IRIS MODEL P520 APPLICATION MANUAL
Page 30
The PbS element used in the S512 is 2.0 x 2.0 mm
square. If you take the area of this element (4 mm
2
)
and find a circle of the same area, the diameter will
be 2.2568 mm. This was derived as follows:
Area circle =
p
R
2
p
R
2
= 4 mm
2
So
R = (4/p)
-2
= 1.1284
And
dia = 1.1284 X 2 = 2.2568 mm
or
dia = 0.0889 inches
Using the same 2 inch focal length lens and making
this diameter equal to d we get:
q
= 2 tan-
1
d/2F
q
= 2 tan
-1
0.0889/2 X 2
q
= 2.545°
The equation for angel of view of a camera lens is
derived from:
where tan
q
/2 = R/L and R = L tan
q
/2
The diameter d = 2Ltan
q
/2 which is the same equa-
tion as before with F = L but now d, will be the di-
ameter instead of the diagonal.
If you use
q
= 2.545°, then the above equation re-
solves to:
dia = L (.0444)
The table in Figure 15 shows the various distances
(L) versus the diameter of the circle of view for the
S512 viewing head.
APPLICATION OF IRIS VIEWING
HEADS
It is impossible to provide steadfast rules for each
type of viewing head and what application it should
be used for. The applications are becoming more
difficult because of the wide range of fuels being
used, in addition to recent changes in burner design
to comply with clean air standards.
The S506 UV viewing head will always result in
excellent discrimination between burners. The key
factor in using the UV type detector is obtaining a
consistent and reliable signal under all conditions.
UV radiation is very susceptible to being absorbed
and blocked by non-hydrocarbon elements and un-
burned fuel, as explained before. UV type detectors
usually work very well on natural gas. However,
low NOx type burners (controlled combustion) uti-
lizing fuel gas recirculation (FGR) can cause prob-
lems with UV flame detection.
The S509 “two-colour” photodetector viewing head has
been very successful in sulfur recovery applications
(Claus reactors) in the gas processing and petrochemi-
cal industries. The basic drawback is the nonlinearity
of the Si channel caused by the AGC action, as previ-
ously explained (see section S509 VIEWING HEAD,
and section S512 VIEWING HEAD). Also, the Si
channel will not see natural gas.
The S511 Ge viewing head will detect all types of
flames (fuels) and has been very successful in de-
tecting flame in lime kilns and sulfur recovery reac-
tors. The only drawback is the poor discrimination
between burners.
L
A
I
D
T
F
S
E
H
C
N
I
S
E
H
C
N
I
2
4
2
7
0
.
1
3
6
3
0
6
.
1
6
2
7
0
2
.
3
2
1
4
4
1
9
3
.
6
6
1
2
9
1
3
5
.
8
FIGURE 15 - VIEWING HEAD: ANGLE OF
VIEW - DISTANCE AND DIAMETER
L
R
θ
Summary of Contents for P520
Page 1: ...FLAME MONITORING SYSTEM MODEL P520 SIGNAL PROCESSOR APPLICATION MANUAL ...
Page 12: ...IRIS MODEL P520 APPLICATION MANUAL Page 12 FIGURE 7 IRIS P520 I O MODULE SCHEMATIC ...
Page 35: ...IRIS MODEL P520 APPLICATION MANUAL Page 35 FIGURE 17 BASIC BURNER START CIRCUIT ...
Page 45: ...IRIS MODEL P520 APPLICATION MANUAL Page 45 NOTES ...
