31
Dry Standard
Flow-chamber
Optical
Receiver
Optical
Emitter
Drain
Valve
Inlet/Isolating
Valve
FTU value
indication
ST
A
N
D.
N
U
7
MAINTENANCE…
…7.2.1
Procedure
Model 7997 300
a) Shut off sample water using the isolating valve installed
upstream of the sensing unit.
b) Drain the unit by closing the inlet and opening the drain valve.
Carefully unscrew and remove the wiper unit to aid complete
drainage of the system. When the system is empty, close the
outlet valve.
c) Thoroughly dry the inner chamber using clean tissue and
wipe clean the emitter and receiver lenses. Ensure that no
greasy marks are left on the lenses and that the lenses are
dry.
Note.
If the sample was cold, condensation could form on
the windows. It may be necessary, therefore, to leave the
sensor open for a short while to allow the windows to reach
ambient temperature before attempting calibration.
d) Close the drain valve and fill the chamber with high purity water.
Note the reading on the display.
If readings are out of spec. (
2% FSD), repeat the procedure
from c). If reading is still out of spec., calibrate the sensor –
Section 5.2.2.
e) Insert the Dry Calibration Standard so that the turbidity value on the
label is facing the emitter. Note the reading on the display.
f)
Take out the Dry Calibration Standard; dry/clean off any
moisture before storing the Standard in the supplied storage
container – see also Section 7.4.1 – Care and Maintenance
of Dry Calibration Standards.
g) Fit the wiper Unit and screw it down firmly.
h) Open the inlet and outlet valves. Set the sample rate to 0.5 to
6.0 l min
–1
Fig. 7.3 Model 7997 300
Fig. 7.4 Dry Calibration Standards for 7997 300 Sensors
Summary of Contents for 4670 Series
Page 1: ...Turbidity Systems 4670 Series User Guide IM 4670_13 ...
Page 49: ...47 NOTES ...
Page 50: ...48 NOTES ...
