Calibration Verification With A Secondary Standard - ABB 4690 Series Operating Instruction

12 4 6 9 0 S E R I E S | T U R B I D I T Y S E N S O R | O I/AT S 4 1 0 - E N R E V. A
Calibration verification with a secondary
standard
To check the calibration:
1 Close the isolating valve that is 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 (see Figure 9 or Figure 10) facing the optical
receiver, ensuring the locating lug engages correctly. Refer
to Figure 11.
10 Note the reading on the display.
11 Remove the dry standard, turn it through 180° and refit it,
ensuring that the NTU value indication (refer to Figure 9 or
Figure 10) faces the receiver and the locating lug engages
correctly. Refer to Figure 11.
12 Note the reading on the display.
13 If the readings noted at steps 9 and 10 exceed ±5 % of dry
standard value:
a Repeat the procedure from step 7.
b If the readings are still outside this range, calibrate the
sensor.
14 Remove the dry standard and put it in its storage container.
15 Refit the wiper unit (7998 011 and 012) or wiper plug
(7998 016 and 017).
16 Open the inlet valve and ensure that the flow through the
sensor is 0.5 to 1.5 L/min .
–1
NTU value indication
Figure 9 Dry calibration standard for low range sensors
NTU value indication
Figure 10 Dry calibration standard for high range sensors
NTU value Zero NTU
indication indication
Figure 11 Inserting dry standard
Zero NTU indication
Zero NTU indication
Locating lug
Optical
emitter
Optical
receiver