Performing A Calibration Verification With A Secondary Standard - ABB 4690 User Manual

4690 Series
Turbidity systems
To minimize deterioration of the secondary standard:

Carefully wipe off any residual moisture after use.

Clean the prism with lint-free cloth.

Avoid direct contact with the dry standard rod –
fingerprints on the surface may alter its stated value.

Store in the container provided when not in use and keep
in a dry place.
7.2 Performing a Calibration Verification with a
Secondary Standard
To check the calibration:
1. Close the isolating valve installed upstream of the sensor.
2. Close the sensor inlet valve and open the drain valve.
Allow the sensor to drain.
3. Carefully remove the wiper unit (7998 001, 002, 011 and
012) or the wiper plug (7998 006, 007, 016 and 017) to
aid complete drainage of the system. When the system is
empty, close the drain valve.
Caution. When removing the wiper unit do not put
excessive leverage on the wiper as there is a risk of
bending the wiper arm out of 90 °. On removal of
wiper, check wiper arm has not been bent.
4. Thoroughly dry the flow chamber internally using clean
tissue.
5. Thoroughly clean and dry the emitter and receiver lenses
using clean tissue.
Note. If condensation forms on the emitter and
receiver lenses, leave the sensor open to enable the
lenses to reach
attempting calibration.
6. Insert the dry calibration standard with the zero NTU
indication (see Figs 7.2 or 7.3) facing the optical receiver,
ensuring the locating lug engages correctly – see Fig. 7.4.
IM/4690–EN Rev. A
ambient temperature before
NTU value Indication
Fig. 7.2 Dry Calibration Standard for Low Range Sensors
NTU value indication
Fig. 7.3 Dry Calibration Standard for High Range Sensors
Zero NTU
NTU value
Indication
Indication
Fig. 7.4 Inserting Dry Standard
7. Note the reading on the display.
7 Calibration
Zero NTU Indication
Zero NTU indication
Locating
Lug
Optical
Emitter
Optical
Receiver
21