EXFO FTB-3930 MultiTest - Manual (Page 28)

Measuring Power or Loss
22 FTB-3930
Nulling Electrical Offsets
Nulling Electrical Offsets
Temperature and humidity variations affect the performance of electronic
circuits and optical detectors. Nulling the electrical offsets eliminate these
effects.
Your unit has been designed not to require offset nulling under normal
operation, but you should perform it whenever environmental conditions
change significantly or when measuring very low power values.
Note: Starting a nulling automatically deactivates all light sources on the unit.
To perform an offset nulling:
1. From the main window, select the Power Meter tab.
2. Press Nulling.
3. Tighten the protective caps on the power meter and F
AS
T
ES
T ports, then
press OK.
The nulling process takes approximately 10 seconds. Nulling status is
indicated in the data display. If light is still detected, you will need to
place the caps properly and restart.
I
MPORTANT
Light must not reach detectors when nulling offsets. Always use an
EUI or protective screw cap. Do not use a soft rubber cover.