25
5.8
Cleaning and Maintenance of the Sensors
All oxygen sensors can be sterilized with ethylene oxide (EtO) and
can be cleaned with peroxide (3% H2O2), soap solution or ethanol.
They can be applied in gas phases, aqueous solutions, ethanol,
methanol and isopropanol. Other organic solvents and gaseous
chlorine (Cl2) induce interferences with the sensor reading. No
cross-sensitivity is found for pH 1-14, CO2, CH4, H2S and any ionic
species.
A signal drift of the sensor can indicate photobleaching of the
oxygen-sensitive
REDFLASH
indicator
, depending on the ambient
light intensity, as well as the intensity of the excitation light and
the sample frequency. This can necessitate a recalibration of the
sensor and eventually also a readjustment of the
Sensor Settings
(LED intensity; see also chapter 6.2.2). In case of sensor spots, this
could require a re-positioning of the optical fiber on the sensor
spot and a subsequent new calibration. If the signal intensity is
getting too low, as indicated by the
horizontal indicator bar in the
Pyro Oxygen Logger
software and by the
respective warning
(see
chapter 6)
, the sensor needs to be replaced.
A reasonable normal range oxygen sensor shows signal intensities
well above 20 (typically 50-500).
After finalization of the measurements, the sensor tip of the
needle-type and bare fiber oxygen sensors, as well as the robust
probes should be rinsed carefully with demineralized water.
Especially after application in seawater, it is recommended to
clean the sensor thoroughly with demineralized water to prevent
salt crystallization in the needle which can cause breaking of the
sensor tip.
In case of retractable sensors, retract the sensor tip into the needle
after drying. For all needle-type sensors, put on the protective cap
onto the needle to protect the sensor tip and to avoid injuries.
