Honeywell Searchline Excel Open-Path Technical Handbook page 47

MAN0530 Issue 09 October 03
2104M0506
3. INSTALLATION AND OPERATION
Important Notes:
1) The overall objective of alignment is to maximise the SIG level. Maximised SIG
corresponds to optimal alignment.
2) The Instrument Assisted Alignment (IAA) system only allows Excel to be initialised if the
SIG level is greater than or equal to the TGT level when Enter is pressed.
3) The smallest TGT signal level that is initially set will be equivalent to 70% (0.700) of the
signal expected for the installation's path length.
4) The TGT level will increase gradually if the current SIG level is larger than the TGT level.
The TGT signal level only ever increases. If the current SIG level falls below the TGT
level, TGT will remain at its previous highest value. In order to initialise the gas detector
the SIG level must be brought back above the TGT level.
5) If the SIG level is less than 50% of the expected level, the bar graphs are not displayed.
Instead both SIG and TGT levels are displayed as numbers.
(10) Now carry out one of the procedures described under Options.
Options
The next procedure to be followed depends on the type of alignment telescope and mounting
initially used to set up the Excel gas detector.
Bayonet-style Trident-type telescope assembly
If this type of alignment telescope was used with a Trident-type Excel gas detector, there is no
need to further optimise the alignment using the SHC1 Handheld Interrogator.
When the SIG and TGT bar graphs are displayed on the SHC1 screen, SIG will always be
greater than TGT and installation can proceed to the next stage by pressing Enter and following
step 12.
Latch-style Trident-type telescope assembly
If this type of alignment telescope was used with a Trident-type Excel gas detector, there is no
need to further optimise the alignment using the SHC1 Handheld Interrogator.
If this type of alignment telescope was used with a non-Trident Excel it may be necessary to
further optimise the alignment in the following way in order to achieve best performance.
(a) After the SIG and TGT bar graphs are displayed on the SHC1 screen as previously
described, let the TGT level reach its initial maximum by waiting for approximately
10 seconds.
During this time the TGT level will move up towards the current SIG level.
(b) Whilst watching the SIG level closely, make a small mechanical adjustment in either
the horizontal or vertical alignment and note whether the SIG level goes up or down.
(c) If the SIG level goes up, make another small mechanical adjustment in the same
direction as before.
(d) If the SIG level goes down, change the direction of adjustment.
Maximise the SIG level by making small adjustments in only one plane at a time.
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Searchline Excel