EXFO FOT-930 Multifunction Loss Tester - Manual (Page 40)

Measuring Power or Loss
32 FOT-930
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. Press Menu, then select Setup > Power Meter.
OR
From the Power Meter pane, press Setup (F1/F2 key).
2. Press Nulling (F1/F2 key).
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. Check marks appear next to nulled
detectors. 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.