Agilent Technologies FieldFox N9913A User Manual page 136

Zeroing
The Agilent USB Power Sensors perform Internal Zeroing automatically. Because
Agilent USB Power Sensors have an internal switch, Internal Zeroing does NOT
require that the power source be turned OFF.
For highest measurement accuracy, when measuring power levels below –30
dBm, External Zeroing should be performed.
During External Zeroing, the power source MUST be turned OFF or the power
sensor disconnected from the power source (device under test). Power is OFF
when power sensor measurements are below –60 dBm. When power higher than
this is detected at the sensor, a warning message is shown on the FieldFox and
External Zeroing will not proceed.
NOTE External Zeroing is NOT allowed on the U2020 X-series Power Sensors.
How to perform External Zeroing
 Press Cal 5 .
External Zero.
 Then
While either Internal or External Zeroing is being performed, "Zeroing..." is
shown on the FieldFox screen. While this message is present, do NOT make any
changes to the FieldFox.
In addition, once External Zeroing has started, the power source must be OFF for
the entire time that the Zeroing message is present. Otherwise, the calibration
will be compromised but NO warning is shown.
Frequency
A table of correction factors versus frequency is stored within the Agilent U2000
Series Power Sensors. The frequency of the power to be measured is entered in
the FieldFox so that the appropriate correction factor can be used.
The frequency of the power measurement is NOT limited by the frequency range
of the FieldFox, but the frequency range of the power sensor, which can be much
wider.
How to enter Frequency of the Power Measurement
 Press Freq/Dist or Meas Setup 4 .
 Then Frequency.
 Then type a value using the numeric keypad. The default frequency is 50 MHz.
 Then press a multiplier key. Learn about multiplier abbreviations on page 19.
The current frequency is shown on the FieldFox screen.
Scale
The scale of the Power Meter display can be set manually or automatically. The
major and minor ticks are set automatically and can NOT be changed. Although
the scale settings are limited, you can view measurements beyond these settings
by performing Autoscale.
136 FieldFox User's Guide