46
MAN0530 Issue 10 - 11/09
Searchline Excel
2104M0506
3. INSTALLATION AND OPERATION
The second line of the display shows the magnitude of the current
target
signal level as
a horizontal bar graph -
tGt:
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.
