Leveling Head Adjustment - 75 Ω - Fluke 9640A Series Instruction Manual

Leveling Head Adjustment – 75
Equipment required:
•
AC Measurement Standard
• Precision feedthrough termination, 75 Ω
• 75 Ω Type-N female-to-50 Ω Type-N male adapter
•
Power Meter
• Power Sensor, 75 Ω
•
Spectrum Analyzer/Measuring Receiver
• Precision Adapter, Type-N female-to-female, 75 Ω
• 75 Ω to 50 Ω impedance-matching pad
Base Adjustment must be performed before attempting Head adjustment.
Once Base adjustment has been performed, Head adjustment can take place
in any order (50 Ω or 75 Ω first).
If the Reference Frequency or Base Adjustment was just completed, omit
steps 1 through 4, below.
1. Ensure a 75 Ω Leveling Head is connected to the UUT base.
2. On the UUT, press  , followed by the soft key Calibration and then softkey
Calibrate Instrument .
3. Using the keypad, enter the password, followed by the ENTER key.
4. Press the soft key Adjust Head .
5. Connect the UUT Leveling Head to the input of the AC Measurement Standard via a
precision 75 Ω feedthrough termination. (If a Type-N feedthrough termination is not
available, use a 75 Ω BNC feedthrough termination and appropriate adapters.)
It is recommended that for measurements made with the AC Measurement
Standard during calibration adjustment a common mode choke is used as
described in the Level Accuracy Test, with the choke input low connected to
the AC Measurement Standard chassis ground. Keep the ground connection
as short as possible and set the AC Measurement Standard to Internal
Guard.
6. Set the UUT to OPER .
The following steps facilitate the low frequency flatness adjustment of the
Ω
75 Leveling Head using the AC Measurement Standard.
7. Using the blue arrow keys and rotary knob, edit the UUT Actual output until the AC
Measurement Standard indicates the Target value stated. Press Accept Target .
If the AC Measurement Standard used does not read the UUT output in
dBm directly, calculate the desired value using the following formula:
Ω
Note
Note
Note
Note
Note
 
2
V
 
( )
75
Ω =
dBm 75 10 log
 
−3
 10 
 
Calibration 5
Calibration Adjustments
5-59