LBXXXA Series USB Powe
™
Product Manual PMA (Power Meter Application)
Revision: 08/02/11
- 20 -
Pulse Measurement Criteria (LB4XXA/LB6XXA models only)
This value determines the portion of the pulse to be used to measure pulse power. Select
Measurement > Measured
Pulse Setup
from the menu bar to access this facility as shown below. The default or automatic value is 3 dB below
the measured peak value or the 50% down points. You can also set the criteria and leave the automatic feature on.
Then by turning the auto feature on and off you can switch between the automatic value (dB) and the value you have
chosen. For instance, if you set the criteria to 6 dB and turn the auto criteria on and off, you will be toggling between 3
dB and 6 dB below peak. This can also give you some sense of rise time or slope and the sensitivity to this criteria.
P
ulse criteria is assumed to be specifed as “dB below peak.” If the peak value is -30 dBm and the criteria is 3 dB, then
the pulse criteria will be -33 dB during the measurement. Normally you will specify a positive value. Likewise, if you
chose 6 dB you would be using -36 dB as the criteria. Provided overshoot is minimal and rise time is relatively steep,
the automatic criteria is adequate for most applications. The diagrams below are intended to help clarify pulse criteria.
In diagram A, the peak value is -30 dBm and the pulse criteria is 3 dB. The shaded area represents the portion of the
pulse that will be used to determine pulse power and duty cycle.
