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2.3.1 7997 201 and 7997 202
These sensors are designed to operate at very low turbidity
values of less than 0.1 NTU. At these values it is most important
that additional sources of light scattering, such as gas bubbles in
the sample, are eliminated. In this case an optional debubbler
(part number 7997 500) is available to eliminate the effect of gas
bubbles.
2.3.2 7997 200 Series and 7997 300
The flowrate should be maintained at a reasonable level (i.e.
-1
0.5 l min
) to prevent possible solids settling out in the
pipework. If this becomes a problem higher flowrates may be
required. The maximum flow rate of 6.0 l min
exceeded.
2.3.3 7997 400 Series
The dip sensor should be mounted in a position where a
representative sample is always monitored (i.e. not in an obscure
corner away from the main flow path). The dip tube should not
be totally submerged, but the sensor assembly at the end of the
dip tube must always be in the sample despite any change in
liquid level, to enable a correct turbidity measurement to be
achieved.
In applications with excessive flowrate, the sensor should be
mounted with the arrow on the top of the dip tube, in line with the
direction of flow – see Fig. 2.6.
2.3.4 7997 450 Series
The flowrate should be maintained at a reasonable level (i.e.
0.5 l min
-1
) to prevent possible solids settling out in the
pipework. If this becomes a problem higher flowrates may be
required. The maximum flow rate of 6.0 l min
exceeded.
2.3.5 Flow Unit Dimensions – Table 2.1
M
o
d
l e
H
e
g i
t h
7
9
9
7
2 /
0
0
4
0
0
0 .
m
m
7
9
9
7
3 /
0
0
4
0
0
0 .
m
m
7
9
9
7
4 /
0
0
9
3
5 .
m
m
a
p
p
o r
. x
3
0
0
7
9
9
7
4 /
5
0
s (
e e
N
o
e t
b
e
N
t o
. e
2
4
0
m
m
+
3
0
m
m
f
r o
h t
e
f
r o
h t
e
r b
c a
e k
. t
Table 2.1 Overall Dimensions in mm
-1
should not be
-1
should not be
W
d i
h t
D
e
p
2
9
4
5 .
m
m
3
2
9
0 .
2
9
4
5 .
m
m
1
6
0
0 .
8
2
0 .
m
m
2
1
2
5 .
m
m
1
3
5
0 .
m
m
1
3
5
0 .
o l
) w
a c
b
e l
g
a l
n
d
+
a
p
r p
x o
m i
a
e t
y l
3
0
2.3.6 Mounting the Sensor – Figs. 2.7 (7997 200
and 300 Series), 2.8 (7997 200 Series), 2.9 (7997
300), 2.10 (7997 400 Series) and 2.11 (7997 450)
Mount the sensor in the attitude shown in the appropriate
illustration using the bracket(s) provided, where required.
Connect the sample and drain tubes.
Important Note. Mount units within 5 of their vertical axes.
Fig. 2.7 Models 7997 200 Series and 300 (viewed from
the side) Location of Sample Outlet Connector
h t
m
m
m
m
m
m
m
m
Drain
(12 mm i.d. flexible
m
m
hose connection).
Fig. 2.8 Model 7997 200 Series Mounting Information
2 MECHANICAL INSTALLATION...
Sample Outlet
Connector
for 6 mm i.d.
Tube Located
Behind the
Sensor Body
46.5
155.5
Sample outlet,
see Fig. 2.8
for location.
Sample inlet
(12 mm i.d. flexible
hose connection).
118
Six holes 7
for mounting
9
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