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T U R B I D I T Y SEN S O R | O I/AT S 410 - EN R E V. A
13
Calibration with a primary standard
Before you do a wet standard calibration, make sure that a
stock formazine solution is available. If a stock solution is not
available, 24 hours must elapse before a freshly prepared
solution can be used.
To prepare the sensor assembly for wet (Formazine)
calibration:
1
Close the isolating valve installed upstream of the sensor.
2
Close the sensor inlet valve.
3
Open the drain valve. Let the sensor drain.
NOTICE
When you remove the wiper unit, do not put too much force
on the wiper because it can bend the wiper arm out of 90°.
When you remove the wiper, make sure that the wiper arm is
not bent.
4
Carefully remove the wiper unit (7998 011 and 012) or the
wiper plug (7998 016 and 017) to aid complete drainage of
the system.
5
When the system is empty, close the drain valve.
6
Thoroughly dry the flow chamber internally using clean
tissue.
7
Thoroughly clean and dry the emitter and receiver lenses
using clean tissue.
8
If there is condensation on the emitter and receiver lenses:
a
Leave the sensor open to let the lenses reach ambient
temperature before you do the calibration.
9
Insert the dry calibration standard with the zero NTU
indication (refer to Figure 12 or Figure 13) facing the optical
receiver, ensuring the locating lug engages correctly. Refer
to Figure 14.
NOTICE
Do not touch the light-reflecting parts of the standard.
N
U
STA
N
D.
N
U
NTU value indication
Zero NTU indication
Figure 12 Dry calibration standard for low range sensors
STA
N
D.
N
U
STA
N
D.
N
U
NTU value indication
Zero NTU indication
Figure 13 Dry calibration standard for high range sensors
NTU value
indication
Zero NTU
indication
Locating lug
Optical
emitter
Optical
receiver
Figure 14 Inserting dry standard
