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out the polishing paper from the accessories and polish the surface of the gold chip at cathode, wipe
it with clean flannel or tissue paper, rinse the electrode with pure water and allow it to dry. Add some
electrolyte into the membrane cap, screw it on tightly and then perform full saturation and zero oxygen
calibration, follow the steps of 5.3.1 and 5.4.1.
5.4.2
Salinity calibration
Dissolved oxygen measurement mode has automatic salinity compensation function, so salinity calibration
is required. Salinity calibration is generally only needed when a new electrode is replaced and the
instrument has not been used for a long time. It is not needed in daily usage. The meter has been salinity
calibrated before it leaves factory, so it is not necessary to calibrate it for the first use. The salinity
calibration steps are as follows:
a)
Switch the meter to parameter setting P4.2, see Diagram
–
10 (a).
b)
Press to enter salinity calibration mode. Use 12.88mS/cm conductivity calibration solution to
calibrate. If the electrode is empty or the calibration solution is not accurate,
Er1
icon displays at the
bottom right of LCD. Immerse the electrode into 12.88mS/cm conductivity standard solution (Note
that the solution should exceed the height of the salinity electrode). Stir gently and wait until the
salinity value becomes stable and the stable icon displays on LCD, press to calibrate, see
Diagram
–
10 (b), press twice to return to measurement mode, see Diagram
–
10 (c).
5.4.3
Adjust the air pressure value
The meter has the function of manual air pressure compensation. When the air pressure of the location
where the instrument is used changes greatly, it is recommended to set according to the value of the
standard barometer or altitude of different regions (see Appendix – 5 and Appendix – 6) to ensure the
accuracy of the air pressure compensation of the meter. Refer to parameter setting P4.3 to adjust the air
pressure value.
5.5
Measurement of water samples
5.5.1
Measurement in laboratory
Use a stirrer to measure: Pour the water sample into a large beaker, install the electrode on the electrode
holder, turn on the stirrer and test. This method requires a suitable stirring speed to balance the oxygen
consumed by the dissolved oxygen electrode and the oxygen absorbed when the solution is stirred. Adjust
the stirring speed slowly and repeatedly, and then get the reading until the reading value becomes stable.
Diagram 10
(a)
(b)
(c)
