IRIS S55XX SERIES VIEWING HEADS APPLICATION MANUAL
PAGE 12
the current UV gain with the range 00 - 99.
A gain of 00 turns off the sensor. To change
the UV gain use the up or down push buttons.
Press YES to store the new value. Pressing NO
will discard any changes.
CHECKING OR CHANGING THE IR FILTER
This next step allows changes to the IR filter. The
display will show “ArFN” where N is the cur-
rent filter selected ranging from 1 to 8.
Use the up and down push-buttons to change the
filter if required. See the section “MODEL
S550B GENERAL DESCRIPTION” on page
3 for a listing of the high-pass frequencies for
these filters.
Press YES to accept a new filter value or NO to
ignore and discard any changes you may have
made. It is recommended that the #3 default
filter (33Hz cutoff) be used for all of the initial
setup procedures described in this manual.
CHECKING OR CHANGING IR GAIN
A final adjustment of the IR gain can now be made. Af-
ter the filter selection, the display will show “ANNN”
where NNN, the IR gain, ranges from 000 to 699. The
up and down push buttons can be used to change the
IR gain. Changed values can be accepted by pressing
YES or discarded by pressing NO.
If the S550B settings are changed, the display will
show “----” indicating that the values are stored in EE-
PROM, before continuing with the normal numerical
display.
If you do change the IR gain you may find that the
displayed gain values “jump” as you scroll through
them. As you increase the gain from zero you will see
the following sequence:
000 - 099
150 - 199
250 - 299
350 - 399
450 - 499
550 - 599
650 - 699
The two least significant digits are linear gain mul-
tipliers; e.g., from 150 to 199 is a 99/50 increase in
gain. But the most significant digit is nonlinear; with
each step change in the most significant digit, the gain
doubles. For example, a setting of 250 has twice the
gain as a setting of 150. Now it is possible to see why,
as the gain is increased from 150 to 199 the next step
is to 250; an increase from 150 to 199 is an increase
of 99/50, which is a gain increase of almost 2, but the
next step to 250 is to a gain increase, theoretically, to
exactly 2. This relationship is true of all the gains to
699. The two least significant digits can be used be-
low 050 down to 000; 000, of course, selects a gain of
zero (which turns OFF the sensor). When the display
is ramped down from 699 the following sequence will
be seen:
673 - 637
573 - 537
473 - 437
373 - 337
273 - 237
173 - 137
073 - 000
This approach makes a wide range available for gain
multiplier changes using the two least significant
digits. For example, over a range of 137 to 199 the
gain is changed by a ratio of 99/37. It is advantageous
for moderate changes in gain to change only the gain
multiplier digits because the response to these chang-
es is very linear. When changes are made in the most
significant gain digit, the gain change is not always
exactly an ideal 2:1 step change.
MANUAL SETUP OF THE S550B
The steps below for manual setup should result in the
P520 or P522 displaying a reading close to 1200 with
flame on. This procedure should provide similar gain
settings for each selected sensor as in the “
Calibra-
tion Procedure”
described earlier.
1) Bring the firing rate of the burner to a low fire
condition.
2) Ensure that the external input for CHAN SEL is
properly set for the channel calibration (A or B)
that is currently being set and the channel LED is
illuminated.
3) Determine whether to setup using the UV or IR
sensor before aiming the viewing head. In some