Storage And Maintenance Of Oxygen Electrodes - Tintometer Lovibond SD 315 Oxi Instrucciones

When measuring dissolved oxygen, the following procedure must be observed:
Remove Rinse the
the electrode with
storage distilled water
bottle
a) b)

5.6 Storage and maintenance of oxygen electrodes

The oxygen sensor comprises a platinum cathode, a lead anode,
and potassium hydroxide (KOH) as the internal electrolyte. If oxygen is
present, this is reduced at the platinum cathode and the sensor delivers
an electrical signal. The measurement of dissolved oxygen (DO) depletes
the anode, ageing the sensor. The membrane, which is open to diffusion,
also causes the sensor to lose water, especially if it is stored in dry air.
If the electrode can no longer be calibrated, or if it returns unstable mea-
surement values only, it must be serviced or the membrane head must be
replaced. In principle, maintenance is carried out in the same way as an
Refill
initial filling. First, the membrane head is unscrewed and the old electro-
opening
lyte is removed. Any residual electrolyte solution must be wiped off using
a paper towel. If the membrane is undamaged, the membrane head can
Sensor
be reused. Otherwise, it must be replaced.
shaft
O-ring
Visible residue inside the membrane cap:
During operation, products from the reaction at the lead anode include
Membra-
lead oxide (brown/red, from the reaction with oxygen) and lead carbonate
ne head
(white, from the reaction with carbon dioxide). Although these substances
can collect on the membrane, they do not generally affect the measuring
function and can largely be removed during sensor maintenance. Before the membrane cap
is screwed on, they should be removed in order to avoid trapping particles between the
membrane and the platinum dome. Rapid formation after commissioning, or excessive lead
carbonate build-up, is an indicator of air in the sensor (incomplete filling / leaks due to the
cap / filling screw not being screwed on correctly, or a leak in the membrane).
50
3 cm
Observe an Allow the tempera-
immersion ture of the
depth of at sensor (T
least 3 cm sample (T
to equilibrate!
Immerse the oxygen sensor in the measuring solution.
Ensure sufficient flow, e.g. by
a) using a magnetic stirrer with agitator (recommended)
or
b) continuously swirling the sensor in the solution.
Always read off the measurement value while
stirring!
T
Elec
=
T
Sample
Hold the sensor
as vertically as
) and possible in order
Elec
) to avoid touching
Sample
the vessel.
SD_315_DO_1 06/2020
°
90