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6.2.2 Calibration Page
Calibration involves standardizing the instrument and the sensor by exposing the sensor to air.
During a calibration, retransmission and alarm outputs are automatically held to prevent inadvertent operation of ancillary
equipment.
– – – – –
SENSOR CAL.
0 0 0 0 0
Cal. User Code
– – – – –
Expose to Air
.
8 7 9
Calibrating Air
– – – – –
Sensor O/P
0 0 0 0 0
SECURITY CODE
Caution. Take care that the membrane at the end of the sensor does not come into contact with any hard or
sharp objects.
Note.
•
The air should be saturated with water vapour. This can be conveniently achieved by suspending the sensor
inside a bottle containing a few drops of water.
•
Errors in the calibration procedure, e.g. water droplets on the sensor membrane, can cause Calibration Fail
to be displayed.
– press to advance to next parameter
or
– press to Advance to Access to Secure Parameters Page, Section 7.1
Calibration Access
Enter the required calibration code number, between 00000 and 19999. If an incorrect
value is entered, access to calibration is prevented and Calibration Page is displayed.
Expose the sensor to air, before depressing the
procedure:
1) shut off the sample flow – see Fig. 2.7A,
2) remove the sensor from the flowcell – see Section 4.1),
3) carefully dry the sensor with a soft tissue, and
4) expose the sensor to air;
or
by using suitably installed valves (see Fig. 2.7B) isolate the flowcell and drain out the
water; first open valve V2, then close valve V1.
Calibrating Air
Displayed for three to five minutes, allowing the sensor response to become stable. During this
period the oxygen value displayed is calculated using the data from the previous calibration.
If the sensor output is satisfactorily large and stable then Calibration Pass is displayed and the new,
corrected oxygen concentration is displayed on return to the Operating Page.
Sensor Output
Provides an indication of the sensor performance in the form of a 5 bar display. When 5
bars are displayed, the sensor has maximum life remaining.
When 2 bars are displayed and flashing, the sensor is exhausted.
A replacement sensor should be ordered when three bars are displayed.
If a calibration is carried out and 2 flashing bars are displayed, the calibration is ignored
and the values obtained from the previous calibration are used.
Return the system to normal by either a):
1) Dry the interior of the flowcell with an absorbent tissue, and replace the oxygen
sensor – see Section 4.1.
2) Start the sample water flow – see Fig. 2.7.
or b):
Start the sample water flow by opening valve V1, then closing valve V2 – see Fig. 2.7B
Advance to Access to Secure Parameters Page, Section 7.1
...6 START UP AND OPERATION
button, using the following
17
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