Honeywell Searchline Excel Open-Path Technical Handbook page 78

MAN0530 Issue 09 October 03
2104M0506
Fault/Problem Causes
Electrical installation
problem
Heavy contamination of
optics
Very low visibility along
beam path due to dense fog,
blizzard or sand-storm
conditions
Output is 2.5mA. Beam path is blocked
(BEAM BLOCK)
Transmitter or Receiver
misaligned
Output is 3mA Heavy contamination of
(LOW SIGNAL) optics
Transmitter or Receiver
misaligned
Output is 2mA Unit has been inhibited by
(INHIBIT) the Interrogator
Unit executing power-up
routine
6. PROBLEM SOLVING
Remedies
1) Check that the +24V supply is reaching the unit.
Voltage at the unit should be between +18V and +32V.
2) Check cables and connections to the unit, especially
the 4-20mA loop connections.
3) Check that the unit has the correct type of 4-20mA
output for use with the controller that it is connected to.
Check the Transmitter and Receiver windows for build up of
contamination. Clean the windows if required. Re-zero unit.
1) Check that the Transmitter can be seen from the
Receiver. If Transmitter can be seen, even with some
difficulty, low visibility is unlikely to be the problem.
2) If the Transmitter cannot be seen from the Receiver,
very low visibility could be the problem. Wait until
visibility improves and verify that the unit then
returns to operational status.
Check that the beam path is clear from the Transmitter to
Receiver. Remove any obstruction if present.
1) Connect SHC1 Interrogator to unit and check signal
levels.
2) If signal levels are low, use the telescope and SHC1
Interrogator to optimise Receiver alignment.
3) If signal levels remain low after re-aligning Receiver,
check the Transmitter alignment using the telescope.
4) Re-zero the unit after alignment. See Appendix A.5.3.4.
Check the Transmitter and Receiver windows for build up of
contamination. Clean windows if required. Re-zero the unit.
1) Use the telescope and Interrogator to optimise
Receiver alignment.
2) If signal levels remain low after re-aligning Receiver,
check the Transmitter alignment using the telescope.
3) Re-zero the unit after alignment. See Appendix A.5.3.4.
Release output from INHIBIT state using SHC1 Interrogator.
1) Wait for 1 minute. When power-up routine is completed
satisfactorily the unit s output should exit the INHIBIT
state.
2) If unit remains in INHIBIT, check the +24V supply is
reaching the unit. If the voltage is below +18V or is
fluctuating above and below +18V, the unit may be
being prevented from completing power-up. (This is an
electrical installation problem.)
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