Oxygen Sensor; Sensor Layout - Lovibond SD 310 Oxi Mode D'emploi

7. Oxygen sensor

7.1 Sensor layout

General
The oxygen sensor is an active sensor. It comprises a platinum cathode, a
lead anode and potassium hydroxide (KOH) as the electrolyte. If oxygen is
present, this will be reduced on the platinum cathode and the sensor sends a
signal. If no oxygen is present, no signal is sent. The anode becomes depleted
from measuring the oxygen. The sensor is prone to aging. The water vapor
permeable membrane causes the sensor to lose water especially if the sensor
is stored in dry air.
It should be checked and serviced regularly (see: 'Sensor maintenance').
Refill
opening
i
Sensor
shaft
O-ring
Membrane
cap
Layout
The sensor housing is made from ABS. With the exception of the shaft, all parts must be
serviced regularly and replaced, if necessary.
• Storage flask: The storage flask is used to moisten the membrane. This increaes the service
life of the sensor. The storage flask contains deionized water.
Caution! Only store water in this flask, never use KOH electrolyte or potassium chloride (KCl)
as is necessary to store pH electrodes.
• Membrane cap: The membrane head is covered with a Teflon membrane. If the membrane
is damaged or large air bubbles or an air bubble ring in the membrane, this causes
incorrect measurements. This can also be the reason why a sensor cannot be calibrated.
The membrane cap is a spare part and can be re-ordered with the service set.
• Refill opening: When a sensor is serviced or used at high temperatures, the electrolyte
must be filled/re-filled. Also refer to the instructions below.
!
Service life:
At the end of the sensor's service life, the quality of the sensor signal drops relatively quickly.
The sensor evaluation in % can only be used as a reference value. An evaluation of 70 %
does not mean that exactly 70 % of the service life is still available. The sensor signal is 70
% of a comparable signal.
Note: The sensor evaluation is updated by the measurement device after the oxygen
sensor has been successfully calibrated.
The nominal service life can be significantly reduced by use.
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The oxygen sensor must always be kept moist!
- in a storage flask filled with deionized water or
- placed in a vessel filled with water
If a fungal or algae coating has formed on the membrane after a
long storage period, clean the membrane with a soft paper towel
prior to measurement.
Caution! The membrane is sensitive and if it is damaged, caustic
electrolyte will leak and the sensor will send an incorrect signal
Be particularly careful when working with the electrolyte:
The electrolyte is caustic. (strong alkali, KOH)
Avoid skin contact and protect your eyes!
SD_310_2 07/2018