EXFO AXS-100 Series OTDR - Manual (Page 91)

Measuring Power or Loss
OTDR 83
Nulling Offsets
Nulling Offsets
Temperature and humidity variations affect the performance of electronic
circuits and optical detectors, which can offset measurement results. To
compensate for this offset, the unit is equipped with an offset nulling
function.
Your unit is 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: When you start an offset nulling operation, all light sources on the unit are
automatically deactivated.
To perform an offset nulling operation:
1. Press Menu and select Setup > Power
Meter, and then press Enter.
OR
From the Power Meter pane, press Setup
(F1/F2 key).
2. Use the left/right function arrows until you
see Offset Nulling, and then display the pane (F1/F2 key).
3. Screw the protective cap on the power meter port, and then press OK.
The offset nulling process takes a few seconds. If light is still detected,
make sure that you are using an appropriate protective cap and that it
is tightly screwed on the power meter port. Restart the nulling
operation.
I
MPORTANT
Light must not reach detectors when performing an offset nulling
operation. Always use a protective screw cap. Do not use a soft
rubber cover.