Checking Whether The Probe Is Zero Current Free - wtw TriOxmatic 700IN Operating Manual

Maintenance, cleaning, disposal, spare parts
Test solution
Course of the check
Test criterion
32
4.4 Checking whether the probe is zero current
free
The probe is zero current free. Therefore, it is not possible
to calibrate the probe in air free of oxygen.
It is possible, however, to check whether the probe is zero
current free
according to DIN EN 25814/ISO 5814. This is required in
case of a suspected malfunction.
1 g/L aqueous sodium sulfite solution, Na
(adding 1 mg/L of a cobaltous salt accelerates the removal
of oxygen from the solution.)
The probe should have been in operation for at least one
hour before the check.
l Perform an exterior cleaning of the probe.
l Switch the measuring instrument to the % saturation
operating mode.
l
Immerse the probe into the test solution.
l
Wait for one hour.
Note
Leave the probe in the test solution for one hour.
The probe is OK when the measuring instrument displays <
2 % oxygen saturation.
If the measured value is > 2 %:
l
Reinigen der Platin-Arbeitselektrode und Wechsel von
Elektrolyt und Membrankopf.
l If necessary, also clean the counter electrode (see
section 4.2.1 C
to section 4.3 R
ELECTRODE
LEANING OF THE PLATINIUM WORKING
EFILLING THE MEMBRANE HEAD
SO
2 3
)