Giga-tronics 8650A Series, Operation Manual

Page: 149 / 240

Remote Operation
Manual 31470, Rev. E, April 2001 3-75
3.8 Crest Factor
The Crest Factor feature holds on to the highest instantaneous power measured from the time the
feature is enabled until it is reset; it is similar to the Peak Hold feature, except that the measurement is
expressed as a ratio in relation to average power.
Like the Peak Hold feature, the Crest Factor feature also has the same minimum average power level
restriction of -20 dBm. Beginning in firmware version 1.51, this has been implemented to increase
accuracy and maintain wide bandwidth of Crest Factor measurement over the peak power range of
-20 dBm to +20 dBm. The Crest Factor selection will also affect Histogram measurement if there is
power below -20 dBm. To obtain accurate average power measurements below -20 dBm, the Crest
Factor feature should be disabled.
3.8.1 Enabling the Crest Factor Feature
The Crest Factor feature is enabled or disabled by one of two function codes:
Syntax : [AE or BE] [CR0 or CR1]
Examples : OUTPUT 713;AE CR1 ! Enable the Crest Factor feature for sensor A
OUTPUT 713;BE CR0 ! Disable the Crest Factor feature for sensor B
Description : Like the PH0 and MN0 commands, the CR0 command will disable Peak Hold and Min/
Max measurements. Sending a CR1 command after the Crest Factor is enabled will reset
both the Crest Factor and Peak Hold (see Section 3.19.7).
3.8.2 Reading the Crest Factor Value
The Crest Factor value is read over the bus using a simple command:
Syntax : [AE or BE] CRF
Example : OUTPUT 713;AE CRF ! Send the crest factor value for sensor A
The Crest Factor feature monitors the maximum power as it is measured, but does not provide any
feedback to the controller until a CRF command is received. To monitor for a limit violation, the Limits
feature may be more useful (see Section 3.15).
The Crest Factor feature returns the current ratio between held power and average power, as displayed
on the front panel. A CRF command does not initiate data collection in same manner as a trigger
command, such as TR1. To get a good reading of the Peak Hold value, the procedure is:
1. Set up the signal being measured, and send CR1 to reset the Crest Factor measurement.
2. Send TR2.
3. Read the TR2 data, or wait for the data ready service request (this allows for settling).
4. Send CRF.
5. Read the Crest Factor value.
NOTE:
The Crest Factor feature can only be used in the standard measurement collections
modes (not in the fast modes), and only in a modulated measurement mode (MAP, PAP, or
BAP). Crest Factor is not recommended for use in combination with the V
PROP
F function.
☛ ☛ ☛ ☛