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Aquaprobe
®
AP-5000 Instruction Manual
10401-00906 Rev M
It follows, therefore, that in order to provide stable, repeatable readings, the environment in
which the measurements are made must be completely stable and repeatable. For this
reason, the AP-5000 is constructed with a matt black aluminium sleeve and end cap that
enclose the sensing electrodes and provide a closed, constant condition, non reflective
measurement chamber.
In order to obtain consistent results, the measurement chamber created within the
Aquaprobe
®
must remain physically constant during both calibration and
measurement. It is therefore essential that both the sleeve and sleeve end cap are
fitted during calibration and operation of all types of optical electrodes.
If an optical electrode is calibrated under one set of conditions then used to measure under
another set of conditions, the readings will naturally be erroneous, especially at low
concentrations. A perfect example of this is calibrating with the end cap removed then
measuring with the end cap fitted (or vice-versa). By changing the physical characteristics
of the measurement chamber, you also change the calibration and response of the
electrode.
Another particular problem when trying to measure very low
concentrations is air in the form of both visible and microscopic
bubbles. These act like tiny prisms and can refract and reflect both the
excitation light and the return signal being measured. The photograph
to the right was taken in a calibration tube after fresh water was
poured in. The bubbles are clearly visible in the light beam.
2.5. Top Tips for successful measurements using optical electrodes
➢
Always keep the measurement chamber and electrode lenses clean.
➢
Always fit the sleeve and end cap during both calibration and measurement.
➢
Always allow the readings to settle completely during both calibration and
measurement.
➢
Always try to eliminate air bubbles by agitating the Probe after insertion both during
calibration and measurement.
➢
Always calibrate and zero the electrode as close to your sample temperature as
possible. This is especially important with the Ref-Oil electrode.
➢
Always zero the optical electrodes just prior to use in clean water (bottled still
mineral water is ideal) then deploy
without disturbing the measurement chamber
.
This is especially important when using the Turbidity electrode.
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®
Ltd.
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