- 5 -
4.2
Storage of the DO electrode
The surface of the sensitive membrane of the dissolved electrode should be kept moist to prevent the
electrolyte at the cathode from drying out. There’s a sponge at the bottom of the calibration sleeve (see
Diagram - 9), always keep it moist. Once the sponge is dry, add a few drops of distilled or deionized water
into it, make sure the sponge is wet while no water flows out, and tighten the calibration lock-up ring to
keep the dissolved oxygen electrode under humid conditions.
4.3
Clean the salinity electrode
The built-in salinity sensor (see Diagram - 9) is coated with platinum black to minimize electrode
polarization and expand measuring range. DO NOT brush the salinity sensor as it may damage the platinum
black. If the platinum black sensor is stained, rinse it in distilled or deionized water or gently clean it in
warm water containing detergent or alcohol.
4.4
Replace the membrane cap
When the electrode response time is long and the measured value shows obvious deviation, or the
sensitive membrane of the dissolved oxygen electrode looks wrinkled, cracked or damaged, the
membrane cap should be replaced in time according to the following steps.
4.4.1
Unscrew the membrane cap, clean the electrode with distilled or deionized water, allow it to dry,
use a clean flannel or tissue paper to wipe the surface of the cathode (gold chip) with a bit of force.
4.4.2
Inject the electrolyte into a new membrane cap slowly, make sure no air bubbles is generated.
Flick the membrane cap with fingers to eliminate the bubbles. Then put the membrane cap on the table
and slowly screw in the electrode clockwise vertically until the membrane cap is firmly screwed on. At this
time, the excess electrolyte will be squeezed out, wipe it with a tissue paper and wash the electrode in
distilled or deionized water.
4.4.3
Check and make sure there
’
s no air bubbles in the electrolyte (except the tiny bubbles). Otherwise
the membrane cap should be unscrewed, add the electrolyte and reassemble.
4.4.4
Do not touch the sensitive membrane when using the electrode or replacing the membrane cap,
because the sweat and oil from the skin will affect the membrane quality and reduce the oxygen
permeability.
5
Calibration and Measurement of Dissolved Oxygen
5.1
Connect the DO electrode
The meter uses 8-pin socket. When the electrode is connected to the meter, please rotate it slowly to find
the position of the bayonet and connect it, and then tighten the cap nut. Be careful not to pull the cable
forcefully to prevent poor contact and keep the plug clean and dry.
5.2
Preparation for calibration
The meter is only suitable for air calibration with the calibration sleeve. When calibrating, make sure that
the air temperature and the temperature of the measured water solution to be close (temperature
difference
≤
10
℃
). If the temperature difference is large, the electrode should be immersed in the
