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CHECK AND REPLACEMENT OF ELECTROCHEMICAL OXYGEN SENSOR
18 - 1
ETC00303(1) BINOS E e (2.0) 11/00
Rosemount Analytical
18. Check / Replacement of electrochemical Oxygen Sensor
Through measuring principle the oxygen sensor will have only a limited life time.
The life time of the oxygen sensor is depending on the sensor itself and on the measured
oxygen concentration and is calculated as follows:
life time =
The so-called “sensor time” (operation without oxygen at 20 °C ) is
approx. 900.000 hours for sensor with a response time of about 12 s
The sensors will have the following life time at approx. 21 % Oxygen and 20 °C :
approx. 42.857 hours (approx. 5 years) for sensor with a response time of about 12 s
Note !
The values stated above are presented as guidelines only. The values are depending on
operation temperatures (the result of higher temperatures, for example 40 °C, could be the half
life time) and measured concentrations.
Note !
Depending on measuring principle the electrochemical O
2
cell needs a minimum internal consumption
of oxygen (residual humidity avoids drying of the cell). Supply cells continuously with dry sample gas
of low grade oxygen concentration or with oxygenfree sample gas could result a reversible detuning
of O
2
sensitivity. The output signal will become unstable.
For correct measurement the cells have to be supplied with O
2
concentrations of at least 0.1 Vol.-%.
We recommend to use the cells in intervall measurement (purge cells with conditioned (dust removal
but no drying) ambient air during measurement breaks).
If it is necessary to interrupt oxygen supply for several hours or days, the cell has to regenerate (supply
cell for about one day with ambient air). Temporary flushing with nitrogen (N
2
) for less than 1 h (e.g.
analyzer zeroing) will have no influence to measuring value.
All analyzers with electrochemical O
2
cell have to be purged with conditioned ambient air prior to
disconnect the gas lines ! Then the gas line fittings have to be closed for transport or depositing
analyzer.
sensor time (hours)
O
2
concentration (%)