11. TROUBLESHOOTING
75
The grade setting
value of the TP-L5
and the measured
grade value are not
equal.
1) Incorrect grade value was entered.
2) The bubble on the bubble tube
display of the instrument or the
bubble on the target was not
adjusted correctly.
3) The laser beam is refracted due to
temperature differences within the
pipe.
1) Confirm the input value (
‰
or %)
and reset.
2) Adjust the laser and/or target so
the bubble is centered.
3) When the pipe is laid, the trench
must be backfilled immediately
to help maintain temperature
stability.
Use a blower (commercially-
available) to move air through
the pipe to keep temperature
Conditions
Causes
Countermeasures
