured value, and the crest factor represents the ratio between the
new maximum level and the new average level. In the bottom graph, there is no reset after the power
drop, and the crest factor represents the ratio between the old maximum level and the new average
level. For this reason, the crest factor feature should be reset after an input power level change.
Figure 2-19: Crest Factor
Crest Factor With a Power Drop Followed by a Reset
Crest Factor With a Power Drop But No Reset
Hold
Hold
Hold
Hold
Hold
Hold
Crest
Factor (dB)
Crest
Factor (dB)
(Reset)
Time
P
ower
Avg.
Avg.
Hold
Hold
Hold
Hold
Crest
Factor (dB)
Crest
Factor (dB)
Time
P
ower
Avg.
Avg.